NAVLE (North American Veterinary Licensing Exam) — Questions and Answers

Question 1: A 3-year-old male neutered domestic ferret presents with episodic weakness, muscle fasciculations, and apparent 'stargazing' that resolves after eating. Blood glucose at presentation is 42 mg/dL. After dextrose bolus, the ferret stabilizes. Abdominal ultrasound reveals a 0.8 cm hypoechoic nodule in the left pancreatic lobe. Which statement about medical management while awaiting surgery is MOST accurate?

Diazoxide at 5–30 mg/kg/day is preferred over prednisone as first-line because it avoids adrenal suppression in a species prone to hyperadrenocorticism (Correct answer)
Prednisone at 0.5–1 mg/kg PO BID is the preferred first-line medical management for insulinoma in ferrets
Frequent high-protein, low-carbohydrate meals alone are sufficient medical management for insulinoma without pharmacologic intervention
Octreotide SC injections are the first-line treatment of choice due to superior efficacy over prednisone in ferrets

Correct answer: Diazoxide at 5–30 mg/kg/day is preferred over prednisone as first-line because it avoids adrenal suppression in a species prone to hyperadrenocorticism

Diazoxide inhibits insulin secretion and is actually the preferred first-line pharmacologic agent in ferrets when medical management is needed, particularly because ferrets are extremely prone to adrenocortical disease (hyperadrenocorticism). Using prednisone long-term risks masking adrenal disease signs and contributes to iatrogenic immunosuppression and muscle wasting. Diazoxide at 5–30 mg/kg/day (divided BID) avoids these concerns. Dietary management alone is insufficient for documented insulinoma with severe hypoglycemia. Octreotide has variable efficacy in ferrets and is not first-line. Prednisone is used but carries significant species-specific drawbacks that make diazoxide preferable when available.

Question 2: A 1,200-head commercial feedlot is experiencing an increased rate of liver condemnations at slaughter (18% vs. the target <10%). Rumen pH monitoring via rumenocentesis on 12 randomly selected cattle 6 hours post-feeding shows a mean rumen pH of 5.8 with 4 animals below 5.5. The current ration uses dry-rolled corn at 85% of dry matter. Which management change will MOST directly address the primary pathophysiological mechanism driving the liver condemnation rate?

Switch from dry-rolled to high-moisture corn to slow starch fermentation rate
Increase dietary roughage inclusion from 5% to 12% to buffer rumen pH
Add monensin at 200–360 mg/head/day to shift ruminal fermentation toward propionate (Correct answer)
Add virginiamycin at 17 g/ton to suppress lactic acid-producing Streptococcus bovis

Correct answer: Add monensin at 200–360 mg/head/day to shift ruminal fermentation toward propionate

Liver abscesses (the primary cause of liver condemnations in feedlots) result from rumenitis → rumen wall ulceration → bacteremia with Fusobacterium necrophorum seeding the liver. Subacute rumen acidosis (SARA, pH 5.5–5.8) is the driver of rumenitis. Monensin, an ionophore, shifts fermentation away from butyrate/propionate ratios that damage the rumen epithelium, reduces lactic acid accumulation, and directly reduces liver abscess rates by ~50% — the most validated single intervention. High-moisture corn actually ferments more rapidly than dry-rolled corn, potentially worsening acidosis. Increasing roughage helps buffer pH but is less targeted and reduces energy density. Virginiamycin specifically targets acute lactic acidosis (Streptococcus bovis/Lactobacillus), which is not the predominant concern here given pH values in the SARA range rather than <5.0.

Question 3: A 6-year-old horse is presented with a history of spontaneous, severe epistaxis (nosebleed) from the right nostril. Endoscopic examination reveals a large, diphtheritic membrane on the dorsal aspect of the right guttural pouch, overlying the internal carotid artery. What is the most definitive treatment to prevent a fatal hemorrhage in this horse?

Transarterial coil embolization of the affected artery (Correct answer)
Surgical removal of the fungal plaque
Daily lavage of the guttural pouch with povidone-iodine
Long-term systemic antifungal therapy

Correct answer: Transarterial coil embolization of the affected artery

Guttural pouch mycosis with erosion of a major artery, such as the internal carotid, is a life-threatening emergency due to the risk of fatal hemorrhage. The most effective and definitive treatment to prevent bleeding is to occlude blood flow to the affected arterial segment. Transarterial coil embolization is the preferred method to achieve this. While medical management with antifungal drugs is part of the overall treatment to resolve the infection, it does not address the immediate risk of catastrophic bleeding.

Question 4: A 7-year-old intact male cat develops acute urethral obstruction. After relief of the obstruction, the cat develops profound bradycardia (HR 48 bpm), peaked T waves on ECG, and a serum potassium of 8.9 mEq/L. Which treatment should be administered FIRST?

Regular insulin + dextrose IV to drive potassium into cells
Calcium gluconate IV to stabilize cardiac membrane potential (Correct answer)
Furosemide IV to promote renal potassium excretion
Sodium bicarbonate IV to shift potassium intracellularly

Correct answer: Calcium gluconate IV to stabilize cardiac membrane potential

In life-threatening hyperkalemia with cardiac arrhythmias, calcium gluconate is the immediate priority. It does not lower serum potassium but rapidly stabilizes cardiomyocyte membrane potential, buying time to address the underlying cause. Insulin/dextrose and sodium bicarbonate do shift potassium intracellularly but take longer to act and do not protect the heart as immediately. Furosemide requires adequate renal function and acts too slowly in an acute crisis.

Question 5: A 7-year-old German Shepherd presents with progressive rear limb ataxia. Spinal MRI reveals a well-defined, intradural extramedullary lesion at T10-T11 that is isointense on T1, hyperintense on T2, and demonstrates marked homogeneous contrast enhancement. The adjacent cord shows a 'cap sign' (hemosiderin deposition). Which diagnosis is MOST consistent with these findings?

Arachnoid diverticulum
Meningioma (Correct answer)
Peripheral nerve sheath tumor
Nephroblastoma (spinal)

Correct answer: Meningioma

Meningiomas are the most common intradural extramedullary spinal tumors in dogs, typically appearing isointense on T1, hyperintense on T2, with intense homogeneous contrast enhancement. The 'cap sign'—hemosiderin staining at the poles of the mass—is a specific MRI feature strongly associated with spinal meningiomas due to chronic microhemorrhage. Nephroblastomas occur in young dogs and are typically intramedullary. Peripheral nerve sheath tumors tend to extend through neural foramina. Arachnoid diverticula do not enhance with contrast.

Question 6: A cat presents with a 'ground-glass' opacity on thoracic radiographs. Which condition is MOST associated with this finding?

Rib fracture
Pneumothorax
Pulmonary edema (Correct answer)
Pleural effusion

Correct answer: Pulmonary edema

Ground-glass opacity reflects partial alveolar filling, most commonly seen with pulmonary edema in cats.

Question 7: During anesthesia of a ball python for surgical removal of a retained spectacle, the veterinarian notes apnea persisting more than 10 minutes after isoflurane is discontinued. Which of the following BEST explains why reptiles are particularly susceptible to prolonged post-anesthetic apnea compared to mammals?

Reptiles have a higher metabolic rate and consume anesthetic agents more rapidly, leading to prolonged tissue saturation
Reptiles rely primarily on peripheral chemoreceptors sensitive to PO2 rather than central CO2/pH-driven ventilatory drive, making hypercapnia a poor respiratory stimulus (Correct answer)
Reptiles have a tripartite heart with significant right-to-left cardiac shunting that recirculates anesthetic vapor and delays washout
The reptilian lung has a more extensive blood-gas barrier that delays anesthetic elimination via pulmonary routes

Correct answer: Reptiles rely primarily on peripheral chemoreceptors sensitive to PO2 rather than central CO2/pH-driven ventilatory drive, making hypercapnia a poor respiratory stimulus

Reptiles have a blunted central chemoreceptor response to hypercapnia compared to mammals. Their ventilatory drive depends more on peripheral oxygen sensing, and they tolerate wide swings in PCO2 with minimal respiratory response. This means rising CO2 after anesthesia does not reliably stimulate breathing, causing prolonged apnea. The cardiac shunt (option D) contributes to anesthetic uptake/elimination differences but is not the primary reason for post-anesthetic apnea.

Question 8: Bovine trichomoniasis (caused by Tritrichomonas foetus) is a venereal disease affecting beef cattle. Which control strategy is most effective in eliminating trichomoniasis from an infected beef herd?

Vaccination of all cows with the T. foetus vaccine to prevent abortion
Systemic metronidazole treatment of all infected bulls
Culling infected bulls and resting infected cows for 90+ days to allow self-clearance (Correct answer)
Antibiotic treatment of all cattle and 30-day quarantine

Correct answer: Culling infected bulls and resting infected cows for 90+ days to allow self-clearance

Bulls are permanent carriers and cannot be treated; culling PCR-positive bulls and resting exposed cows (which self-clear in approximately 90 days of sexual rest) is the standard eradication approach.

Question 9: How would you handle FIP with ocular involvement?

Glycopyrrolate
Topical steroids and atropine (Correct answer)
Topical antibiotics (2'bacterial infections)
Topical pilocarpine

Correct answer: Topical steroids and atropine

Ocular involvement in FIP often manifests as uveitis, causing inflammation, pain, and vision impairment. Topical steroids (e.g., prednisolone acetate) are used to reduce inflammation, while topical atropine is used to relieve ciliary spasm, dilate the pupil, and prevent synechia formation. This combination effectively manages the pain and complications associated with FIP-related uveitis.

Question 10: A 12-year-old Warmblood dressage horse presents with a 6-month history of progressive hindlimb ataxia and symmetric weakness. Cervical radiographs show dynamic stenosis at C3-C4. Myelography confirms spinal cord compression only during neck flexion. The owners request surgical intervention. Which procedure is most appropriate?

Dorsal laminectomy at C3-C4
Subtotal corpectomy with polymethylmethacrylate stabilization
Foraminotomy to decompress nerve roots bilaterally
Ventral stabilization using a Bagby basket (cervical vertebral interbody fusion) (Correct answer)

Correct answer: Ventral stabilization using a Bagby basket (cervical vertebral interbody fusion)

Cervical vertebral interbody fusion using a Bagby basket (or modified basket/screw technique) is the surgical standard for dynamic cervical stenosis (Wobbler syndrome) in horses. It eliminates instability-driven compression by fusing the affected motion segment. Dorsal laminectomy is unsuitable because the compression in dynamic cases is typically ventral/lateral, and the equine cervical anatomy makes dorsal approach impractical for decompression.

Question 11: You are administering a constant rate infusion (CRI) of medetomidine to a 10 kg dog at 1 mcg/kg/hr for intraoperative analgesia. The surgeon notes the surgical field has excessive hemorrhage and requests a vasopressor. Which vasopressor is CONTRAINDICATED in this patient due to risk of life-threatening hypertension when combined with medetomidine?

Norepinephrine
Epinephrine (Correct answer)
Phenylephrine
Vasopressin

Correct answer: Epinephrine

Epinephrine combined with alpha-2 agonists like medetomidine or dexmedetomidine carries a significant risk of severe, potentially fatal hypertension. Alpha-2 agonists cause pronounced peripheral vasoconstriction (alpha-2B receptor mediated). Adding epinephrine's potent alpha-1 and alpha-2 agonist properties can cause an exaggerated hypertensive crisis. Vasopressin and norepinephrine carry lower risk in this context and are sometimes used cautiously, while phenylephrine's pure alpha-1 activity is more predictable, though still requires care.

Question 12: A 6-year-old neutered male Dalmatian presents with recurrent urolithiasis. Stones have previously been typed as urate uroliths. The owner reports the dog is fed a standard commercial diet. Which of the following explains why Dalmatians are predisposed to urate urolithiasis compared to other breeds, even when consuming the same dietary purine levels?

Dalmatians have a defect in the renal proximal tubular transporter URAT1 (encoded by SLC22A12) that impairs uric acid reabsorption, combined with reduced hepatic uricase activity (Correct answer)
Dalmatians lack hepatic uricase entirely due to an autosomal recessive mutation in the uricase gene, making them physiologically similar to humans
Dalmatians have a hepatic uricase enzyme that converts uric acid to allantoin at a slower rate than other breeds due to a missense mutation in the SLC2A9 gene
Dalmatians overexpress xanthine oxidase in the liver, producing excess uric acid from purine catabolism that overwhelms normal uricase activity

Correct answer: Dalmatians have a defect in the renal proximal tubular transporter URAT1 (encoded by SLC22A12) that impairs uric acid reabsorption, combined with reduced hepatic uricase activity

Dalmatians have a dual defect: (1) reduced hepatic uricase activity compared to other dogs (they do have uricase, unlike humans, but at lower functional levels), and (2) a defect in renal tubular uric acid reabsorption mediated by the SLC22A12/URAT1 transporter. This combination results in higher serum uric acid concentrations and markedly elevated urinary uric acid excretion. The SLC2A9 mutation seen in humans causes hypouricemia by increasing renal uric acid excretion, which is a different mechanism. Dalmatians are not uricase-null (option B describes humans), and xanthine oxidase overexpression (option D) is not the established mechanism.

Question 13: A 4-year-old African grey parrot presents with progressive ataxia, regurgitation, and marked crop dilation. Radiographs reveal a markedly dilated proventriculus. PCR testing confirms Avian Bornavirus (ABV). Which of the following statements about the pathophysiology of Proventricular Dilatation Disease (PDD) is most accurate?

ABV directly destroys smooth muscle cells of the proventriculus, leading to dilation
ABV triggers a T-cell mediated lymphoplasmacytic ganglioneuritis targeting the autonomic ganglia of the GI tract (Correct answer)
ABV replicates exclusively in the crop epithelium, causing retrograde neurodegeneration
ABV induces an IgE-mediated hypersensitivity reaction in the enteric nervous system

Correct answer: ABV triggers a T-cell mediated lymphoplasmacytic ganglioneuritis targeting the autonomic ganglia of the GI tract

PDD results from Avian Bornavirus causing lymphoplasmacytic ganglioneuritis — a T-cell mediated inflammatory infiltrate that destroys the autonomic ganglia innervating the gastrointestinal tract. The loss of ganglionic innervation results in failure of peristalsis and progressive dilation of the proventriculus and ventriculus, not direct myocyte destruction. ABV does not cause IgE-mediated hypersensitivity, and replication is not limited to crop epithelium.

Question 14: On a ventrodorsal thoracic radiograph, the cardiac silhouette of a healthy dog should not exceed what percentage of the thoracic width at the level of the 8th rib?

60% (Correct answer)
70%
75%
50%

Correct answer: 60%

The cardiac silhouette on a VD projection normally occupies no more than 60% of the thoracic width at the level of the 8th intercostal space.

Question 15: A producer is implementing a control program for Bovine Viral Diarrhea Virus (BVDV). What is the most critical step to eliminate the primary reservoir of the virus within the herd?

Vaccinating all adult cows annually with a modified-live virus (MLV) vaccine.
Culling all animals that test positive on a BVDV antibody ELISA.
Implementing strict fly control measures during summer months.
Identifying and removing all persistently infected (PI) animals. (Correct answer)

Correct answer: Identifying and removing all persistently infected (PI) animals.

Persistently infected (PI) animals are the primary reservoir for BVDV, as they continuously shed large amounts of the virus throughout their lives. Identifying and removing these animals is the cornerstone of any successful BVDV eradication program. While vaccination is an important tool for herd immunity, it cannot eliminate the virus if PI animals remain. Culling based on antibody status would remove previously exposed and immune animals, not just the PI shedders. Fly control is not a primary method of BVDV transmission.

Question 16: A rabbit presents with acute respiratory distress, cyanosis, and sudden death of several cage-mates over 24 hours. Necropsy reveals multifocal hepatic necrosis and pulmonary hemorrhage. The most likely etiologic agent is:

Encephalitozoon cuniculi
Myxoma virus
Pasteurella multocida
Rabbit hemorrhagic disease virus (RHDV) (Correct answer)

Correct answer: Rabbit hemorrhagic disease virus (RHDV)

Rabbit hemorrhagic disease virus causes peracute mortality with hepatic necrosis, disseminated intravascular coagulation, and pulmonary hemorrhage, often affecting multiple animals rapidly.

Question 17: A 2-year-old bearded dragon (Pogona vitticeps) is presented with open-mouth breathing, neck extension, and mucus accumulation in the glottis. Radiographs show increased pulmonary opacity in the caudal lung fields. A tracheal wash reveals Gram-negative rods, and the owner reports the animal is maintained at 85°F ambient temperature with a basking spot of 95°F. Which factor is MOST directly contributing to immunosuppression in this patient?

Inadequate photoperiod causing melatonin-mediated thymic involution
High-protein diet causing hepatic stress and reduced acute-phase protein synthesis
Excessive humidity above 40% promoting bacterial overgrowth in the respiratory tract
Suboptimal thermal environment reducing enzymatic activity of immune effector cells (Correct answer)

Correct answer: Suboptimal thermal environment reducing enzymatic activity of immune effector cells

Reptiles are ectotherms whose immune function is temperature-dependent. Bearded dragons require a thermal gradient of 80–85°F ambient with a basking spot of 100–110°F. A basking spot of only 95°F is suboptimal. Immune cell enzymatic activity, phagocyte function, lymphocyte proliferation, and complement activity all depend on achieving the Preferred Optimal Temperature Zone (POTZ). An inadequate thermal gradient directly impairs the immune response, allowing opportunistic Gram-negative bacteria (commonly Aeromonas, Pseudomonas, or Enterobacteriaceae) to cause respiratory infection. Correcting husbandry is as therapeutically important as antibiotic therapy.

Question 18: A 7-year-old intact male Golden Retriever presents with progressive exercise intolerance, muffled heart sounds, and jugular venous distension. Echocardiography reveals a large pericardial effusion. Cytology of the pericardial fluid shows hemorrhagic fluid with no neoplastic cells identified. Which of the following is the MOST likely underlying etiology?

Hemangiosarcoma of the right atrium (Correct answer)
Chemodectoma of the heart base
Idiopathic pericardial effusion
Mesothelioma

Correct answer: Hemangiosarcoma of the right atrium

In large-breed dogs, particularly Golden Retrievers and German Shepherds, hemorrhagic pericardial effusion is most commonly caused by hemangiosarcoma of the right atrium/auricle. Despite the hemorrhagic nature, cytology is frequently non-diagnostic because neoplastic cells exfoliate poorly into effusions and are difficult to distinguish from reactive mesothelial cells. Idiopathic pericarditis is the second most common cause but is a diagnosis of exclusion. Mesothelioma and chemodectoma occur but are less frequent than hemangiosarcoma in this breed and presentation.

Question 19: A green iguana is presented with metabolic bone disease. Which nutritional deficiency is most commonly responsible?

Vitamin E deficiency
Phosphorus deficiency
Calcium deficiency and/or inadequate UV-B exposure (Correct answer)
Vitamin A deficiency

Correct answer: Calcium deficiency and/or inadequate UV-B exposure

Metabolic bone disease in iguanas is primarily caused by calcium deficiency, improper Ca:P ratio, and lack of UV-B light needed for vitamin D3 synthesis.

Question 20: A 7-year-old DSH cat presents with acute dyspnea. Thoracic radiographs show a 'mediastinal mass' with a rounded soft-tissue opacity in the cranial mediastinum. Ultrasound reveals an anechoic, thin-walled structure with no internal vascularity on Doppler. Which diagnosis is MOST consistent with these findings?

Ectopic thyroid adenoma
Mediastinal cyst (branchial or thymic) (Correct answer)
Cranial mediastinal lymphoma
Chemodectoma

Correct answer: Mediastinal cyst (branchial or thymic)

Mediastinal cysts (branchial cleft or thymic remnant cysts) appear as well-defined anechoic structures with thin walls and no internal blood flow on color Doppler. Lymphoma, the most common cranial mediastinal mass in cats, typically shows heterogeneous echogenicity and detectable vascularity. Ectopic thyroid tissue and chemodectomas are vascularized solid masses. The purely anechoic, avascular ultrasound appearance is the key distinguishing feature of a benign cyst.

Question 21: Which MRI sequence best demonstrates hemorrhage of varying ages due to its sensitivity to paramagnetic effects of blood breakdown products?

T1-weighted with contrast
T2-weighted FLAIR
Gradient echo (GRE/T2*) (Correct answer)
Diffusion-weighted imaging (DWI)

Correct answer: Gradient echo (GRE/T2*)

Gradient echo sequences are highly sensitive to susceptibility effects caused by hemosiderin and deoxyhemoglobin, making them ideal for detecting hemorrhage.

Question 22: Which of the following is considered the most effective method for long-term monitoring of glycemic control in a diabetic dog, reflecting average blood glucose over the preceding 2-3 months?

Fructosamine concentration
Serial blood glucose curve
Urine glucose strips
Glycosylated hemoglobin (HbA1c) concentration (Correct answer)

Correct answer: Glycosylated hemoglobin (HbA1c) concentration

Glycosylated hemoglobin (HbA1c) is formed by the irreversible binding of glucose to hemoglobin within red blood cells. Its concentration reflects the average blood glucose level over the lifespan of the erythrocyte (approximately 2-3 months in dogs), making it an excellent tool for assessing long-term glycemic control and less susceptible to short-term fluctuations from stress or diet. Fructosamine reflects control over the preceding 2-3 weeks. Glucose curves and urine strips only provide a snapshot of glucose levels at a specific point in time.

Question 23: A 7-year-old intact male Boxer with a known history of dilated cardiomyopathy requires anesthesia for a splenic mass removal. Which induction protocol is MOST appropriate to minimize myocardial depression while providing adequate anesthesia depth?

Ketamine 5 mg/kg IV with diazepam 0.5 mg/kg IV combination
Propofol 4 mg/kg IV bolus followed by isoflurane maintenance
Alfaxalone 2 mg/kg IV bolus followed by sevoflurane maintenance
Etomidate 1–2 mg/kg IV with midazolam 0.2 mg/kg IV premedication (Correct answer)

Correct answer: Etomidate 1–2 mg/kg IV with midazolam 0.2 mg/kg IV premedication

Etomidate is the induction agent of choice in critically ill or cardiovascularly compromised patients because it produces minimal myocardial depression and maintains cardiac output and vascular tone better than propofol or alfaxalone. Midazolam co-induction reduces the etomidate dose needed and provides muscle relaxation without significant cardiovascular effects. Propofol and alfaxalone both cause dose-dependent vasodilation and myocardial depression. Ketamine, while a sympathomimetic, is contraindicated in patients with pre-existing tachyarrhythmias (common in Boxers with DCM) as it can exacerbate ventricular dysrhythmias.

Question 24: A 9-year-old cat with a 6-month history of recurrent upper respiratory signs, bilateral corneal sequestra, and chronic gingivostomatitis has positive FHV-1 PCR on conjunctival swab. The owner asks about antiviral therapy. Which statement regarding famciclovir use in cats is MOST accurate?

Famciclovir requires concurrent l-lysine supplementation to competitively inhibit viral DNA polymerase activity synergistically
Famciclovir should be avoided in cats because feline cytochrome P450 enzymes convert it to a nephrotoxic methylated metabolite
Acyclovir is preferred over famciclovir in cats because famciclovir has poor oral bioavailability due to incomplete first-pass intestinal conversion
Famciclovir is effective because cats efficiently convert it to penciclovir via intestinal and hepatic ester hydrolases, achieving therapeutic penciclovir concentrations (Correct answer)

Correct answer: Famciclovir is effective because cats efficiently convert it to penciclovir via intestinal and hepatic ester hydrolases, achieving therapeutic penciclovir concentrations

Famciclovir is the antiviral of choice for FHV-1 in cats precisely because cats CAN efficiently metabolize famciclovir (the prodrug) to penciclovir (the active compound) via intestinal ester hydrolases and hepatic aldehyde oxidase — unlike dogs, which do so poorly. This is the opposite of the situation with acyclovir: acyclovir has low bioavailability in cats and is potentially nephrotoxic at higher doses due to renal tubular precipitation. Famciclovir at 40–90 mg/kg PO q8–12h achieves therapeutic penciclovir levels. l-Lysine does NOT work synergistically with famciclovir — its proposed mechanism (arginine competition) is now considered clinically ineffective by current evidence.

Question 25: A 4-year-old Quarter Horse undergoes emergency surgery for a right dorsal colon displacement (right dorsal displacement of the large colon). Intraoperatively, the pelvic flexure is exteriorized and the colon is repositioned. Postoperatively on day 3, the horse develops profuse watery diarrhea, hypoproteinemia, and peripheral edema. Repeat gastric reflux yields 8 liters. Which complication best explains this clinical picture?

Enterocolitis caused by Salmonella spp. secondary to colonic ischemia-reperfusion injury
Right dorsal colitis secondary to perioperative NSAID toxicity (Correct answer)
Recurrence of the large colon displacement with secondary ileus
Proximal enteritis (duodenitis-proximal jejunitis) with concurrent colonic dysfunction

Correct answer: Right dorsal colitis secondary to perioperative NSAID toxicity

Right dorsal colitis (RDC) is a well-recognized sequela of excessive NSAID administration (particularly phenylbutazone) in the perioperative period. It causes focal ulceration and inflammation of the right dorsal colon, leading to protein-losing enteropathy (hypoproteinemia, edema) and diarrhea. The concurrent large-volume gastric reflux results from ileus secondary to the colonic inflammation. While Salmonella is possible, the clinical context of recent intensive NSAID therapy for colic surgery makes RDC the most likely diagnosis.

Question 26: The multimodal approach to perioperative pain management is preferred because it primarily achieves which goal?

Reduces overall side effects while maintaining or improving analgesia through synergistic mechanisms (Correct answer)
Allows higher doses of each individual analgesic to be used safely
Eliminates the requirement for preoperative fasting in elective surgeries
Avoids the need to use federally controlled substances in the practice

Correct answer: Reduces overall side effects while maintaining or improving analgesia through synergistic mechanisms

Multimodal analgesia combines drugs from different classes (opioids, NSAIDs, local anesthetics, alpha-2 agonists, NMDA antagonists) that act at different pain pathway targets, allowing lower doses of each agent while achieving superior pain control and reducing class-specific adverse effects.

Question 27: A 6-year-old male neutered Domestic Shorthair cat is evaluated for a 6-month history of weight loss despite polyphagia, intermittent vomiting, and hyperactivity. T4 is 7.8 µg/dL (reference: 0.8–4.0). You initiate methimazole therapy. Four weeks later, the owner reports the cat is less active and has developed facial pruritus and excoriations. Repeat T4 is now 1.2 µg/dL. Creatinine has risen from 1.2 to 3.8 mg/dL. Which pathophysiological explanation BEST accounts for the creatinine increase?

Dehydration secondary to decreased water intake now that polydipsia has resolved
Methimazole-induced immune-mediated glomerulonephritis
Unmasking of pre-existing chronic kidney disease as hyperthyroidism-driven hyperfiltration is corrected (Correct answer)
Reduced muscle mass from prolonged hyperthyroid catabolism causing decreased creatinine production masking true GFR

Correct answer: Unmasking of pre-existing chronic kidney disease as hyperthyroidism-driven hyperfiltration is corrected

Hyperthyroidism increases cardiac output and renal blood flow, creating a state of hyperfiltration that artificially elevates GFR and masks underlying chronic kidney disease (CKD). When hyperthyroidism is treated and T4 normalizes, renal perfusion returns to baseline, revealing the true (and reduced) GFR. This is a well-recognized clinical phenomenon in cats—treating hyperthyroidism can unmask occult CKD, and creatinine rising post-treatment reflects true underlying renal insufficiency, not treatment-induced nephrotoxicity. Methimazole can rarely cause immune-mediated glomerulonephritis, but the facial excoriations here represent a common idiosyncratic skin reaction to methimazole, not nephritis. The timing and magnitude of creatinine rise best fits unmasking rather than dehydration or muscle wasting.

Question 28: A 4-year-old female Labrador Retriever undergoes gastropexy during a routine splenectomy following splenic torsion. Three days post-operatively she develops melena, hematemesis, and a PCV drop from 38% to 22%. Endoscopy reveals multiple deep gastric ulcers along the greater curvature. Which mechanism BEST explains this complication?

Ischemia-reperfusion injury to the gastric mucosa from prior gastric hypoperfusion (Correct answer)
Portal hypertension secondary to splenic vein ligation causing gastric venous congestion
NSAID toxicity from intraoperative ketorolac administration
Stress ulceration from high-dose perioperative corticosteroids

Correct answer: Ischemia-reperfusion injury to the gastric mucosa from prior gastric hypoperfusion

Splenic torsion is commonly associated with concurrent gastric dilatation-volvulus (GDV) or significant gastric hypoperfusion. Ischemia-reperfusion injury to the gastric mucosa — occurring when blood flow is restored after a period of ischemia — generates reactive oxygen species that disrupt mucosal barrier integrity, leading to ulceration. The greater curvature is particularly vulnerable due to its vascular territory. While portal hypertension and NSAIDs can cause ulcers, ischemia-reperfusion injury is the most physiologically consistent explanation given the surgical context and ulcer distribution.

Question 29: A dog is presented with acute onset of non-ambulatory tetraparesis following a traumatic event. Spinal radiographs reveal atlantoaxial subluxation. What is the definitive treatment of choice?

Surgical stabilization of the atlantoaxial joint (Correct answer)
Corticosteroid therapy
Strict cage rest alone
Cervical splinting with a neck brace

Correct answer: Surgical stabilization of the atlantoaxial joint

Surgical stabilization via ventral fixation or dorsal wiring provides definitive correction of atlantoaxial subluxation, which otherwise risks life-threatening spinal cord compression.

Question 30: A 6-year-old castrated male DSH is prescribed oral diazepam (1 mg PO BID) for urine marking behavior. On day 4, the owner reports acute lethargy, jaundice, and anorexia. ALT is 1,840 U/L and total bilirubin is 8.2 mg/dL. What is the most accurate characterization of this adverse reaction?

Cholestatic hepatopathy caused by benzodiazepine-induced bile duct compression in cats with subclinical biliary disease
Predictable accumulation of diazepam's active metabolite desmethyldiazepam due to impaired feline glucuronidation
Type B hypersensitivity reaction triggered by benzodiazepine ring oxidation products in genetically susceptible cats
Idiosyncratic acute hepatic necrosis unique to cats receiving oral benzodiazepines, unrelated to dose or duration (Correct answer)

Correct answer: Idiosyncratic acute hepatic necrosis unique to cats receiving oral benzodiazepines, unrelated to dose or duration

Oral diazepam causes idiosyncratic acute hepatic necrosis in cats — a reaction that is unpredictable, not dose-dependent, and appears to be specific to the oral route. Affected cats can deteriorate rapidly within 2–5 days of initiating therapy. The mechanism is not fully elucidated but is not simply pharmacokinetic accumulation. IV diazepam carries much lower risk. This is why oral diazepam is generally contraindicated in cats, with alternatives such as gabapentin or environmental modification preferred for behavioral indications.

Question 31: A 7-year-old Labrador Retriever presents with progressive hindlimb paresis. MRI of the thoracolumbar spine reveals a T2-hyperintense, T1-isointense intradural-extramedullary mass at T10-T11 that shows homogeneous contrast enhancement. The most likely diagnosis is:

Meningioma (Correct answer)
Nephroblastoma
Nerve sheath tumor
Intramedullary astrocytoma

Correct answer: Meningioma

Meningiomas are the most common intradural-extramedullary spinal tumors in dogs. Their MRI characteristics include T2 hyperintensity, T1 isointensity relative to spinal cord, homogeneous contrast enhancement, and a 'dural tail' sign. They are extramedullary (outside the cord but inside the dura), distinguishing them from intramedullary tumors like astrocytomas. Nerve sheath tumors are also intradural-extramedullary but more commonly affect nerve roots and show heterogeneous enhancement. Nephroblastoma occurs in the spinal cord of young dogs but is intramedullary.

Question 32: A 3-year-old Thoroughbred filly in training develops acute hindlimb lameness after a workout. A 'popping' sound was heard at the moment of injury, and there is marked stifle effusion. The MOST likely diagnosis is:

Upward fixation of the patella
Patellar fracture or cranial cruciate ligament injury (Correct answer)
Femoral nerve paralysis
Hip luxation

Correct answer: Patellar fracture or cranial cruciate ligament injury

Acute onset of severe stifle lameness with an audible pop and joint effusion in a performance horse is most consistent with patellar fracture or stifle ligament injury.

Question 33: A 5-year-old Thoroughbred racehorse undergoes nuclear scintigraphy for investigation of right forelimb lameness that has not localized with nerve blocks. The bone scan shows markedly increased radiopharmaceutical uptake (IRU) in the mid-diaphysis of the right third metacarpal bone on the lateral cortex. What is the most appropriate next diagnostic step to characterize this lesion before formulating a treatment plan?

Ultrasonography of the lateral aspect of the cannon bone to evaluate the periosteum
MRI of the distal forelimb in the standing horse to rule out concurrent navicular disease
CT of the right forelimb to characterize cortical integrity and quantify stress fracture propagation (Correct answer)
Repeat nuclear scintigraphy in 4 weeks to assess progression of uptake

Correct answer: CT of the right forelimb to characterize cortical integrity and quantify stress fracture propagation

Focal high IRU in the diaphyseal cortex of the third metacarpus in a racehorse is highly suspicious for a stress fracture, which carries risk of complete catastrophic fracture if the horse is exercised. CT provides detailed cross-sectional characterization of cortical integrity, fracture line orientation, and propagation depth — information critical to differentiating a stable incomplete cortical stress fracture from one approaching propagation, which directly determines surgical vs. conservative management. Repeat scintigraphy delays diagnosis without adding anatomical detail. Ultrasonography evaluates periosteal soft tissue but cannot adequately assess cortical fracture geometry. Standing MRI of the distal limb does not image the mid-diaphysis.

Question 34: Which drug is the specific reversal agent for alpha-2 adrenergic agonist sedation (e.g., medetomidine, dexmedetomidine) in veterinary patients?

Naloxone
Neostigmine
Atipamezole (Correct answer)
Flumazenil

Correct answer: Atipamezole

Atipamezole is a selective alpha-2 adrenergic antagonist that rapidly reverses the sedation, analgesia, and cardiovascular effects of alpha-2 agonists such as medetomidine and dexmedetomidine.

Question 35: On abdominal ultrasound of a cat with stranguria, a hyperechoic structure is identified in the center of the urinary bladder. The structure produces a clean, dark vertical band beneath it that obscures deeper tissues. Which of the following best describes this artifact and the most likely identity of the structure?

Reverberation artifact from a gas bubble
Side lobe artifact from a polyp
Acoustic shadowing from a urolith (Correct answer)
Acoustic enhancement from a cyst

Correct answer: Acoustic shadowing from a urolith

A urolith (bladder stone) is a mineralized, dense structure that is hyperechoic (bright) on ultrasound. It strongly reflects or attenuates the ultrasound beam, preventing it from passing through to the tissues below. This creates a signal void, or 'acoustic shadow,' which appears as a dark band deep to the stone. A gas bubble would also shadow but typically creates a 'dirty' shadow with reverberation. A blood clot is typically hyperechoic but not dense enough to cause shadowing. A polyp is a soft tissue structure and would not cause shadowing.

Question 36: A 10-year-old mixed-breed dog presents with weight gain, alopecia, hyperpigmentation, and a pot-bellied appearance. Urine cortisol:creatinine ratio is elevated. LDDS test shows no suppression. HDDS test shows >50% suppression. What is the most likely diagnosis?

Hypoadrenocorticism
Pituitary-dependent hyperadrenocorticism (Correct answer)
Adrenal-dependent hyperadrenocorticism
Iatrogenic hyperadrenocorticism

Correct answer: Pituitary-dependent hyperadrenocorticism

Suppression on the high-dose dexamethasone suppression test (>50%) indicates the excess ACTH source is pituitary-dependent (PDH).

Question 37: A German Shepherd presents with chronic intermittent diarrhea, weight loss, and a serum cobalamin level of 85 ng/L (reference: 251-908). Serum folate is markedly elevated. What is the most likely diagnosis?

Inflammatory bowel disease
Protein-losing enteropathy
Exocrine pancreatic insufficiency
Small intestinal bacterial overgrowth (Correct answer)

Correct answer: Small intestinal bacterial overgrowth

Small intestinal bacterial overgrowth causes bacteria to consume cobalamin (lowering serum levels) while producing excess folate, resulting in low cobalamin and high folate.

Question 38: Intra-articular injection of which substance is used as a visco-supplementation therapy to improve synovial fluid quality in horses with joint disease?

Hyaluronic acid (sodium hyaluronate) (Correct answer)
Platelet-rich plasma (PRP)
Polysulfated glycosaminoglycan (Adequan)
Methylprednisolone acetate

Correct answer: Hyaluronic acid (sodium hyaluronate)

Sodium hyaluronate (hyaluronic acid) is injected intra-articularly to restore viscosity and lubrication of synovial fluid, acting as visco-supplementation in arthritic joints.

Question 39: During fluoroscopic esophagram in a 2-year-old German Shepherd, liquid barium rapidly opacifies the esophagus but you observe persistent, focal retention of barium in a fusiform dilation of the esophagus at the level of the heart base. The esophagus proximal and distal to this region is normal in caliber. Manometric data (if available) would MOST likely show which of the following?

Normal esophageal peristalsis with elevated resting lower esophageal sphincter pressure
Reduced amplitude contractions in the caudal esophageal segment only
Absent peristalsis throughout the entire esophagus
Failure of lower esophageal sphincter relaxation (achalasia-like) (Correct answer)

Correct answer: Failure of lower esophageal sphincter relaxation (achalasia-like)

Focal, persistent barium retention in a fusiform dilation at the heart base, with normal esophageal caliber proximal and distal, is the classic fluoroscopic appearance of a vascular ring anomaly—specifically persistent right aortic arch (PRAA) with entrapment of the esophagus. However, in an adult dog with acquired focal heart-base dilation, the most likely diagnosis is a functional obstruction analogous to achalasia (failure of the lower esophageal sphincter or distal esophageal segment to relax). This would produce failure of LES relaxation on manometry. True idiopathic megaesophagus shows absent peristalsis throughout the entire esophagus (choice B), not focal dilation. Choices C and D do not correspond to a mechanism that produces focal fusiform retention.

Question 40: A 5-year-old Siberian Husky is presented with zinc toxicosis after ingesting pennies minted after 1982. Which hematologic finding best explains the hemolysis observed?

Heinz body formation from oxidative RBC damage (Correct answer)
Microangiopathic RBC destruction from vasculitis
Direct autoantibody binding to RBC membranes
Aplastic anemia from bone marrow suppression

Correct answer: Heinz body formation from oxidative RBC damage

Zinc causes oxidative damage to RBC membranes and hemoglobin, leading to Heinz body formation and intravascular hemolytic anemia.

Question 41: A 12-year-old Warmblood sport horse presents with a 6-month history of intermittent right forelimb lameness that worsens after collected work. Radiographs reveal subchondral cystic lesions in the medial femoral condyle. Intra-articular anesthesia of the femoropatellar joint abolishes 70% of the lameness, but the stifle shows no significant synovial effusion. Which surgical treatment has demonstrated the best long-term outcomes for large (>15 mm diameter) subchondral cystic lesions of the medial femoral condyle in sport horses?

Intra-cyst injection of triamcinolone acetonide via arthroscopic or fluoroscopic guidance (Correct answer)
Arthroscopic debridement and curettage of the cyst lining with corticosteroid injection
Extracorporeal shock wave therapy to the medial femoral condyle under standing sedation
Transcondylar screw implantation across the cyst to induce compression and fibrocartilage fill

Correct answer: Intra-cyst injection of triamcinolone acetonide via arthroscopic or fluoroscopic guidance

Intra-cyst injection of triamcinolone acetonide (via arthroscopic visualization or fluoroscopic guidance) has emerged as the superior treatment for large subchondral cystic lesions of the medial femoral condyle, yielding return-to-athletic-function rates of 65–80% in sport horses. The mechanism involves suppression of the inflammatory signaling within the cyst wall, reducing osteoclastic resorption. Transcondylar screws carry significant implant-related complications and inconsistent outcomes. Simple arthroscopic debridement alone produces inferior results for large lesions (>15 mm). ESWT has limited evidence for cystic lesions specifically. Peripheral (intra-articular) corticosteroid without direct cyst access is less effective.

Question 42: A 10-year-old Andalusian stallion used for breeding has a 6-month history of insidious right hindlimb lameness. Rectal palpation reveals firm enlargement of the right sacroiliac region. Intra-articular sacroiliac injection under ultrasound guidance produces 70% improvement. Bone scan shows focal increased radiopharmaceutical uptake at the right sacral wing. Which additional finding on standing MRI of the pelvis would MOST specifically confirm active sacroiliac joint disease versus sacral stress fracture as the primary lesion?

Disruption of the interosseous sacroiliac ligament with periarticular edema on T2-STIR (Correct answer)
T2-hyperintense signal within the sacral wing cancellous bone
Asymmetric gluteal muscle atrophy visible on T2-weighted sequences
Cortical irregularity of the dorsal sacral foramina on T1 sequences

Correct answer: Disruption of the interosseous sacroiliac ligament with periarticular edema on T2-STIR

Disruption or thickening of the interosseous sacroiliac ligament with periarticular soft tissue edema on T2-STIR sequences is specifically diagnostic of sacroiliac joint disease (sacroiliitis or desmopathy), distinguishing it from a primary sacral stress fracture. T2-hyperintense signal in cancellous bone is consistent with bone marrow edema from either a stress fracture or joint disease. Cortical irregularity of sacral foramina and gluteal atrophy are indirect, nonspecific findings. The interosseous ligament finding directly localizes pathology to the joint interface, correlating with the analgesia response and scintigraphic uptake pattern.

Question 43: You perform a palmar digital nerve block (PDN block) in a horse with a 3/5 lameness. Lameness improves by only 30%. You then perform an abaxial sesamoid nerve block, and lameness improves by 70% from the original score. What is the most accurate interpretation of these sequential block results?

Pain is localized to the palmar pastern and digital flexor tendon sheath below the fetlock
The pain source lies entirely within the pastern region innervated by the abaxial block but not the PDN
The PDN block failed due to poor technique; the abaxial block localized pain to the hoof capsule
There is a pain source in the heel/caudal foot region AND a second source more proximal in the pastern or fetlock region (Correct answer)

Correct answer: There is a pain source in the heel/caudal foot region AND a second source more proximal in the pastern or fetlock region

Sequential distal-to-proximal nerve blocks are additive. A 30% improvement with PDN (desensitizes caudal foot/heel) plus an additional 40% improvement with abaxial sesamoid block (adds the pastern/fetlock region) indicates two pain contributors: one in the heel/caudal foot and a second source in the region additionally desensitized by the abaxial block (pastern, proximal interphalangeal joint, palmar fetlock). Neither block alone accounted for the full lameness.

Question 44: A radiograph of a cat's elbow shows periarticular soft tissue swelling and subchondral bone lysis without significant new bone production. This pattern is most consistent with:

Osteochondrosis dissecans
Hypertrophic osteodystrophy
Septic arthritis (Correct answer)
Degenerative joint disease

Correct answer: Septic arthritis

Septic arthritis characteristically causes joint space narrowing, subchondral bone lysis, and periarticular soft tissue swelling with minimal productive bone response.

Question 45: When performing a high plantar nerve block (high 2-point block) in the horse, the targeted nerves are located:

At the level of the proximal sesamoid bones
Midway up the cannon bone, abaxial to the suspensory ligament (Correct answer)
Just proximal to the fetlock, medial and lateral to the flexor tendons
At the level of the tarsus, caudal to the saphenous vein

Correct answer: Midway up the cannon bone, abaxial to the suspensory ligament

The high plantar (high 2-point) block is performed midway up the cannon bone, anesthetizing the medial and lateral plantar nerves abaxial to the suspensory ligament.

Question 46: A 2-year-old Miniature Schnauzer is presented to the emergency clinic with acute onset of vomiting and profuse hemorrhagic diarrhea, described as 'raspberry jam' in appearance. The dog is tachycardic, has weak pulses, and a PCV of 62% with normal total solids. What is the most critical initial treatment for this patient?

Subcutaneous fluids and anti-emetics
Aggressive intravenous fluid therapy (Correct answer)
Oral metronidazole
Immediate blood transfusion

Correct answer: Aggressive intravenous fluid therapy

This presentation is classic for Acute Hemorrhagic Diarrhea Syndrome (AHDS), formerly known as hemorrhagic gastroenteritis (HGE). The hallmark is a markedly elevated PCV due to profound hemoconcentration from fluid loss into the gut. The most critical, life-saving initial treatment is aggressive intravenous fluid therapy to correct hypovolemic shock and dehydration. Subcutaneous fluids are inadequate for this degree of fluid loss.

Question 47: Guinea pigs are unable to synthesize vitamin C endogenously. What is the recommended daily dietary requirement?

50–100 mg/kg/day
100–200 mg/kg/day
1–5 mg/kg/day
10–30 mg/kg/day (Correct answer)

Correct answer: 10–30 mg/kg/day

Guinea pigs lack the enzyme L-gulonolactone oxidase for vitamin C biosynthesis and require 10–30 mg/kg/day through dietary sources to prevent scurvy.

Question 48: Which of the following imaging modalities is considered the gold standard for achieving a definitive diagnosis of a deep digital flexor tendon lesion within the equine hoof capsule?

Nuclear Scintigraphy
Radiography
Diagnostic Ultrasonography
Magnetic Resonance Imaging (MRI) (Correct answer)

Correct answer: Magnetic Resonance Imaging (MRI)

Magnetic Resonance Imaging (MRI) is the gold standard for imaging soft tissues within the hoof capsule because it provides superior detail and is not impeded by the hoof wall. Radiography is best for bone, diagnostic ultrasound cannot effectively penetrate the hoof capsule to visualize all relevant structures, and nuclear scintigraphy identifies areas of increased bone metabolism ('hot spots') but lacks specific soft tissue detail.

Question 49: A One Health investigation links a series of human Cryptosporidium parvum cases to a municipal watershed used for drinking water. Environmental sampling finds oocysts at 2.7 oocysts/10L in the raw water intake. The watershed is shared by a confined dairy operation upstream. Which characteristic of C. parvum oocysts most limits the effectiveness of standard municipal water chlorination as the sole treatment barrier?

C. parvum rapidly develops chlorine resistance through plasmid-mediated mechanisms after repeated exposure
Oocysts are larger than 1 µm and clog conventional slow-sand filters
The oocyst wall confers extraordinary chlorine resistance, requiring CT values far exceeding those achievable with standard disinfection doses (Correct answer)
Oocysts are effectively killed by chlorine only at pH < 5, which is incompatible with drinking water standards

Correct answer: The oocyst wall confers extraordinary chlorine resistance, requiring CT values far exceeding those achievable with standard disinfection doses

Cryptosporidium oocysts are highly resistant to chlorine disinfection due to their thick, proteinaceous oocyst wall. Achieving a 3-log (99.9%) reduction requires CT (concentration × time) values of >7,200 mg·min/L at 25°C — far beyond what is operationally feasible in municipal systems (typical CT for Giardia is ~55 mg·min/L). This is why the EPA Surface Water Treatment Rule requires filtration (which physically removes oocysts) rather than relying on chlorination alone. C. parvum does not acquire chlorine resistance through plasmid-mediated mechanisms (it is a protozoan, not a bacterium), and the pH sensitivity described is incorrect — UV irradiation and filtration are the validated control strategies.

Question 50: Among the currently used inhalant anesthetics, which has the LOWEST blood:gas partition coefficient, resulting in the fastest induction and recovery?

Isoflurane
Desflurane (Correct answer)
Halothane
Sevoflurane

Correct answer: Desflurane

Desflurane has the lowest blood:gas partition coefficient (~0.42), meaning it equilibrates rapidly between blood and alveoli, producing the fastest induction and recovery of the available inhalants.

Question 51: A 3-year-old intact female Cocker Spaniel is presented with a fever, mucopurulent vaginal discharge, PU/PD, and leukocytosis. Abdominal ultrasound confirms uterine distension. What is the definitive treatment?

Prostaglandin F2α therapy alone
Broad-spectrum antibiotics for 4 weeks
Progesterone receptor antagonist therapy
Ovariohysterectomy (Correct answer)

Correct answer: Ovariohysterectomy

Ovariohysterectomy is the definitive and safest treatment for pyometra, removing the source of infection and preventing recurrence.

Question 52: A cat rescue organization routinely tests all cats for FeLV and FIV using a point-of-care ELISA combo test. A 2-year-old cat tests FIV antibody-positive. The organization plans to euthanize the cat per their protocol. The attending veterinarian recommends Western blot confirmatory testing. Which scenario would produce the MOST clinically significant false-positive FIV ELISA result and thus most strongly justify confirmatory testing?

The cat received a blood transfusion from an FIV-positive donor 2 weeks ago
The cat has concurrent FeLV viremia causing cross-reactive antibody production
The cat is a kitten under 6 months with maternally derived antibodies from an FIV-positive queen
The cat received an FIV vaccination (Fel-O-Vax FIV) within the past 4 years (Correct answer)

Correct answer: The cat received an FIV vaccination (Fel-O-Vax FIV) within the past 4 years

Vaccination with the killed whole-virus FIV vaccine (Fel-O-Vax FIV, no longer commercially available but cats vaccinated years ago may still be seropositive) induces antibodies that are indistinguishable from natural infection antibodies on standard ELISA and IFA tests — this is the most clinically important cause of false-positive FIV serology in adult cats. Western blot can help differentiate in some cases, but even WB may be positive post-vaccination. PCR is the most reliable confirmatory test in vaccinated cats. FeLV does not cause cross-reactive FIV antibodies. Blood transfusion-transferred antibodies would wane by 2 weeks and are not a major confounder. Maternal antibody interference is significant in kittens under 6 months but the question asks for the most significant false-positive in the described adult context.

Question 53: A 5-year-old event horse has hindlimb lameness localized to the sacroiliac region by positive pressure on the tuber sacrale and a positive response to gluteal muscle palpation. The BEST imaging modality for confirming sacroiliac pathology is:

CT scan of the hindlimb
Radiography of the pelvis
Nuclear scintigraphy or ultrasound of the sacroiliac joint (Correct answer)
Radiography of the lumbar spine only

Correct answer: Nuclear scintigraphy or ultrasound of the sacroiliac joint

The sacroiliac joint is difficult to image radiographically due to its deep location; nuclear scintigraphy and transrectal or transcutaneous ultrasound are the most effective modalities for evaluating this region.

Question 54: A 10-year-old Quarter Horse mare has medial meniscal damage confirmed on MRI. What is the most accurate statement regarding equine stifle meniscal injuries?

Meniscal injuries rarely cause stifle effusion
Lateral meniscal tears are more common than medial tears in horses
Arthroscopic debridement is the preferred surgical treatment for partial tears (Correct answer)
Medial meniscal tears heal reliably with intra-articular steroids alone

Correct answer: Arthroscopic debridement is the preferred surgical treatment for partial tears

Arthroscopic debridement of damaged meniscal tissue is the preferred surgical approach for partial meniscal tears in horses, providing access to the caudal pouch of the femorotibial joint.

Question 55: A cockatiel presents with symmetrical feather loss over the head and neck, with pin feathers that appear hemorrhagic and dystrophic. The most appropriate diagnostic test is:

Complete blood count
PCR for Psittacine Beak and Feather Disease virus (Correct answer)
Bacterial culture of feather follicle
Fungal culture

Correct answer: PCR for Psittacine Beak and Feather Disease virus

Psittacine Beak and Feather Disease (PBFD) caused by circovirus is best diagnosed via PCR testing and presents with dystrophic feathers and immunosuppression.

Question 56: Pinkeye (Infectious Bovine Keratoconjunctivitis) in a cow herd is most commonly caused by which organism?

Listeria monocytogenes
Mycoplasma bovis
Moraxella bovis (Correct answer)
Pasteurella multocida

Correct answer: Moraxella bovis

Moraxella bovis is the primary causative agent of IBK, producing a pilus that allows corneal attachment and a hemolysin that damages corneal epithelium.

Question 57: A 6-month-old calf dies acutely. Necropsy reveals a 'paint-brush' hemorrhage pattern on the epicardium, fibrinonecrotic plaques in the abomasum, and hemorrhagic lymph nodes. Which pathologic process most likely caused these lesions?

Copper toxicity with intravascular hemolysis
Vitamin E/selenium deficiency (white muscle disease)
Septicemia with gram-negative lipopolysaccharide-mediated disseminated intravascular coagulation (DIC) (Correct answer)
Johne's disease with chronic protein-losing enteropathy

Correct answer: Septicemia with gram-negative lipopolysaccharide-mediated disseminated intravascular coagulation (DIC)

Petechial/ecchymotic hemorrhages (paint-brush pattern) on serosal surfaces combined with hemorrhagic lymph nodes and mucosal necrosis are classic findings of endotoxemia-induced DIC in calves, most commonly from gram-negative septicemia (e.g., Salmonella, E. coli). LPS activates the coagulation cascade, consuming clotting factors and causing bleeding diathesis. White muscle disease shows pale streaking of skeletal/cardiac muscle.

Question 58: Xylazine and dexmedetomidine produce sedation and analgesia through which primary mechanism of action?

GABA-A receptor potentiation
Alpha-2 adrenergic receptor agonism (Correct answer)
Mu-opioid receptor agonism
NMDA receptor antagonism

Correct answer: Alpha-2 adrenergic receptor agonism

Alpha-2 adrenergic agonists such as xylazine and dexmedetomidine bind presynaptic and postsynaptic alpha-2 receptors in the CNS and periphery, producing dose-dependent sedation, muscle relaxation, and analgesia.

Question 59: A dog has a myelogram that shows a contrast column that is deviated to one side and compressed at a single level but does not completely stop. This pattern is most consistent with:

Extradural compression (disc herniation) (Correct answer)
Normal variant
Intradural-extramedullary mass
Intramedullary lesion (tumor/edema)

Correct answer: Extradural compression (disc herniation)

Extradural lesions (such as disc material or vertebral bone) deviate and compress the contrast column from the outside without interrupting the intrathecal flow completely.

Question 60: A veterinarian is called to a swine operation to investigate an outbreak of high fever, anorexia, and vesicular lesions on the snouts and coronary bands of multiple pigs. What is the most critical and immediate first action for the veterinarian to take?

Contact the State Veterinarian or USDA-APHIS Area Veterinarian in Charge. (Correct answer)
Euthanize affected pigs to prevent further spread and collect post-mortem samples.
Advise the producer to quarantine the farm and ship samples to a local diagnostic lab.
Initiate treatment with broad-spectrum antibiotics to prevent secondary infections.

Correct answer: Contact the State Veterinarian or USDA-APHIS Area Veterinarian in Charge.

Vesicular lesions in swine are clinically indistinguishable from Foot-and-Mouth Disease (FMD), a highly contagious and economically devastating foreign animal disease (FAD). The legal and professional obligation of any veterinarian suspecting an FAD is to immediately report it to state and/or federal animal health officials. This action triggers a specific, high-priority response to confirm the diagnosis and contain the potential outbreak.

Question 61: A 12-year-old hyperthyroid cat is treated with methimazole and achieves euthyroidism. Six weeks later, serum creatinine rises from 1.4 to 3.8 mg/dL and BUN from 22 to 68 mg/dL. Urine specific gravity is 1.018. What is the most accurate explanation for this finding?

Euthyroidism causes a physiologic decrease in muscle mass, artificially elevating creatinine
Hyperthyroidism had been masking pre-existing chronic kidney disease by increasing GFR (Correct answer)
Methimazole is directly nephrotoxic and should be discontinued immediately
The cat has developed acute kidney injury secondary to dehydration from the antithyroid medication

Correct answer: Hyperthyroidism had been masking pre-existing chronic kidney disease by increasing GFR

Hyperthyroidism increases cardiac output and renal blood flow, artificially elevating GFR and masking underlying CKD. When euthyroidism is restored, renal perfusion normalizes (decreases), and true CKD becomes apparent. This is a well-recognized phenomenon in feline medicine — it underscores the importance of renal function assessment before and after initiating treatment. Methimazole is not directly nephrotoxic in this manner, and the urine specific gravity of 1.018 indicates reduced concentrating ability consistent with CKD, not dehydration alone.

Question 62: A 5-year-old outdoor cat presents with a chronic non-healing ulcer on the nasal planum, conjunctivitis with corneal ulceration, and recurrent mucopurulent nasal discharge. Herpesvirus (FHV-1) is confirmed by PCR from conjunctival swab. The owner asks about long-term management. Which antiviral strategy has the STRONGEST evidence base for reducing FHV-1-associated ocular disease severity in cats, with the LEAST systemic toxicity concern?

Topical 0.5% cidofovir ophthalmic solution applied twice daily to the affected eye(s) (Correct answer)
Systemic acyclovir at 50 mg/kg PO q8h due to its established safety in cats
Topical 3% vidarabine ointment applied 5 times daily combined with oral lysine supplementation at 500 mg/day
Oral famciclovir 90 mg/kg PO q8h as the first-line systemic antiviral

Correct answer: Topical 0.5% cidofovir ophthalmic solution applied twice daily to the affected eye(s)

Topical 0.5% cidofovir (a nucleotide analog) applied twice daily has been shown in clinical studies to significantly reduce FHV-1 conjunctival disease severity and viral shedding with minimal systemic absorption and low local toxicity — making it superior in the topical antiviral category for feline herpesvirus ocular disease. Famciclovir is the preferred oral antiviral (prodrug converted to penciclovir in cats), but the dose is 90 mg/kg PO q12h (NOT q8h) and it is reserved for severe systemic disease. Acyclovir is CONTRAINDICATED in cats due to severe nephrotoxicity and bone marrow suppression. Lysine supplementation has been shown in multiple systematic reviews to have NO benefit for FHV-1 management and is no longer recommended by the American Association of Feline Practitioners (AAFP).

Question 63: On abdominal ultrasound, an anechoic structure with distal acoustic enhancement in the kidney is MOST consistent with:

Simple renal cyst (Correct answer)
Renal abscess
Transitional cell carcinoma
Nephrolithiasis

Correct answer: Simple renal cyst

Simple cysts are anechoic with a thin wall and show distal acoustic enhancement due to the lack of sound attenuation by fluid.

Question 64: A 350-cow dairy in the upper Midwest has a bulk tank somatic cell count (BTSCC) persistently between 320,000–380,000 cells/mL over the past 6 months. Milk culture of individual quarter samples from 40 randomly selected cows identifies: Staphylococcus aureus (6 cows), Streptococcus agalactiae (12 cows), coagulase-negative staphylococci (CNS) (8 cows), and no growth (14 cows). Which statement BEST describes the appropriate herd-level eradication target for this situation?

All culture-positive cows should receive immediate intramammary therapy with pirlimycin to resolve infection before dry-off
CNS should be targeted first with intramammary therapy because they represent the largest numerical contributor to the elevated BTSCC
Staphylococcus aureus should be the primary eradication target because it has higher within-herd transmission potential than Streptococcus agalactiae
Streptococcus agalactiae should be targeted for herd eradication because it is an obligate intramammary pathogen that can be eliminated with a blitz dry-cow therapy program (Correct answer)

Correct answer: Streptococcus agalactiae should be targeted for herd eradication because it is an obligate intramammary pathogen that can be eliminated with a blitz dry-cow therapy program

Streptococcus agalactiae is an obligate pathogen of the bovine mammary gland — it does not survive long in the environment — making it the only major mastitis pathogen amenable to true herd eradication. A 'blitz' program (treating all infected cows simultaneously with intramammary penicillin + stringent milking hygiene + test and cull if refractory) can eliminate S. agalactiae from a herd within weeks. With 12/40 cows infected (30%), this organism is almost certainly the dominant driver of the elevated BTSCC. S. aureus has very poor cure rates with lactating cow therapy (<25%) and is not eradicable herd-wide. CNS generally cause mild, self-limiting IMI and rarely require active treatment. Blanket intramammary pirlimycin for all positive cows is not evidence-based and raises antimicrobial stewardship concerns.

Question 65: A 7-year-old intact male Labrador Retriever presents with a 3-day history of polyuria, polydipsia, and a purulent penile discharge. Physical exam reveals a fluctuant abdominal mass caudal to the umbilicus. Abdominal ultrasound shows a fluid-filled uterus-like structure. Which of the following best explains this finding?

Peritoneal inclusion cyst secondary to prior abdominal surgery
Ectopic ureter with secondary hydronephrosis and hydroureter
Retained Müllerian duct remnant (persistent Müllerian duct syndrome) with secondary infection (Correct answer)
Prostatic abscess with paraprostatic cyst formation

Correct answer: Retained Müllerian duct remnant (persistent Müllerian duct syndrome) with secondary infection

Persistent Müllerian duct syndrome (PMDS) occurs in male dogs when Müllerian-inhibiting substance (MIS/AMH) fails to cause regression of the paramesonephric ducts, resulting in a uterus-like structure (uterus masculinus). Miniature Schnauzers are most commonly affected, but it can occur in any breed. The structure can develop pyometra-like infections in intact males, explaining the purulent discharge and systemic signs. Prostatic disease is a common differential but would not produce a distinct fluid-filled midline uterus-like structure separate from the prostate on ultrasound.

Question 66: A veterinarian observes a horse trotting on a hard, flat surface and notes a consistent head nod. The lameness is not apparent at a walk but is easily seen at the trot. According to the American Association of Equine Practitioners (AAEP) Lameness Scale, what is the most appropriate grade?

Grade 3 (Correct answer)
Grade 1
Grade 4
Grade 2

Correct answer: Grade 3

The AAEP Lameness Scale defines a Grade 3 lameness as one that is consistently observable at a trot under all circumstances. Grade 2 lameness is difficult to observe at a trot in a straight line but is consistent under specific circumstances (e.g., circling). Grade 1 is difficult to observe, and Grade 4 is obvious at a walk. The description of a lameness not seen at a walk but consistently visible with a head nod at a trot fits Grade 3.

Question 67: A veterinarian conducting a pre-export health certificate inspection for cattle destined to a country in the EU discovers one animal with an ear-tag discrepancy — the tag number does not match the USDA premises registration record but the animal otherwise appears healthy. Under the USDA-APHIS Export Verification Program and EU import requirements, what is the MOST appropriate immediate action?

Accept the animal and annotate the health certificate with a notation that the tag was visually verified but registry entry is pending correction
Reject the animal from the export lot, document the discrepancy on Form VS 17-140, and notify the APHIS District Office — the animal cannot be certified without verified identity (Correct answer)
Retest the animal for all required export diseases and issue a conditional certificate pending APHIS review within 30 days
Replace the ear tag with a new USDA official tag, update the premises record, and proceed with certification after confirming no other discrepancies

Correct answer: Reject the animal from the export lot, document the discrepancy on Form VS 17-140, and notify the APHIS District Office — the animal cannot be certified without verified identity

Under USDA-APHIS Export Verification (EV) programs and EU Regulation (EU) 2016/429 requirements, traceability — including verified official identification linked to premises of origin — is a non-negotiable prerequisite for export certification. An animal whose tag cannot be matched to a USDA premises record has an unverifiable identity chain; certifying it would constitute a false official statement on a federal document (VS 17-140), which carries both regulatory and criminal liability. The correct action is to reject the animal from the consignment, document the discrepancy, and notify the APHIS District Veterinarian. Re-tagging and retroactively updating records at the time of certification is not permissible under federal traceability rules — the identity must have been established prior to certification, not created to enable it.

Question 68: Which antifungal drug is currently the first-line treatment for aspergillosis in birds?

Ketoconazole
Voriconazole (Correct answer)
Griseofulvin
Amphotericin B

Correct answer: Voriconazole

Voriconazole is the preferred antifungal for avian aspergillosis due to its superior efficacy and safety compared to older azoles.

Question 69: Would you ever administer antibiotics to a cat with FIP?

Yes (Correct answer)
No

Correct answer: Yes

While FIP is a viral disease and antibiotics do not directly treat the virus, they are often administered to FIP patients. Cats with FIP are immunocompromised and highly susceptible to secondary bacterial infections, which can complicate the disease and worsen their condition. Antibiotics are used to manage these opportunistic bacterial infections.

Question 70: Which of the following is a primary therapeutic goal in the management of a dog with chronic kidney disease (CKD) and proteinuria?

Controlling systemic hypertension and reducing phosphorus intake (Correct answer)
Administering loop diuretics to increase GFR
Increasing dietary protein to counteract losses
Supplementing with high doses of Vitamin D to manage secondary hyperparathyroidism

Correct answer: Controlling systemic hypertension and reducing phosphorus intake

Management of canine CKD focuses on slowing disease progression and improving quality of life. Key goals include controlling systemic hypertension, which can exacerbate kidney damage, and reducing dietary phosphorus intake to manage renal secondary hyperparathyroidism. Protein restriction (not increase) is often indicated, and while diuretics have a role in specific situations, they don't increase GFR. Vitamin D supplementation must be done cautiously to avoid hypercalcemia.

Question 71: A producer wants to implement a PRRSV (Porcine Reproductive and Respiratory Syndrome Virus) control program. Wait—this is a bovine herd. Which respiratory virus causes 'shipping fever' complex and is commonly controlled with modified-live virus vaccines in beef cattle?

Bovine coronavirus (BCoV)
Parainfluenza-3 virus (PI3)
Infectious bovine rhinotracheitis virus (IBRV/BHV-1) (Correct answer)
Bovine respiratory syncytial virus (BRSV)

Correct answer: Infectious bovine rhinotracheitis virus (IBRV/BHV-1)

IBRV (BHV-1) is a primary viral pathogen in the bovine respiratory disease complex, and modified-live IBR vaccines are a cornerstone of BRD prevention programs in beef cattle.

Question 72: A 3-year-old dairy goat presents with progressive weight loss, decreased milk production, and bilateral carpal swelling. Lung auscultation reveals diffuse crackles. Cerebrospinal fluid analysis shows mononuclear pleocytosis. The most likely diagnosis is:

Maedi-Visna virus infection
Caseous lymphadenitis (Corynebacterium pseudotuberculosis)
Mycoplasma mycoides subsp. capri polyarthritis
Caprine Arthritis Encephalitis (CAE) virus infection (Correct answer)

Correct answer: Caprine Arthritis Encephalitis (CAE) virus infection

CAE virus (a lentivirus) in adult goats classically presents as chronic progressive polyarthritis (especially carpal joints) combined with interstitial pneumonia and occasional leukoencephalomyelitis. Maedi-Visna is the sheep equivalent but does not cause arthritis as prominently. Caseous lymphadenitis causes abscessation, not arthritis + pneumonia. Mycoplasma causes acute febrile arthritis.

Question 73: A cat presents with acute onset of severe muscle tremors, hyperthermia, and mydriasis after the owner applied a canine-specific flea and tick spot-on product. Which of the following toxicities is most likely, and what is the primary therapeutic agent used to control the tremors?

Ethylene glycol toxicity; Fomepizole
Organophosphate toxicity; Atropine
Permethrin toxicity; Methocarbamol (Correct answer)
Ivermectin toxicity; Intralipid emulsion

Correct answer: Permethrin toxicity; Methocarbamol

The clinical signs described are classic for permethrin toxicity, which occurs when concentrated canine flea products containing this pyrethroid are applied to cats. Cats are deficient in the enzymes needed to metabolize permethrin effectively. The primary treatment for the resulting muscle tremors and fasciculations is the centrally-acting muscle relaxant, methocarbamol. Atropine is for organophosphate toxicity, fomepizole for ethylene glycol, and intralipid emulsion is an adjunctive therapy for lipid-soluble toxins like ivermectin.

Question 74: An 8-year-old Cavalier King Charles Spaniel undergoes brain MRI for evaluation of vestibular signs and progressive cerebellar ataxia. Sagittal T2-weighted images reveal caudal displacement of the cerebellar vermis through the foramen magnum with effacement of the cisterna magna. There is no hydrocephalus. Additionally, a longitudinal fluid-filled cavity is identified within the cervical spinal cord parenchyma that is isointense to CSF on all sequences. Which TWO conditions are being described together?

Cerebellar cortical abiotrophy and central canal dilation
Dandy-Walker malformation and hydromyelia
Caudal occipital malformation syndrome (COMS) and syringomyelia (Correct answer)
Chiari-like malformation type II and diplomyelia

Correct answer: Caudal occipital malformation syndrome (COMS) and syringomyelia

Caudal occipital malformation syndrome (COMS), also called Chiari-like malformation, is extremely prevalent in the Cavalier King Charles Spaniel breed. It is characterized by caudal displacement of the cerebellum through the foramen magnum, effacement of the cisterna magna, and obstruction of CSF flow. This impaired CSF circulation leads to the formation of a syrinx (syringomyelia)—a CSF-filled cavity within the spinal cord parenchyma that is isointense to CSF on all MRI sequences. The combination of COMS + syringomyelia is a well-described clinicopathological entity in this breed. Dandy-Walker involves cerebellar hypoplasia with a cystic posterior fossa, not caudal herniation.

Question 75: An 8-year-old Hanoverian mare undergoes standing laparoscopic right ovariectomy for an ovarian granulosa-theca cell tumor. Forty-eight hours postoperatively, she develops progressive signs of colic, tachycardia (72 bpm), and tachypnea. On rectal examination, distended small intestinal loops are palpable. Nasogastric reflux yields 8 liters of fluid. Which laparoscopic complication is the most likely cause of this acute deterioration?

Pneumoperitoneum-induced mesenteric traction leading to ileus of the descending colon
Carbon dioxide absorption causing hypercarbia-induced vagal stimulation and intestinal hypomotility
Inadvertent ligation of the right uterine artery causing uterine ischemia and visceral pain
Herniation of small intestine through the right flank cannula port site (Correct answer)

Correct answer: Herniation of small intestine through the right flank cannula port site

Herniation of small intestine through a flank cannula port site (incisional hernia with bowel entrapment) is a well-recognized and serious complication of standing flank laparoscopy in horses, particularly when 10–12 mm ports are used without proper fascial closure. The 12 mm port sites in the right flank create a defect large enough for small intestinal herniation, which can rapidly progress to strangulation — explaining the large nasogastric reflux, distended small intestinal loops, and systemic signs of ischemia. CO2-induced ileus and mesenteric traction ileus would not typically produce 8 L of reflux within 48 hours. Uterine artery ligation would cause hemorrhage and uterine signs rather than small intestinal obstruction.

Question 76: A 12-year-old female spayed Domestic Shorthair cat is presented with a 2-month history of progressive weight loss despite a ravenous appetite (polyphagia). The owner also reports occasional vomiting and restlessness. On physical examination, you note a heart rate of 230 bpm, a thin body condition, and an unkempt haircoat. Which of the following is the most likely diagnosis?

Hyperthyroidism (Correct answer)
Chronic kidney disease
Diabetes mellitus
Inflammatory bowel disease

Correct answer: Hyperthyroidism

The combination of weight loss with polyphagia, tachycardia, and hyperactivity in an older cat is classic for hyperthyroidism. Diabetes mellitus can cause weight loss and polyphagia but is not typically associated with tachycardia or hyperactivity. Chronic kidney disease usually presents with weight loss and polyuria/polydipsia, but often with a decreased appetite. Inflammatory bowel disease typically involves weight loss, vomiting, and/or diarrhea, but not the other clinical signs noted.

Question 77: A 6-year-old German Shepherd has chronic small bowel diarrhea, weight loss, and hypocobalaminemia. Serum folate is elevated. What is the most likely diagnosis?

Small intestinal bacterial overgrowth (SIBO) / dysbiosis (Correct answer)
Lymphangiectasia
Inflammatory bowel disease
Exocrine pancreatic insufficiency

Correct answer: Small intestinal bacterial overgrowth (SIBO) / dysbiosis

Elevated folate (produced by bacteria) combined with low cobalamin (consumed by bacteria) is the classic pattern for small intestinal bacterial overgrowth/dysbiosis.

Question 78: A public health veterinarian is reviewing a food establishment's HACCP plan for a ready-to-eat deli meat facility. The plan identifies internal temperature of 160°F (71.1°C) as a Critical Control Point (CCP) for lethality. An inspector finds that logs show 12 consecutive batches reached only 158°F (70°C). Under HACCP principles, which action is MOST appropriate?

Suspend the HACCP plan and revert to traditional inspection methods pending retesting
Require immediate corrective action documentation, reassess the disposition of all 12 affected batches, and evaluate root cause (Correct answer)
Issue a warning but allow product to proceed since 158°F is close to the CCP limit
Adjust the CCP limit downward to 158°F to reflect actual operational capacity

Correct answer: Require immediate corrective action documentation, reassess the disposition of all 12 affected batches, and evaluate root cause

Under HACCP Principle 5, when a critical limit is not met, a pre-established corrective action must be implemented immediately. This includes: (1) correcting the process deviation, (2) determining the disposition of affected product (hold, test, or destroy), and (3) documenting the corrective action. All 12 batches where the CCP was not met require individual disposition decisions — they cannot proceed without evaluation. Adjusting CCP limits to match operational failure would compromise food safety integrity and violates HACCP validation requirements.

Question 79: A veterinarian is performing a complete blood count on a red-tailed hawk (Buteo jamaicensis) and notices large, round, pale-staining intracytoplasmic inclusions within erythrocytes, affecting approximately 15% of cells. The bird is mildly lethargic but otherwise clinically stable. Which of the following is the MOST accurate statement regarding this finding?

This is Plasmodium sp., which is the primary avian malaria parasite requiring immediate chloroquine treatment
This is Haemoproteus sp. and is considered non-pathogenic in raptors; treatment is unnecessary
This is Leucocytozoon sp., which is transmitted by blackflies and can cause fatal anemia in accipiters (Correct answer)
These inclusions represent viral intranuclear inclusions displaced to the cytoplasm during erythrocyte maturation

Correct answer: This is Leucocytozoon sp., which is transmitted by blackflies and can cause fatal anemia in accipiters

The large, round intracytoplasmic inclusions in erythrocytes of a raptor are most consistent with Leucocytozoon sp. gametocytes. Unlike Haemoproteus (which has halter-shaped gametocytes in erythrocytes and is generally non-pathogenic), Leucocytozoon can cause severe hemolytic anemia, particularly in accipiters (Accipiter spp.) and young birds. It is transmitted by Simulium (blackflies) and Culicoides. Plasmodium produces smaller, irregular inclusions with hemozoin pigment granules. Leucocytozoon gametocytes are large enough to distort the host cell, which helps distinguish them.

Question 80: A 500-cow Holstein dairy has a bulk tank somatic cell count (BTSCC) averaging 380,000 cells/mL over 6 months. Individual cow linear scores show 22% of cows with linear score ≥5 (SCC ≥200,000). New infection rate (NIR) during lactation is 8%/month; cure rate (CR) during dry-off is 55%. The herd veterinarian wants to reduce BTSCC to <200,000 within 12 months. Which intervention is predicted to have the GREATEST single impact on achieving this goal, based on the epidemiologic data provided?

Add post-milking teat dipping with an iodine-based barrier dip to reduce the 8%/month new infection rate
Cull all cows with linear score ≥5 at current lactation stage to rapidly reduce the high-SCC reservoir
Improve dry cow therapy outcomes by switching to an internal teat sealant plus antibiotic DCT protocol for all eligible cows, targeting the 55% dry-period cure rate (Correct answer)
Implement a selective dry cow therapy program to reduce antibiotic use and focus resources on culture-positive quarters

Correct answer: Improve dry cow therapy outcomes by switching to an internal teat sealant plus antibiotic DCT protocol for all eligible cows, targeting the 55% dry-period cure rate

The epidemiologic data identifies two leverage points: an 8%/month NIR (high, normal is <2%) and a 55% dry-period cure rate (low, target is >75%). The BTSCC is driven by the large chronic reservoir (22% of cows with LS≥5). Improving dry-period cures from 55% to >75% by ensuring all eligible cows receive a combination of antibiotic DCT plus an internal teat sealant (which creates a physical barrier reducing new IMI during the dry period as well) would both eliminate existing chronic infections and prevent new ones during the critical dry period — the period of highest cure probability. This single intervention addresses chronic prevalence (the numerator of BTSCC) most powerfully. Culling all LS≥5 cows would reduce the reservoir acutely but would remove ~110 cows (economically catastrophic) and not address incoming infections. Improving post-dipping would reduce NIR, but at 8%/month the effect on the established chronic reservoir would take 12+ months to manifest meaningfully. Selective DCT, while appropriate for antibiotic stewardship, would likely lower cure rates further in this herd.

Question 81: During inhalant anesthesia maintenance in a dog, the end-tidal CO2 (EtCO2) rises to 65 mmHg despite manual ventilation at 15 breaths/min with a tidal volume of 15 mL/kg. Arterial blood gas confirms PaCO2 of 70 mmHg. Which condition is the MOST likely cause of this disproportionately elevated PaCO2 relative to minute ventilation?

Increased dead space ventilation from pulmonary thromboembolism (Correct answer)
Malignant hyperthermia
Rebreathing from an exhausted CO2 absorbent
Severe bronchospasm causing V/Q mismatch

Correct answer: Increased dead space ventilation from pulmonary thromboembolism

The key finding is that PaCO2 is disproportionately elevated relative to what should be adequate minute ventilation (15 mL/kg × 15 breaths/min = ~225 mL/kg/min is above normal). Pulmonary thromboembolism significantly increases physiologic dead space—areas that are ventilated but not perfused—so CO2 is not eliminated despite adequate ventilation effort. This creates an elevated PaCO2-to-EtCO2 gradient (normally <5 mmHg; a gradient of 5 mmHg here suggests shunt/dead space). Malignant hyperthermia causes rapid CO2 rise with hyperthermia and rigidity. Exhausted CO2 absorbent would cause rebreathing reflected as elevated inspired CO2 on capnography. Bronchospasm causes hypoxemia via V/Q mismatch but less dramatically impairs CO2 clearance.

Question 82: A 7-year-old intact male Golden Retriever presents with polyuria, polydipsia, bilateral symmetric alopecia, and a pendulous abdomen. CBC shows a mild non-regenerative anemia. Serum chemistry reveals elevated ALP at 850 U/L and hypercholesterolemia. Urine specific gravity is 1.008. Low-dose dexamethasone suppression test (LDDST) shows cortisol at 1.9 µg/dL at 4 hours and 2.1 µg/dL at 8 hours. Which of the following is the most accurate interpretation?

The pattern is consistent with adrenal-dependent hyperadrenocorticism (ADH) (Correct answer)
The result rules out hyperadrenocorticism and atypical Cushing's should be investigated
The pattern is consistent with pituitary-dependent hyperadrenocorticism (PDH)
The test result is non-diagnostic and a high-dose DST should be performed next

Correct answer: The pattern is consistent with adrenal-dependent hyperadrenocorticism (ADH)

In the LDDST, failure to suppress at 8 hours (cortisol >1.4 µg/dL) confirms hyperadrenocorticism. The key discriminating feature here is that cortisol at 4 hours (1.9 µg/dL) is also elevated without any intermediate suppression. PDH cases classically show >50% suppression at 4 hours (escape phenomenon), while ADH shows no suppression at either time point. Both the 4-hour and 8-hour values exceeding 1.4 µg/dL without the escape pattern strongly suggests an autonomously secreting adrenal tumor (ADH). Abdominal ultrasound to evaluate adrenal size is the appropriate next step.

Question 83: Which of the following best describes the primary mechanism by which non-steroidal anti-inflammatory drugs (NSAIDs) can induce acute kidney injury in a cat that is dehydrated or hypotensive?

Inhibition of prostaglandin-mediated renal vasodilation (Correct answer)
Direct nephron apoptosis via oxidative damage
Immune-mediated glomerulonephritis
Formation of obstructive crystals within the renal tubules

Correct answer: Inhibition of prostaglandin-mediated renal vasodilation

In states of decreased renal perfusion (like dehydration or hypotension), the kidneys rely on locally produced prostaglandins (PGE2 and PGI2) to cause afferent arteriole vasodilation, which maintains glomerular filtration rate (GFR). NSAIDs inhibit cyclooxygenase (COX) enzymes, thereby blocking prostaglandin synthesis. This inhibition prevents the compensatory vasodilation, leading to a profound reduction in renal blood flow, decreased GFR, and potential ischemic acute tubular necrosis.

Question 84: A 10-year-old DSH cat presents with polyuria, polydipsia, and a serum potassium of 2.8 mEq/L. Blood pressure is 195 mmHg. Aldosterone-to-renin ratio is markedly elevated. CT reveals a 1.2 cm unilateral adrenal mass. Which of the following is the MOST appropriate next step in management?

Low-dose dexamethasone suppression test to rule out concurrent hypercortisolism
Adrenalectomy after preoperative potassium and blood pressure stabilization (Correct answer)
Bilateral adrenalectomy given the risk of contralateral subclinical disease
Lifelong spironolactone and amlodipine without surgery

Correct answer: Adrenalectomy after preoperative potassium and blood pressure stabilization

Feline primary hyperaldosteronism (Conn's syndrome) caused by a unilateral adrenal adenoma or carcinoma is best treated with adrenalectomy, which is curative. Preoperative stabilization with potassium supplementation and amlodipine (the preferred antihypertensive in cats) is essential to reduce anesthetic risk. Medical management alone is reserved for bilateral disease or poor surgical candidates. A dexamethasone suppression test is not indicated here as there is no evidence of hypercortisolism. Bilateral adrenalectomy is inappropriate for confirmed unilateral disease.

Question 85: A 35 kg Labrador Retriever is receiving a morphine CRI at 0.1 mg/kg/hr post-orthopedic surgery. Six hours postoperatively, the dog is dysphoric, vocalizing, scratching at the face, and mildly ataxic, with a heart rate of 58 bpm. The MOST appropriate next step is:

Administer low-dose naloxone 0.002 mg/kg IV and reassess pain score (Correct answer)
Switch to a fentanyl CRI and add acepromazine 0.02 mg/kg for sedation
Administer naloxone 0.04 mg/kg IV to reverse opioid toxicity
Increase the morphine CRI to 0.2 mg/kg/hr to deepen analgesia

Correct answer: Administer low-dose naloxone 0.002 mg/kg IV and reassess pain score

The clinical picture—dysphoria, facial scratching (opioid-induced pruritus), ataxia, and bradycardia—represents morphine-induced side effects rather than undertreated pain. Full reversal with a standard naloxone dose (0.04 mg/kg) would eliminate analgesia, causing acute pain rebound. Low-dose naloxone (0.001–0.004 mg/kg IV) selectively reverses side effects such as dysphoria, pruritus, and excessive sedation while largely preserving analgesic efficacy. Increasing the CRI would worsen the side effect profile. Acepromazine can deepen sedation but does not address the underlying opioid-mediated dysphoria and may mask neurologic deterioration.

Question 86: A horse presents with acute onset of severe bilateral forelimb lameness, leaning back on the hindlimbs, and bounding digital pulses. The MOST likely diagnosis is:

Bilateral navicular bursitis
Equine protozoal myeloencephalitis (EPM)
Laminitis (Correct answer)
Bilateral coffin joint sepsis

Correct answer: Laminitis

Acute laminitis classically presents with bilateral forelimb pain causing a characteristic saw-horse stance, bounding digital pulses, and reluctance to walk.

Question 87: A rabbit (Oryctolagus cuniculus) is presented for acute anorexia and abdominal distension. On physical exam, there is tympany in the cecal region, hypothermia (98.4°F), and the cecum is palpably enlarged and doughy. Radiographs confirm massive cecal dilation with a gas cap. The rabbit has been on a high-pellet, low-hay diet. Which statement MOST accurately describes the pathophysiology of cecal dysbiosis in this patient?

Dietary carbohydrate overload reduces cecal volatile fatty acid production, causing mucosal barrier failure and systemic endotoxemia
Low-fiber diet reduces cecotroph production, leading to B-vitamin deficiency and secondary immunosuppression
Excess simple carbohydrates shift cecal pH toward alkaline conditions, favoring Clostridium spiroforme overgrowth and iota-toxin production (Correct answer)
High-protein diet increases cecal ammonia concentrations, causing direct mucosal necrosis and secondary Escherichia coli bacteremia

Correct answer: Excess simple carbohydrates shift cecal pH toward alkaline conditions, favoring Clostridium spiroforme overgrowth and iota-toxin production

In rabbits, cecal dysbiosis (often called rabbit enterotoxemia or mucoid enteropathy complex) is precipitated by excess fermentable carbohydrates reaching the cecum. This substrate shift favors proliferation of Clostridium spiroforme, which produces iota-toxin (a binary toxin similar to Clostridium perfringens iota-toxin). The normal cecal pH is mildly acidic (5.9–6.8); carbohydrate overload and disrupted VFA production raise the pH, creating an environment favorable for clostridial overgrowth. Iota-toxin disrupts actin cytoskeleton of enterocytes, causing fluid secretion, mucosal damage, and the classic cecal dilation and tympany seen here. The condition carries a guarded to poor prognosis.

Question 88: A 4-year-old African grey parrot presents with progressive ataxia, regurgitation, and a dilated proventriculus on radiograph. Crop biopsy reveals lymphoplasmacytic infiltration of the myenteric ganglia. Which of the following is the MOST accurate statement regarding the etiologic agent?

It is a double-stranded DNA virus in the family Herpesviridae that induces T-cell lymphoma in the myenteric plexus
It is a positive-sense, single-stranded RNA virus in the family Coronaviridae that primarily damages proventricular smooth muscle
It is a negative-sense, single-stranded RNA virus in the family Bornaviridae that targets glial cells and neurons of the enteric and central nervous systems (Correct answer)
It is a negative-sense, segmented RNA virus in the family Orthomyxoviridae that causes secondary demyelination of enteric nerves

Correct answer: It is a negative-sense, single-stranded RNA virus in the family Bornaviridae that targets glial cells and neurons of the enteric and central nervous systems

Proventricular Dilatation Disease (PDD) is caused by Avian Bornavirus (ABV), a non-segmented, negative-sense, single-stranded RNA virus in the family Bornaviridae. It targets neurons and glial cells of both the enteric (myenteric plexus) and central nervous systems, producing lymphoplasmacytic ganglioneuritis. The other options describe incorrect viral families or pathomechanisms.

Question 89: Foot rot (Fusobacterium necrophorum infection) is common in beef feedlots. Which environmental management change has the greatest impact on reducing foot rot incidence?

Reducing mud and standing water in pen areas to minimize skin maceration (Correct answer)
Routine zinc supplementation in the diet
Trimming hooves every 60 days on all feedlot cattle
Prophylactic copper sulfate foot baths for all cattle

Correct answer: Reducing mud and standing water in pen areas to minimize skin maceration

Wet, muddy conditions cause skin maceration between the claws, allowing Fusobacterium necrophorum to invade; pen drainage and mud management are the most impactful environmental interventions.

Question 90: A dog's abdominal ultrasound reveals a splenic mass with a 'target' or 'bull's-eye' lesion appearance (hypoechoic halo around a hyperechoic center). This pattern is most associated with:

Nodular hyperplasia
Splenic hematoma
Metastatic neoplasia (Correct answer)
Splenic abscess

Correct answer: Metastatic neoplasia

A target or bull's-eye lesion pattern in the spleen is classically associated with metastatic disease, where a necrotic center is surrounded by viable tumor tissue.

Question 91: Pinkeye (infectious bovine keratoconjunctivitis) caused by Moraxella bovis is most prevalent in summer months. Which management practice MOST effectively reduces its spread in a beef herd?

Surgical correction of entropion in all affected animals
Systemic antibiotic treatment of clinically affected animals and fly control (Correct answer)
Vaccination alone with no other interventions
Mandatory 30-day quarantine of all affected cattle

Correct answer: Systemic antibiotic treatment of clinically affected animals and fly control

Prompt treatment of clinical cases with long-acting oxytetracycline combined with fly control (the primary vector for Moraxella bovis transmission) is the most effective two-pronged management approach.

Question 92: Feline infectious peritonitis (FIP) wet form is characterized by accumulation of effusion. Which laboratory finding is most consistent with FIP effusion?

Hemorrhagic effusion with high RBC count
High protein (>3.5 g/dL) with low cellularity and high albumin:globulin ratio
Low protein (<2.5 g/dL) transudate
High protein (>3.5 g/dL) with low cellularity and low albumin:globulin ratio (Correct answer)

Correct answer: High protein (>3.5 g/dL) with low cellularity and low albumin:globulin ratio

FIP effusion is a high-protein (>3.5 g/dL) modified transudate with low cellularity and a low albumin:globulin ratio (<0.4), reflecting the vasculitis-driven protein leak.

Question 93: A 6-year-old Bernese Mountain Dog presents with progressive exercise intolerance and a 3-week history of ascites. Physical exam reveals jugular venous distension, muffled heart sounds, and hepatomegaly. Echocardiography demonstrates a large pericardial effusion. Pericardiocentesis is performed, yielding 600 mL of serosanguineous fluid. Cytology of the fluid is non-diagnostic. Which of the following is the most common underlying etiology in this breed and age group, and what is the most appropriate long-term management?

Aortic body (chemodectoma) tumor; recommend palliative pericardiectomy with guarded prognosis
Mesothelioma; recommend intracavitary cisplatin after pericardiectomy
Right atrial hemangiosarcoma; recommend pericardiectomy plus doxorubicin-based chemotherapy (Correct answer)
Idiopathic pericardial effusion; recommend subtotal pericardiectomy after two recurrences

Correct answer: Right atrial hemangiosarcoma; recommend pericardiectomy plus doxorubicin-based chemotherapy

In large and giant breeds, particularly Bernese Mountain Dogs, Golden Retrievers, and German Shepherds, right atrial hemangiosarcoma (HSA) is the most common cause of pericardial effusion. Idiopathic pericardial effusion is more common in medium breeds. Aortic body tumors (chemodectoma) are more common in brachycephalic breeds. Hemangiosarcoma carries a very poor prognosis; median survival with pericardiectomy alone is approximately 4 months. Doxorubicin-based chemotherapy (e.g., VAC protocol) is the standard of care adjunct, extending median survival to approximately 4–6 months. Non-diagnostic cytology is typical of HSA, as these tumors shed poorly and hemorrhagic effusions mask neoplastic cells.

Question 94: A 7-year-old Poodle presents with a PCV of 18%, MCV of 110 fL (macrocytosis), and a low serum cobalamin (B12). What is the most likely cause?

Cobalamin deficiency causing megaloblastic anemia (Correct answer)
Chronic disease anemia
Feline leukemia virus-like anemia
Iron deficiency anemia

Correct answer: Cobalamin deficiency causing megaloblastic anemia

Cobalamin deficiency impairs DNA synthesis in RBC precursors, causing large, immature red cells (macrocytosis) and non-regenerative megaloblastic anemia.

Question 95: A gilt in a farrow-to-finish operation develops diamond-shaped, raised, red skin lesions over the trunk 2 days after moving to the breeding barn. The most appropriate treatment is:

Ivermectin SC and topical antifungal
Florfenicol IM and supportive care
Enrofloxacin IM and corticosteroids
Penicillin G IM, NSAIDs, and isolation (Correct answer)

Correct answer: Penicillin G IM, NSAIDs, and isolation

Diamond-shaped urticarial skin lesions (diamond skin disease) are classic for Erysipelothrix rhusiopathiae infection in pigs. Erysipelas responds well to penicillin G; NSAIDs reduce fever and inflammation. Corticosteroids are contraindicated in bacteremic animals; enrofloxacin has poor activity against Erysipelothrix.

Question 96: In avian anatomy, the proventriculus is best described as which of the following?

The avian equivalent of the small intestine
A food storage pouch along the esophagus
The glandular stomach that secretes HCl and pepsin (Correct answer)
The muscular gizzard that grinds food

Correct answer: The glandular stomach that secretes HCl and pepsin

The proventriculus is the glandular (true) stomach of birds that secretes hydrochloric acid and digestive enzymes before food enters the ventriculus.

Question 97: A cat presents with pleural effusion. On thoracic radiographs, which finding best differentiates pleural effusion from pulmonary consolidation?

Air bronchograms within the opacity
Retraction of lung lobes from the thoracic wall (Correct answer)
Loss of cardiac silhouette border
Increased opacity in the perihilar region

Correct answer: Retraction of lung lobes from the thoracic wall

Pleural effusion causes lung lobes to retract away from the thoracic wall, whereas consolidated lung lobes remain in contact with the chest wall.

Question 98: Which antibiotic classes are contraindicated in rabbits due to the risk of fatal clostridial enterotoxemia?

Trimethoprim-sulfonamide combinations
Chloramphenicol
Fluoroquinolones (e.g., enrofloxacin)
Penicillins and lincosamides (e.g., clindamycin, ampicillin) (Correct answer)

Correct answer: Penicillins and lincosamides (e.g., clindamycin, ampicillin)

Penicillins, amoxicillin, and lincosamides disrupt cecal flora and allow Clostridium species overgrowth, causing fatal enterotoxemia in rabbits.

Question 99: A 10-year-old intact female dog presents with vaginal discharge, PU/PD, and leukocytosis with a left shift. Radiographs show a fluid-filled uterus. Which finding would support a closed-cervix pyometra over an open-cervix pyometra?

Lower serum progesterone
Presence of vaginal discharge
Lower white blood cell count
More severe azotemia and toxemia (Correct answer)

Correct answer: More severe azotemia and toxemia

Closed-cervix pyometra prevents drainage, leading to greater systemic toxemia, azotemia, and more severe clinical signs compared to open-cervix cases.

Question 100: A county health department requests a veterinary public health consultation after identifying a Brucella melitensis cluster: 3 human cases linked to consumption of imported soft cheese from a country where small ruminant brucellosis is enzootic. The cheese was sold at a single specialty grocery. Under the FDA Food Safety Modernization Act (FSMA) and related frameworks, which of the following agency actions and legal authorities most accurately describes the coordinated federal response?

USDA-FSIS issues the mandatory recall because Brucella is a Class A bioterrorism agent and all biological threat responses fall under USDA jurisdiction; CDC conducts the outbreak investigation under the Emergency Operations Center framework
FDA issues a mandatory recall under FSMA Section 206 authority (Mandatory Recall) for the implicated cheese lot; CDC coordinates human case investigation under Epi-Aid protocol; USDA-APHIS is NOT involved because the cheese is an imported finished food product, not live animals or animal semen (Correct answer)
CDC has primary recall authority for foodborne illness outbreaks involving zoonotic pathogens because CDC is the lead agency for all zoonotic disease response under the Public Health Service Act Section 361
FDA and USDA-FSIS have co-equal recall authority for all imported foods; both agencies must jointly sign any mandatory recall order, creating a mandatory 72-hour interagency consultation period before any public notification

Correct answer: FDA issues a mandatory recall under FSMA Section 206 authority (Mandatory Recall) for the implicated cheese lot; CDC coordinates human case investigation under Epi-Aid protocol; USDA-APHIS is NOT involved because the cheese is an imported finished food product, not live animals or animal semen

Under FSMA (21 USC §350l), FDA has mandatory recall authority for food products — including imported cheese — when there is reasonable probability the food is adulterated or misbranded and will cause serious adverse health consequences. Before FSMA (2011), FDA only had voluntary recall authority. The CDC coordinates human epidemiological investigation (case finding, exposure interviews, Epi-Aid deployment) but does not have recall authority. USDA-FSIS regulates meat, poultry, and egg products — not dairy imported as finished food. USDA-APHIS is relevant for live animal imports and animal product imports that could introduce foreign animal disease, but imported pasteurized/semi-soft cheese falls under FDA. Brucella melitensis is indeed a Tier 1 select agent, but that designation triggers additional USDA/CDC select agent program notification, not a transfer of recall authority to USDA-FSIS.

Question 101: On abdominal radiographs, a 'gravel sign' (multiple small mineral opacities) within a bowel loop is most suggestive of:

Feline hyperthyroidism-related GI changes
Urolithiasis with passed stones
Small intestinal foreign body obstruction (Correct answer)
Chronic pancreatitis with calcification

Correct answer: Small intestinal foreign body obstruction

The 'gravel sign' represents accumulation of mineral debris proximal to a small intestinal obstruction where normal transit is blocked, concentrating ingested minerals.

Question 102: During anesthesia of a 6-month-old intact female rabbit for an ovariohysterectomy, the patient develops sudden bradycardia (HR 80 bpm, baseline 220 bpm), hypotension (MAP 32 mmHg), and hypothermia (35.1°C) twenty minutes after intubation. Isoflurane vaporizer reads 2.5%. Which intervention takes highest priority?

Increase IV fluid rate to 10 mL/kg/hr to support blood pressure
Reduce isoflurane to 1.0–1.5% and initiate active warming (Correct answer)
Administer epinephrine 0.01 mg/kg IV for refractory hypotension
Administer atropine 0.04 mg/kg IV to treat vagally-mediated bradycardia

Correct answer: Reduce isoflurane to 1.0–1.5% and initiate active warming

Rabbits are highly sensitive to isoflurane-induced cardiovascular depression; an end-tidal isoflurane of 2.5% is markedly excessive for this species (typical maintenance is 1.5–2.0% at most). The combined bradycardia, hypotension, and hypothermia in a young rabbit at high isoflurane concentrations most likely represent anesthetic overdose. Reducing the vaporizer immediately is the highest-priority intervention. Active warming addresses hypothermia, which potentiates anesthetic depth and cardiac depression. Atropine may be needed but does not address the root cause (excessive anesthetic depth). Epinephrine is reserved for cardiac arrest. Aggressive fluid loading at 10 mL/kg/hr risks pulmonary edema in a small exotic patient without addressing the overdose.

Question 103: A 4-year-old Labrador Retriever is presented for episodic weakness and collapse after exercise. The owner reports the dog recovers within 10–20 minutes of rest. On examination, the dog is normal between episodes. Serum chemistry and CBC are unremarkable. An ECG during an induced episode shows a wide complex tachycardia at 280 bpm. Which breed-specific genetic mutation is most directly responsible for this presentation?

Dynamin 1 (DNM1) gene mutation causing exercise-induced collapse (Correct answer)
Phosphofructokinase (PFK) deficiency causing hemolytic anemia with exertion
MDR1 (ABCB1) gene mutation causing P-glycoprotein deficiency
Pyruvate kinase (PK) deficiency causing compensatory erythrocytosis

Correct answer: Dynamin 1 (DNM1) gene mutation causing exercise-induced collapse

Exercise-Induced Collapse (EIC) in Labrador Retrievers is caused by an autosomal recessive mutation in the Dynamin 1 (DNM1) gene, which encodes a GTPase critical for synaptic vesicle recycling. During intense exercise, the dysfunctional DNM1 leads to failure of neuromuscular transmission, resulting in collapse. The wide-complex tachycardia during the episode represents a ventricular arrhythmia secondary to the collapse event, not a primary cardiac disease. MDR1 mutations cause drug sensitivity. PFK deficiency causes hemolytic episodes with exercise but shows marked regenerative anemia. PK deficiency causes chronic hemolytic anemia.

Question 104: Which preanesthetic agent is CONTRAINDICATED in patients with suspected splenic masses because it causes splenic engorgement and sequestration of red blood cells?

Acepromazine (Correct answer)
Dexmedetomidine
Midazolam
Butorphanol

Correct answer: Acepromazine

Acepromazine (a phenothiazine) causes splenic engorgement by relaxing the splenic capsule, which can significantly enlarge an existing splenic mass and complicate diagnosis or surgery.

Question 105: Ketamine is commonly used as an induction agent, particularly in cats. What is its PRIMARY mechanism of anesthetic action?

GABA-A receptor potentiation
Alpha-2 adrenergic agonism
NMDA receptor antagonism (Correct answer)
Mu-opioid receptor agonism

Correct answer: NMDA receptor antagonism

Ketamine produces dissociative anesthesia primarily by non-competitive antagonism of NMDA (N-methyl-D-aspartate) glutamate receptors, which also contributes to its analgesic properties.

Question 106: A 12-year-old Quarter Horse mare presents with a 48-hour history of weight shifting, bilateral forelimb lameness, and divergent hoof rings. Digital pulses are bounding in all four feet. Radiographs reveal a 12-degree rotation of P3 with a 6 mm sole depth in the left front foot. Which statement regarding prognosis and management is most accurate?

Venography is contraindicated in chronic laminitis cases with rotation due to risk of increased lamellar ischemia
A sole depth ≥5 mm after rotation carries a favorable prognosis; corrective shoeing alone is sufficient treatment
The combination of >11.5-degree rotation AND <6 mm sole depth defines a negative prognosis threshold; this case is borderline and surgical options such as deep digital flexor tenotomy should be considered (Correct answer)
Coffin bone rotation beyond 10 degrees is an absolute indication for euthanasia regardless of sole depth

Correct answer: The combination of >11.5-degree rotation AND <6 mm sole depth defines a negative prognosis threshold; this case is borderline and surgical options such as deep digital flexor tenotomy should be considered

The critical prognostic thresholds in equine laminitis are rotation >11.5 degrees AND sole depth <6 mm simultaneously — this combination correlates strongly with poor outcome. This mare sits right at these thresholds (12-degree rotation, 6 mm sole depth), making her prognosis guarded and warranting serious consideration of deep digital flexor tenotomy (DDFT tenotomy) to relieve pull on the distal phalanx. Sole depth ≥5 mm is actually a relatively negative threshold, not favorable. Rotation alone beyond 10 degrees is not an absolute euthanasia criterion. Venography is actually valuable in these cases to assess lamellar blood flow and guide prognosis.

Question 107: A 4-year-old Labrador Retriever presents with acute respiratory distress after ingesting rat poison 2 days ago. PT and aPTT are severely prolonged; patient has pleural hemorrhage. Which rodenticide is most likely responsible?

Bromethalin
Strychnine
Zinc phosphide
Brodifacoum (second-generation anticoagulant) (Correct answer)

Correct answer: Brodifacoum (second-generation anticoagulant)

Second-generation anticoagulant rodenticides like brodifacoum inhibit vitamin K epoxide reductase, causing prolonged coagulopathy and hemorrhage 1–5 days post-ingestion.

Question 108: A 10 kg dog receives a constant rate infusion of lidocaine at 50 µg/kg/min for ventricular arrhythmia management post-cardiac surgery. After 8 hours, the dog develops muscle tremors and seizures. Serum lidocaine concentration is 8 µg/mL (toxic range >6 µg/mL in dogs). Which factor most likely contributed to lidocaine accumulation in this patient?

Lidocaine accumulation is driven by renal tubular reabsorption during sustained alkaline urine
Prolonged infusion saturates plasma protein binding, increasing the volume of distribution
Lidocaine undergoes zero-order kinetics at infusion rates above 25 µg/kg/min
Reduced hepatic blood flow or hepatic dysfunction impairs lidocaine clearance, since it is a high-extraction drug (Correct answer)

Correct answer: Reduced hepatic blood flow or hepatic dysfunction impairs lidocaine clearance, since it is a high-extraction drug

Lidocaine is a high hepatic extraction ratio drug (extraction ratio ~0.7 in dogs), meaning its clearance is primarily limited by hepatic blood flow rather than enzyme capacity. In post-surgical patients, reduced cardiac output, hepatic hypoperfusion, or overt hepatic dysfunction can dramatically reduce lidocaine clearance, leading to accumulation during CRI. This is distinct from low-extraction drugs where enzyme activity is the rate-limiting step. CNS toxicity (tremors, seizures) is the primary manifestation of lidocaine overdose in dogs.

Question 109: Soft tissue swelling along the dorsal aspect of the fetlock with pain on palpation of the dorsal pastern in a young racing Quarter Horse is MOST suggestive of:

Sesamoiditis
Fetlock synovitis (Correct answer)
Ringbone (high)
Extensor tendon laceration

Correct answer: Fetlock synovitis

Fetlock synovitis with joint effusion presents as dorsal soft tissue swelling and pain on palpation, commonly seen in young performance horses under heavy training loads.

Question 110: A dog that has been struck by a car typically has non-weight-bearing foreleg lameness. Physical examination reveals no fractures that can be felt. Without any movement or pain, the limb simply hangs there. It is also discovered that the dog has Horner's syndrome. What medical condition is most likely to account for these exam results?

Radial nerve paralysis
Brachial plexus avulsion (Correct answer)
Cervical disc disease
Arterial thromboembolism

Correct answer: Brachial plexus avulsion

The combination of non-weight-bearing foreleg lameness, a flaccid limb that 'just hangs there,' and the presence of Horner's syndrome is highly indicative of a brachial plexus avulsion. Horner's syndrome (miosis, ptosis, enophthalmos) occurs due to damage to sympathetic nerve fibers within the brachial plexus. The flaccid paralysis results from severe nerve root damage, typically from a traumatic pull on the limb.

Question 111: A 10-year-old Quarter Horse presents with a chronic, intermittent, bilateral forelimb lameness that worsens on hard surfaces. The horse points the affected feet and shows a shortened cranial phase of the stride. Hoof tester application across the heels elicits a painful response. A palmar digital nerve block significantly improves the lameness. Which of the following is the most likely diagnosis?

Laminitis
Coffin joint septic arthritis
Navicular syndrome (Correct answer)
Sole abscess

Correct answer: Navicular syndrome

Navicular syndrome is a chronic degenerative condition affecting the navicular bone and associated soft tissue structures in the heel of the foot. The clinical signs described—chronic bilateral forelimb lameness, pointing, pain on hoof testers over the heel, and improvement with a palmar digital nerve block—are all classic indicators of this condition. While other conditions can cause heel pain, the chronicity and bilateral nature strongly suggest navicular syndrome.

Question 112: A 5-year-old intact female German Shepherd Dog presents with a 3-week history of protein-losing enteropathy confirmed by a serum albumin of 1.1 g/dL and alpha-1 protease inhibitor fecal test positivity. Endoscopic biopsies reveal lymphangiectasia with marked villous blunting and diffuse mucosal infiltration with CD3+ lymphocytes and plasma cells. Despite 6 weeks of dietary hydrolyzed protein with ultra-low fat and prednisolone (2 mg/kg/day), albumin remains at 1.2 g/dL. What is the MOST appropriate next therapeutic escalation?

Addition of cyclosporine at 5 mg/kg/day PO as a steroid-sparing immunomodulator (Correct answer)
Initiate total parenteral nutrition to bypass the diseased intestinal mucosa
Switch to chlorambucil and prednisolone protocol for presumptive alimentary lymphoma
Add cobalamin supplementation and reassess in 4 weeks before escalating immunosuppression

Correct answer: Addition of cyclosporine at 5 mg/kg/day PO as a steroid-sparing immunomodulator

In refractory protein-losing enteropathy (PLE) with immunoproliferative enteropathy in German Shepherd Dogs, failure to respond adequately to dietary management and corticosteroid monotherapy warrants addition of a second immunosuppressive agent. Cyclosporine at 5 mg/kg/day has demonstrated efficacy as a steroid-sparing agent in refractory inflammatory bowel disease and PLE in dogs, reducing corticosteroid requirements and improving clinical outcomes. While cobalamin deficiency is common in chronic enteropathy and should be addressed concurrently, this dog has already been treated for 6 weeks without response, making a watchful waiting approach inappropriate. Switching to a chlorambucil protocol is premature without histologic evidence of clonality (e.g., PARR testing) confirming lymphoma. Total parenteral nutrition is a temporizing measure but does not address the underlying immune-mediated pathology.

Question 113: A ferret presents with episodic weakness, ptyalism, pawing at the mouth, and hypoglycemia (BG 42 mg/dL) that resolves with dextrose. Abdominal ultrasound reveals a 1.2 cm hypoechoic pancreatic nodule. Intraoperative exploration reveals a solitary mass in the left limb of the pancreas with no visible metastasis. Which of the following perioperative management strategies carries the GREATEST risk of iatrogenic harm in this patient?

Performing partial pancreatectomy using the fracture-crush technique with vessel ligation
Monitoring blood glucose every 30 minutes intraoperatively
Initiating a constant rate infusion of 2.5% dextrose in 0.9% NaCl postoperatively
Administering a bolus of 50% dextrose IV immediately before mass removal (Correct answer)

Correct answer: Administering a bolus of 50% dextrose IV immediately before mass removal

Administering a concentrated dextrose bolus (50%) before or during insulinoma surgery is dangerous because it acutely stimulates the tumor to release a massive surge of insulin, potentially precipitating severe rebound hypoglycemia during or immediately after surgery. The correct approach is to maintain euglycemia with a dilute dextrose CRI (e.g., 2.5%) rather than bolus high-concentration dextrose. The fracture-crush technique is an accepted method for ferret pancreatectomy, and frequent glucose monitoring is appropriate and safe.

Question 114: Which MRI finding is characteristic of syringomyelia (syrinx) in a Cavalier King Charles Spaniel with Chiari-like malformation?

Contrast-enhancing ring lesion within the cord
T2 hyperintense fluid-filled cavity within the spinal cord (Correct answer)
T1 hyperintense intramedullary lesion
T2 hypointense lesion in the dorsal columns

Correct answer: T2 hyperintense fluid-filled cavity within the spinal cord

A syrinx appears as a T2 hyperintense (fluid signal) cavity within the spinal cord parenchyma on MRI, reflecting the accumulation of CSF-like fluid.

Question 115: A warmblood dressage horse presents with bilateral hindlimb toe-dragging and a shuffling gait. Neurological examination reveals hindlimb ataxia. The MOST important differential diagnosis to rule out first is:

Bilateral upward fixation of the patella
Bilateral bone spavin
Cervical vertebral stenotic myelopathy (Wobbler syndrome) (Correct answer)
Bilateral proximal suspensory desmitis

Correct answer: Cervical vertebral stenotic myelopathy (Wobbler syndrome)

Cervical vertebral stenotic myelopathy (Wobbler syndrome) causes compressive spinal cord disease manifesting as hindlimb ataxia and toe-dragging and must be differentiated from primary joint lameness.

Question 116: A bearded dragon is presented with a black beard, lethargy, and yellow-white caseous plugs in the intestine on necropsy. The causative agent is:

Entamoeba invadens (Correct answer)
Histomonas meleagridis
Cryptosporidium varanii
Salmonella enterica

Correct answer: Entamoeba invadens

Entamoeba invadens causes severe ulcerative enterocolitis in reptiles, particularly lizards, presenting with caseous intestinal lesions and rapid death.

Question 117: A 7-year-old intact male Labrador Retriever presents with a 3-week history of progressive pelvic limb weakness, fecal tenesmus, and perineal swelling. Rectal palpation reveals a large, doughy mass lateral to the rectum that deviates it medially. Urinalysis shows isosthenuria. Which of the following is the MOST likely cause of the isosthenuria in this patient?

Retroflexion of the urinary bladder into the perineal hernia causing partial urethral obstruction and post-renal azotemia (Correct answer)
Age-related chronic interstitial nephritis as an incidental finding unrelated to the perineal mass
Paraneoplastic syndrome from a perianal adenocarcinoma causing hypercalcemia-induced nephrogenic diabetes insipidus
Concurrent benign prostatic hyperplasia compressing the urethra and leading to hydronephrosis

Correct answer: Retroflexion of the urinary bladder into the perineal hernia causing partial urethral obstruction and post-renal azotemia

Perineal hernias in intact male dogs can lead to retroflexion of the urinary bladder into the hernia sac. When the bladder retroflexes, the urethra becomes kinked or obstructed at an abnormal angle, causing post-renal azotemia and secondary isosthenuria due to medullary washout from the obstructive uropathy. This is a life-threatening complication requiring emergency surgical reduction. Benign prostatic hyperplasia is unlikely to cause hydronephrosis acutely, and perianal adenocarcinomas (rather than adenomas) secrete PTHrP — but the scenario describes a perineal hernia anatomy, not a perianal tumor. The isosthenuria in this context is mechanistically linked to the hernia complication.

Question 118: Which internal parasite of cattle causes 'bottle jaw' (submandibular edema) due to hypoproteinemia?

Cooperia oncophora
Ostertagia ostertagi
Haemonchus placei (Correct answer)
Trichostrongylus axei

Correct answer: Haemonchus placei

Haemonchus placei is a blood-sucking abomasal parasite that causes significant protein loss, leading to hypoproteinemia and the classic sign of submandibular edema (bottle jaw).

Question 119: A 450 kg dairy cow at 10 days postpartum develops acute septic metritis with a fetid red-brown uterine discharge, fever of 40.8°C, and milk drop. Culture yields a pure growth of Trueperella pyogenes. Her BCS at dry-off was 4.0/5.0, and she had a twins delivery. You elect to treat with intrauterine cephapirin. Which additional systemic treatment is MOST pharmacologically justified given the likely concurrent metabolic status of this cow?

Flunixin meglumine IV to reduce endotoxemia and support uterine motility
Propylene glycol oral drench to address subclinical ketosis compounding immunosuppression (Correct answer)
Oxytocin IM to enhance uterine involution and lochia drainage
Dexamethasone IM to suppress the systemic inflammatory cascade

Correct answer: Propylene glycol oral drench to address subclinical ketosis compounding immunosuppression

This cow is at high risk for subclinical or clinical ketosis: she was over-conditioned at dry-off (BCS 4.0/5.0) and carried twins, both major risk factors for negative energy balance postpartum. Ketosis causes significant immunosuppression — neutrophil function is directly impaired by elevated BHBA — which underlies her susceptibility to metritis. Propylene glycol drenching addresses this by serving as a gluconeogenic precursor to restore energy balance and normalize immune function. Flunixin is reasonable for pain and anti-endotoxin effects but does not address the root immunosuppression. Oxytocin has limited efficacy beyond 48 hours post-partum once receptors downregulate. Dexamethasone is contraindicated as it will further suppress immunity.

Question 120: What is the most typical cause of dystocia and egg binding in caged birds?

Obesity
Genetic predisposition
Oviduct damage
Hypocalcemia (Correct answer)

Correct answer: Hypocalcemia

Hypocalcemia is the most common cause of dystocia and egg binding in caged birds, particularly in reproductively active hens. Calcium is crucial for proper uterine muscle contractions during egg laying and for eggshell formation. A deficiency can lead to weak contractions, resulting in the egg becoming stuck in the oviduct (egg binding) and subsequent dystocia.

Question 121: Cytology of a fine-needle aspirate from a splenic mass in a 9-year-old Golden Retriever shows large cells with abundant cytoplasm containing hemosiderin, erythrophagocytosis, and rare mitotic figures with no distinct cell clusters. The most appropriate interpretation is:

Extramedullary hematopoiesis — benign, no treatment needed
Hemangiosarcoma — poorly exfoliating, cytology likely non-diagnostic
Histiocytic sarcoma — aggressive malignancy requiring staging (Correct answer)
Round cell tumor consistent with lymphoma

Correct answer: Histiocytic sarcoma — aggressive malignancy requiring staging

Large pleomorphic cells with erythrophagocytosis and abundant cytoplasm on splenic aspirates are characteristic of histiocytic sarcoma, an aggressive malignancy particularly prevalent in Golden Retrievers and Bernese Mountain Dogs. Hemangiosarcoma is notoriously poorly exfoliating on FNA (blood only usually). Lymphoma shows small-to-large lymphocytes. Extramedullary hematopoiesis lacks pleomorphic large macrophagic cells.

Question 122: A pregnant veterinary technician is assisting with a feline dystocia. The queen, a former stray, expels a large amount of brownish placental fluid. The supervising veterinarian should advise the technician that she is at an increased risk of exposure to which zoonotic agent via aerosolization of these birth fluids?

Bartonella henselae
Microsporum canis
Coxiella burnetii (Correct answer)
Toxoplasma gondii

Correct answer: Coxiella burnetii

*Coxiella burnetii*, the causative agent of Q fever, is shed in extremely high concentrations in the birth products (placenta, amniotic fluid) of infected animals, including cats. Transmission to humans often occurs through the inhalation of infectious aerosols, posing a significant risk to individuals assisting with parturition, especially pregnant women.

Question 123: A 10-year-old female Labrador Retriever presents with a history of panting, pot-bellied appearance, bilateral symmetrical alopecia, and PU/PD. Urine cortisol:creatinine ratio is elevated. Which test best differentiates pituitary-dependent from adrenal-dependent hyperadrenocorticism?

Urine cortisol:creatinine ratio
Low-dose dexamethasone suppression test (LDDST)
ACTH stimulation test
High-dose dexamethasone suppression test (HDDST) (Correct answer)

Correct answer: High-dose dexamethasone suppression test (HDDST)

The HDDST suppresses cortisol by >50% in most pituitary-dependent cases because the tumor retains some feedback sensitivity, while adrenal tumors do not suppress.

Question 124: A beef herd experiences an 'abortion storm' in the last trimester of gestation. Histopathology of several aborted fetal brains reveals multifocal, nonsuppurative necrotizing encephalitis with associated protozoal cysts. What is the most likely etiologic agent?

Neospora caninum (Correct answer)
Leptospira interrogans
Bovine Herpesvirus 1 (IBR)
Brucella abortus

Correct answer: Neospora caninum

Neospora caninum is a leading protozoal cause of abortion in cattle, often occurring in outbreaks during the second and third trimesters. The pathognomonic lesion for neosporosis is multifocal, nonsuppurative necrotizing inflammation in the fetal brain and heart, often with identifiable protozoal cysts. IBR typically causes multifocal hepatic necrosis in the fetus, Leptospirosis causes interstitial nephritis, and Brucellosis causes severe placentitis.

Question 125: Under the Food Safety Modernization Act (FSMA), which rule specifically addresses hazard analysis and preventive controls for human food facilities?

Foreign Supplier Verification Rule
Produce Safety Rule
Sanitary Transportation Rule
Preventive Controls for Human Food Rule (Correct answer)

Correct answer: Preventive Controls for Human Food Rule

The Preventive Controls for Human Food Rule requires food facilities to implement hazard analysis and risk-based preventive controls.

Question 126: On ultrasound, a hypoechoic halo surrounding a hepatic mass in a dog is called:

Target lesion (Correct answer)
Reverberation artifact
Acoustic enhancement
Comet tail artifact

Correct answer: Target lesion

A hypoechoic halo surrounding a mass on ultrasound is referred to as a target or bull's-eye lesion, often associated with metastatic disease.

Question 127: A 3-year-old intact male dog presents with a draining tract near the anus with recurrent abscesses. Probing reveals a communication with the rectum. What is this condition?

Perianal fistula (anal furunculosis) (Correct answer)
Rectal prolapse
Perineal hernia
Anal sac impaction

Correct answer: Perianal fistula (anal furunculosis)

Perianal fistulas (anal furunculosis) are chronic inflammatory tunneling tracts around the anus communicating with the rectum, most commonly seen in German Shepherds.

Question 128: A 2-year-old female Weimaraner presents with recurrent urinary tract infections despite appropriate antibiotic therapy. Vaginal examination reveals a band of tissue at the vestibulovaginal junction. What is the likely diagnosis?

Vestibulovaginal stenosis (vaginal stricture) (Correct answer)
Urethral sphincter mechanism incompetence
Transitional cell carcinoma
Ectopic ureter

Correct answer: Vestibulovaginal stenosis (vaginal stricture)

Vestibulovaginal stenosis creates a pool of urine anterior to the stricture that acts as a reservoir for bacterial colonization, causing recurrent UTIs.

Question 129: A 6-year-old intact male English Bulldog is scheduled for soft palate resection. During inhalant anesthesia with isoflurane, the patient develops a ventricular bigeminy rhythm. Which of the following inhalant agents, if used instead, would have posed the GREATEST risk for sensitizing the myocardium to catecholamine-induced arrhythmias in this patient?

Isoflurane
Halothane (Correct answer)
Sevoflurane
Desflurane

Correct answer: Halothane

Halothane is well-documented to sensitize the myocardium to catecholamine-induced arrhythmias, a property far more pronounced than with modern agents like isoflurane, sevoflurane, or desflurane. This is particularly relevant in brachycephalic patients where hypoxia and hypercapnia can elevate endogenous catecholamines. Halothane's arrhythmogenic potential was a major reason it fell out of favor in veterinary and human anesthesia.

Question 130: A commercial feedlot is experiencing a higher-than-expected prevalence of respiratory disease in newly arrived cattle. Bovine Respiratory Disease Complex (BRDC) risk modeling suggests the cattle are high-risk. The veterinarian is evaluating metaphylaxis protocols. Which of the following statements BEST reflects evidence-based practice regarding metaphylactic antimicrobial selection?

Tulathromycin is preferred because its 14-day tissue half-life provides sustained bacteriostatic activity, eliminating the need for re-treatment in most animals
Enrofloxacin is the most effective metaphylactic agent because fluoroquinolones are concentration-dependent and achieve high lung-to-plasma ratios
Florfenicol should be avoided in metaphylaxis because it selects for multi-drug resistant Mannheimia haemolytica
The antimicrobial selected for metaphylaxis should be a different class from the anticipated treatment antimicrobial to preserve treatment options (Correct answer)

Correct answer: The antimicrobial selected for metaphylaxis should be a different class from the anticipated treatment antimicrobial to preserve treatment options

Evidence-based antimicrobial stewardship in feedlot medicine recommends that the drug class used for metaphylaxis (mass treatment at arrival) should differ from the class reserved for treatment of clinical cases. If the same class is used for both, animals that fail metaphylaxis and develop BRD are then treated with a related drug to which the pathogen may already have reduced susceptibility. Using a different class preserves efficacy at the treatment step. Option A overstates tulathromycin's efficacy — a significant proportion of animals still require re-treatment. Option B is not supported by evidence as a primary reason to avoid florfenicol. Option D is misleading: enrofloxacin (a fluoroquinolone) is a critically important antimicrobial class and its use in metaphylaxis is controversial from a stewardship standpoint, and it is not the most effective choice for this reason.

Question 131: A closed beef herd of 300 Angus cows has had three consecutive years of late-gestation abortions (>7 months), averaging 4.5% abortion rate. Aborted fetuses show autolysis. Paired serology on 15 aborting cows shows no significant titer rise to IBR, BVD, leptospirosis (5-serovar panel), or Neospora caninum. Fetal abomasal content culture is negative. The pastures border a large white-tailed deer population. Which diagnostic step has the HIGHEST probability of identifying the etiology?

Test the herd for bovine viral diarrhea virus (BVDV) persistent infection by antigen ELISA ear notch on all animals
Perform Brucella abortus serology on all cows using card test and ELISA, with culture of placenta on Farrell's medium
Submit soil and water samples from border pastures for Nitrate/nitrite quantification and mycotoxin panel
Submit fresh and formalin-fixed fetal tissues for PCR and histopathology targeting Epizootic Hemorrhagic Disease virus (EHD) and Bluetongue virus (Correct answer)

Correct answer: Submit fresh and formalin-fixed fetal tissues for PCR and histopathology targeting Epizootic Hemorrhagic Disease virus (EHD) and Bluetongue virus

The epidemiologic profile — late-gestation abortions, proximity to white-tailed deer (the primary amplifying host), and negative results for common abortifacients — strongly implicates an Orbivirus. EHD virus (serotypes 1, 2, 6, 7) and Bluetongue virus are transmitted by Culicoides midges, are amplified in deer populations, and can cause late-term abortion, fetal edema, and hemorrhage in cattle — often with autolytic fetuses making serology the only ante-mortem option in the dam. Importantly, EHD is frequently under-diagnosed because standard bovine abortion panels do not routinely include it. PCR on fresh fetal spleen, lung, and brain, combined with histopathology showing fetal vasculitis, would be confirmatory. Brucellosis is a legitimate consideration but would be unusual in a closed, vaccinated herd with no travel history and is mandatorily reportable, making it higher-profile. BVDV-PI cattle cause early losses, not clustering in late gestation.

Question 132: In a dairy herd investigation of reproductive failure, you find a 28% first-service conception rate and multiple cows with endometritis diagnosed via cytology (>18% PMNs at 21–33 days post-partum). Mycoplasma bovigenitalium is cultured from uterine swabs of several affected cows. Which of the following is MOST accurate regarding treatment of this herd?

Prostaglandin F2α administered at diagnosis will resolve mycoplasma endometritis by inducing luteolysis and restoring estrous cyclicity
Intrauterine infusion of oxytetracycline is the treatment of choice because Mycoplasma lacks a cell wall and oxytetracycline penetrates uterine secretions well
Ceftiofur intrauterine infusion is effective because third-generation cephalosporins have broad-spectrum gram-negative coverage including Mycoplasma
Mycoplasma species lack a cell wall and are therefore intrinsically resistant to all beta-lactam antibiotics; systemic fluoroquinolones or tetracyclines are more appropriate, but treatment success is poor (Correct answer)

Correct answer: Mycoplasma species lack a cell wall and are therefore intrinsically resistant to all beta-lactam antibiotics; systemic fluoroquinolones or tetracyclines are more appropriate, but treatment success is poor

Mycoplasma spp. lack a peptidoglycan cell wall, which confers intrinsic resistance to all beta-lactam antibiotics (penicillins, cephalosporins, and carbapenems) regardless of generation or spectrum (rules out A and C). Drugs targeting cell wall synthesis have no activity against cell-wall-free organisms. Tetracyclines and fluoroquinolones have in vitro activity, but clinical treatment success for Mycoplasma genital infections in cattle is notoriously poor, often requiring culling of chronically infected animals and biosecurity measures. Prostaglandin (D) supports uterine clearance in bacterial endometritis but does not address Mycoplasma specifically and is not curative.

Question 133: A 3-year-old indoor cat presents with pleural effusion, hyperglobulinemia (total protein 10.2 g/dL), and a pleural fluid albumin-to-globulin ratio of 0.3. FIP coronavirus PCR on the effusion is positive. Which additional finding would MOST strongly support effusive FIP over other causes of pleural effusion?

Serum alpha-1 acid glycoprotein (AGP) >1,500 µg/mL (Correct answer)
Rivalta test positive on the effusion with protein >3.5 g/dL and cell count <5,000 cells/µL
Pleural fluid neutrophilia >85% with a degenerate left shift
Positive FCoV antibody titer >1:3200 on serum ELISA

Correct answer: Serum alpha-1 acid glycoprotein (AGP) >1,500 µg/mL

Serum alpha-1 acid glycoprotein (AGP) >1,500 µg/mL has high sensitivity and specificity for FIP in cats with compatible clinical signs. While the Rivalta test is supportive of FIP-type effusion, it is not specific enough alone. High FCoV titers indicate exposure but not necessarily FIP (many healthy cats have high titers). Neutrophilic effusion with degenerate shift suggests bacterial pyothorax. AGP is an acute-phase protein markedly elevated in FIP and serves as one of the most diagnostically useful adjunct markers.

Question 134: A green iguana presents with dysecdysis (retained shed). What is the safest and most appropriate initial treatment?

Soaking in warm water for 15–30 minutes (Correct answer)
Applying petroleum-based lubricants
Administering systemic corticosteroids
Forcibly removing the retained shed manually

Correct answer: Soaking in warm water for 15–30 minutes

Warm water soaks hydrate and soften retained shed safely, making it the recommended first-line intervention for dysecdysis.

Question 135: A ventrodorsal thoracic radiograph of a 4-year-old Maine Coon cat shows a 'reverse D' or 'D-shaped' cardiac silhouette with straightening of the right heart border, tracheal deviation to the left, and post-stenotic dilation of the main pulmonary artery. Echocardiography confirms pulmonic stenosis. Which radiographic measurement, if applied, would MOST accurately quantify cardiac enlargement in this cat?

Cardiothoracic ratio on the VD view
Vertebral Heart Score (VHS) using lateral projection (Correct answer)
Right heart-to-thoracic ratio on the VD view
Vertebral Left Atrial Score (VLAS) on lateral projection

Correct answer: Vertebral Heart Score (VHS) using lateral projection

The Vertebral Heart Score (VHS), measured on the lateral projection, is the validated, species-specific method for quantifying cardiac enlargement in cats (normal ≤ 8.0 vertebrae). It accounts for thoracic conformation variability and is the standard reference used in feline cardiology publications. The cardiothoracic ratio is unreliable in cats due to their narrow, deep thorax. VLAS specifically quantifies left atrial size and is used for HOCM monitoring — not right-sided disease. A right heart-to-thoracic ratio is not a validated feline-specific metric. In pulmonic stenosis, the VHS captures the overall right heart enlargement on the lateral view.

Question 136: You are evaluating thoracic radiographs of an older cat with a history of a previously removed mammary carcinoma. The lung fields show multiple, well-defined, variably sized nodules of soft tissue opacity. Which of the following is the most likely interpretation of this pulmonary pattern?

Fungal pneumonia
Metastatic neoplasia (Correct answer)
Cardiogenic pulmonary edema
Allergic bronchitis (asthma)

Correct answer: Metastatic neoplasia

The presence of multiple, well-defined, soft tissue nodules (often called a 'cannonball' pattern, though they can be small) throughout the lung fields is the classic radiographic appearance of hematogenous metastatic neoplasia. Fungal pneumonia can also be nodular but is often less defined. Feline asthma typically presents with a bronchial pattern ('donuts' and 'tram lines'). Cardiogenic edema usually appears as an unstructured interstitial to alveolar pattern, often with a patchy distribution.

Question 137: Which fungal organism causes 'yellow fungus disease' (invasive necrotizing mycosis) in bearded dragons?

Nannizziopsis guarroi (Correct answer)
Aspergillus fumigatus
Fusarium solani
Candida albicans

Correct answer: Nannizziopsis guarroi

Nannizziopsis guarroi causes yellow fungus disease in bearded dragons, producing invasive, necrotizing cutaneous lesions that are often fatal.

Question 138: A beef producer asks about strategies to reduce the use of medically important antimicrobials in the feedlot. Which intervention is the best alternative for reducing bovine respiratory disease (BRD) morbidity?

Eliminating all antibiotic use and relying on supportive care only
Increasing the dose of antibiotics to prevent resistance
Switching from injectable to in-feed antibiotics exclusively
Implementing metaphylaxis only for high-risk cattle combined with optimization of vaccination protocols (Correct answer)

Correct answer: Implementing metaphylaxis only for high-risk cattle combined with optimization of vaccination protocols

Targeted metaphylaxis in high-risk cattle combined with robust vaccination programs reduces BRD morbidity while minimizing overall antibiotic use, consistent with antimicrobial stewardship principles.

Question 139: During a herd health visit to a 600-cow commercial beef operation, you identify a 4% prevalence of footrot (Fusobacterium necrophorum / Trueperella pyogenes) over the past 60 days despite routine zinc sulfate footbathing. Environmental assessment reveals persistently saturated soil near the water tanks. The producer asks about strategic use of long-acting oxytetracycline (LA-OTC) as a herd-level preventive. Under which circumstance is this practice MOST appropriately justified?

As a twice-weekly injection program in feedlot pens exhibiting greater than 2% monthly footrot incidence
As a permanent substitute for footbathing in herds where compliance with bath maintenance is consistently poor
As a once-monthly mass medication of the entire herd regardless of environmental conditions to maintain subclinical suppression of Fusobacterium
As a targeted 3–5 day pulse administered to at-risk groups when known high-risk periods (e.g., prolonged wet season) cannot be mitigated environmentally (Correct answer)

Correct answer: As a targeted 3–5 day pulse administered to at-risk groups when known high-risk periods (e.g., prolonged wet season) cannot be mitigated environmentally

Strategic pulse use of LA-OTC during defined high-risk periods—when wet, muddy conditions cannot be corrected—is the most defensible application of antimicrobial prevention for footrot. It limits antimicrobial use to temporally justified windows, reducing selection pressure. Mass medication as a routine monthly program regardless of risk violates antimicrobial stewardship principles. Replacing footbathing entirely with antimicrobials is not appropriate because environmental management is the cornerstone of prevention. Twice-weekly injections represent inappropriate use frequency and dosing regimen for preventive purposes and are inconsistent with any approved label indication.

Question 140: A 10-year-old Miniature Schnauzer with a history of hyperlipidemia presents with acute onset of vomiting, anorexia, and cranial abdominal pain. Physical examination reveals a 'praying posture.' Laboratory findings include neutrophilia, elevated amylase, and markedly elevated lipase. Which of the following is the most appropriate initial treatment?

High-fat, high-protein diet to stimulate appetite
Aggressive intravenous fluid therapy, analgesia, and antiemetics (Correct answer)
Immediate exploratory laparotomy
Broad-spectrum antibiotics and oral corticosteroids

Correct answer: Aggressive intravenous fluid therapy, analgesia, and antiemetics

The signalment, history, and clinical signs are classic for acute pancreatitis. The cornerstone of treatment is supportive care, which includes aggressive intravenous fluid therapy to correct dehydration and maintain pancreatic perfusion, potent analgesia to manage pain, and antiemetics to control vomiting. A low-fat diet is indicated once the patient can tolerate oral intake, and surgery is not typically the first-line treatment unless complications like an abscess or obstruction are present.

Question 141: During a routine examination of a sulcata tortoise (Centrochelys sulcata), you identify a soft-tissue swelling of the left ear region. Fine-needle aspirate reveals keratinaceous laminated debris with no organisms on Gram stain. What is the MOST appropriate next step in management?

Perform surgical debridement via aural abscess removal with curettage of the caseous plug and tympanic cavity (Correct answer)
Lance and flush the abscess under sedation using dilute chlorhexidine, followed by topical antibiotic ointment
Initiate itraconazole therapy for fungal otitis and recheck in 4 weeks
Initiate systemic fluoroquinolone therapy for 6 weeks targeting Pseudomonas aeruginosa

Correct answer: Perform surgical debridement via aural abscess removal with curettage of the caseous plug and tympanic cavity

Reptilian aural abscesses (middle ear disease) contain solid, caseous pus that cannot be flushed due to its cheese-like consistency — unlike mammalian liquid pus. The laminated keratinaceous material is characteristic of reptilian abscess contents. Management requires surgical removal of the entire caseous mass, curettage of the tympanic membrane and middle ear cavity, and often partial or complete tympanectomy. Simply lancing and flushing is ineffective and will result in recurrence. Post-surgical culture guides antibiotic selection, but systemic antibiotics alone without surgery are also insufficient. Empiric fluoroquinolone or beta-lactam coverage is typically initiated post-surgically.

Question 142: Which ultrasound finding is most specific for portal hypertension in a dog?

Acquired portosystemic shunting vessels (Correct answer)
Hepatic parenchymal hypoechogenicity
Decreased portal vein diameter
Decreased hepatic artery Doppler flow

Correct answer: Acquired portosystemic shunting vessels

Acquired portosystemic collateral vessels (multiple tortuous vessels in the region of the left kidney or spleen) are the most specific ultrasound sign of portal hypertension.

Question 143: A horse is diagnosed with suspensory ligament desmitis in the proximal metacarpal region. Which diagnostic imaging modality provides the BEST detail of proximal suspensory pathology in this region?

Nuclear scintigraphy
Ultrasonography (Correct answer)
Radiography
Thermography

Correct answer: Ultrasonography

Ultrasonography is the modality of choice for soft tissue structures like the proximal suspensory ligament, providing real-time imaging of fiber pattern disruption, core lesions, and enthesopathy.

Question 144: A 10-year-old Warmblood shows grade 3/5 forelimb lameness that worsens on the lunge circle with the affected limb on the inside. Lameness is abolished by an abaxial sesamoid nerve block. The NEXT most appropriate diagnostic step is:

Radiographs of the pastern
MRI of the foot
Intra-articular anesthesia of the fetlock joint (Correct answer)
Low 4-point nerve block

Correct answer: Intra-articular anesthesia of the fetlock joint

After an abaxial sesamoid block confirms pain distal to the fetlock, intra-articular anesthesia of the fetlock joint helps differentiate fetlock joint pathology from other sources in that region.

Question 145: A 10-year-old cat dies of renal failure. Necropsy shows bilaterally small, pale, irregularly pitted kidneys. Histology reveals tubular atrophy, interstitial fibrosis, glomerulosclerosis, and lymphoplasmacytic interstitial infiltrate. The most accurate pathologic diagnosis is:

Feline infectious peritonitis (FIP) pyogranulomatous nephritis
Chronic tubulointerstitial nephritis (end-stage kidney disease) (Correct answer)
Acute tubular necrosis secondary to nephrotoxin
Renal lymphoma with parenchymal replacement

Correct answer: Chronic tubulointerstitial nephritis (end-stage kidney disease)

Chronic tubulointerstitial nephritis is the most common cause of chronic kidney disease (CKD) in cats. The classic gross appearance is bilaterally symmetrical small, pale, granular kidneys. Histologically the hallmark is tubular atrophy, interstitial fibrosis, and lymphoplasmacytic infiltrate — representing end-stage scarring. Acute tubular necrosis shows tubular swelling and necrosis without fibrosis. FIP nephritis is pyogranulomatous with vasculitis.

Question 146: During fluoroscopic evaluation of a 9-month-old Labrador Retriever with regurgitation, barium swallow demonstrates a persistent filling defect in the dorsal esophagus at the level of the heart base that does not change shape with peristalsis. A 'reversed 3 sign' or 'E sign' is noted on the aortic knob region. What is the most likely diagnosis?

Esophageal foreign body at the thoracic inlet
Persistent right aortic arch (PRAA) with secondary megaesophagus (Correct answer)
Aberrant left subclavian artery causing extrinsic esophageal compression
Esophageal leiomyoma at the gastroesophageal junction

Correct answer: Persistent right aortic arch (PRAA) with secondary megaesophagus

The classic radiographic and fluoroscopic presentation of persistent right aortic arch (PRAA) in a young large-breed dog includes: cranial esophageal dilation (megaesophagus cranial to the heart base), a persistent filling defect at the level of the heart base that does not peristalse away, and — on plain radiographs or fluoroscopy — a 'reversed 3 sign' or 'E sign' on the left lateral view, reflecting the anomalous aortic arch indenting the esophagus. PRAA is the most common vascular ring anomaly in dogs. Aberrant left subclavian artery causes a more caudal/lateral compression and lacks the classic reversed-3 sign. The location (heart base, not thoracic inlet) excludes foreign body.

Question 147: In nuclear scintigraphy used in veterinary medicine, which radiopharmaceutical is most commonly used for bone scanning in dogs?

Gallium-67 citrate
Technetium-99m pertechnetate
Technetium-99m methylene diphosphonate (MDP) (Correct answer)
Iodine-131

Correct answer: Technetium-99m methylene diphosphonate (MDP)

Tc-99m MDP (methylene diphosphonate) accumulates in areas of active bone remodeling and is the standard radiopharmaceutical for skeletal scintigraphy in small animals.

Question 148: A 4-year-old blue-fronted Amazon parrot presents with progressive feather destructive behavior, intermittent regurgitation, and a 3-week history of weight loss. Endoscopy reveals thickened proventricular mucosa with dilated ventricular outflow. PCR of a crop biopsy returns positive for Avian Bornavirus (ABV). Which pathological mechanism best explains the neurological component of this disease?

Immune-mediated destruction of enteric neurons via CD8+ T-cell infiltration of ganglia (Correct answer)
Vascular occlusion of the celiac artery causing ischemic neuropathy of the proventriculus
Direct cytopathic destruction of enteric neurons in the myenteric and submucosal plexuses
ABV-encoded protease directly cleaving neurofilament proteins in vagal efferent fibers

Correct answer: Immune-mediated destruction of enteric neurons via CD8+ T-cell infiltration of ganglia

Proventricular Dilatation Disease (PDD) caused by Avian Bornavirus is characterized by a T-cell-mediated (predominantly CD8+) lymphoplasmacytic infiltration of enteric ganglia. The virus itself is relatively non-cytopathic; the immune response against infected neurons destroys the myenteric and submucosal plexuses, leading to dysmotility, dilatation, and malabsorption. This immune-mediated mechanism is why immunosuppressive therapy (e.g., meloxicam/COX-2 inhibition, corticosteroids in some protocols) can improve clinical signs without eliminating the virus.

Question 149: A veterinary public health officer receives a report of a ranch hand who developed cutaneous anthrax after handling a cow carcass. Soil samples from the pasture confirm Bacillus anthracis spores at 4 × 10⁴ CFU/gram at depths up to 15 cm. Which regulatory authority and specific action is the MOST appropriate immediate response under U.S. law?

Notify USDA-APHIS and state animal health officials; impose a state-level quarantine, vaccinate remaining animals with Sterne strain vaccine, and safely dispose of the carcass by deep burial or incineration on-site (Correct answer)
Notify CDC and initiate a select-agent registration audit of the farm under 42 CFR Part 73
Notify USDA-APHIS and condemn the herd under the Animal Health Protection Act; request EPA Superfund designation for soil remediation
Notify OSHA under 29 CFR 1910.1030 (bloodborne pathogens standard) and require the ranch to implement an exposure control plan

Correct answer: Notify USDA-APHIS and state animal health officials; impose a state-level quarantine, vaccinate remaining animals with Sterne strain vaccine, and safely dispose of the carcass by deep burial or incineration on-site

Anthrax is a state-regulated foreign animal disease reportable condition in most U.S. states. The immediate veterinary public health response involves notifying USDA-APHIS and state animal health officials, imposing quarantine to prevent movement of potentially exposed animals, vaccinating the surviving herd with the licensed Sterne 34F2 strain (the only USDA-licensed veterinary anthrax vaccine), and disposing of the carcass by on-site deep burial (≥6 feet with lime) or incineration — never necropsy or movement off-site, as opening the carcass sporulates the organism. EPA Superfund is not applicable here; CDC select-agent regulations apply to laboratories, not farms with natural anthrax; OSHA bloodborne pathogens standard does not cover B. anthracis (a Category A bioterrorism agent covered separately).

Question 150: A 6-year-old Maine Coon cat presents in acute respiratory distress. Physical exam reveals a heart murmur, gallop rhythm, and crackles on lung auscultation. A thoracic radiograph shows cardiomegaly and pulmonary edema. Echocardiography confirms hypertrophic cardiomyopathy (HCM). In addition to oxygen therapy, which medication is most critical for initial stabilization of this cat's congestive heart failure?

Benazepril
Atenolol
Furosemide (Correct answer)
Clopidogrel

Correct answer: Furosemide

Furosemide, a potent loop diuretic, is the most critical initial medication for a cat in congestive heart failure (CHF) secondary to HCM. Its primary function is to reduce fluid volume by promoting urination, which alleviates pulmonary edema and relieves respiratory distress. Clopidogrel is an anti-platelet drug used to prevent aortic thromboembolism but does not treat CHF. Atenolol (a beta-blocker) and benazepril (an ACE inhibitor) may be used for long-term management but are not the first-line emergency drugs for reducing pulmonary edema.

Question 151: A shelter veterinarian is investigating a cluster of deaths in kittens 6–10 weeks old. Affected kittens show sudden onset of vomiting, hemorrhagic diarrhea, marked leukopenia (WBC 800/µL), and high mortality within 24–48 hours despite supportive care. Serology and PCR confirm feline panleukopenia virus (FPV). A litter of 4-week-old kittens born in the shelter to an unvaccinated queen survived without illness. Which explanation BEST accounts for the age-dependent mortality pattern?

Neonatal kittens produce higher levels of type I interferons that suppress viral replication before clinical disease
Maternal antibodies are insufficient in neonates because FPV is a non-enveloped virus that resists passive transfer
FPV preferentially targets bone marrow erythroid precursors in neonates, causing anemia rather than leukopenia
Neonates lack the mature rapidly dividing intestinal crypt cells that serve as the primary FPV replication target (Correct answer)

Correct answer: Neonates lack the mature rapidly dividing intestinal crypt cells that serve as the primary FPV replication target

FPV (a parvovirus) requires rapidly dividing cells for replication. In neonates under 4 weeks, intestinal crypt epithelium is not yet mature/rapidly dividing, so the GI tract is largely spared. Instead, FPV in neonates and fetuses targets the cerebellum (Purkinje cells during cerebellar development), causing cerebellar hypoplasia. Kittens 6–10 weeks have highly mitotically active intestinal crypts and rapidly dividing bone marrow progenitors — making them maximally susceptible. Maternal antibodies DO transfer effectively via colostrum (IgG passes via Fc receptors), but if the queen is unvaccinated, no protection is conferred.

Question 152: A 6-year-old male Dachshund presents acutely with inability to walk in the hind limbs and deep pain perception is absent bilaterally. MRI confirms a thoracolumbar Hansen type I disc extrusion at T13-L1. What is the most critical prognostic indicator?

Degree of spinal cord swelling on MRI
Duration of clinical signs before surgery
Body weight of the patient
Presence or absence of deep pain perception (Correct answer)

Correct answer: Presence or absence of deep pain perception

Presence or absence of deep pain perception is the single most important prognostic factor; dogs with intact deep pain have >90% recovery rates while those without have significantly lower rates.

Question 153: A 900-cow Holstein dairy herd participates in a reproductive program using GnRH-based synchronization (Ovsynch). Despite high estrus synchronization compliance, 21-day pregnancy rates have plateaued at 18%. Detailed records show: AI submission rate 92%, conception rate (CR) 21%, pregnancy loss 12% (day 28–56). The reproductive specialist suspects subclinical endometritis. Which diagnostic criterion BEST defines subclinical endometritis in lactating dairy cows, and what is the recommended threshold for treatment intervention in this herd?

Rectal palpation detecting a uterus >10 cm diameter at 28 days postpartum; treat with PGF2α to induce luteolysis
Vaginoscopy revealing mucopurulent discharge (Metricheck score ≥2) at any point in the first 60 days in milk; treat with systemic ceftiofur at 35 DIM
Uterine cytology showing ≥8% PMNs (≥35–47 days postpartum) or ≥18% PMNs (≥20–33 days postpartum); treat cows above threshold with intrauterine cefapirin (Correct answer)
Uterine cytology showing ≥5% polymorphonuclear neutrophils (PMNs) at 21–33 days postpartum; treat all cows exceeding this threshold with intrauterine cefapirin

Correct answer: Uterine cytology showing ≥8% PMNs (≥35–47 days postpartum) or ≥18% PMNs (≥20–33 days postpartum); treat cows above threshold with intrauterine cefapirin

Subclinical endometritis (SCE) is definitively diagnosed by uterine cytology (cytobrush or lavage) rather than visual discharge scoring. The validated thresholds differ by postpartum timing: ≥18% PMNs at 20–33 DIM and ≥8% PMNs at 34–47 DIM, reflecting the physiological decline in uterine PMNs as the postpartum period progresses. Intrauterine cefapirin (a first-generation cephalosporin with broad uterine penetration and no systemic withdrawal concerns) is the most evidence-supported treatment for SCE. Vaginoscopy and Metricheck detect clinical endometritis/metritis but miss subclinical disease by definition. Systemic ceftiofur is used for acute puerperal metritis, not SCE. Uterine diameter by palpation does not reliably diagnose SCE.

Question 154: Osteochondrosis dissecans (OCD) in horses most commonly affects which joint when presenting as tarsal lameness in young Thoroughbreds?

Distal intertarsal joint
Tarsometatarsal joint
Proximal interphalangeal (pastern) joint
Tarsocrural (tibiotarsal) joint (Correct answer)

Correct answer: Tarsocrural (tibiotarsal) joint

OCD most commonly affects the tarsocrural joint in horses, particularly the distal intermediate ridge of the tibia and the lateral trochlear ridge of the talus.

Question 155: A dog presents with a rapidly growing subcutaneous mass on the trunk. Fine needle aspirate shows granules that stain metachromatically with toluidine blue. What is the diagnosis and recommended initial treatment?

Sebaceous adenoma; CO2 laser ablation
Mast cell tumor; wide surgical excision with 2-3 cm margins (Correct answer)
Lipoma; surgical excision with narrow margins
Histiocytoma; conservative management as spontaneous regression occurs

Correct answer: Mast cell tumor; wide surgical excision with 2-3 cm margins

Mast cell tumors contain metachromatic granules and require wide surgical margins of 2-3 cm laterally and one fascial plane deep to reduce local recurrence.

Question 156: A dairy herd is diagnosed with Brucella abortus. Which federal program mandates testing and slaughter of reactor animals in the US?

Voluntary Johne's Disease Herd Status Program
Brucellosis Eradication Program (Correct answer)
National Poultry Improvement Plan
National Animal Health Monitoring System

Correct answer: Brucellosis Eradication Program

The USDA Brucellosis Eradication Program requires identification, testing, and depopulation of Brucella-positive herds.

Question 157: A 12-year-old cat with known hyperthyroidism controlled on methimazole develops acute azotemia (creatinine 3.8 mg/dL, BUN 58 mg/dL) after 3 weeks of therapy. Pre-treatment creatinine was 1.1 mg/dL. Which pathophysiologic explanation is most accurate?

Unmasking of pre-existing chronic kidney disease as GFR normalizes with euthyroid state (Correct answer)
Direct tubular toxicity from methimazole metabolites accumulating in renal cortex
Hypertensive nephrosclerosis worsening as cardiac output drops with treatment
Methimazole-induced immune-mediated glomerulonephritis

Correct answer: Unmasking of pre-existing chronic kidney disease as GFR normalizes with euthyroid state

Hyperthyroidism increases cardiac output and causes hyperfiltration, artificially elevating GFR and suppressing serum creatinine. When hyperthyroidism is treated and GFR normalizes, underlying CKD that was masked by the hyperfiltration state becomes apparent. This 'unmasking' phenomenon is well-documented in feline medicine and is why pre-treatment renal biomarkers can be misleadingly normal. The pre-treatment creatinine of 1.1 mg/dL was falsely low due to increased GFR, not because the kidneys were truly healthy.

Question 158: A veterinary technician performing a loco-regional block for feline dental extractions inadvertently injects bupivacaine 0.5% at a total dose of 4 mg/kg. Within 10 minutes the cat develops ventricular tachycardia refractory to lidocaine administration. Which treatment is MOST likely to restore sinus rhythm?

IV bretylium tosylate 5 mg/kg as an alternative antiarrhythmic
IV lipid emulsion (20%) 1.5 mL/kg bolus followed by a CRI (Correct answer)
IV sodium bicarbonate 1 mEq/kg to alkalinize plasma and displace bupivacaine from sodium channels
Immediate cardioversion with 2 J/kg biphasic defibrillation

Correct answer: IV lipid emulsion (20%) 1.5 mL/kg bolus followed by a CRI

Bupivacaine systemic toxicity produces cardiotoxicity that is notoriously refractory to standard antiarrhythmics and resuscitation because the drug avidly binds cardiac sodium channels. Intravenous lipid emulsion (ILE) therapy ('lipid rescue') works by creating a lipid sink that sequesters the highly lipophilic bupivacaine away from cardiac tissue, rapidly reducing free plasma concentrations. The protocol is 1.5 mL/kg of 20% lipid emulsion IV bolus, followed by a CRI of 0.25 mL/kg/min for 10–60 minutes. Sodium bicarbonate helps with lidocaine toxicity and can transiently help sodium-channel blockade but is not the primary rescue therapy for bupivacaine cardiac arrest. Bretylium is no longer commercially available in North America. Electrical cardioversion does not address the pharmacologic cause and is unlikely to maintain sinus rhythm while bupivacaine is still bound to channels.

Question 159: Which statement correctly describes the feline estrous cycle?

Queens are spontaneous ovulators with a 21-day cycle similar to dogs
Queens are seasonally polyestrous induced ovulators with luteal phase length of 2–3 weeks after infertile mating
Queens ovulate spontaneously mid-estrus and develop a functional CL regardless of mating
Queens are induced ovulators; without mating or coital stimulation, they undergo repeated estrous cycles during the breeding season (Correct answer)

Correct answer: Queens are induced ovulators; without mating or coital stimulation, they undergo repeated estrous cycles during the breeding season

Cats are seasonally polyestrous (long-day breeders) and induced ovulators — ovulation requires coital stimulation of the vagina/cervix causing a neuroendocrine GnRH surge. Without mating, queens cycle repeatedly through estrus (lasting 4–7 days) and interestrus periods throughout the breeding season without forming a CL. If mating occurs but does not result in pregnancy, a pseudopregnancy of ~35–40 days follows.

Question 160: A 3-year-old Quarter Horse mare is given detomidine (20 µg/kg IV) and butorphanol (0.02 mg/kg IV) for standing sedation during a laceration repair. Thirty minutes later the mare becomes ataxic and recumbent. The veterinarian decides to partially reverse the sedation. Which reversal strategy is MOST pharmacologically precise?

Administer yohimbine IV to fully reverse both detomidine and butorphanol
Administer atipamezole IV to selectively reverse detomidine, accepting residual opioid sedation (Correct answer)
Administer naloxone IV only, as opioid reversal will restore enough arousal without alpha-2 reversal
Administer atipamezole IV to reverse detomidine, and naloxone IV to reverse butorphanol

Correct answer: Administer atipamezole IV to selectively reverse detomidine, accepting residual opioid sedation

Atipamezole is a highly selective alpha-2 adrenergic antagonist with high affinity for alpha-2 receptors, making it the most appropriate reversal agent for detomidine. Administering atipamezole alone allows partial reversal — removing the more profound alpha-2 component (responsible for most of the sedation and ataxia in horses) while leaving mild butorphanol analgesia intact, which is beneficial for a painful laceration repair. Full reversal with naloxone would eliminate analgesia. Yohimbine is a less selective alpha-2 antagonist (it also blocks alpha-1 receptors) with a lower therapeutic index in horses and is not the preferred reversal agent. Atipamezole is licensed for small animals but used off-label in horses; medetomidine and atipamezole are better-matched pairs, though atipamezole still reverses detomidine effectively.

Question 161: During exploratory laparotomy on a 4-year-old Border Collie for suspected intestinal foreign body, you discover a 6 cm segment of jejunum that is dark purple-black, lacks peristalsis, and does not bleed when cut. The mesenteric vessels to this segment appear grossly intact. You resect the segment. Intraoperatively, which suture pattern for the jejunojejunostomy anastomosis has been shown to produce the LEAST luminal narrowing in small-diameter bowel?

Single-layer simple interrupted appositional pattern (Correct answer)
Two-layer inverting pattern using Cushing followed by Lembert
Single-layer inverting Connell pattern
Single-layer continuous Gambee pattern

Correct answer: Single-layer simple interrupted appositional pattern

Single-layer simple interrupted appositional (end-to-end) anastomosis produces the least luminal narrowing because it avoids the inversion of tissue that inherently reduces the anastomotic diameter. Two-layer inverting patterns and continuous inverting patterns (Connell) reduce lumen diameter by folding tissue inward, which is particularly problematic in the small-bore jejunum of dogs. The Gambee pattern is a modified appositional pattern that also reduces inversion, but simple interrupted appositional remains the gold standard for minimizing stricture in veterinary small intestinal surgery. Healing strength and leak rates are comparable or superior for single-layer appositional techniques.

Question 162: A horse has progressive weight-bearing lameness and perineural anesthesia of the ulnar and median nerves abolishes the lameness. Which region is MOST likely the source of pain?

Elbow joint
Carpus and distal forelimb (Correct answer)
Fetlock joint
Foot and pastern region

Correct answer: Carpus and distal forelimb

Median and ulnar nerve blocks desensitize the carpal region and distal limb below the elbow, so abolition of lameness localizes pain to the carpus or below.

Question 163: A 6-month-old intact male puppy presents with bilateral cryptorchidism confirmed on exam. What is the recommended course of action?

Wait until 18 months and recheck
Testosterone supplementation to encourage descent
Castration including removal of both undescended testes (Correct answer)
Removal of scrotal testes only

Correct answer: Castration including removal of both undescended testes

Both retained and scrotal testes must be removed because cryptorchid testes carry a significantly higher risk of Sertoli cell tumor and seminoma, and the condition is heritable.

Question 164: Which opioid analgesic is classified as a partial mu-opioid receptor agonist and exhibits a ceiling effect for analgesia at higher doses?

Buprenorphine (Correct answer)
Fentanyl
Morphine
Hydromorphone

Correct answer: Buprenorphine

Buprenorphine is a partial mu-opioid agonist with very high receptor affinity; because it is a partial agonist, increasing the dose beyond a threshold does not produce proportionally greater analgesia, resulting in a ceiling effect.

Question 165: On thoracic radiographs of a cat, you identify a soft tissue opacity causing ventral displacement of the trachea at the thoracic inlet and dorsal displacement of the thoracic esophagus. The opacity silhouettes with the cranial cardiac border. Which structure most likely accounts for this pattern?

Cranial mediastinal cyst
Branchial arch remnant
Thymic lymphoma (Correct answer)
Ectopic thyroid carcinoma

Correct answer: Thymic lymphoma

In cats, cranial mediastinal masses that ventral-displace the trachea and dorsal-displace the esophagus while silhouetting with the cranial cardiac silhouette are classically thymic lymphoma. This is the most common cranial mediastinal mass in cats and frequently causes pleural effusion. Ectopic thyroid carcinoma is much rarer and tends to be more cranially positioned at the thoracic inlet. Cranial mediastinal cysts are uncommon and typically incidental; they would not show the described displacement pattern to the same degree. Branchial arch remnants are cervical, not thoracic.

Question 166: A dairy herd has a high prevalence of digital dermatitis (Mortellaro's disease). Which treatment is most effective for active, painful lesions?

Hoof trimming and copper sulfate footbath only
Systemic oxytetracycline injection
Surgical debridement under general anesthesia
Topical oxytetracycline applied to the lesion and wrapped with a bandage (Correct answer)

Correct answer: Topical oxytetracycline applied to the lesion and wrapped with a bandage

Topical oxytetracycline or lincomycin applied directly to digital dermatitis lesions after cleaning and drying, covered with a bandage, achieves the highest cure rates for active M2 lesions.

Question 167: Which reportable disease of cattle causes vesicular lesions on the tongue, feet, and teats, and must be immediately reported to state and federal authorities if suspected?

Infectious Bovine Rhinotracheitis (IBR)
Foot-and-Mouth Disease (FMD) (Correct answer)
Bovine papular stomatitis
Vesicular stomatitis virus (VSV) infection

Correct answer: Foot-and-Mouth Disease (FMD)

Foot-and-Mouth Disease is a foreign animal disease (FAD) and federally reportable emergency; any suspected case must be immediately reported to USDA APHIS and state veterinary officials due to its catastrophic trade and production consequences.

Question 168: A 5-year-old male Dalmatian presents with recurrent urinary tract infections and struvite uroliths. Urate crystals are also identified on urinalysis. Which metabolic defect predisposes Dalmatians to urate urolithiasis?

Impaired renal tubular secretion of allantoin
Deficiency of uricase enzyme
Reduced hepatic conversion of uric acid to allantoin (Correct answer)
Increased xanthine oxidase activity

Correct answer: Reduced hepatic conversion of uric acid to allantoin

Dalmatians have impaired hepatic conversion of uric acid to allantoin and reduced renal tubular reabsorption of urate, leading to uric acid excretion and urate uroliths.

Question 169: Ovine Progressive Pneumonia (OPP) caused by Maedi-Visna virus is best controlled in a flock through which strategy?

Parenteral ivermectin to eliminate the arthropod vector
Prophylactic long-term tetracycline administration in feed
Annual vaccination with killed-virus OPP vaccine
Test-and-cull seropositive animals combined with separating lambs from seropositive ewes at birth (Correct answer)

Correct answer: Test-and-cull seropositive animals combined with separating lambs from seropositive ewes at birth

Maedi-Visna/OPP is a lentiviral infection with no vaccine or cure. Control relies on identifying seropositive animals via AGID or ELISA and removing them, combined with preventing transmission to lambs via infected colostrum/milk by separating and heat-treating or discarding colostrum. There is no arthropod vector; it is spread by close contact and milk.

Question 170: During a routine equine breeding soundness evaluation (BSE) in a 4-year-old Thoroughbred stallion, semen evaluation reveals: total motility 65%, progressive motility 45%, morphology 55% normal sperm. Per AAEP guidelines, how should this stallion be classified?

Questionable potential breeder (Correct answer)
Satisfactory potential breeder
Unsatisfactory potential breeder
Deferred — repeat evaluation in 30 days

Correct answer: Questionable potential breeder

AAEP minimum standards for a satisfactory equine BSE are: total motility ≥60%, progressive motility ≥60%, normal morphology ≥60%. This stallion fails progressive motility (45% vs. ≥60% required) and morphology (55% vs. ≥60% required), placing him in the 'questionable' category — not outright unsatisfactory, which requires multiple parameters clearly below threshold.

Question 171: The following types of inflammation are typically linked to FIP:

Pyogranulonatous (Correct answer)
Purulent
No inflammation associated
Serous

Correct answer: Pyogranulonatous

Feline Infectious Peritonitis (FIP) is characterized by a distinctive inflammatory response known as pyogranulomatous inflammation. This type of inflammation involves a mixture of neutrophils and macrophages, leading to the formation of characteristic lesions in various organs, especially in the 'wet' form with effusions and in the 'dry' form with granulomas.

Question 172: A 320-cow spring-calving beef herd experiences a 22% calf scours rate in calves aged 3–10 days, with 6 deaths. ELISA fecal antigen testing of 12 affected calves yields: Cryptosporidium parvum positive in 10/12, rotavirus positive in 5/12, and coronavirus positive in 2/12. Bulk colostrum Brix refractometer readings average 18%. Which management interpretation is MOST accurate?

Rotavirus is the index pathogen because its prevalence exceeds coronavirus; vaccination targeting rotavirus alone would control this outbreak
The colostrum quality is inadequate; failure of passive transfer (FPT) is the primary predisposing cause, and the dominant pathogen profile reflects FPT-associated opportunistic infections
Cryptosporidium parvum is a secondary opportunist; the 10/12 prevalence reflects co-infection only and does not warrant targeted anti-cryptosporidial treatment
Colostrum quality is acceptable; the outbreak is driven by environmental pathogen pressure from a calving area that has exceeded its safe carrying capacity (Correct answer)

Correct answer: Colostrum quality is acceptable; the outbreak is driven by environmental pathogen pressure from a calving area that has exceeded its safe carrying capacity

A Brix reading of ≥22% is the standard threshold for high-quality bovine colostrum (correlating with IgG ≥50 g/L). At 18% average Brix, colostrum quality is actually borderline-to-acceptable (most thresholds are ≥21–22% for 'excellent'), but notably the dominant pathogen is Cryptosporidium parvum—which is NOT prevented by colostrum-derived antibodies in any meaningful clinical sense because C. parvum pathogenesis occurs intraluminally and FPT does not specifically predispose to cryptosporidiosis. The 10/12 prevalence of C. parvum with calves 3–10 days old is the classic epidemiologic signature of environmental fecal-oral contamination pressure, typically amplified by overcrowding, reuse of calving areas, and accumulation of oocysts in the environment (the 'herd effect' or Ames Iowa model). The calving area has almost certainly exceeded its safe pathogen load. While colostrum quality should still be optimized, the outbreak driver here is environmental pressure, not FPT.

Question 173: Gabapentin is increasingly used in veterinary patients for chronic and neuropathic pain. What is its primary mechanism of action?

Cyclooxygenase-2 inhibition
Mu-opioid receptor agonism
Voltage-gated calcium channel alpha-2-delta subunit inhibition (Correct answer)
NMDA glutamate receptor blockade

Correct answer: Voltage-gated calcium channel alpha-2-delta subunit inhibition

Gabapentin binds to the alpha-2-delta subunit of voltage-gated calcium channels in the dorsal horn of the spinal cord, reducing excitatory neurotransmitter release and dampening central sensitization.

Question 174: A 5-year-old intact male ferret presents with bilateral symmetric alopecia starting at the tail base and progressing cranially, mild pruritus, and a swollen vulva-like perineal swelling. The owner reports the ferret has been increasingly lethargic over the past month. Serum estradiol is markedly elevated. Which underlying cause is most likely?

Exogenous estrogen exposure from a housemate cat on transdermal estradiol therapy
Sertoli cell tumor producing excess estrogen
Functional ovarian remnant from incomplete gonadectomy
Adrenal cortical disease causing excess sex hormone production (Correct answer)

Correct answer: Adrenal cortical disease causing excess sex hormone production

Adrenal gland disease (hyperadrenocorticism in ferrets) is the most common cause of bilaterally symmetric alopecia, pruritus, elevated sex hormones, and signs of hyperestrogenism (including vulvar swelling in spayed females OR perineal gland swelling in males) in ferrets. Ferret adrenal disease is distinct from Cushing's disease in dogs — it involves excess androgen and estrogen production (primarily), not cortisol. Early spay/neuter, a standard US practice, is a major predisposing factor. A Sertoli cell tumor is possible in intact male ferrets, but this ferret's presentation with bilateral symmetric alopecia AND a perineal swelling (often mistaken for a vulva) is classic for adrenal disease. Exogenous estrogen exposure and ovarian remnant are far less likely in this context.

Question 175: A dog presents with a suspected diaphragmatic hernia. Which radiographic finding would MOST suggest a peritoneopericardial diaphragmatic hernia (PPDH) rather than a traumatic diaphragmatic hernia?

Enlarged globoid cardiac silhouette without pleural effusion (Correct answer)
Discontinuity of the diaphragmatic line
Acute onset following trauma
Gas-filled bowel loops in the pleural space

Correct answer: Enlarged globoid cardiac silhouette without pleural effusion

PPDH is a congenital defect where abdominal organs herniate into the pericardial sac, causing an enlarged cardiac silhouette, unlike traumatic hernias where organs enter the pleural space.

Question 176: A dog presents with polydipsia, polyuria, and a urine specific gravity of 1.006. A water deprivation test is performed; after 8 hours the USG remains 1.007. Following ADH administration, USG rises to 1.022. What is the diagnosis?

Central diabetes insipidus (Correct answer)
Renal medullary washout
Nephrogenic diabetes insipidus
Primary (psychogenic) polydipsia

Correct answer: Central diabetes insipidus

Response to exogenous ADH (desmopressin) with concentration of urine confirms the kidneys can respond, indicating deficient ADH production from the pituitary — central diabetes insipidus.

Question 177: Necropsy of an 8-year-old dog reveals a 4 cm hepatic mass with a tan cut surface, no central necrosis, and a pushing border compressing but not invading adjacent parenchyma. Histology shows well-differentiated hepatocytes in a solid pattern. The most appropriate classification is:

Nodular hyperplasia — no treatment required
Hepatocellular carcinoma — aggressive treatment warranted
Metastatic carcinoma — full staging required
Hepatocellular adenoma (hepatoma) — typically benign, wide surgical excision curative (Correct answer)

Correct answer: Hepatocellular adenoma (hepatoma) — typically benign, wide surgical excision curative

Hepatocellular adenomas (hepatomas) are well-encapsulated, well-differentiated benign tumors in dogs with a pushing border and no invasion. Hepatocellular carcinoma shows vascular invasion, necrosis, and nuclear pleomorphism. Nodular hyperplasia is typically multifocal and small (≤1 cm). Metastatic carcinoma would show an infiltrative pattern and non-hepatocyte histology.

Question 178: A horse presents with a sudden onset of severe, non-weight bearing lameness of the left hindlimb. The tarsocrural joint is markedly distended, warm, and painful on palpation. Arthrocentesis reveals a turbid, yellow synovial fluid with a total protein of 5.2 g/dL and a nucleated cell count of 95,000 cells/µL, with 92% neutrophils. What is the most critical and effective treatment for this condition?

Application of a cast and long-term NSAID administration
Intra-articular corticosteroids and bandaging
Systemic antibiotics and stall rest alone
Joint lavage and systemic broad-spectrum antibiotics (Correct answer)

Correct answer: Joint lavage and systemic broad-spectrum antibiotics

The clinical signs and synovial fluid analysis are indicative of septic arthritis, a true medical emergency in horses. The cornerstone of successful treatment is aggressive and immediate intervention to eliminate the infection and remove inflammatory mediators from the joint. This is best accomplished through joint lavage (flushing the joint with large volumes of sterile fluid), often performed arthroscopically, combined with systemic broad-spectrum antibiotics. Administering only systemic antibiotics is insufficient, and intra-articular corticosteroids are contraindicated in the face of infection.

Question 179: During a herd health visit to a 600-head beef cow-calf operation, you identify an outbreak of respiratory disease in calves 3–8 weeks of age. Morbidity is 28% and case-fatality rate is 9%. Nasal swabs from 6 acutely affected calves yield Mannheimia haemolytica in 4 and Histophilus somni in 2. Colostrum management records are excellent. Which pathogen-level finding MOST strongly suggests a vaccine-preventable gap in this herd's prevention program?

Bovine respiratory syncytial virus (BRSV) antigen detected on immunofluorescence of nasal swabs (Correct answer)
Mannheimia haemolytica isolation in calves under 3 weeks of age
Histophilus somni isolation in calves 3–8 weeks of age with neurological signs
Pasteurella multocida type A isolated from a calf that died despite florfenicol treatment

Correct answer: Bovine respiratory syncytial virus (BRSV) antigen detected on immunofluorescence of nasal swabs

BRSV is a primary viral pathogen in young calves that acts as a 'door-opener' for secondary bacterial pneumonia by disrupting mucociliary clearance and innate immunity. Its presence in calves this age with high morbidity despite good colostrum transfer points directly to a gap in dam vaccination (modified-live BRSV given pre-calving provides colostral antibody protection) or to inadequate calf vaccination timing. Mannheimia and Histophilus are secondary bacterial opportunists commonly cultured from BRD cases regardless of vaccination status. Pasteurella multocida type A treatment failure most suggests antimicrobial resistance or inadequate drug selection, not a specific vaccine gap.

Question 180: Which diagnostic nerve block would be used to specifically desensitize the coffin joint without affecting the navicular bursa?

Low palmar (low 4-point) nerve block
Abaxial sesamoid nerve block
Palmar digital nerve block
Intra-articular distal interphalangeal joint block (Correct answer)

Correct answer: Intra-articular distal interphalangeal joint block

Direct intra-articular injection into the coffin joint (DIP joint) selectively anesthetizes the joint space while sparing the navicular bursa, unlike perineural blocks that affect both structures.

Question 181: A veterinarian recommends a Selective Dry Cow Therapy (SDCT) program instead of blanket dry cow therapy. What is the PRIMARY advantage of SDCT?

It eliminates the need for teat sealants at dry-off
It prevents new environmental mastitis infections during the dry period
It reduces antibiotic use by treating only cows with existing infections or high SCC (Correct answer)
It increases milk production in the subsequent lactation

Correct answer: It reduces antibiotic use by treating only cows with existing infections or high SCC

SDCT reduces antimicrobial use by reserving intramammary antibiotic tubes for cows with evidence of infection, supporting antibiotic stewardship while maintaining udder health outcomes in low-SCC cows.

Question 182: A veterinary public health officer is evaluating the risk of vCJD (variant Creutzfeldt-Jakob Disease) transmission through a bovine-derived pharmaceutical product manufactured from cattle slaughtered in a country where BSE has been detected. The product involves a purification process with a documented 10⁴-fold reduction in prion titer. If the input material carries an estimated infectious dose burden of 10² infectious units per dose equivalent, what is the residual risk characterization?

The product poses a theoretical but unquantifiable risk because prion assays cannot confirm zero infectivity
The product is unsafe because any bovine-derived material from a BSE-positive country must be rejected regardless of processing
The product is safe because the reduction factor exceeds the initial infectious burden, yielding a negative log-risk (Correct answer)
The product requires re-testing with Western blot to determine residual PrPSc content before release

Correct answer: The product is safe because the reduction factor exceeds the initial infectious burden, yielding a negative log-risk

Risk assessment for prion-containing biologics uses a log-reduction model: starting burden (10²) minus log reduction (10⁴) yields a theoretical residual of 10⁻² infectious units — effectively below one infectious unit per dose. When the clearance factor exceeds the input titer by multiple log steps, the margin of safety renders theoretical residual risk negligible under regulatory frameworks (e.g., EMA/FDA). While no biological process can guarantee absolute zero infectivity, the quantitative risk model supports a 'safe' characterization. Blanket rejection of all bovine-derived materials from BSE-positive countries regardless of processing is not aligned with current risk-based regulatory standards (such as USP <1> or WHO prion guidance).

Question 183: According to USDA-APHIS regulations, which of the following diseases requires IMMEDIATE notification by an accredited veterinarian to state or federal animal health officials if suspected?

Johne's Disease
Anaplasmosis
Foot-and-Mouth Disease (FMD) (Correct answer)
Bovine Viral Diarrhea (BVD)

Correct answer: Foot-and-Mouth Disease (FMD)

Foot-and-Mouth Disease (FMD) is a highly contagious foreign animal disease (FAD) with severe economic consequences. Under USDA-APHIS regulations, any suspicion of an FAD like FMD is classified as a 'notifiable disease' and must be reported immediately to the State Animal Health Official (SAHO) and/or the USDA Area Veterinarian in Charge (AVIC). The other diseases listed, while potentially reportable under certain state or program rules, do not carry the same immediate, emergency notification requirement as an FAD.

Question 184: A primiparous Labrador Retriever bitch delivered 6 puppies 18 hours ago. She is now febrile (40.5°C), depressed, and has a malodorous dark vaginal discharge. Abdominal palpation reveals uterine discomfort. The most likely diagnosis and first-line treatment are:

Subinvolution of placental sites — supportive care and monitoring
Eclampsia — IV calcium gluconate 10% slowly to effect
Mastitis — hot-pack mammary glands and oxytocin to promote drainage
Acute metritis — broad-spectrum antibiotics (amoxicillin-clavulanate), oxytocin, and supportive care (Correct answer)

Correct answer: Acute metritis — broad-spectrum antibiotics (amoxicillin-clavulanate), oxytocin, and supportive care

Acute postpartum metritis presents with fever, depression, malodorous uterine discharge, and uterine pain within the first week after delivery. Treatment includes broad-spectrum antibiotics (covering gram-negative organisms and anaerobes), oxytocin or PGF2α to promote uterine evacuation, and IV fluid support. Eclampsia presents with tetany/seizures, not discharge.

Question 185: A cat with chronic kidney disease (CKD) stage 3 is found to have a blood pressure of 195/130 mmHg. Which antihypertensive is considered first-line therapy in cats?

Hydralazine
Enalapril
Atenolol
Amlodipine (Correct answer)

Correct answer: Amlodipine

Amlodipine, a calcium channel blocker, is the first-line antihypertensive in cats due to its efficacy and tolerability.

Question 186: A 7-year-old intact male dog is being treated with ketoconazole for a systemic fungal infection. The owner also mentions the dog is on cyclosporine for immune-mediated thrombocytopenia. Which pharmacokinetic mechanism best explains the expected drug interaction between these two agents?

Cyclosporine competitively inhibits ketoconazole absorption at intestinal transporters
Ketoconazole induces P-glycoprotein, increasing cyclosporine efflux from enterocytes
Ketoconazole displaces cyclosporine from plasma protein binding sites, increasing free drug
Ketoconazole inhibits CYP3A4, reducing cyclosporine metabolism and increasing its plasma concentration (Correct answer)

Correct answer: Ketoconazole inhibits CYP3A4, reducing cyclosporine metabolism and increasing its plasma concentration

Ketoconazole is a potent inhibitor of cytochrome P450 3A4 (CYP3A4), the primary enzyme responsible for cyclosporine metabolism. Inhibition of this enzyme markedly reduces cyclosporine clearance, leading to elevated plasma concentrations and potential nephrotoxicity and neurotoxicity. Clinicians sometimes exploit this interaction intentionally to reduce cyclosporine dosing costs, but it requires careful monitoring.

Question 187: Cats develop more severe Heinz body hemolytic anemia from propylene glycol exposure than dogs given equivalent doses. Which mechanistic explanation best accounts for this species difference?

Cats lack hepatic glucuronyl transferase activity, causing propylene glycol to accumulate in erythrocytes and directly oxidize membrane phospholipids
Cats metabolize propylene glycol via alcohol dehydrogenase to methylglyoxal, which preferentially binds feline hemoglobin at the Bohr effect site
Propylene glycol is converted to hydrogen peroxide by feline erythrocyte catalase at a rate 4-fold higher than in canine red cells
Feline hemoglobin contains approximately 8 reactive sulfhydryl groups per molecule — roughly twice as many as canine hemoglobin — making it disproportionately susceptible to oxidative denaturation (Correct answer)

Correct answer: Feline hemoglobin contains approximately 8 reactive sulfhydryl groups per molecule — roughly twice as many as canine hemoglobin — making it disproportionately susceptible to oxidative denaturation

Feline hemoglobin is uniquely vulnerable to oxidative injury due to the greater number of reactive sulfhydryl (–SH) groups on its globin chains (~8 per molecule vs. ~4 in dogs). These free cysteine-associated sulfhydryl groups are readily oxidized, causing hemoglobin denaturation and Heinz body formation. This explains why cats are exquisitely sensitive to oxidant compounds — including propylene glycol, acetaminophen, benzocaine, onions, and methylene blue — that are tolerated at much higher doses in dogs. Propylene glycol was removed from cat foods specifically because of this risk.

Question 188: A 5-year-old Golden Retriever is presented for acute-onset cervical pain and tetraparesis. MRI reveals a T2-hyperintense, well-defined intramedullary lesion at C5-C6 with a characteristic 'golf ball on a tee' appearance. CSF analysis shows xanthochromia with elevated protein and no pleocytosis. Which condition BEST explains these findings?

Neospora caninum myelitis with focal granuloma formation
Spinal cord astrocytoma with intratumoral hemorrhage
Fibrocartilaginous embolism (FCE) affecting the cervical spinal cord
Acute non-compressive nucleus pulposus extrusion (ANNPE) (Correct answer)

Correct answer: Acute non-compressive nucleus pulposus extrusion (ANNPE)

Acute non-compressive nucleus pulposus extrusion (ANNPE) presents with peracute onset of pain and neurological deficits, often following exercise. MRI shows an intramedullary T2-hyperintense lesion that can have a 'golf ball on a tee' or 'smoke signal' appearance due to the nucleus pulposus material extruded directly into the cord parenchyma. CSF xanthochromia with elevated protein and no pleocytosis is consistent with parenchymal injury without inflammation. FCE also presents acutely and is non-painful after the initial event, but the MRI appearance and CSF xanthochromia better fit ANNPE. Neospora would show pleocytosis, and astrocytoma would be a more gradual progression.

Question 189: A cat is presented for evaluation of recurrent upper respiratory signs and oral ulcerations. FHV-1 PCR is positive on conjunctival swab. Which of the following statements about feline herpesvirus-1 pathophysiology is MOST accurate?

Latency is established exclusively in trigeminal ganglia, and reactivation consistently produces clinical disease
Antiviral treatment with famciclovir eliminates latent virus and prevents future recurrence
The virus establishes persistent viremia, making antigen testing on serum the preferred diagnostic method
Latency is established in trigeminal ganglia; reactivation may be subclinical and shedding can occur without overt signs (Correct answer)

Correct answer: Latency is established in trigeminal ganglia; reactivation may be subclinical and shedding can occur without overt signs

FHV-1 establishes latency primarily in the trigeminal ganglia. Reactivation, triggered by stress or immunosuppression, does not always produce overt clinical disease — cats can shed virus asymptomatically, which has significant implications for multi-cat environments. Persistent viremia does not occur; PCR on conjunctival or nasal swabs is the preferred diagnostic approach. Famciclovir reduces viral replication and severity of clinical signs but does not eliminate latent virus — recurrence remains possible.

Question 190: A 7-year-old Labrador Retriever presents with polyuria, polydipsia, and bilateral cataracts. Fasting blood glucose is 420 mg/dL. Which insulin type is most commonly used for initial management of canine diabetes mellitus?

Regular insulin
Glargine (Lantus)
Detemir (Levemir)
NPH insulin (Correct answer)

Correct answer: NPH insulin

NPH insulin is the first-line choice for canine diabetes mellitus due to its intermediate duration matching the dog's twice-daily feeding schedule.

Question 191: Lily (Lilium spp.) ingestion in cats primarily targets which organ system?

Renal system (Correct answer)
Central nervous system
Hepatic system
Cardiovascular system

Correct answer: Renal system

True lily ingestion in cats causes acute renal failure due to nephrotoxic steroidal glycosides; even small amounts can be fatal.

Question 192: A 4-year-old male Shar-Pei presents with recurrent fever episodes lasting 1–3 days, swollen hocks, and intermittent vomiting. Between episodes the dog appears normal. CBC and chemistry during a febrile episode show neutrophilia with a left shift and mildly elevated BUN. Urinalysis shows 3+ proteinuria. Which underlying pathophysiologic mechanism is most directly responsible for the proteinuria in this dog?

Pyelonephritis from recurrent bacteremia during febrile crises
Immune-complex glomerulonephritis secondary to chronic interleukin-6 overproduction
Tubular proteinuria from aminoglycoside nephrotoxicity used to treat febrile episodes
Renal amyloid A deposition in glomeruli and medullary interstitium leading to nephrotic syndrome (Correct answer)

Correct answer: Renal amyloid A deposition in glomeruli and medullary interstitium leading to nephrotic syndrome

Shar-Peis are predisposed to Shar-Pei Autoinflammatory Disease (SPAID), formerly called Familial Shar-Pei Fever, caused by dysregulation of the inflammasome with markedly elevated IL-6 and IL-18. Chronic inflammation drives sustained serum amyloid A (SAA) production. SAA fibrils deposit as reactive amyloid A (AA amyloidosis) preferentially in the renal medullary interstitium and glomeruli in Shar-Peis, causing progressive proteinuria and eventual renal failure — a pattern distinct from other breeds where hepatic deposition predominates. Immune-complex GN is a feature of some breeds but is not the primary mechanism in SPAID-associated renal disease.

Question 193: A 10-year-old dog with severe hepatic insufficiency requires a pain management protocol following abdominal surgery. The clinician wants to avoid drugs with significant hepatic first-pass metabolism and those relying on hepatic glucuronidation. Which opioid is MOST appropriate for this patient?

Methadone CRI (Correct answer)
Codeine PO
Buprenorphine OTM
Morphine CRI

Correct answer: Methadone CRI

Methadone is the most appropriate choice here. It undergoes N-demethylation (CYP3A4) but has minimal first-pass effect when given parenterally, and does NOT rely on glucuronidation for elimination. Importantly, methadone's large volume of distribution and its partial tissue binding makes it less reliant on single-pass hepatic clearance. Morphine is highly dependent on hepatic glucuronidation (to morphine-6-glucuronide and morphine-3-glucuronide)—these metabolites accumulate in hepatic failure, causing prolonged sedation and respiratory depression. Codeine requires hepatic CYP2D6 conversion to morphine for effect and has high first-pass metabolism. Buprenorphine (OTM/sublingual) bypasses GI first-pass but still requires hepatic metabolism; its very high protein binding is also a concern in hypoalbuminemic hepatic patients.

Question 194: During a pre-purchase examination, you find a 4/5 grade on the AAEP lameness scale in the right forelimb. According to the AAEP scale, this means the horse:

Is lame only under certain circumstances (hard surface, circles)
Is non-weight-bearing at all times
Consistently lame but weight-bearing at the walk and trot
Lame at the walk, occasionally non-weight-bearing (Correct answer)

Correct answer: Lame at the walk, occasionally non-weight-bearing

AAEP grade 4/5 describes a horse that is lame at the walk and consistently lame at the trot, occasionally non-weight-bearing; grade 5 is non-weight-bearing at all times.

Question 195: Which electrolyte abnormality is most commonly associated with hypoadrenocorticism (Addison's disease) in dogs?

Hypernatremia and hypokalemia
Hyponatremia and hyperkalemia (Correct answer)
Hypomagnesemia and hypochloremia
Hypercalcemia and hyperphosphatemia

Correct answer: Hyponatremia and hyperkalemia

Lack of mineralocorticoids in Addison's disease leads to sodium wasting and potassium retention, producing hyponatremia and hyperkalemia with a Na:K ratio below 27.

Question 196: A 9-year-old neutered male Cocker Spaniel is diagnosed with immune-mediated hemolytic anemia (IMHA). Despite 72 hours of prednisolone (2 mg/kg/day), azathioprine, and heparin therapy, his PCV continues to decline from 18% to 12%. He is now dyspneic and tachycardic. Crossmatch reveals no compatible donor. Which transfusion strategy is MOST appropriate?

Initiate exchange transfusion to simultaneously remove antibody-coated cells and replace RBC mass
Administer human intravenous immunoglobulin (hIVIG) and reassess in 24 hours before transfusing
Delay transfusion and increase prednisolone to 4 mg/kg/day
Transfuse with incompatible packed red blood cells, accepting accelerated hemolysis as an acceptable risk (Correct answer)

Correct answer: Transfuse with incompatible packed red blood cells, accepting accelerated hemolysis as an acceptable risk

In life-threatening anemia (PCV <12–15% with cardiorespiratory compromise), transfusion is indicated even when crossmatch-incompatible, because the risk of death from anemia outweighs the risk of accelerated hemolytic transfusion reaction. The transfused cells may survive only hours, but this 'buy time' approach can stabilize the patient while immunosuppression takes effect. Exchange transfusion is not standard of care for IMHA in dogs. Increasing steroids alone or delaying transfusion in a hemodynamically compromised patient is dangerous. hIVIG may be used as an adjunct but takes time to work and does not address immediate oxygen-carrying capacity.

Question 197: When treating a reptile patient, why is it essential to maintain the animal within its preferred optimal temperature zone (POTZ)?

POTZ only affects reproductive behavior, not clinical outcomes
POTZ is important only for feeding, not medical treatment
Reptiles are ectotherms, so immune function and drug metabolism depend on environmental temperature (Correct answer)
Temperature has no effect on antibiotic efficacy in reptiles

Correct answer: Reptiles are ectotherms, so immune function and drug metabolism depend on environmental temperature

As ectotherms, reptiles rely on external heat sources for all metabolic processes including immune response and pharmacokinetics.

Question 198: A 6-year-old cat is referred for evaluation of refractory hypertension (BP consistently >200 mmHg systolic) unresponsive to amlodipine at 0.625 mg/cat PO q24h. Serum aldosterone is markedly elevated. Abdominal CT reveals a 1.2 cm unilateral adrenal mass. Which diagnosis best explains this clinical picture, and what is the definitive treatment?

Adrenal carcinoma with ectopic ACTH secretion; palliative mitotane
Primary hyperaldosteronism (Conn's syndrome); adrenalectomy or medical management with spironolactone (Correct answer)
Adrenal-dependent hyperadrenocorticism; trilostane therapy
Pheochromocytoma; adrenalectomy after pre-operative alpha-blockade with phenoxybenzamine

Correct answer: Primary hyperaldosteronism (Conn's syndrome); adrenalectomy or medical management with spironolactone

Feline primary hyperaldosteronism (Conn's syndrome) is an underrecognized cause of refractory systemic hypertension in cats. It results from autonomous aldosterone secretion (usually by an adrenal adenoma or carcinoma), causing sodium retention, hypokalemia, and pressure-resistant hypertension. Markedly elevated aldosterone with a unilateral adrenal mass is the classic presentation. Definitive treatment is unilateral adrenalectomy; medical management with the mineralocorticoid antagonist spironolactone ± potassium supplementation is used when surgery is not feasible. Pheochromocytoma causes catecholamine excess (not aldosterone excess) and would require phenoxybenzamine pre-operatively. Hyperadrenocorticism does not typically cause marked aldosterone elevation.

Question 199: On a lateral abdominal radiograph of a vomiting 8-year-old Shih Tzu, you identify a mineralized opacity within the pyloric antrum. The opacity has a faceted, angular appearance with multiple distinct densities on the orthogonal view. What is the most likely diagnosis?

Choleliths that have migrated through a biliary-enteric fistula into the pylorus (Correct answer)
Neoplastic mineralization within a pyloric adenocarcinoma
Dystrophic mineralization within a chronic mural hematoma
Gastric foreign body composed of multiple compacted mineral fragments (enterolith)

Correct answer: Choleliths that have migrated through a biliary-enteric fistula into the pylorus

Faceted, angular, radiopaque calculi within the stomach or pylorus with distinct layering/multiple density facets are characteristic of choleliths (gallstones) that have migrated into the GI tract via a cholecystoduodenal or biliary-enteric fistula — a rare but well-documented condition called Bouveret syndrome (gastric outlet obstruction by a gallstone). The faceted morphology and mixed mineral densities (mixed cholesterol/calcium bilirubinate composition) are hallmarks of cholecystolithiasis. Simple enteroliths tend to be round/oval and form distally. Neoplastic mineralization is typically amorphous and associated with a soft tissue mass.

Question 200: A 4-year-old Thoroughbred racehorse presents with acute onset severe (grade 4/5) right forelimb lameness following a morning workout. Ultrasonography reveals a complete core lesion of the superficial digital flexor tendon (SDFT) at the mid-metacarpal level with a cross-sectional area 40% greater than the contralateral limb. The owner inquires about intralesional platelet-rich plasma (PRP) therapy. Which statement most accurately reflects current evidence-based understanding of PRP in equine SDFT repair?

PRP accelerates early fiber alignment and reduces re-injury rates in racehorses when injected within the first 30 days
PRP provides superior outcomes compared to adipose-derived stem cells for core lesions >30% cross-sectional area
PRP increases the ratio of type I to type III collagen in healed tendon, improving biomechanical strength
PRP has not consistently demonstrated improved long-term outcomes over controlled exercise rehabilitation alone in controlled trials (Correct answer)

Correct answer: PRP has not consistently demonstrated improved long-term outcomes over controlled exercise rehabilitation alone in controlled trials

Despite widespread clinical use, PRP has not consistently shown superior long-term outcomes compared to controlled exercise rehabilitation alone in rigorous controlled clinical trials for equine SDFT injuries. While PRP contains growth factors (TGF-β, PDGF, IGF-1) that theoretically promote tendon healing, prospective blinded studies in racehorses have failed to demonstrate significant differences in re-injury rates or return-to-sport timelines. The evidence base remains limited by small sample sizes and methodological heterogeneity, making controlled exercise rehabilitation the only consistently evidence-supported intervention.

Question 201: A veterinarian discovers a dog imported from a rabies-endemic country without documentation of vaccination. The appropriate immediate action under US regulations is:

Vaccinate and release within 24 hours
Quarantine the dog for up to 6 months (Correct answer)
File a report with the CDC within 72 hours
Euthanize the dog immediately

Correct answer: Quarantine the dog for up to 6 months

CDC regulations require dogs imported from high-risk countries without valid rabies vaccination to be quarantined for up to 6 months.

Question 202: A 450-cow commercial dairy herd has a 21-day pregnancy rate of 12% and a conception rate of 32%. The reproductive program manager wants to improve the 21-day pregnancy rate to 20%. Which metric most directly limits achieving this goal given the current data?

Conception rate, which should be improved to at least 40%
Voluntary waiting period, which should be shortened to less than 45 days
Services per conception, which need to be reduced below 3.0
21-day estrus detection rate, which must be increased from approximately 38% to at least 50% (Correct answer)

Correct answer: 21-day estrus detection rate, which must be increased from approximately 38% to at least 50%

The 21-day pregnancy rate = estrus detection rate × conception rate. With a 32% conception rate and 12% PR, the estrus detection rate is approximately 12/32 = 37.5%. To achieve a 20% PR at the same conception rate: 20/32 = 62.5% EDR. Even if conception rate were improved moderately, the primary bottleneck is the low estrus detection rate. Estrus detection (now often called 'submission rate' under synchronization programs) must be the primary target. The other options are not directly calculable constraints from the given data.

Question 203: A horse presents with a positive flexion test of the distal limb and lameness that is abolished by a palmar digital nerve block. Which structure is MOST likely affected?

Pastern joint
Coffin joint
Digital flexor tendon sheath
Navicular bone or navicular bursa (Correct answer)

Correct answer: Navicular bone or navicular bursa

A palmar digital nerve block desensitizes the navicular region, and a positive distal limb flexion test implicates the navicular apparatus as the primary source of pain.

Question 204: A cat is diagnosed with diabetes mellitus. Which insulin type is currently recommended as first-line therapy in cats?

Regular insulin (short-acting)
Detemir insulin
Glargine insulin (long-acting) (Correct answer)
NPH insulin

Correct answer: Glargine insulin (long-acting)

Glargine (insulin glargine) is preferred in cats because its long, peakless action matches the feline glucose profile and facilitates diabetic remission.

Question 205: Which anatomical site is preferred for intramuscular injections in birds?

Quadriceps muscle
Pectoral muscle (Correct answer)
Wing web
Epaxial muscle

Correct answer: Pectoral muscle

The pectoral muscle is the preferred IM injection site in birds because of its large mass and easy accessibility.

Question 206: Which positional radiograph is recommended to evaluate for pneumothorax when only a small amount of free pleural air is suspected in a dog?

Ventrodorsal with horizontal beam
Lateral recumbency with affected side down
Standing lateral with horizontal beam (Correct answer)
Dorsoventral with horizontal beam

Correct answer: Standing lateral with horizontal beam

A standing lateral with a horizontal beam allows free pleural air to rise to the highest point (dorsal), making even small pneumothoraces visible between the lung and dorsal thoracic wall.

Question 207: Which radiographic sign on a lateral thoracic view indicates right-sided cardiomegaly in a dog?

Widening of the caudal vena cava shadow
Dorsal displacement of the trachea
Increased sternal contact (more than 3 sternal segments) (Correct answer)
Loss of the cranial waist on the VD view

Correct answer: Increased sternal contact (more than 3 sternal segments)

Right heart enlargement causes the cardiac silhouette to contact more sternal segments than normal (typically more than 3), displacing the apex ventrally.

Question 208: A feedlot veterinarian is evaluating a pen of 200 steers. Over 10 days, 18 steers have been pulled and treated for bovine respiratory disease (BRD). The pen morbidity is 9%. The consulting nutritionist notes the ration has a high silage inclusion with a low-quality corn silage (pH 4.9, but ammonia-N/total-N ratio = 28%). Which consequence of this silage quality is MOST likely to be contributing to the BRD outbreak?

Excessive ammonia absorption from poorly fermented silage leading to hepatic ammonia loading and impaired neutrophil oxidative burst
Mycotoxin contamination from clostridial overgrowth in poorly fermented silage directly suppressing lymphocyte proliferation
Reduced dry matter intake secondary to poor palatability, causing negative energy balance and impaired pulmonary macrophage function (Correct answer)
High butyric acid content causing subclinical rumenitis, disrupting the mucosal barrier and promoting systemic bacterial translocation

Correct answer: Reduced dry matter intake secondary to poor palatability, causing negative energy balance and impaired pulmonary macrophage function

An ammonia-N/total-N ratio >15% indicates poorly fermented (clostridial or secondary fermentation) silage with significant protein degradation to non-protein nitrogen. The most direct herd health consequence is severe palatability reduction, causing steers to eat far below their energy requirements. This negative energy balance directly impairs pulmonary alveolar macrophage function and neutrophil activity, dramatically increasing susceptibility to the Mannheimia-Pasteurella-Histophilus complex driving BRD. High butyric acid is also a marker of clostridial silage but is less directly linked to respiratory immunity than energy balance. Mycotoxins are associated with Fusarium contamination, not clostridial fermentation. Ammonia absorption occurs but hepatic urea cycle capacity typically prevents acute neutrophil dysfunction at silage ammonia levels.

Question 209: A Quarter Horse presents with acute, severe forelimb lameness and a draining tract near the coronary band. Radiographs show gas lucency within the third phalanx. What condition do these findings most strongly suggest?

Coffin joint septic arthritis
Subsolar abscess with secondary osteomyelitis of the distal phalanx (Correct answer)
Sequestrum formation of the proximal phalanx
Navicular bone fracture

Correct answer: Subsolar abscess with secondary osteomyelitis of the distal phalanx

A draining tract at the coronary band combined with gas and lytic changes in the third phalanx are classic findings of a chronic subsolar abscess that has ascended and caused osteomyelitis of the distal phalanx.

Question 210: A 5-year-old spayed female Border Collie presents with a 6-week history of progressive right forelimb lameness. Radiographs show a permeative lytic lesion at the distal radius with cortical destruction and a Codman's triangle. Fine-needle aspirate cytology reveals large polygonal cells with marked anisokaryosis. You initiate staging workup. Which finding would MOST significantly worsen the prognosis compared to the baseline expected survival with standard of care?

Bone scintigraphy showing increased uptake at the ipsilateral scapula
Pulmonary nodules >1 cm visible on thoracic CT but not plain radiographs
Serum alkaline phosphatase (ALP) > 110 IU/L
Regional axillary lymph node enlargement confirmed as metastatic on aspirate (Correct answer)

Correct answer: Regional axillary lymph node enlargement confirmed as metastatic on aspirate

Regional lymph node metastasis (confirmed histologically or cytologically) is a well-established negative prognostic indicator in canine appendicular osteosarcoma and upstages the disease. It is associated with significantly shortened survival times compared to dogs without nodal metastasis, even with amputation and chemotherapy. Elevated ALP is a negative prognostic factor but is common and does not change staging definitively. Pulmonary nodules detected only on CT but not radiographs are of uncertain significance and may be inflammatory. Skip metastasis to the scapula (detected by scintigraphy) suggests polyostotic disease, which is poor, but confirmed nodal spread is the most clearly documented survival-shortening finding listed.

Question 211: Which radiographic sign is MOST characteristic of a diaphragmatic hernia in a dog?

Loss of diaphragmatic outline with abdominal organs in the thorax (Correct answer)
Pleural fissure lines at the lung margins
Increased sternal contact of the cardiac silhouette
Air bronchograms within the pulmonary parenchyma

Correct answer: Loss of diaphragmatic outline with abdominal organs in the thorax

Loss of the normal diaphragmatic outline combined with abdominal viscera (e.g., intestinal loops, stomach) visible in the thoracic cavity is the hallmark of diaphragmatic hernia.

Question 212: A 6-year-old domestic shorthair cat with vocal discomfort is examined for acute bilateral hind limb paralysis. A grade 3/6 left-sided systolic murmur is audible during a physical examination. The patient's footpads are chilly and pallid, and there are no femoral pulses. Additionally, the gastrocnemius and quadriceps muscles have painful contracture. Which of the following ailments has the highest likelihood of being diagnosed?

Arterial thromboembolism (Correct answer)
Intervertebral dis disease
Fibrocartilaginous infarct
Spinal cord neoplasia

Correct answer: Arterial thromboembolism

Acute bilateral hind limb paralysis, vocal discomfort, cold and pale footpads, absence of femoral pulses, and painful contracture of hind limb muscles in a cat with a heart murmur are pathognomonic signs of an arterial thromboembolism (ATE), often referred to as 'saddle thrombus.' This condition typically results from a thrombus (blood clot) originating in the heart (often due to underlying heart disease like hypertrophic cardiomyopathy) that dislodges and lodges at the aortic trifurcation, blocking blood flow to the hind limbs.

Question 213: A cat is prescribed methimazole for hyperthyroidism. Which adverse effect is most commonly reported in the first 1–3 months of therapy?

Bone marrow aplasia
Hepatotoxicity
Facial pruritus and excoriation (Correct answer)
Peripheral neuropathy

Correct answer: Facial pruritus and excoriation

Facial pruritus, excoriation, and self-induced facial lesions are the most common early adverse effects of methimazole in cats.

Question 214: A 6-year-old Arabian endurance horse presents with acute right forelimb lameness of 4 days' duration following a 100-mile ride. The horse is grade 4/5 lame, resents flexion of the fetlock, and has a marked digital pulse. Radiographs are unremarkable. MRI reveals a complete palmar annular ligament desmitis with concurrent proximal digital annular ligament thickening and significant fluid accumulation within the digital flexor tendon sheath (DFTS). After conservative management fails at 6 weeks, you plan a surgical intervention. Which procedure is MOST appropriate to address the primary compressive pathology?

Deep digital flexor tendon splitting via the palmar approach to decompress intrathecal pressure
Tenoscopic release of the palmar annular ligament (PAL) with concurrent digital flexor tendon sheath lavage (Correct answer)
Open desmotomy of the proximal digital annular ligament via a palmar midline approach
Neurectomy of the palmar digital nerves combined with palmar annular ligament desmotomy

Correct answer: Tenoscopic release of the palmar annular ligament (PAL) with concurrent digital flexor tendon sheath lavage

Tenoscopic (endoscopic within the tendon sheath) release of the palmar annular ligament is the gold-standard surgical procedure for constricting palmar annular ligament syndrome confirmed on MRI, especially when accompanied by concurrent DFTS effusion. Tenoscopy allows direct visualization of the DFTS contents, assessment of the flexor tendon surfaces, concurrent debridement of damaged tissue, complete sheath lavage, and PAL transection under direct visualization with superior cosmesis and lower complication rates than open approaches. Open PAL desmotomy is an acceptable alternative but carries higher wound complication risk. Proximal digital annular ligament desmotomy addresses a different structure. Neurectomy is not appropriate as a primary treatment and carries welfare and regulatory concerns in competition horses. DDFT splitting is reserved for core DDFT lesions, not annular ligament compression.

Question 215: A sugar glider presents with self-mutilation of the scrotum and hindquarters. The most common underlying cause is:

Nutritional secondary hyperparathyroidism
Ectoparasite infestation
Stress and/or inappropriate husbandry (Correct answer)
Fungal dermatitis

Correct answer: Stress and/or inappropriate husbandry

Self-mutilation in sugar gliders is most commonly associated with stress, social isolation, or inappropriate diet and environmental conditions.

Question 216: A veterinarian administers detomidine to a horse for standing sedation. This drug produces reliable sedation, muscle relaxation, and analgesia by acting as a potent agonist at which of the following receptors?

NMDA receptor
Alpha-2 adrenergic receptor (Correct answer)
GABA receptor
Mu-opioid receptor

Correct answer: Alpha-2 adrenergic receptor

Detomidine is a potent alpha-2 adrenergic agonist. Stimulation of these receptors in the central and peripheral nervous system inhibits the release of norepinephrine, which results in sedation, analgesia, and muscle relaxation. This class of drugs is commonly used for sedation in large animals.

Question 217: A 4-year-old DSH cat is being treated for chronic pain with buprenorphine. The owner inadvertently administers a full tablet of acetaminophen (500 mg) intended for herself. Which mechanism is primarily responsible for acetaminophen toxicity in cats compared to dogs and humans?

Cats lack glutathione reductase, preventing regeneration of glutathione stores
Cats lack sufficient UDP-glucuronosyltransferase 1A6 (UGT1A6) activity to conjugate NAPQI, leading to accumulation (Correct answer)
Cats preferentially shunt acetaminophen through the sulfation pathway, producing toxic sulfate conjugates
Cats have enhanced CYP2E1 activity that produces excessive NAPQI from acetaminophen

Correct answer: Cats lack sufficient UDP-glucuronosyltransferase 1A6 (UGT1A6) activity to conjugate NAPQI, leading to accumulation

Cats are exceptionally susceptible to acetaminophen toxicity due to a genetic deficiency in UGT1A6 (and related isoforms), the glucuronidation enzyme responsible for conjugating NAPQI — the reactive intermediate produced by CYP450 metabolism of acetaminophen. Without adequate glucuronidation capacity, NAPQI accumulates, depletes glutathione, and binds covalently to hemoglobin (causing methemoglobinemia and Heinz body formation) and hepatocytes (causing hepatic necrosis). Dogs and humans can glucuronidate NAPQI efficiently; cats largely cannot. The sulfation pathway is also limited in cats and becomes quickly saturated.

Question 218: On thoracic radiographs of a dog, you notice the cardiac silhouette occupies more than 75% of the thoracic width on the VD view. What does this most likely indicate?

Pneumothorax
Pleural effusion
Cardiomegaly (Correct answer)
Pulmonary consolidation

Correct answer: Cardiomegaly

A cardiac silhouette exceeding 75% of thoracic width on the VD view is consistent with cardiomegaly.

Question 219: A 7-year-old male neutered Labrador Retriever presents with a 3-week history of progressive tetraparesis. MRI of the cervical spine reveals a T2-hyperintense, T1-isointense intramedullary lesion at C4-C5 that does not enhance with gadolinium contrast. The lesion has a 'flame-shaped' appearance on sagittal sequences. Which diagnosis is MOST consistent with these imaging findings?

Intramedullary astrocytoma
Intramedullary meningioma
Spinal cord infarction (fibrocartilaginous embolism) (Correct answer)
Syringomyelia

Correct answer: Spinal cord infarction (fibrocartilaginous embolism)

Spinal cord infarction (fibrocartilaginous embolism, FCE) classically appears as a T2-hyperintense, T1-isointense intramedullary lesion with a characteristic 'flame-shaped' or wedge-shaped appearance on sagittal MRI sequences. Crucially, FCE lesions do NOT enhance with gadolinium because there is no disruption of the blood-brain barrier by a mass—this distinguishes them from most intramedullary tumors. Syringomyelia appears as a fluid-filled cavity (CSF-isointense on all sequences). Astrocytomas and meningiomas typically show some degree of contrast enhancement.

Question 220: Ultrasound-guided fine-needle aspiration of a splenic mass in a 10-year-old Golden Retriever yields a non-diagnostic sample. On ultrasound, the mass is a 4-cm, cavitary, mixed echogenicity lesion. Contrast-enhanced ultrasound (CEUS) shows rapid arterial enhancement followed by marked washout in the late portal phase, resulting in a 'Swiss cheese' enhancement pattern. Which splenic pathology does this CEUS pattern MOST strongly suggest?

Splenic hematoma
Splenic hemangiosarcoma (Correct answer)
Splenic hemangioma
Nodular hyperplasia

Correct answer: Splenic hemangiosarcoma

Hemangiosarcoma on CEUS characteristically shows rapid, heterogeneous arterial phase enhancement (due to abnormal tumor vasculature) followed by early and marked washout during the portal/late phase—producing the so-called 'Swiss cheese' or heterogeneous enhancement pattern with hypoechoic regions corresponding to necrosis or hemorrhage. Hemangiomas also enhance early but tend to show more uniform, persistent enhancement ('fill-in' pattern). Nodular hyperplasia shows isoenhancement or mild hyperenhancement without early washout. Hematomas show little to no vascular enhancement. Early washout is the key discriminator favoring malignancy.

Question 221: Which of the following reproductive strategies describes the boa constrictor?

Ovoviviparous — retains eggs internally and gives birth to live young (Correct answer)
Parthenogenetic — reproduces without fertilization
Viviparous — has a true placenta like mammals
Oviparous — lays eggs that develop externally

Correct answer: Ovoviviparous — retains eggs internally and gives birth to live young

Boa constrictors are ovoviviparous; eggs are retained and develop internally with the female giving birth to live young without a true placenta.

Question 222: Histologic examination of a canine skin biopsy shows epidermal hyperplasia, parakeratosis, Munro microabscesses (neutrophil collections in the stratum corneum), and perivascular lymphocytic infiltrate in the superficial dermis. This pattern is most consistent with:

Mast cell tumor with epidermal reaction
Superficial bacterial pyoderma
Pemphigus foliaceus
Psoriasiform-lichenoid dermatitis (Correct answer)

Correct answer: Psoriasiform-lichenoid dermatitis

Psoriasiform-lichenoid dermatitis in dogs is characterized histologically by epidermal hyperplasia (psoriasiform), parakeratosis, intracorneal neutrophil accumulations (Munro microabscesses), and a lichenoid (interface) or superficial perivascular infiltrate. Pemphigus foliaceus shows acantholytic cells and subcorneal pustules; pyoderma shows suppurative folliculitis.

Question 223: In equine radiography, 'rotation' of the distal phalanx relative to the hoof wall is measured by which imaging technique?

Ultrasound of the deep digital flexor tendon
Lateral radiograph with a reference marker on the dorsal hoof wall (Correct answer)
Nuclear scintigraphy of the foot
Dorsopalmar radiograph of the foot

Correct answer: Lateral radiograph with a reference marker on the dorsal hoof wall

Lateral radiographs with a radio-opaque marker placed on the dorsal hoof wall allow measurement of the palmar angle and rotation of P3 in laminitic horses.

Question 224: A 5-year-old Thoroughbred racehorse undergoes emergency surgery for a complete lateral condylar fracture of the right third metacarpal bone sustained during a race. The fracture is repaired with lag screw fixation. Three weeks postoperatively, the horse develops acute non-weight-bearing lameness and radiographs show implant loosening with bone lysis around the screw tracks. Bacterial culture of joint fluid grows Staphylococcus aureus resistant to beta-lactam antibiotics. Which systemic antibiotic protocol is most appropriate while awaiting full susceptibility results?

Enrofloxacin 5 mg/kg IV once daily (Correct answer)
Vancomycin 7.5 mg/kg IV TID with therapeutic drug monitoring
Chloramphenicol 50 mg/kg PO QID
Trimethoprim-sulfamethoxazole 30 mg/kg PO BID

Correct answer: Enrofloxacin 5 mg/kg IV once daily

Enrofloxacin is the most practical systemic option for methicillin-resistant Staphylococcus aureus (MRSA) or beta-lactam-resistant staphylococcal infections in horses pending full susceptibility data. Fluoroquinolones achieve excellent bone and synovial fluid penetration and have demonstrated efficacy against many resistant staphylococci in equine clinical practice. Vancomycin is theoretically ideal for MRSA but is nephrotoxic in horses, poorly studied pharmacokinetically, and logistically challenging (TID IV). TMP-sulfa has variable efficacy against S. aureus and poor bone penetration. Chloramphenicol has public health implications (aplastic anemia risk in humans via residues) and is rarely used in performance horses.

Question 225: During a foot-and-mouth disease (FMD) outbreak response, a foreign animal disease diagnostician (FADD) must apply a stamping-out policy. Which of the following best describes the correct depopulation zone hierarchy under the USDA-APHIS FAD PReP guidelines, and what is the primary reason wildlife surveillance is included in the response plan?

Infected Premises → Contact Premises → Free Zone → Export Zone; wildlife surveillance is performed to assess DIVA vaccine efficacy in non-target species
Infected Premises → Buffer Zone → Control Area → Surveillance Zone; wildlife surveillance is required solely to comply with OIE notification standards
Infected Premises → Dangerous Contact Premises → Suspect Premises → Monitored Premises; wildlife surveillance detects spillover into feral swine or white-tailed deer that could sustain transmission after livestock depopulation (Correct answer)
Quarantine Zone → Protection Zone → Surveillance Zone → Free Zone; wildlife surveillance targets migratory birds as the primary maintenance host of FMD virus

Correct answer: Infected Premises → Dangerous Contact Premises → Suspect Premises → Monitored Premises; wildlife surveillance detects spillover into feral swine or white-tailed deer that could sustain transmission after livestock depopulation

USDA FAD PReP protocols define concentric zone classifications: Infected Premises (confirmed positive), Dangerous Contact Premises (high-risk exposure), Suspect Premises (clinical signs, awaiting confirmation), and Monitored Premises (under surveillance). Wildlife surveillance — particularly of feral swine and white-tailed deer — is critical because these species are susceptible to FMD and could serve as maintenance hosts after livestock depopulation, undermining eradication. Migratory birds are not significant FMD hosts. OIE notification is a consequence, not the primary driver of wildlife surveillance.

Question 226: A 9-year-old spayed female Border Collie is evaluated for a 3-month history of polydipsia, polyuria, and bilateral symmetric alopecia of the flanks. Serum cortisol post-LDDS test is 3.2 µg/dL at 8 hours (non-suppressed). An HDDS test shows 85% suppression. Abdominal ultrasound reveals bilateral adrenal enlargement. Which diagnosis BEST fits this presentation?

Occult hyperadrenocorticism with normal LDDS
Pituitary-dependent hyperadrenocorticism (PDH) with a macroadenoma (Correct answer)
Adrenal-dependent hyperadrenocorticism (ADH)
Ectopic ACTH syndrome

Correct answer: Pituitary-dependent hyperadrenocorticism (PDH) with a macroadenoma

The key discriminator here is HDDS suppression. In pituitary-dependent hyperadrenocorticism (PDH), the pituitary adenoma retains some glucocorticoid feedback sensitivity, and >50% suppression on HDDS is considered diagnostic of PDH. Adrenal-dependent tumors are autonomous and do not suppress with either low- or high-dose dexamethasone. Bilateral adrenal enlargement (bilateral adrenocortical hyperplasia) is characteristic of PDH because bilateral ACTH stimulation drives bilateral hypertrophy. A macroadenoma can cause more severe disease and sometimes poor LDDS response, yet still suppresses on HDDS. Ectopic ACTH is extremely rare in dogs.

Question 227: A llama is treated with flunixin meglumine IV at the bovine label dose for 5 consecutive days for GI pain. Which adverse effect is MOST likely due to the species-specific pharmacokinetic difference compared to cattle?

Nephrotoxicity worsened by the llama's slower drug elimination half-life (Correct answer)
Bone marrow suppression from camelid sensitivity to NSAIDs
Right dorsal colitis from prolonged COX-1 inhibition in the hindgut
Hepatotoxicity from cytochrome P450 accumulation

Correct answer: Nephrotoxicity worsened by the llama's slower drug elimination half-life

Camelids (llamas, alpacas) have a significantly longer elimination half-life for flunixin meglumine (~10-12 hours) compared to cattle (~3-4 hours). Using the bovine dose and frequency leads to drug accumulation in camelids, with renal papillary necrosis and nephrotoxicity being the primary concern due to sustained COX-1 inhibition reducing renal prostaglandin synthesis. Right dorsal colitis is classically associated with horses on prolonged NSAIDs, not camelids.

Question 228: A dairy herd has an elevated somatic cell count (SCC) averaging 500,000 cells/mL. What SCC threshold is used by the USDA as the legal limit for Grade A milk in the US?

750,000 cells/mL (Correct answer)
400,000 cells/mL
250,000 cells/mL
1,000,000 cells/mL

Correct answer: 750,000 cells/mL

The US legal limit for bulk tank SCC in Grade A milk is 750,000 cells/mL, though the EU standard is stricter at 400,000 cells/mL.

Question 229: A 4-year-old Soft Coated Wheaten Terrier is presented for chronic small bowel diarrhea, significant weight loss, and peripheral edema. Bloodwork reveals severe panhypoproteinemia (both albumin and globulin are low). Which of the following conditions is the most likely underlying cause?

Chronic hepatitis
Protein-losing enteropathy (PLE) (Correct answer)
Exocrine pancreatic insufficiency (EPI)
Protein-losing nephropathy

Correct answer: Protein-losing enteropathy (PLE)

The combination of chronic diarrhea, weight loss, and panhypoproteinemia (low albumin and globulin) is characteristic of a protein-losing enteropathy (PLE). In PLE, proteins are lost through the gastrointestinal tract. While protein-losing nephropathy and chronic hepatitis cause hypoalbuminemia, globulins are typically normal or elevated. EPI causes weight loss and diarrhea but does not typically cause significant protein loss. Soft Coated Wheaten Terriers are also predisposed to PLE.

Question 230: A 6-year-old Doberman Pinscher is being treated for dilated cardiomyopathy with digoxin. The dog develops acute renal failure secondary to a urinary obstruction. Which pharmacokinetic change requires the MOST urgent dose adjustment?

Increased volume of distribution due to fluid redistribution
Decreased hepatic first-pass metabolism increasing bioavailability
Enhanced protein binding reducing free drug concentration
Reduced renal clearance causing digoxin accumulation and toxicity (Correct answer)

Correct answer: Reduced renal clearance causing digoxin accumulation and toxicity

Digoxin is primarily eliminated by renal excretion (60-75% unchanged in urine). Acute renal failure dramatically reduces digoxin clearance, causing drug accumulation and a narrow therapeutic index means toxicity (arrhythmias, GI signs, neurological effects) develops rapidly. Dose reduction or extended dosing intervals are mandatory. Digoxin has minimal hepatic first-pass effect, and renal failure typically decreases (not increases) protein binding and volume of distribution.

Question 231: A 4-year-old male Dalmatian has recurrent stranguria. Survey abdominal radiographs are unremarkable. Given this breed's predisposition to radiolucent uroliths, which contrast study is most appropriate to definitively identify their presence within the bladder?

Positive contrast cystogram
Double contrast cystogram (Correct answer)
Negative contrast cystogram
Excretory urogram

Correct answer: Double contrast cystogram

Dalmatians are prone to forming urate uroliths, which are often radiolucent and not visible on survey radiographs. A double contrast cystogram is the ideal study in this case. This technique uses a small amount of positive contrast medium to coat the bladder wall and any uroliths, followed by distention with negative contrast (gas). The radiolucent uroliths are then outlined by the positive contrast, making them visible against the dark, gas-filled lumen. A positive contrast study alone could obscure the stones.

Question 232: A 6-week-old kitten from an unvaccinated litter presents in lateral recumbency with intention tremors, broad-based ataxic gait, and dysmetria. The dam had an unknown vaccine history. The kitten otherwise appears normally developed and alert. Which of the following MOST accurately explains the timing of viral injury required to produce this neurological syndrome?

FPV infection occurred after 4 weeks of age when the blood-brain barrier becomes more permeable, allowing viral access to mature cerebellar Purkinje cells.
Feline herpesvirus-1 caused meningoencephalitis in the neonatal period, selectively destroying Purkinje cells of the cerebellum and sparing cortical neurons.
Feline calicivirus caused neonatal cerebellar hypoplasia by infecting ependymal cells of the fourth ventricle, leading to obstructive hydrocephalus and secondary cerebellar compression.
Feline panleukopenia virus (FPV) infected the kitten in utero or within the first two weeks of postnatal life, targeting rapidly dividing granule cell precursors in the external germinal layer of the cerebellum. (Correct answer)

Correct answer: Feline panleukopenia virus (FPV) infected the kitten in utero or within the first two weeks of postnatal life, targeting rapidly dividing granule cell precursors in the external germinal layer of the cerebellum.

Feline panleukopenia virus is highly mitotropic and requires actively dividing cells. Cerebellar hypoplasia results from FPV infection during late gestation or within the first 1–2 weeks of life when the external germinal layer (EGL) of the cerebellum—a transient population of proliferating granule cell precursors—is present. Viral destruction of these precursors results in a hypoplastic cerebellum with characteristic non-progressive ataxia and tremors. After EGL involution (~2–3 weeks postnatal), FPV no longer produces cerebellar hypoplasia. FHV-1 and FCV are not causative agents of this syndrome.

Question 233: During a shelter outbreak investigation, 6 of 12 adult cats develop severe erosive stomatitis, limb edema, and pneumonia over 10 days with 2 fatalities. Kittens in the same ward are largely unaffected. Feline calicivirus (FCV) PCR is positive. Which strain characteristic BEST explains this outbreak pattern?

A recombinant FCV strain with enhanced tropism for endothelial cells causing virulent systemic FCV (VS-FCV) (Correct answer)
Reactivation of a latent FCV strain due to shelter stress causing immunosuppression
An FCV strain with truncated ORF2 capsid protein causing incomplete immune recognition
A hypermutable quasispecies FCV variant that evades neutralization by maternally derived antibodies

Correct answer: A recombinant FCV strain with enhanced tropism for endothelial cells causing virulent systemic FCV (VS-FCV)

Virulent systemic FCV (VS-FCV), also called hemorrhagic fever FCV, is characterized by endotheliotropism causing facial and limb edema, hemorrhagic diatheses, high fever, and mortality rates up to 67% in adult cats. Critically, VS-FCV preferentially affects adults because maternal antibodies from queens (who lack VS-FCV immunity) do NOT protect kittens against this antigenically distinct strain — however, adult cats with prior FCV immunity can still succumb because VS-FCV escapes neutralization by antibodies generated against classical FCV strains. The mortality pattern skewing toward adults is a hallmark of VS-FCV outbreaks.

Question 234: A goat herd experiences multiple does with profuse watery diarrhea, weight loss, and bottle jaw (submandibular edema) over several months. Fecal egg counts reveal heavy Haemonchus contortus burdens. Which anthelmintic resistance testing method is most appropriate to guide drug selection?

Fecal Egg Count Reduction Test (FECRT) comparing pre- and post-treatment counts (Correct answer)
Larval development assay using pooled fecal cultures
Baermann technique to detect larvae in feces
McMaster flotation to identify the species causing disease

Correct answer: Fecal Egg Count Reduction Test (FECRT) comparing pre- and post-treatment counts

The Fecal Egg Count Reduction Test (FECRT) is the gold-standard field test for anthelmintic resistance. Fecal egg counts are performed before and 14 days after treatment; <95% reduction indicates resistance. The Baermann technique detects lungworm larvae, not strongyles. McMaster identifies eggs but not resistance status.

Question 235: Which anesthetic protocol is most commonly associated with post-anesthetic myopathy in horses undergoing prolonged recumbency?

Total intravenous anesthesia with ketamine-xylazine-guaifenesin
Epidural analgesia with detomidine
Inhalant anesthesia with hypotension and poor padding (Correct answer)
Regional nerve blocks prior to induction

Correct answer: Inhalant anesthesia with hypotension and poor padding

Post-anesthetic myopathy in horses is most strongly associated with inhalant anesthesia combined with hypotension and inadequate padding, leading to compartment syndrome of dependent muscles.

Question 236: On abdominal radiographs, which finding is MOST consistent with a congenital portosystemic shunt in a young dog?

Hepatomegaly with ascites
Normal liver size with splenic mineralization
Splenomegaly with portal vein dilation
Microhepatica (small liver) with renomegaly (Correct answer)

Correct answer: Microhepatica (small liver) with renomegaly

Congenital portosystemic shunts divert hepatotrophic factors away from the liver, causing microhepatica; compensatory renal hypertrophy often produces concurrent renomegaly.

Question 237: A cat presents with acute onset of hindlimb paralysis, cold limbs, and absent femoral pulses. What is the most likely diagnosis?

Fibrocartilaginous embolism
Traumatic spinal cord injury
Intervertebral disc disease
Aortic thromboembolism (Correct answer)

Correct answer: Aortic thromboembolism

Aortic thromboembolism (saddle thrombus) classically presents in cats with acute hindlimb paresis/paralysis, cold extremities, and absent femoral pulses, often secondary to cardiomyopathy.

Question 238: After falling from a 25-foot cliff, a 6-year-old corgi develops opisthotonus, thoracic limb hyperextension, and rear limb paraplegia. Which of the following is the lesion's most likely location?

C6-T2
S1-S3
C1-C5
T3-L3 (Correct answer)

Correct answer: T3-L3

Opisthotonus, thoracic limb hyperextension (Schiff-Sherrington posture), and rear limb paraplegia are classic signs of a severe spinal cord lesion in the thoracolumbar region (T3-L3). The Schiff-Sherrington posture indicates a lesion between T3 and L3, which disinhibits the extensor muscles of the thoracic limbs, while the paraplegia points to the primary lesion affecting the spinal cord segments controlling the hind limbs.

Question 239: A 4-year-old intact female Doberman Pinscher presents with acute collapse. Echocardiography reveals a large hypoechoic space surrounding the heart with compression of the right atrium during diastole. The most appropriate NEXT imaging step to identify the underlying etiology is:

Radiographic measurement of the vertebral heart scale (VHS) to differentiate effusion from cardiomegaly
Contrast-enhanced ultrasound (CEUS) of the right auricular appendage after pericardiocentesis
CT angiography of the thorax with IV contrast after stabilization via pericardiocentesis (Correct answer)
Repeat echocardiography in 48 hours following pericardiocentesis to assess for mass lesion

Correct answer: CT angiography of the thorax with IV contrast after stabilization via pericardiocentesis

In a Doberman with cardiac tamponade, after life-saving pericardiocentesis, CT angiography with IV contrast is the superior next step for identifying the etiology. Hemangiosarcoma of the right auricle and heart base tumors (chemodectoma) are the most common causes. CT provides superior soft tissue characterization, detects small auricular masses invisible on echocardiography (especially post-pericardiocentesis when fluid is removed), and evaluates for concurrent thoracic or abdominal metastatic disease. CEUS can visualize auricular masses but has more limited anatomic coverage. Repeat echo alone after 48 hours is inferior — CT is now the standard of care for neoplastic pericardial effusion workup.

Question 240: On abdominal ultrasound of a 6-year-old intact female Rottweiler, the adrenal glands are both enlarged (left: 1.8 cm, right: 2.1 cm in maximum width) with rounded poles and heterogeneous echogenicity. ACTH stimulation test is equivocal. Urine cortisol:creatinine ratio is elevated on two samples. Low-dose dexamethasone suppression test (LDDST) shows failure to suppress. Which additional imaging finding would MOST strongly support pituitary-dependent hyperadrenocorticism (PDH) over adrenal-dependent hyperadrenocorticism (ADH)?

Bilateral adrenal enlargement with preserved corticomedullary ratio on CT
A unilateral adrenal mass >2 cm with contralateral adrenal atrophy
Adrenal mineralisation on CT with loss of normal architecture
A pituitary mass >6 mm on contrast-enhanced MRI (pituitary macroadenoma) (Correct answer)

Correct answer: A pituitary mass >6 mm on contrast-enhanced MRI (pituitary macroadenoma)

A pituitary macroadenoma (>6 mm) on contrast-enhanced MRI is the most definitive imaging finding confirming PDH, as it directly identifies the source of excess ACTH. Bilateral adrenal enlargement is consistent with PDH but does not distinguish it from other bilateral adrenal diseases. Preserved corticomedullary ratio supports hyperplasia (PDH) but is not definitive. Unilateral adrenal mass >2 cm with contralateral atrophy is the classic finding for ADH (functional adrenal cortical tumor), not PDH. Adrenal mineralization can occur in both functional and non-functional masses.

Question 241: A 5-year-old intact male Cocker Spaniel presents with acute vomiting, fever, and a painful cranial abdomen. Serum lipase is markedly elevated. Which dietary fat level is most appropriate during recovery?

Low fat (<10% DM) (Correct answer)
Moderate fat (15-20% DM)
High fat (>25% DM)
Fat-free diet

Correct answer: Low fat (<10% DM)

Dogs recovering from pancreatitis should receive a low-fat diet (<10% DM) to minimize pancreatic stimulation and reduce recurrence risk.

Question 242: When calculating an IV constant rate infusion (CRI) of fentanyl for a 4.2 kg cat, the clinician wants to deliver 3 mcg/kg/hr. Available fentanyl is 50 mcg/mL concentration. The CRI is to be added to a 250 mL bag of 0.9% NaCl running at 10 mL/hr. How many mL of fentanyl stock should be added to the bag to achieve the desired dose rate (round to nearest 0.1 mL)?

6.3 mL (Correct answer)
12.6 mL
2.5 mL
3.2 mL

Correct answer: 6.3 mL

Step 1 — Desired delivery rate: 3 mcg/kg/hr × 4.2 kg = 12.6 mcg/hr. Step 2 — Fluid delivery rate: 10 mL/hr. Step 3 — Required concentration in the bag: 12.6 mcg/hr ÷ 10 mL/hr = 1.26 mcg/mL. Step 4 — Total drug needed in the 250 mL bag: 1.26 mcg/mL × 250 mL = 315 mcg. Step 5 — Volume of stock to add: 315 mcg ÷ 50 mcg/mL = 6.3 mL. The 6.3 mL of fentanyl stock is added to the 250 mL bag (bag will slightly exceed 250 mL total, which is clinically acceptable). This confirms 6.3 mL is correct.

Question 243: A 5-year-old intact female Boxer presents for abdominal radiographs due to acute vomiting. Radiographs reveal a markedly distended, gas-filled stomach with a soft tissue band ('shelf sign') in the mid-gastric region and the pylorus positioned to the left of midline on the VD projection. A small amount of free peritoneal gas is also noted. Which combination of conditions does this radiographic constellation represent?

Gastric dilatation-volvulus (GDV) with gastric perforation (Correct answer)
Hiatal hernia with secondary pneumoperitoneum
Gastric foreign body with pyloric obstruction and diaphragmatic hernia
Simple gastric dilatation with concurrent pneumoperitoneum from recent abdominocentesis

Correct answer: Gastric dilatation-volvulus (GDV) with gastric perforation

The combination of marked gastric gas distension, a 'shelf sign' (also called the 'double bubble' or compartmentalization created by torsion of the gastric wall), and pyloric displacement to the LEFT of midline on the VD view is pathognomonic for GDV. In GDV, the pylorus rotates clockwise (viewed from the patient's caudal aspect) to end up cranial and to the left. The presence of free peritoneal gas (pneumoperitoneum) indicates gastric rupture/perforation, which is a grave complication confirming the need for immediate surgical intervention. This constellation—GDV + perforation—carries the worst prognosis.

Question 244: A horse undergoes exploratory laparotomy for small intestinal volvulus. After 3 hours of surgery, the horse develops tachycardia, hypotension, and pale mucous membranes. Lactate is 12 mmol/L. What does this lactate value primarily indicate?

Normal response to surgical stress
Hepatic failure from anesthetic agents
Excessive intraoperative fluids causing hemodilution
Severe tissue hypoperfusion and anaerobic metabolism (Correct answer)

Correct answer: Severe tissue hypoperfusion and anaerobic metabolism

A lactate of 12 mmol/L indicates severe systemic hypoperfusion with anaerobic metabolism, which is a poor prognostic indicator in equine colic surgery.

Question 245: Thoracic CT of an 8-year-old Golden Retriever reveals a 2.5 cm pulmonary nodule with a 'halo sign' (ground-glass opacity surrounding a solid core). No other nodules are present. Tracheal wash cytology is negative. What is the MOST appropriate next diagnostic interpretation of the halo sign in this species?

It most commonly represents hemorrhage around the lesion and warrants evaluation for a fungal or vascular etiology (Correct answer)
It is pathognomonic for primary pulmonary carcinoma and warrants immediate surgical resection
It indicates cavitation and is diagnostic for pulmonary abscess
It represents lymphatic permeation and confirms metastatic disease

Correct answer: It most commonly represents hemorrhage around the lesion and warrants evaluation for a fungal or vascular etiology

The CT 'halo sign' (ground-glass opacity around a solid nodule) in dogs most commonly reflects perinodular hemorrhage, seen with angioinvasive organisms (Aspergillus, other fungi) or vascular lesions, rather than representing a specific neoplastic pattern as in human radiology. In people, the halo sign is associated with invasive aspergillosis in immunocompromised patients — the same pathophysiology applies in veterinary patients. It is not pathognomonic for carcinoma, does not indicate cavitation (that would be a lucency within the nodule), and does not specifically indicate lymphatic spread. Fungal serology and bronchoalveolar lavage should be prioritized.

Question 246: A 9-year-old Miniature Schnauzer presents with acute pancreatitis confirmed on abdominal ultrasound and elevated spec cPL. Three days into hospitalization with IV fluids and analgesia, the dog develops icterus. Bilirubin is 8.2 mg/dL (predominantly direct). ALP is 1,200 U/L and GGT is 180 U/L. The dog remains anorexic. Abdominal ultrasound now shows a dilated common bile duct at 6 mm. What is the most likely underlying cause of the new icterus?

Hepatic lipidosis developing from prolonged anorexia
Concurrent immune-mediated hemolytic anemia triggered by pancreatitis
Drug-induced cholestasis from opioid administration
Extrahepatic biliary obstruction (EHBO) secondary to pancreatic inflammation (Correct answer)

Correct answer: Extrahepatic biliary obstruction (EHBO) secondary to pancreatic inflammation

The combination of acute pancreatitis, predominantly direct (conjugated) hyperbilirubinemia, markedly elevated ALP and GGT (cholestatic pattern), and a dilated common bile duct (>5 mm in dogs is abnormal) is classic for extrahepatic biliary obstruction (EHBO). Pancreatic inflammation causes edema and compression of the common bile duct as it traverses the mesoduodenum adjacent to the pancreas. IMHA would cause predominantly indirect (unconjugated) hyperbilirubinemia with spherocytes and a positive Coombs test. Hepatic lipidosis is more characteristic of cats. Opioid-induced sphincter of Oddi spasm can cause mild biliary dilation but typically does not cause this degree of bilirubinemia.

Question 247: A radiograph of a 3-year-old Quarter Horse reveals periarticular bone proliferation and subchondral bone lucency at the distal interphalangeal joint with a linear radiolucent defect extending from the articular surface of the distal phalanx. This finding is MOST consistent with:

Septic pedal osteitis
Subchondral bone cyst (osseous cyst-like lesion) (Correct answer)
Palmar/plantar process fracture of the distal phalanx
Keratoma

Correct answer: Subchondral bone cyst (osseous cyst-like lesion)

Osseous cyst-like lesions (subchondral bone cysts) of the distal phalanx in horses appear as radiolucent defects communicating with the articular surface, typically at the distal interphalangeal joint. The periarticular new bone production and the subchondral lucency with articular communication are hallmark findings. Palmar/plantar process fractures are linear lucencies at the palmar/plantar aspect of P3 not centered on the articular surface. Keratoma is a space-occupying soft tissue lesion within the hoof capsule causing focal pressure remodeling of the solar margin. Septic pedal osteitis produces irregular lysis without the discrete cyst-like architecture.

Question 248: A horse with chronic forelimb lameness shows 'pointing' at rest — standing with the affected limb extended cranially. This posture is MOST commonly associated with:

Coffin joint arthritis
Laminitis
Extensor tendon injury
Navicular syndrome (Correct answer)

Correct answer: Navicular syndrome

Pointing at rest is a classic postural sign of navicular syndrome, as the horse reduces weight on the heel to relieve pressure on the navicular apparatus.

Question 249: Which test is used to diagnose pregnancy toxemia (ketosis) in beef cows and can be performed on-farm using a handheld meter?

Blood beta-hydroxybutyrate (BHB) measurement (Correct answer)
Packed cell volume (PCV)
Serum calcium measurement
Serum total protein

Correct answer: Blood beta-hydroxybutyrate (BHB) measurement

Handheld ketone meters measuring blood beta-hydroxybutyrate (BHB) provide rapid on-farm diagnosis of subclinical and clinical ketosis, with subclinical ketosis defined as BHB ≥1.2 mmol/L.

Question 250: A 9-year-old spayed female Bernese Mountain Dog is evaluated for a 6-month history of polyuria/polydipsia, weight loss, and a pendulous abdomen. Bloodwork shows a persistent lymphopenia (400 cells/μL), eosinopenia, elevated ALP (1,800 U/L), and mildly elevated ALT. Urine cortisol:creatinine ratio is elevated on two morning samples. A low-dose dexamethasone suppression test (LDDST) shows less than 50% suppression at 4 hours but greater than 50% suppression at 8 hours. What is the MOST appropriate next diagnostic step?

Endogenous ACTH concentration measurement
High-dose dexamethasone suppression test (HDDST) to confirm PDH vs. ADH
No further testing is needed; the 8-hour suppression pattern is diagnostic for pituitary-dependent hyperadrenocorticism (PDH) (Correct answer)
Adrenal ultrasonography to rule out adrenal-dependent hyperadrenocorticism

Correct answer: No further testing is needed; the 8-hour suppression pattern is diagnostic for pituitary-dependent hyperadrenocorticism (PDH)

In interpreting the LDDST, suppression of cortisol to <50% of baseline at the 4-hour or 8-hour time point is diagnostic for PDH (pituitary-dependent hyperadrenocorticism). When there is escape at 4 hours but suppression at 8 hours, this pattern (called 'delayed suppression') is considered diagnostic for PDH with approximately 98% specificity — meaning no further differentiation testing is required. The 8-hour suppression (>50% below baseline) essentially rules out an autonomously functioning adrenal tumor, which would not suppress at any time point. An HDDST would be redundant, and while ultrasound and endogenous ACTH are useful adjuncts, the 8-hour LDDST suppression pattern alone confirms PDH.

Question 251: A 5-year-old Dachshund presents with sudden-onset paraplegia, absent deep pain perception in both pelvic limbs, and urinary retention. The lesion localizes to T3-L3 myelopathy. MRI confirms an acute Hansen Type I disc extrusion at T12-T13. The most important prognostic indicator for functional recovery is:

Presence or absence of deep pain perception in the pelvic limbs (Correct answer)
Duration of clinical signs before surgery
Age of the patient at time of surgery
Severity of disc extrusion on MRI (Grasso scale grade)

Correct answer: Presence or absence of deep pain perception in the pelvic limbs

Presence of deep pain perception (DPP) is the single most important prognostic factor in spinal cord injury from IVDD. Dogs that retain DPP have >90% chance of functional recovery with decompressive surgery. Dogs that have lost DPP have approximately 50–60% recovery rates, and those with absent DPP for >48 hours have a significantly poorer prognosis. Duration matters but DPP status is the most critical indicator.

Question 252: A 4-year-old spayed DSH with phenobarbital-refractory epilepsy is started on potassium bromide (KBr) as add-on therapy. Eight weeks later she presents with progressive coughing, expiratory dyspnea, and eosinophilia (1,800 cells/µL). Thoracic radiographs reveal a diffuse bronchial-interstitial pattern. The most likely diagnosis is:

Aspiration pneumonia secondary to postictal laryngeal dysfunction
Secondary bacterial pneumonia from phenobarbital-induced immunosuppression
Potassium bromide–induced eosinophilic bronchopneumopathy (Correct answer)
Feline idiopathic asthma triggered by bromide-induced mast cell degranulation

Correct answer: Potassium bromide–induced eosinophilic bronchopneumopathy

Potassium bromide causes eosinophilic bronchopneumopathy (EBP) in cats — a serious, species-specific adverse effect not observed in dogs. Clinical signs include coughing, dyspnea, and radiographic interstitial infiltrates with peripheral eosinophilia, typically developing weeks to months after initiation. This is distinct from feline asthma and resolves with KBr discontinuation. Because of this risk, KBr is generally avoided in cats; phenobarbital, levetiracetam, or zonisamide are preferred antiepileptic agents in this species.

Question 253: A 7-year-old spayed female cat is presented for progressive weight loss, hyperglobulinemia (total protein 10.8 g/dL, globulins 7.2 g/dL), and a serum albumin:globulin ratio of 0.4. Serum protein electrophoresis reveals a polyclonal gammopathy. Abdominal ultrasound shows mesenteric lymphadenopathy and a focal hyperechoic jejunal mass. Fine needle aspirate of the mass reveals macrophages with intracytoplasmic coronavirus antigen confirmed by immunofluorescence. Which statement regarding antigen testing in this context is MOST accurate?

Polyclonal gammopathy effectively rules out FIP because FIP characteristically produces a monoclonal spike
A positive result confirms systemic FeLV co-infection, which is required for macrophage tropism of feline coronavirus
Positive immunostaining for coronavirus antigen within macrophages in a granulomatous lesion is highly specific for FIP and distinguishes virulent from avirulent FCoV strains (Correct answer)
Immunofluorescent detection of coronavirus in macrophages has low specificity because enteric FCoV can also infect macrophages in healthy cats

Correct answer: Positive immunostaining for coronavirus antigen within macrophages in a granulomatous lesion is highly specific for FIP and distinguishes virulent from avirulent FCoV strains

Immunohistochemistry (IHC) or immunofluorescence detecting coronavirus antigen within macrophages in pyogranulomatous tissue is considered highly specific for FIP — it reflects the macrophage-tropic phenotype of the mutant virulent FCoV. This distinguishes FIP from enteric (avirulent) FCoV infection, in which the virus remains confined to intestinal epithelium and does not productively infect monocytes/macrophages. Polyclonal (not monoclonal) gammopathy is the classic finding in FIP. FeLV co-infection is not required for macrophage tropism. While no test is 100% sensitive/specific, antigen-positive macrophages in a granuloma represent the closest thing to a definitive antemortem FIP diagnosis.

Question 254: A cat is being anesthetized with an alfaxalone TIVA protocol for a lengthy orthopedic repair. Approximately 90 minutes into the procedure, the cat begins showing signs of awareness (purposeful movement, increased HR/BP) despite what appears to be an adequate infusion rate. Which mechanism BEST explains this phenomenon?

Accumulation of an active excitatory metabolite of alfaxalone
Tachyphylaxis to alfaxalone due to GABA-A receptor downregulation (Correct answer)
Cytochrome P450 induction causing accelerated alfaxalone metabolism
Redistribution from effect site to peripheral compartments over time

Correct answer: Tachyphylaxis to alfaxalone due to GABA-A receptor downregulation

Alfaxalone acts on GABA-A receptors (specifically the neurosteroid binding site on β subunits). With prolonged, continuous exposure, GABA-A receptor internalization and desensitization (tachyphylaxis) can occur, requiring higher infusion rates over time to maintain the same depth of anesthesia. This is a clinically documented phenomenon with alfaxalone TIVA, particularly in cats during extended procedures. CYP induction is not rapid enough to explain intraoperative changes. Redistribution (option C) would actually deepen anesthesia as context-sensitive half-time increases. Alfaxalone does not have known clinically significant excitatory metabolites.

Question 255: A dog is prescribed phenobarbital for seizure control. Which of the following is the most important monitoring parameter for long-term therapy?

Serum bile acids and liver enzymes (Correct answer)
Complete blood count
Serum electrolytes
Urinalysis

Correct answer: Serum bile acids and liver enzymes

Phenobarbital induces hepatic enzymes and can cause hepatotoxicity with long-term use, so serum bile acids and liver enzymes must be monitored regularly.

Question 256: A 7-year-old Golden Retriever presents with polyuria, polydipsia, and a pendulous abdomen. Urinalysis reveals isosthenuria (USG 1.008) and glucosuria with a normal blood glucose of 95 mg/dL. Abdominal ultrasound shows bilateral adrenomegaly. Which mechanism best explains the glucosuria in this patient?

Concurrent diabetes mellitus with stress-induced blood glucose normalization at time of sampling
Renal tubular dysfunction secondary to hypercortisolism causing a Fanconi-like syndrome (Correct answer)
Occult postprandial hyperglycemia exceeding the renal threshold transiently
Primary renal glucosuria due to SGLT2 transporter mutation

Correct answer: Renal tubular dysfunction secondary to hypercortisolism causing a Fanconi-like syndrome

Hyperadrenocorticism (Cushing's syndrome) can cause proximal renal tubular dysfunction resembling Fanconi syndrome, leading to glucosuria, aminoaciduria, and phosphaturia despite normoglycemia. The bilateral adrenomegaly, classic clinical signs, and isosthenuria all point to pituitary-dependent hyperadrenocorticism. The glucosuria here is not due to hyperglycemia exceeding the renal threshold but rather impaired tubular reabsorption. Primary renal glucosuria from SGLT2 mutations is rare in dogs, and the clinical picture does not support transient hyperglycemia or stress normalization.

Question 257: A 5-year-old Thoroughbred racehorse presents with acute-onset bilateral forelimb lameness, a classic sawhorse stance, and refusal to move. The trainer reports the horse received a phenylbutazone injection yesterday for a minor muscle strain. Careful examination reveals bilateral forelimb digital pulses of 4/4 and marked heat in all four feet. Which diagnostic finding would most strongly support laminitis secondary to phenylbutazone toxicosis rather than sepsis-induced laminitis in this horse?

Symmetric rotation on radiographs with ventral lamellar wedge formation
Protein-losing enteropathy with hypoalbuminemia on chemistry panel (Correct answer)
Serum amyloid A concentration >1000 µg/mL
Elevated fecal alpha-1 protease inhibitor indicating GI inflammation

Correct answer: Protein-losing enteropathy with hypoalbuminemia on chemistry panel

NSAID toxicosis (right dorsal colitis or gastric ulceration) causes protein-losing enteropathy through mucosal damage, resulting in hypoalbuminemia. This decreased oncotic pressure promotes digital lamellar edema and precipitates laminitis via a distinct vascular mechanism separate from inflammatory cytokine cascades. Hypoalbuminemia on a chemistry panel, combined with the recent NSAID exposure and absence of a septic focus, strongly implicates phenylbutazone-induced colitis as the trigger. Elevated SAA suggests systemic inflammation but is nonspecific. Radiographic rotation is a consequence of laminitis, not a cause-differentiator. Fecal alpha-1 PI elevation confirms enteropathy but is more useful for chronic protein loss confirmation.

Question 258: A 6-year-old cat is presented for evaluation of a suspected portosystemic shunt. Fasting ammonia is 210 µmol/L (ref <60). On abdominal ultrasound, multiple tortuous vessels are identified in the splenic and left gastric regions but no single large shunting vessel. Which statement about this cat's condition is most accurate?

This represents portal vein hypoplasia (microvascular dysplasia) with compensatory collateral formation
This pattern is consistent with a congenital extrahepatic portosystemic shunt requiring surgical attenuation
Multiple acquired portosystemic shunts indicate portal hypertension, most likely from hepatic fibrosis or cirrhosis (Correct answer)
Multiple shunts in this distribution are typical of right divisional intrahepatic shunts with collateral reconstitution

Correct answer: Multiple acquired portosystemic shunts indicate portal hypertension, most likely from hepatic fibrosis or cirrhosis

Multiple acquired portosystemic shunts (APSS) develop as a consequence of portal hypertension, typically from hepatic parenchymal disease causing increased sinusoidal resistance — most commonly hepatic fibrosis, cirrhosis, or non-cirrhotic portal hypertension in cats. Unlike congenital shunts (which are typically single large vessels), acquired shunts are multiple small vessels that open as portosystemic pressure gradients increase. In cats, hepatic lipidosis, cholangitis, and inflammatory bowel disease can drive fibrosis. Surgery is contraindicated in APSS; treating underlying hepatic disease is the goal.

Question 259: A 7-year-old Warmblood gelding presents with acute onset right forelimb lameness and a positive flexion test of the distal limb. Nerve blocks reveal pain originating from the palmar digital nerves. Radiographs show pedal osteitis. Which treatment is most appropriate for long-term management?

Deep digital flexor tenotomy
Coffin joint corticosteroid injection
Palmar digital neurectomy (Correct answer)
Navicular bursa lavage

Correct answer: Palmar digital neurectomy

Palmar digital neurectomy is indicated for horses with chronic foot pain (including pedal osteitis) that have failed conservative management, providing long-term desensitization of the heel and sole.

Question 260: A beef cow herd experiences a cluster of late-term abortions (7–9 months gestation) over 3 weeks. Fetuses show autolysis with placentitis. Serologic titers for Neospora caninum are elevated in affected cows but not in non-aborted herdmates. Which epidemiologic pattern best supports transient epidemic neosporosis rather than endemic neosporosis in this herd?

Affected cows have daughters with high seropositivity, suggesting vertical transmission is the dominant route of introduction
Abortion rate is 2–3% annually and steadily increases each year as new heifers enter the breeding herd
Abortions occur in cows of all ages with no clustering by age cohort and seroprevalence is uniformly distributed across the herd
Abortions are concentrated in first-calf heifers and 2-year-olds with a rapid onset and high attack rate, while older cows are largely spared (Correct answer)

Correct answer: Abortions are concentrated in first-calf heifers and 2-year-olds with a rapid onset and high attack rate, while older cows are largely spared

Epidemic (point-source) neosporosis typically results from a sudden environmental exposure—such as contamination of feed or water with dog feces containing Neospora oocysts. This produces a high attack rate concentrated in a short time window and often disproportionately affects naive younger animals that lack any prior immunity. Endemic neosporosis, by contrast, is maintained by vertical (transplacental) transmission and tends to show a steady low-level abortion rate (1–3%) distributed across all age groups with seropositive dams producing seropositive offspring over successive years.

Question 261: Which drug class is contraindicated in cats due to their deficiency in UDP-glucuronosyltransferase?

Aminoglycosides
NSAIDs metabolized via glucuronidation (Correct answer)
Macrolide antibiotics
Fluoroquinolones

Correct answer: NSAIDs metabolized via glucuronidation

Cats lack sufficient UDP-glucuronosyltransferase activity, making drugs like acetaminophen and certain NSAIDs dependent on glucuronidation highly toxic.

Question 262: A 6-year-old Standardbred pacer presents with hindlimb lameness localized to the hock. Radiographs reveal periarticular osteophytes at the distal intertarsal and tarsometatarsal joints. The MOST appropriate treatment is:

Cunean tenectomy alone
Arthroscopic joint lavage of the tarsocrural joint
Neurectomy of the tibial nerve
Intra-articular corticosteroids into the affected low-motion joints (Correct answer)

Correct answer: Intra-articular corticosteroids into the affected low-motion joints

Bone spavin (osteoarthritis of the low-motion hock joints) is treated with intra-articular corticosteroid injections into the distal intertarsal and tarsometatarsal joints to reduce inflammation and pain.

Question 263: Metabolic bone disease (MBD) in captive reptiles is most commonly caused by which combination of factors?

Hyperthyroidism
Excess vitamin D3 supplementation
Calcium/phosphorus imbalance and UV-B light deficiency (Correct answer)
Bacterial osteomyelitis secondary to trauma

Correct answer: Calcium/phosphorus imbalance and UV-B light deficiency

MBD in reptiles results from inadequate dietary calcium, improper Ca:P ratios, and insufficient UV-B light for endogenous vitamin D3 synthesis.

Question 264: A dog undergoes hindlimb amputation. Which regional anesthetic technique would provide the MOST comprehensive perioperative analgesia for this procedure?

Lumbosacral epidural with morphine and lidocaine (Correct answer)
Wound soaker catheter only
Intrapleural bupivacaine instillation
Brachial plexus block

Correct answer: Lumbosacral epidural with morphine and lidocaine

A lumbosacral epidural combining an opioid (morphine) for prolonged analgesia and a local anesthetic (lidocaine/bupivacaine) for sensory and motor blockade provides the most effective and comprehensive analgesia for hindlimb amputations.

Question 265: Air sac mites (Sternostoma tracheacolum) most commonly cause respiratory disease in which group of birds?

Domestic poultry
Waterfowl
Canaries and finches (Correct answer)
Psittacines (parrots)

Correct answer: Canaries and finches

Air sac mites primarily affect Passeriformes such as canaries and finches, causing respiratory distress and the 'going light' syndrome.

Question 266: A 5-year-old Siamese cat is presented for a chronic, intermittent cough and occasional wheezing. Thoracic radiographs are performed. Which of the following radiographic patterns is most consistent with a diagnosis of feline asthma?

A patchy alveolar pattern concentrated in the cranioventral lung lobes.
Enlarged, tortuous pulmonary arteries and right-sided cardiomegaly.
A diffuse, unstructured interstitial pattern with prominent pulmonary veins.
A prominent bronchial pattern, characterized by 'doughnuts' and 'tramlines', with evidence of lung hyperinflation. (Correct answer)

Correct answer: A prominent bronchial pattern, characterized by 'doughnuts' and 'tramlines', with evidence of lung hyperinflation.

Feline asthma is an inflammatory condition of the lower airways. Radiographically, this manifests as a prominent bronchial pattern due to the accumulation of inflammatory cells around the airways. These thickened bronchial walls are seen as 'doughnuts' (end-on view) and 'tramlines' (long-axis view). Air trapping due to bronchoconstriction can also lead to lung hyperinflation.

Question 267: A free-ranging red-tailed hawk is presented after being found unable to fly. Physical exam reveals bilateral mydriasis unresponsive to light, weakness, and flaccid paralysis of the nictitating membrane. The bird is afebrile and alert. Which toxin is most consistent with this clinical picture, and what is the proposed mechanism?

Organophosphate toxicosis — irreversibly inhibits acetylcholinesterase, causing cholinergic crisis with miosis
Lead toxicosis — inhibits delta-aminolevulinic acid dehydratase disrupting heme synthesis and causing axonal neuropathy
Zinc toxicosis — causes oxidative hemolysis and secondary neurotoxicity via reactive oxygen species
Type C botulinum toxin — cleaves SNAP-25, blocking presynaptic acetylcholine release at the neuromuscular junction (Correct answer)

Correct answer: Type C botulinum toxin — cleaves SNAP-25, blocking presynaptic acetylcholine release at the neuromuscular junction

Limberneck (avian botulism) caused by Clostridium botulinum type C toxin is classic in raptors ingesting maggots or carcasses. The toxin cleaves SNAP-25 (a SNARE complex protein), preventing presynaptic vesicle fusion and blocking acetylcholine release at the neuromuscular junction — producing flaccid paralysis, mydriasis, and weakness of the nictitating membrane. Organophosphates cause miosis (not mydriasis) and cholinergic signs; lead causes CNS signs and GI effects; zinc primarily causes hemolysis.

Question 268: A 2-year-old intact male DSH cat from a multi-cat household presents with progressive weight loss, anorexia, and a palpable abdominal mass. Abdominal effusion is present, and fluid analysis reveals a protein concentration of 5.8 g/dL, a Rivalta test that is positive, and a cell count of 4,200 cells/μL (predominantly non-degenerate neutrophils and macrophages). An immunofluorescence assay on the effusion detects coronavirus antigen within macrophages. Which statement BEST describes the pathogenesis underlying this cat's condition?

Antibody-dependent enhancement allows serum anti-coronavirus IgG to facilitate viral entry into macrophages via Fc receptors, and this is the sole mechanism of monocyte/macrophage infection.
A biotype shift from enteric coronavirus to FIP virus occurs via two key mutations in the spike protein receptor-binding domain and the 3c accessory gene, enabling macrophage tropism and systemic spread. (Correct answer)
The cat was infected with a highly virulent serotype II feline coronavirus strain acquired horizontally from a shedding cat, bypassing the need for any mutational events.
FIP develops exclusively in cats with concurrent FeLV or FIV co-infection, which suppresses regulatory T-cell responses and permits macrophage invasion.

Correct answer: A biotype shift from enteric coronavirus to FIP virus occurs via two key mutations in the spike protein receptor-binding domain and the 3c accessory gene, enabling macrophage tropism and systemic spread.

FIP arises from in-host mutation of feline enteric coronavirus (FECV), most critically in the spike protein (affecting cell tropism) and the 3c gene (disrupting immune evasion), converting FECV into FIP virus (FIPV) with macrophage-tropic capability. This internal mutation model—not horizontal transmission of a FIPV strain—is the current consensus. Co-infection with FeLV/FIV is a risk factor but not a prerequisite. Antibody-dependent enhancement may play a contributory role but is not the sole or primary mechanism.

Question 269: A USDA veterinarian performing post-mortem inspection on a steer carcass finds multiple, well-demarcated, caseous abscesses in the lungs and associated mediastinal lymph nodes. What is the correct disposition for this carcass?

Condemn the entire carcass. (Correct answer)
Pass for cooking only.
Condemn the thoracic organs and pass the rest of the carcass.
Pass for human consumption after trimming affected parts.

Correct answer: Condemn the entire carcass.

The lesions described (caseous necrosis/granulomas in lungs and associated lymph nodes) are classic for bovine tuberculosis (*Mycobacterium bovis*). According to USDA regulations, evidence of generalized tuberculosis, which includes extensive lesions in the thoracic cavity, requires condemnation of the entire carcass due to its significant zoonotic potential and systemic nature.

Question 270: A 3-year-old Quarter Horse mare is presented with a history of recurrent episodes of mild colic, weight loss despite a good appetite, and loose feces. Fecal egg count is 0 EPG. Serum chemistry reveals hypoalbuminemia (2.1 g/dL) and elevated beta-globulins. Rectal palpation reveals thickened large colon walls. Which condition is highest on the differential list?

Cyathostominosis (larval cyathostomiasis) with mucosal larval emergence (Correct answer)
Right dorsal colitis secondary to NSAID toxicity
Granulomatous enteritis (multisystemic eosinophilic epitheliotropic disease)
Equine proliferative enteropathy due to Lawsonia intracellularis

Correct answer: Cyathostominosis (larval cyathostomiasis) with mucosal larval emergence

Larval cyathostomiasis (Type II cyathostominosis) occurs when large numbers of encysted early third-stage (EL3) cyathostomin larvae simultaneously emerge from the intestinal mucosa, causing protein-losing enteropathy, diarrhea, weight loss, and colic. Critically, adult egg-shedding larvae are absent during this phase, so fecal egg counts are zero or very low — this is a key distinguishing feature. Hypoalbuminemia and elevated beta-globulins reflect the protein loss and acute-phase response. Thickened colon walls on rectal palpation support mucosal infiltration. Equine proliferative enteropathy (Lawsonia) is seen primarily in weanlings and yearlings. Right dorsal colitis would have a history of NSAID use. MEED is rare and typically involves multiple organ systems.

Question 271: Which of the following is the recommended first-line treatment for lead toxicosis in birds?

D-Penicillamine
Dimercaprol (BAL)
Calcium EDTA (Correct answer)
Succimer (DMSA)

Correct answer: Calcium EDTA

Calcium EDTA is the chelation agent of choice for acute lead toxicosis in birds and is administered parenterally for rapid effect.

Question 272: In the context of zoonotic disease epidemiology, which of the following pathogens is correctly classified as an obligate maintenance host situation, where humans are ONLY incidental (dead-end) hosts and contribute negligibly to transmission cycles?

Rabies virus in an enzootic raccoon-variant region
Influenza A (H1N1) pdm09 during the 2009 pandemic
Mycobacterium tuberculosis var. bovis in a region with active cattle-to-human spillover and human-to-human transmission documented
Yersinia pestis during a sylvatic plague epizootic in prairie dogs (Correct answer)

Correct answer: Yersinia pestis during a sylvatic plague epizootic in prairie dogs

During sylvatic plague epizootics in prairie dog colonies, Yersinia pestis cycles entirely within wild rodent populations via flea vectors. Humans who become infected (via flea bite or handling infected animals) are true dead-end hosts — they do not sustain or amplify the transmission cycle back into the rodent reservoir or among other humans (pneumonic plague is rare and requires close contact). In contrast, M. bovis can involve human-to-human transmission in high-burden settings, rabies variants can occasionally cycle in human communities with dog-mediated rabies, and influenza H1N1 became a fully sustained human pandemic pathogen.

Question 273: A cat presents with acute-onset ptyalism, vomiting, ataxia, and mydriasis after being seen chewing on a lily bouquet. Bloodwork 36 hours later reveals a BUN of 98 mg/dL and creatinine of 7.2 mg/dL. Which statement BEST describes the mechanism of lily nephrotoxicity in cats?

Lily stamen pollen contains calcium oxalate crystals that deposit in renal tubules and cause obstructive nephropathy
The toxic glycoside tuliposide A is activated in the renal cortex and alkylates mitochondrial DNA of tubular cells
Lycorine alkaloids found in Lilium species competitively inhibit renal organic anion transporters, causing tubular toxin accumulation
The nephrotoxic principle causes direct proximal tubular epithelial cell death via a mechanism not yet fully elucidated at the molecular level, with no known antidote (Correct answer)

Correct answer: The nephrotoxic principle causes direct proximal tubular epithelial cell death via a mechanism not yet fully elucidated at the molecular level, with no known antidote

True lily nephrotoxicity (Lilium and Hemerocallis species) in cats is a well-documented but mechanistically incompletely understood toxidrome. The toxic principle causes acute, severe proximal tubular necrosis, but the exact molecular mechanism has not been definitively identified in peer-reviewed literature. There is no antidote — treatment is aggressive IV fluid diuresis initiated within hours of exposure, before renal injury is established. Calcium oxalate crystals causing obstructive nephropathy are associated with Oxalis and Araceae species (e.g., Philodendron, Dieffenbachia), not true lilies. Lycorine is found in Narcissus/Amaryllidaceae; tuliposide A is found in Tulipa. Cats are uniquely and exquisitely sensitive to Lilium/Hemerocallis; dogs are not.

Question 274: Which of the following is the most critical control point for eliminating Bovine Viral Diarrhea Virus (BVDV) from a beef cow-calf herd?

Vaccinating all adult animals annually with a modified-live virus (MLV) vaccine.
Implementing a comprehensive fly and vector control program.
Identifying and removing persistently infected (PI) animals. (Correct answer)
Treating all clinically ill animals with supportive care and antibiotics.

Correct answer: Identifying and removing persistently infected (PI) animals.

Persistently infected (PI) animals are the primary reservoir and source of BVDV shedding within a herd. They become infected in utero and shed the virus throughout their lives. While vaccination is a key part of prevention, it may not be fully effective in the face of the massive viral load shed by a PI animal. Therefore, the most critical step for eradication is to test for, identify, and remove these PI animals from the population.

Question 275: A 7-year-old intact female Boxer presents with polyuria, polydipsia, and a serum sodium of 157 mEq/L. She is not pregnant. Endogenous ACTH stimulation test is normal. Which diagnosis is most consistent with these findings?

Hyperadrenocorticism
Diestrus-associated acromegaly or progesterone-induced GH excess (Correct answer)
Diabetes insipidus
Primary hyperaldosteronism

Correct answer: Diestrus-associated acromegaly or progesterone-induced GH excess

Progesterone during diestrus stimulates mammary GH secretion in intact females, causing insulin resistance, PU/PD, and hypernatremia (acromegaly-like syndrome).

Question 276: A 5-year-old Great Dane presents with sudden gastric dilation. Radiographs confirm gastric dilatation-volvulus (GDV). After stabilization and surgery, which procedure should be performed concurrently to prevent recurrence?

Splenectomy in all cases
Esophageal banding
Gastropexy (Correct answer)
Pyloromyotomy

Correct answer: Gastropexy

Gastropexy permanently affixes the stomach to the body wall and reduces GDV recurrence from ~70–80% to less than 5%.

Question 277: A 7-year-old intact male German Shepherd presents for progressive pelvic limb ataxia. Myelography reveals an extradural compressive lesion at L7-S1 with a 'golf tee' sign on the lateral view. CT confirms a lateralized, calcified mass with a 'popcorn' mineralization pattern within the intervertebral foramen. Which diagnosis is most consistent with this imaging constellation?

Degenerative lumbosacral stenosis with foraminal osteophytosis
Nerve sheath tumor of the L7 nerve root
Hansen Type I intervertebral disc extrusion with foraminal migration (Correct answer)
Synovial cyst arising from the articular facet joint

Correct answer: Hansen Type I intervertebral disc extrusion with foraminal migration

Hansen Type I disc extrusion can migrate laterally into the intervertebral foramen, producing the classic 'golf tee' extradural sign on myelography. Calcified disc material from Type I (chondroid metaplasia) produces the 'popcorn' mineralization pattern on CT. Nerve sheath tumors are typically non-mineralized and cause foraminal widening/erosion. Synovial cysts are periarticular soft-tissue densities without calcification in this pattern. Degenerative lumbosacral stenosis shows diffuse stenosis rather than a discrete foraminal mass.

Question 278: A cat presents with acute rodenticide toxicosis from ingestion of brodifacoum. Vitamin K1 therapy is initiated. Which statement best describes the pharmacodynamic basis for why high doses and prolonged treatment (3–6 weeks) are required compared to warfarin toxicosis?

Brodifacoum irreversibly alkylates the vitamin K epoxide reductase enzyme complex
Brodifacoum undergoes extensive enterohepatic recirculation, maintaining toxic tissue concentrations long after ingestion (Correct answer)
Brodifacoum has a much shorter half-life than warfarin, requiring more frequent dosing
Brodifacoum depletes stores of vitamins K2 and K3, which cannot be replaced by K1 supplementation alone

Correct answer: Brodifacoum undergoes extensive enterohepatic recirculation, maintaining toxic tissue concentrations long after ingestion

Brodifacoum is a long-acting anticoagulant rodenticide with extensive enterohepatic recirculation and high lipophilicity, resulting in a plasma half-life of weeks to months in companion animals. This prolonged tissue retention means that even after a single ingestion, the drug continues to inhibit vitamin K epoxide reductase for an extended period. Treatment with vitamin K1 must continue until all brodifacoum is eliminated, typically 3–6 weeks, verified by PT/aPTT testing 48–72 hours after cessation.

Question 279: A 5-year-old Labrador Retriever presents with acute onset hemolytic anemia (PCV 14%, spherocytes on smear, positive Coombs test). Which treatment combination is most appropriate as initial therapy?

Prednisone alone
Cyclosporine alone
Dexamethasone + vincristine
Prednisone + azathioprine or mycophenolate (Correct answer)

Correct answer: Prednisone + azathioprine or mycophenolate

Combination immunosuppression with a corticosteroid plus a steroid-sparing agent (azathioprine or mycophenolate) is recommended for IMHA to reduce relapse rates.

Question 280: A horse with forelimb lameness has a positive response to hoof testers over the medial heel region. After palmar digital nerve block the lameness is only partially improved. The MOST appropriate next step is:

Perform an intra-articular coffin joint block (Correct answer)
Repeat the palmar digital block with a higher volume
Apply a bar shoe and reassess in 6 weeks
Block the navicular bursa directly

Correct answer: Perform an intra-articular coffin joint block

When a palmar digital block provides only partial improvement, an intra-articular coffin joint block helps determine whether the DIP joint is contributing to the residual lameness.

Question 281: A 12-year-old Quarter Horse cutting horse presents with chronic bilateral hindlimb stiffness and a 'rope-walking' gait. On rectal palpation, crepitus is noted over the lumbosacral region. Standing radiographs are non-diagnostic. Scintigraphy reveals focal increased radiopharmaceutical uptake at L5-S1. Nuclear scintigraphy-guided infiltration of the lumbosacral space with corticosteroid provides marked temporary improvement. What is the most appropriate long-term management strategy if conservative therapy fails after two injection cycles?

Retirement from cutting, with consideration of mesotherapy along the thoracolumbar epaxial musculature
Extracorporeal shock wave therapy (ESWT) targeted to the lumbosacral facet joints under ultrasound guidance (Correct answer)
Computed tomography-guided chemical neurolysis of the dorsal sacral nerve roots
Sacroiliac joint arthrodesis via percutaneous implant placement

Correct answer: Extracorporeal shock wave therapy (ESWT) targeted to the lumbosacral facet joints under ultrasound guidance

For horses with confirmed lumbosacral pathology refractory to intra-articular corticosteroid, extracorporeal shock wave therapy (ESWT) targeted under ultrasound guidance to the lumbosacral facet articulations is a validated next-line intervention. ESWT delivers acoustic energy that modulates pain via nerve fiber hyperpolarization and stimulates local tissue remodeling. It is minimally invasive, can be repeated, and has demonstrated efficacy in peer-reviewed studies for horses with thoracolumbar and lumbosacral pain. Sacroiliac arthrodesis addresses the SI joint but not lumbosacral facets, and chemical neurolysis is not an accepted equine technique for this indication.

Question 282: A 4-year-old Greyhound is prescribed phenobarbital for epilepsy. Compared to a Labrador Retriever of the same weight, which pharmacokinetic difference most significantly affects dosing in Greyhounds?

Greyhounds exhibit increased P-glycoprotein expression at the blood-brain barrier, reducing CNS penetration
Greyhounds have a lower volume of distribution for lipophilic drugs due to minimal body fat, resulting in higher plasma concentrations (Correct answer)
Greyhounds have accelerated renal tubular secretion of phenobarbital, requiring higher doses to maintain therapeutic levels
Greyhounds have reduced hepatic CYP450 enzyme activity, leading to slower phenobarbital clearance

Correct answer: Greyhounds have a lower volume of distribution for lipophilic drugs due to minimal body fat, resulting in higher plasma concentrations

Greyhounds have exceptionally low body fat (1–3% vs. 15–25% in mixed breeds). Phenobarbital is a lipophilic drug that distributes into adipose tissue. With minimal fat stores, the volume of distribution is reduced, leading to higher peak plasma concentrations at standard mg/kg doses. This means Greyhounds are at greater risk for toxicity and often require lower initial doses. Hepatic clearance differences exist for some drugs (e.g., propofol, thiopental) but are not the primary concern with phenobarbital dosing.

Question 283: A 3-year-old Thoroughbred presents with acute-onset severe lameness. Radiographs of the fetlock region are initially unremarkable. Nuclear scintigraphy (bone phase) shows a focal, intensely increased radiopharmaceutical uptake (IRU) at the palmar/plantar aspect of the proximal sesamoid bones. MRI performed 48 hours later shows a T2-hypointense linear signal defect traversing the body of the medial proximal sesamoid bone. What is the MOST likely diagnosis and its implication?

Sesamoiditis (chronic degenerative change) — requires 4-6 weeks of stall rest
Body fracture of the proximal sesamoid — high risk for catastrophic failure and suspensory apparatus breakdown (Correct answer)
Basilar fracture of the proximal sesamoid — low catastrophic failure risk if managed conservatively
Abaxial fracture of the proximal sesamoid — surgical arthroscopy is curative

Correct answer: Body fracture of the proximal sesamoid — high risk for catastrophic failure and suspensory apparatus breakdown

A T2-hypointense linear defect traversing the body of the proximal sesamoid bone represents a body fracture — the most serious type of sesamoid fracture in racehorses. Unlike apical (tip) or abaxial (side) fractures, body fractures involve the entire cross-section of the bone and risk complete disruption of the suspensory apparatus, which can cause catastrophic breakdown. The scintigraphic hot spot on the palmar/plantar aspect with subsequent MRI correlation is the advanced imaging sequence used when plain radiographs are unremarkable early in the injury. Sesamoiditis causes diffuse rather than focal linear T2 hypointensity. Basilar fractures involve the base and have a better prognosis than body fractures.

Question 284: A 5-year-old Cocker Spaniel presents with acute lethargy, pale mucous membranes, and icterus. A complete blood count reveals a severe regenerative anemia (HCT 15%) with marked spherocytosis and autoagglutination. Which of the following is the most likely diagnosis?

Immune-Mediated Hemolytic Anemia (IMHA) (Correct answer)
Babesiosis
Von Willebrand's disease
Zinc toxicity

Correct answer: Immune-Mediated Hemolytic Anemia (IMHA)

The combination of severe regenerative anemia, spherocytosis, and autoagglutination is pathognomonic for Immune-Mediated Hemolytic Anemia (IMHA). Spherocytes are red blood cells that have lost their biconcave shape due to partial phagocytosis, a hallmark of extravascular hemolysis in IMHA. Autoagglutination is the macroscopic clumping of red blood cells due to antibody coating. While other conditions can cause anemia, this specific combination of findings points strongly to an immune-mediated process.

Question 285: A cat with hyperthyroidism is started on methimazole. Two weeks later, the owner reports the cat is scratching its face intensely and has developed facial excoriations. Which mechanism best explains this idiosyncratic reaction, and what is the appropriate next step?

Methimazole accumulation causing direct neurotoxicity to facial nerve endings; reduce dose by 50%
Type IV delayed hypersensitivity reaction; discontinue methimazole and consider radioiodine or surgical thyroidectomy (Correct answer)
Methimazole-induced mast cell degranulation; administer diphenhydramine and continue methimazole at a lower dose
Compensatory increase in thyroid hormone causing pruritus; increase the methimazole dose

Correct answer: Type IV delayed hypersensitivity reaction; discontinue methimazole and consider radioiodine or surgical thyroidectomy

Facial pruritus and excoriation is a well-documented idiosyncratic adverse effect of methimazole in cats, occurring in approximately 2-3% of treated cats. It represents a Type IV (cell-mediated) delayed hypersensitivity reaction typically appearing within the first month of therapy. This reaction necessitates discontinuation of methimazole; dose reduction is not appropriate as re-exposure will trigger recurrence. Alternative management includes carbimazole (prodrug of methimazole, so cross-reactivity is possible), radioactive iodine (I-131), or surgical thyroidectomy.

Question 286: A ferret presents with progressive hind limb weakness, muscle wasting, and hypoglycemia. Blood glucose is 45 mg/dL. The most likely diagnosis is:

Aleutian disease
Lymphoma
Adrenal gland disease
Insulinoma (Correct answer)

Correct answer: Insulinoma

Insulinoma is the most common pancreatic tumor in ferrets and classically causes episodic hypoglycemia with hind limb weakness.

Question 287: To perform a complete low four-point nerve block on a forelimb, a veterinarian must anesthetize the medial and lateral palmar nerves as well as which other two nerves?

Axillary and musculocutaneous nerves
Medial and lateral cutaneous antebrachial nerves
Deep and superficial branches of the radial nerve
Medial and lateral palmar metacarpal nerves (Correct answer)

Correct answer: Medial and lateral palmar metacarpal nerves

The low four-point block is designed to desensitize the entire fetlock and structures distal to it. This requires blocking the medial and lateral palmar nerves (which run down the back of the leg) and the medial and lateral palmar metacarpal nerves (which run alongside the splint bones and provide deep/dorsal sensation to the fetlock). The other nerve pairs listed are located much more proximally in the equine forelimb.

Question 288: Which of the following medications is a potent, broad-spectrum antiemetic that functions by antagonizing neurokinin-1 (NK-1) receptors in the central vomiting center?

Maropitant (Correct answer)
Metoclopramide
Ondansetron
Famotidine

Correct answer: Maropitant

Maropitant is a neurokinin-1 (NK-1) receptor antagonist. It works by blocking the binding of Substance P, a key neurotransmitter in the emetic pathway, at NK-1 receptors located in the vomiting center and the chemoreceptor trigger zone. This mechanism makes it highly effective against vomiting from both central and peripheral stimuli. Ondansetron is a serotonin (5-HT3) antagonist, metoclopramide is primarily a dopamine (D2) antagonist, and famotidine is an H2-receptor antagonist used to reduce stomach acid.

Question 289: A 10-year-old Quarter Horse with chronic, bilateral forelimb lameness undergoes a radiographic examination of the feet. Which of the following radiographic findings is most indicative of navicular disease (podotrochleosis)?

Narrowing of the distal interphalangeal joint space with extensive periarticular osteophytes.
Rotation and sinking of the distal phalanx (P3) within the hoof capsule.
Smooth, well-defined new bone formation on the extensor process of the distal phalanx.
Enlarged, flask-shaped synovial invaginations ('lollipops') on the distal border of the navicular bone. (Correct answer)

Correct answer: Enlarged, flask-shaped synovial invaginations ('lollipops') on the distal border of the navicular bone.

While many radiographic changes can be seen with navicular disease, the presence of more than 6-7 enlarged, flask-shaped or branching synovial invaginations (vascular channels) on the distal border is a classic and significant finding. Other key signs include flexor cortex erosions and medullary sclerosis.

Question 290: A veterinarian prescribes phenobarbital to a 4-year-old epileptic dog. After 6 months of stable seizure control, breakthrough seizures occur despite unchanged dosing. Serum phenobarbital levels are now below therapeutic range. No drug interactions or compliance issues are identified. What pharmacokinetic phenomenon best explains this finding?

Phenobarbital undergoes tachyphylaxis at GABA-A receptors over time
Enterohepatic recirculation of phenobarbital decreases progressively with hepatic adaptation
Renal tubular secretion of phenobarbital increases with chronic exposure
Phenobarbital induces its own hepatic metabolism (autoinduction) via CYP enzyme upregulation (Correct answer)

Correct answer: Phenobarbital induces its own hepatic metabolism (autoinduction) via CYP enzyme upregulation

Phenobarbital is a classic example of autoinduction — it induces the hepatic cytochrome P450 enzymes (particularly CYP2B and CYP3A) responsible for its own metabolism. With chronic administration, enzyme induction progressively accelerates phenobarbital clearance, causing serum levels to fall below therapeutic range even at a fixed dose. This typically occurs within weeks to months and necessitates dose escalation. Therapeutic drug monitoring is essential; target serum levels in dogs are 20–40 µg/mL.

Question 291: A veterinarian performs an abdominal ultrasound on a dog with acute vomiting and anorexia. Which finding is most specific for a mechanical small intestinal obstruction?

Peristaltic waves are increased to 6-7 contractions per minute throughout the small intestine.
The intestinal wall is diffusely thickened with preserved layering.
A segment of intestine is severely dilated with fluid (>1.6 times the diameter of the aorta) proximal to a distinct transition point. (Correct answer)
Hyperechoic mesenteric fat is noted surrounding the entire small bowel.

Correct answer: A segment of intestine is severely dilated with fluid (>1.6 times the diameter of the aorta) proximal to a distinct transition point.

The most reliable ultrasonographic sign of a mechanical small intestinal obstruction is segmental dilation of the intestine proximal to the obstruction. A commonly used objective criterion is a small intestinal diameter greater than 1.6 times the diameter of the aorta. Other signs include a visible foreign body, plication, or intussusception.

Question 292: A 2-year-old Border Collie presents with episodic muscle tremors and facial rubbing after exercise. Ionized calcium is 0.78 mmol/L (normal 1.12–1.40). Which condition is the most common cause of hypocalcemia in young adult dogs?

Eclampsia (puerperal tetany) (Correct answer)
Chronic renal failure
Vitamin D deficiency
Primary hypoparathyroidism

Correct answer: Eclampsia (puerperal tetany)

Eclampsia due to calcium loss through milk production in periparturient females is the most common cause of acute hypocalcemia in young adult dogs.

Question 293: A 9-year-old DSH cat is diagnosed with oral squamous cell carcinoma and the oncologist considers platinum-based chemotherapy. A technician asks whether cisplatin can be dose-reduced for safer use in this cat. Which statement most accurately describes cisplatin use in cats?

Cisplatin is safe in cats when combined with ondansetron pretreatment to blunt the acute cytokine-mediated response
Cisplatin toxicity in cats manifests primarily as nephrotoxicity and peripheral neuropathy, identical to other species
Cisplatin can be used safely in cats at doses 50% lower than those used in dogs with aggressive IV fluid diuresis
Cisplatin is absolutely contraindicated in cats because it causes fatal pulmonary edema and pleural effusion regardless of dose (Correct answer)

Correct answer: Cisplatin is absolutely contraindicated in cats because it causes fatal pulmonary edema and pleural effusion regardless of dose

Cisplatin is absolutely contraindicated in cats at any dose. Unlike dogs and humans where the primary toxicities are nephrotoxicity and myelosuppression, cats develop fatal acute pulmonary edema and pleural effusion within hours to days of cisplatin administration due to species-specific capillary permeability responses. No dose reduction or supportive care protocol makes cisplatin safe in this species. Carboplatin is the preferred platinum-based alternative for feline oncology patients.

Question 294: Which of the following birds is most susceptible to aspergillosis due to its natural habitat and immune characteristics?

Cockatiel
African grey parrot
Gyrfalcon (Correct answer)
Budgerigar

Correct answer: Gyrfalcon

Gyrfalcons and other Arctic raptors lack prior environmental exposure to Aspergillus and are highly immunologically naive, making them very susceptible.

Question 295: A 10-year-old DSH cat presents with polyuria, polydipsia, and a serum fructosamine of 285 µmol/L (reference: 190–365). Blood glucose is 14.2 mmol/L. Which interpretation is most accurate?

The fructosamine is within normal range, suggesting stress hyperglycemia rather than DM (Correct answer)
The fructosamine confirms sustained hyperglycemia consistent with diabetes mellitus
A fructosamine of 285 µmol/L is diagnostic for hyperthyroidism-induced insulin resistance
Fructosamine is unreliable in cats with concurrent hemolytic anemia and should be repeated

Correct answer: The fructosamine is within normal range, suggesting stress hyperglycemia rather than DM

Feline fructosamine reflects average glycemic control over 1–3 weeks. A value of 285 µmol/L falls within the normal reference range (190–365 µmol/L), indicating the hyperglycemia is likely transient (stress-induced) rather than sustained DM. Stress hyperglycemia is common in cats; fructosamine helps differentiate it from true DM. A fructosamine >400 µmol/L typically confirms DM. The other options misapply the reference values or attribute the finding incorrectly.

Question 296: On thoracic auscultation of an 8-year-old Cavalier King Charles Spaniel, you hear a grade IV/VI left apical systolic heart murmur. Echocardiography shows myxomatous mitral valve disease with moderate left atrial enlargement (LA:Ao ratio 1.7). Which ACVIM staging is most appropriate?

Stage B2 (Correct answer)
Stage C
Stage A
Stage B1

Correct answer: Stage B2

Stage B2 MMVD is defined by cardiac remodeling (LA:Ao ≥1.6 or normalized left ventricular internal diameter in diastole >1.7) without clinical signs of heart failure.

Question 297: In a feedlot, the recommended withdrawal time before slaughter must be observed when using which antibiotic for treatment of bovine respiratory disease?

Vitamin A injection
Flunixin meglumine
Tulathromycin (Correct answer)
Balanced electrolyte solution

Correct answer: Tulathromycin

Tulathromycin (Draxxin) has a meat withdrawal time of 18 days in the US, and compliance is required to ensure drug residue-free beef at slaughter.

Question 298: A 9-year-old dog is presented for chronic, unilateral nasal discharge. To evaluate the extent of disease, including potential bone destruction of the nasal turbinates and integrity of the cribriform plate, which advanced imaging modality is superior?

Dental radiography
Magnetic Resonance Imaging (MRI)
Rhinoscopy with biopsy
Computed Tomography (CT) (Correct answer)

Correct answer: Computed Tomography (CT)

Computed Tomography (CT) is the imaging modality of choice for evaluating the nasal passages because of its excellent spatial resolution and superior ability to detail bone. It eliminates the superimposition of structures seen on radiographs and is better than MRI for assessing fine bony changes like turbinate destruction or lysis of the cribriform plate, which is critical for staging nasal tumors or fungal disease. While rhinoscopy is needed for biopsy, CT provides the best anatomical map for surgical or radiation planning.

Question 299: Postweaning multisystemic wasting syndrome (PMWS) associated with Porcine Circovirus type 2 (PCV2) is diagnosed in a 6-week-old pig. Which histologic lesion in lymph nodes is considered pathognomonic?

Lymphocytic vasculitis with fibrinoid necrosis
Lymphoid depletion with histiocytic replacement and intracytoplasmic basophilic inclusion bodies (Correct answer)
Lymphoid hyperplasia with germinal center formation
Granulomatous lymphadenitis with central caseation

Correct answer: Lymphoid depletion with histiocytic replacement and intracytoplasmic basophilic inclusion bodies

PCV2-associated PMWS characteristically produces lymphoid depletion with replacement by histiocytes/macrophages that contain intracytoplasmic basophilic inclusion bodies (viral antigen). This combination is considered pathognomonic. Lymphoid hyperplasia is the opposite of what occurs.

Question 300: A dairy herd has an elevated somatic cell count (SCC) averaging 450,000 cells/mL despite a rigorous post-dip protocol and dry cow therapy. Bulk tank cultures repeatedly grow Streptococcus agalactiae. Which intervention is MOST likely to eliminate this pathogen from the herd?

Segregate and cull all chronically infected cows, treat all culture-positive cows with intramammary penicillin, and implement herd-level blanket dry cow therapy (Correct answer)
Administer a Streptococcus agalactiae bacterin vaccine to all lactating cows to reduce new infection rate
Switch post-dip solution from iodine to chlorhexidine and increase milking frequency to three times daily
Implement selective dry cow therapy based on individual cow SCC thresholds above 200,000 cells/mL

Correct answer: Segregate and cull all chronically infected cows, treat all culture-positive cows with intramammary penicillin, and implement herd-level blanket dry cow therapy

Streptococcus agalactiae is a contagious mastitis pathogen that is obligately associated with the bovine mammary gland. It is exquisitely sensitive to penicillin and can be eradicated from a herd through a combination of treating all infected cows (culture-positive), applying blanket dry cow therapy, segregating or culling chronic cases, and strict milking hygiene. Switching teat dip chemistry (B) addresses teat-end exposure but does not treat existing infections. There is no licensed S. agalactiae bacterin shown to eliminate an active herd infection (C). Selective dry cow therapy (D) would leave infected cows untreated at dry-off, perpetuating the reservoir.

Question 301: Scrapie is a prion disease of sheep. Which characteristic most accurately describes the diagnostic approach in suspect live animals?

Serum ELISA for PrPSc antibodies
Immunohistochemistry of lymphoid tissue (rectal biopsy or third eyelid) for PrPSc accumulation (Correct answer)
Cerebrospinal fluid analysis showing 14-3-3 protein elevation
PCR of blood for scrapie prion RNA

Correct answer: Immunohistochemistry of lymphoid tissue (rectal biopsy or third eyelid) for PrPSc accumulation

PrPSc (misfolded prion protein) accumulates in lymphoid tissues before neurologic signs appear. Immunohistochemistry (IHC) of rectal mucosa lymphoid tissue or the third eyelid can detect PrPSc antemortem in live sheep. There are no antibodies to prions (immune tolerance), and prions have no nucleic acid, making serology and PCR impossible.

Question 302: Abdominal ultrasound in a 9-year-old spayed Labrador reveals a 3.2 cm splenic mass with a heterogeneous echotexture containing multiple anechoic cavities and a hyperechoic rim. Doppler interrogation shows no internal vascularity within the cavities. Fine-needle aspirate of the solid component yields blood only. Which imaging feature most strongly argues AGAINST a diagnosis of splenic hemangioma in favor of hemangiosarcoma?

Simultaneous detection of a hypoechoic hepatic nodule with similar internal architecture (Correct answer)
Anechoic cavities within the mass representing blood-filled sinusoids
Hyperechoic peripheral rim representing compressed splenic parenchyma
Absence of internal Doppler signal within the cavities

Correct answer: Simultaneous detection of a hypoechoic hepatic nodule with similar internal architecture

Splenic hemangioma and hemangiosarcoma can appear nearly identical on ultrasound — both produce heterogeneous masses with blood-filled cavities, and non-diagnostic FNA is common in both. The single most distinguishing imaging feature suggesting malignancy (hemangiosarcoma) is multifocal involvement: a synchronous hepatic lesion with the same architecture strongly implies metastatic hemangiosarcoma, as the liver is the most common metastatic site. Anechoic cavities and absent Doppler flow within cavities are seen in both benign and malignant vascular tumors. The hyperechoic rim is a nonspecific finding seen with any expansile splenic mass causing parenchymal compression.

Question 303: During abdominal exploratory surgery in a dog, you discover a mesenteric mass with multiple satellite nodules on the intestinal serosa. Histopathology returns as gastrointestinal stromal tumor (GIST). Which treatment has shown the most promise?

Carboplatin monotherapy
Combination chemotherapy with doxorubicin and cyclophosphamide
Radiation therapy alone
Surgical resection combined with toceranib phosphate (Palladia) (Correct answer)

Correct answer: Surgical resection combined with toceranib phosphate (Palladia)

GISTs overexpress c-KIT receptor tyrosine kinase, making them responsive to toceranib (a KIT inhibitor), and surgical debulking combined with toceranib improves outcomes.

Question 304: Rabbits are obligate nasal breathers. Which anatomical feature is responsible for this characteristic?

The tongue occludes the pharynx at rest
The glottis remains closed during oral breathing
The hard palate physically blocks the oral airway
The epiglottis is permanently engaged with the soft palate (Correct answer)

Correct answer: The epiglottis is permanently engaged with the soft palate

In rabbits, the epiglottis is anatomically locked against the soft palate, preventing oral breathing under normal circumstances.

Question 305: A new pen-side antigen test for Bovine Respiratory Syncytial Virus (BRSV) is evaluated in a group of 300 calves. The results are as follows: 85 calves that are truly positive for BRSV test positive. 190 calves that are truly negative for BRSV test negative. 15 truly positive calves test negative. 10 truly negative calves test positive. What is the specificity of this new test?

90.9%
91.7%
95.0% (Correct answer)
85.0%

Correct answer: 95.0%

Specificity measures a test's ability to correctly identify disease-free individuals. The formula is: Specificity = [True Negatives / (True Negatives + False Positives)] * 100. In this scenario, the True Negatives are 190 and the False Positives are 10. Therefore, Specificity = [190 / (190 + 10)] * 100 = [190 / 200] * 100 = 95.0%.

Question 306: On ultrasound, a dog's liver shows hyperechoic parenchyma compared to the spleen and falciform fat. This finding is most consistent with:

Hepatic lipidosis (Correct answer)
Hepatic congestion
Acute hepatitis
Portal hypertension

Correct answer: Hepatic lipidosis

Diffuse hepatic hyperechogenicity compared to the spleen and falciform fat is the classic ultrasound pattern of hepatic lipidosis (fatty liver).

Question 307: A 12-year-old cat with well-regulated hyperthyroidism (post-radioiodine therapy, now euthyroid) develops azotemia (creatinine 3.1 mg/dL, BUN 58 mg/dL). Prior to treatment, renal parameters were within normal limits. What is the MOST likely explanation for this finding?

Radioiodine therapy caused direct nephrotoxicity to the renal tubules
Hyperthyroidism increased GFR and masked pre-existing chronic kidney disease; euthyroidism unmasked it (Correct answer)
Post-treatment hypothyroidism caused renal vasoconstriction and acute ischemic injury
Concurrent pyelonephritis developed secondary to immune suppression from the hyperthyroid state

Correct answer: Hyperthyroidism increased GFR and masked pre-existing chronic kidney disease; euthyroidism unmasked it

Hyperthyroidism increases cardiac output and renal blood flow, artificially elevating GFR and masking underlying CKD by keeping creatinine and BUN within normal limits. Once hyperthyroidism is treated and the cat becomes euthyroid, GFR normalizes (or decreases), and pre-existing CKD is 'unmasked.' This is a well-recognized phenomenon in feline medicine and is why a post-treatment renal function decline does not necessarily indicate a treatment complication. Radioiodine is not directly nephrotoxic, and acute ischemic injury from mild post-treatment hypothyroidism is not a recognized complication.

Question 308: A 7-year-old cat presents with icterus, anemia, and splenomegaly. Blood smear shows intraerythrocytic organisms. Which organism is most likely responsible?

Cytauxzoon felis
Babesia felis
Mycoplasma haemofelis (Correct answer)
Bartonella henselae

Correct answer: Mycoplasma haemofelis

Mycoplasma haemofelis (formerly Haemobartonella felis) is the most common cause of feline infectious anemia, attaching to the surface of red blood cells.

Question 309: A dog is presented with acute onset of severe muscle tremors, hypersalivation, and miosis after potential exposure to a pesticide. Organophosphate toxicity is suspected. Which combination of drugs is the most appropriate treatment to counteract both the muscarinic and nicotinic effects?

Diazepam and Fomepizole
Naloxone and Epinephrine
Vitamin K1 and Methocarbamol
Atropine and Pralidoxime (2-PAM) (Correct answer)

Correct answer: Atropine and Pralidoxime (2-PAM)

The standard treatment for organophosphate toxicity involves a combination of Atropine and Pralidoxime (2-PAM). Atropine is a muscarinic antagonist that controls signs like salivation, urination, and bronchoconstriction. Pralidoxime is a cholinesterase reactivator that works to reverse the nicotinic effects, such as muscle tremors and paralysis, by breaking the bond between the organophosphate and the acetylcholinesterase enzyme.

Question 310: A veterinarian discharges a post-obstructed cat with buprenorphine prescribed for sublingual (oral transmucosal) administration at home. She explains to the owner that this route achieves good bioavailability in cats but would not work nearly as well if given the same way to a dog. Which physiological property of cats most directly explains this species difference in sublingual buprenorphine absorption?

The alkaline salivary pH in cats (~8.5–9.0) maintains buprenorphine predominantly in its non-ionized, lipid-soluble form, facilitating passive mucosal absorption (Correct answer)
Cats have a significantly higher density of mu-opioid receptors in the buccal mucosa, enabling receptor-mediated transcytosis of buprenorphine
Feline sublingual vasculature bypasses hepatic first-pass metabolism via direct lymphatic drainage into the thoracic duct
Cats express lower levels of P-glycoprotein efflux pumps in oral epithelium, reducing active buprenorphine efflux back into the oral cavity

Correct answer: The alkaline salivary pH in cats (~8.5–9.0) maintains buprenorphine predominantly in its non-ionized, lipid-soluble form, facilitating passive mucosal absorption

Cats have an alkaline oral/salivary pH of approximately 8.5–9.0, which is close to buprenorphine's pKa (~8.24). At this pH, a substantial proportion of buprenorphine molecules are in the non-ionized, lipid-soluble form that readily crosses lipid bilayer membranes — achieving approximately 38–53% bioavailability via the oral transmucosal route. In dogs, the more acidic oral pH (~7.5) shifts the equilibrium toward the ionized, water-soluble form that poorly penetrates mucosa, making sublingual administration ineffective. This is a key pharmacokinetic reason why OTM buprenorphine is a practical analgesic route in cats but not dogs.

Question 311: A 450-cow dairy herd has a rolling herd average of 28,000 lbs milk/cow/year but a 21-day pregnancy rate of only 12%. The reproductive technician reports a first-service conception rate of 38%. Which metric most accurately identifies the PRIMARY bottleneck limiting reproductive efficiency in this herd?

The conception rate of 38% is too low and is the primary driver of poor pregnancy rate
High milk production is causing negative energy balance sufficient to suppress ovarian activity in most cows
The interval from calving to first service is too long, causing dilution of the 21-day pregnancy rate
21-day submission rate is likely below 60%, reducing the pregnancy rate independent of conception rate (Correct answer)

Correct answer: 21-day submission rate is likely below 60%, reducing the pregnancy rate independent of conception rate

The 21-day pregnancy rate (PR) = submission rate × conception rate. With a 38% conception rate, achieving a 21-day PR of 18–22% (industry target) requires a submission rate of ~47–58%. A 12% PR with 38% CR implies a submission rate of only ~32%, meaning fewer than one-third of eligible cows are being detected in estrus or enrolled in a timed-AI protocol every 21 days. The conception rate itself is acceptable; the failure to get cows submitted is the primary bottleneck. Addressing detection of estrus or expanding synchronization protocols would have the greatest impact.

Question 312: A 6-year-old Standardbred pacer presents with an acute onset Grade 4/5 right forelimb lameness after a race. On examination there is moderate fetlock effusion, periarticular swelling, and pain on deep palpation of the lateral proximal sesamoid bone. Radiographs reveal a mid-body, sagittal fracture of the lateral proximal sesamoid bone without articular involvement. The horse is otherwise systemically healthy. Which treatment offers the BEST prognosis for return to racing performance in this specific fracture configuration?

Lag screw fixation with a 4.5 mm cortical screw placed perpendicular to the fracture plane under general anesthesia (Correct answer)
Neurectomy of the palmar digital nerve to provide long-term pain control and allow return to work
Sesamoidectomy of the lateral proximal sesamoid bone to prevent non-union
Conservative management with box rest, support bandaging, and NSAIDs for 6–12 months

Correct answer: Lag screw fixation with a 4.5 mm cortical screw placed perpendicular to the fracture plane under general anesthesia

Mid-body sagittal fractures of the proximal sesamoid bone that do not involve the articular surface and are not comminuted carry the best prognosis when treated with lag screw fixation. The lag screw creates interfragmentary compression that promotes primary bone healing and restores the structural integrity of the sesamoid bone, which is essential for resuming the biomechanical demands of racing. Conservative management alone has poor outcomes for racing soundness. Sesamoidectomy is reserved for apical or basal fractures. Neurectomy treats pain but does not address the structural problem and carries welfare concerns for performance horses.

Question 313: A 9-year-old Cairn Terrier has chronic hepatitis with copper accumulation on liver biopsy (>2000 µg/g dry weight). Which chelation agent is most commonly used in dogs to reduce hepatic copper?

D-penicillamine (Correct answer)
EDTA
Deferoxamine
Deferasirox

Correct answer: D-penicillamine

D-penicillamine is the most widely used copper chelator in dogs with copper-associated hepatopathy, mobilizing hepatic copper for urinary excretion.

Question 314: A 7-year-old female spayed Standard Poodle presents with a history of waxing and waning lethargy, vomiting, and anorexia. On physical examination, she is quiet but responsive, with a heart rate of 60 bpm and weak femoral pulses. Bloodwork reveals hyponatremia, hyperkalemia, and azotemia. Which of the following is the most definitive diagnostic test for this dog's suspected condition?

ACTH stimulation test (Correct answer)
Endogenous ACTH concentration
Abdominal ultrasound
Low-dose dexamethasone suppression test

Correct answer: ACTH stimulation test

The clinical signs (lethargy, vomiting, anorexia), signalment (Standard Poodle), and classic electrolyte abnormalities (hyponatremia, hyperkalemia) are highly suggestive of hypoadrenocorticism (Addison's disease). The definitive diagnosis of hypoadrenocorticism is made by performing an ACTH stimulation test, which will show a low resting cortisol and a negligible response to ACTH administration.

Question 315: A veterinarian investigates an increase in periparturient hypocalcemia (milk fever) in a 320-cow Holstein herd. The transition cow TMR has a DCAD (dietary cation-anion difference) of +18 mEq/100 g DM. Urine pH is measured in 15 close-up cows and averages 8.1 (range 7.8–8.3). The nutritionist proposes adding anionic salts. Before altering the ration, what is the most important next step the veterinarian should take?

Perform serum ionized calcium measurements on affected cows at calving to confirm clinical diagnosis before changing the ration
Switch immediately to a negative DCAD diet (−10 to −15 mEq/100 g DM) and recheck urine pH in 5 days
Measure 24-hour dietary dry matter intake of the close-up group to calculate actual anionic salt consumption
Assess forage cation content by submitting the close-up TMR for wet chemistry mineral analysis, because DCAD calculations are only as accurate as the feed mineral values used (Correct answer)

Correct answer: Assess forage cation content by submitting the close-up TMR for wet chemistry mineral analysis, because DCAD calculations are only as accurate as the feed mineral values used

The DCAD of +18 mEq/100 g DM and alkaline urine pH (target for effective anionic supplementation is 6.0–7.0) confirm the diet is not sufficiently acidified. However, before adding anionic salts and reformulating, the most critical step is to verify the accuracy of the mineral inputs used to calculate DCAD. Forages — particularly grass hays and silages — have highly variable potassium content, which dramatically affects DCAD. If the mineral analysis used to calculate DCAD was from a previous cutting or a reference table rather than current wet chemistry analysis, the actual DCAD may differ substantially from the calculated value, and the anionic salt addition could be under- or overdosed. Confirming ionized calcium (A) is diagnostically useful but doesn't guide ration correction. DMI measurement (B) is secondary. Switching immediately without verifying feed chemistry (D) risks over-acidification and reduced DMI.

Question 316: A 9-year-old Miniature Schnauzer presents with vomiting, cranial abdominal pain, and a 'praying' posture. Abdominal radiographs are taken to rule out other causes. Which of the following radiographic signs would be most consistent with acute pancreatitis?

A gas-filled and distended gallbladder (emphysematous cholecystitis).
Mineralization within the soft tissue opacity of the liver.
Focal loss of serosal detail and increased soft tissue opacity in the right cranial abdomen. (Correct answer)
Generalized loss of serosal detail throughout the entire abdomen.

Correct answer: Focal loss of serosal detail and increased soft tissue opacity in the right cranial abdomen.

The radiographic signs of pancreatitis are often subtle and non-specific, but they reflect the focal inflammation and peritonitis in the area of the pancreas. The most common findings are a focal loss of serosal detail (a 'ground glass' appearance) and a soft tissue mass effect in the right cranial abdomen, which may cause widening of the pyloro-duodenal angle.

Question 317: A 1,200-head Holstein dairy uses a voluntary waiting period (VWP) of 50 days. Herd records show mean days to first service = 58 days, mean days open = 145 days, and 12-month rolling culling rate = 32%. The herd veterinarian proposes shortening the VWP to 35 days. Which of the following accurately predicts the PRIMARY unintended consequence of this change in a high-producing herd averaging 95 lbs/cow/day at peak?

Culling rate will increase because shortened inter-calving intervals reduce productive life
Milk yield in the subsequent lactation will decrease because early rebreeding reduces the length of the current lactation
Mastitis incidence will increase due to immunosuppression associated with early resumption of luteal activity
First-service conception rate will decline because insemination will more frequently occur before complete uterine involution and during peak negative energy balance (Correct answer)

Correct answer: First-service conception rate will decline because insemination will more frequently occur before complete uterine involution and during peak negative energy balance

In high-producing dairy cows, the nadir of negative energy balance (NEB) typically occurs between 10–14 days in milk, but NEB persists and substantially impairs reproductive function through ~50–60 DIM. Shortening the VWP to 35 days means many cows will be inseminated while still in NEB, with incomplete uterine involution, suboptimal progesterone profiles, and impaired embryo survival. Research consistently shows that conception rates at early first service in high-producers are 8–15 percentage points lower than services at 50–60 DIM. Additionally, uterine involution is not complete in many cows before 40–45 DIM. The net result is more services per conception and no improvement in days open, negating the intended benefit.

Question 318: Which of the following common canine uroliths is most likely to be radiolucent on survey abdominal radiographs, often requiring contrast cystography or ultrasonography for diagnosis?

Struvite (Magnesium Ammonium Phosphate)
Silica
Ammonium Urate (Correct answer)
Calcium Oxalate Monohydrate

Correct answer: Ammonium Urate

Ammonium urate and cystine uroliths are typically radiolucent or only faintly radiopaque, making them difficult to see on standard radiographs. In contrast, struvite and calcium oxalate uroliths are mineral-dense and almost always radiopaque.

Question 319: A cow-calf producer in a selenium-deficient region is using injectable sodium selenite (0.5 mg Se/lb BW) in neonatal calves to prevent white muscle disease. He now wants to supplement pregnant cows pre-calving to improve passive transfer of selenium via colostrum. He asks about adding selenium to the mineral mix at 120 ppm. Which response is most accurate?

This is inappropriate; the legal maximum for selenium in cattle mineral supplements is 120 ppm, but actual intake must not exceed 3 mg Se/head/day, which requires calculating expected mineral consumption to avoid toxicosis (Correct answer)
This is inappropriate; selenium cannot be supplemented via mineral mixes in cattle and must only be given via injectable or slow-release bolus forms
This is appropriate because dry matter intake of minerals is low enough that 120 ppm selenium is safe and will effectively raise colostral selenium
This is appropriate if the mineral is fed free-choice, because cattle self-regulate selenium intake

Correct answer: This is inappropriate; the legal maximum for selenium in cattle mineral supplements is 120 ppm, but actual intake must not exceed 3 mg Se/head/day, which requires calculating expected mineral consumption to avoid toxicosis

The FDA-mandated maximum for selenium in mineral supplements is 90 ppm in complete feeds and up to 700 ppm in salt-based mineral mixes (with a label restriction to 0.3 mg/kg of total diet DM), but the critical practical constraint is that total selenium intake must not exceed 3 mg/head/day to avoid selenium toxicosis. At 120 ppm Se in a mineral mix, if cows consume even 50 g of mineral/day they intake 6 mg Se — double the safe limit. Cattle do NOT self-regulate selenium intake (option C is false). Selenium CAN be supplemented via minerals (option D is false). The key is that the producer must calculate actual mineral consumption and adjust selenium concentration accordingly to stay ≤3 mg/head/day — the concentration alone does not guarantee safety.

Question 320: A 12-year-old cat with weight loss, diarrhea, and palpable intestinal thickening has a serum cobalamin of 145 ng/L (normal >290). Which diagnosis is most consistent?

Inflammatory bowel disease — eosinophilic type
Exocrine pancreatic insufficiency
Small cell (low-grade) lymphoma (Correct answer)
Feline pancreatitis

Correct answer: Small cell (low-grade) lymphoma

Small cell (low-grade) alimentary lymphoma is the most common feline intestinal tumor and frequently causes hypocobalaminemia due to ileal involvement impairing B12 absorption.

Question 321: Equine degenerative joint disease of the proximal interphalangeal joint (high ringbone) is BEST confirmed with:

Thermography of the lower limb
Intra-articular anesthesia of the coffin joint
Ultrasonography of the pastern
Lateromedial and dorsopalmar radiographs of the pastern (Correct answer)

Correct answer: Lateromedial and dorsopalmar radiographs of the pastern

High ringbone (periarticular or articular osteoarthritis of the PIP joint) is diagnosed radiographically, with lateromedial and dorsopalmar views demonstrating periarticular osteophytes and joint space narrowing.

Question 322: A 6-year-old Rottweiler presents with acute vomiting and melena. Gastroscopy reveals a deep ulcer in the antrum. Which drug class is most effective at preventing NSAID-induced gastrointestinal ulcers in dogs?

H2-receptor antagonists
Sucralfate
Proton pump inhibitors (Correct answer)
Bismuth subsalicylate

Correct answer: Proton pump inhibitors

Proton pump inhibitors (e.g., omeprazole) provide the most potent and sustained acid suppression and are superior to H2 blockers for preventing and treating GI ulcers.

Question 323: A 10-year-old DSH cat presents with polyuria, polydipsia, and a palpable ventral neck mass. Serum T4 is 8.2 µg/dL (normal 0.8–4.0). Which cardiac abnormality is most commonly associated with this condition?

Restrictive cardiomyopathy
Hypertrophic cardiomyopathy (Correct answer)
Pericardial effusion
Dilated cardiomyopathy

Correct answer: Hypertrophic cardiomyopathy

Hyperthyroidism in cats most commonly causes hypertrophic cardiomyopathy due to the chronotropic and inotropic effects of excess thyroid hormone.

Question 324: An 11-year-old Andalusian dressage horse presents with progressive bilateral forelimb 'pottery' gait, stumbling, and a short, stabbing stance phase. Nerve blocks are unhelpful. Radiographs show extensive remodeling and irregular sclerosis of both proximal sesamoid bones with fragmentation at the base. Which long-term structural consequence makes the prognosis for return to full work GUARDED to POOR?

Secondary navicular bone remodeling from altered weight-bearing biomechanics
Progressive failure of the suspensory apparatus with risk of catastrophic fetlock breakdown due to compromised sesamoid bone structural integrity (Correct answer)
Bilateral coffin joint synovitis from compensatory toe-first landing
Chronic deep digital flexor tendon core lesion from altered fetlock alignment

Correct answer: Progressive failure of the suspensory apparatus with risk of catastrophic fetlock breakdown due to compromised sesamoid bone structural integrity

Chronic sesamoiditis with fragmentation and sclerosis represents advanced degenerative disease of the proximal sesamoid bones, which are critical structural components of the suspensory apparatus. The sesamoid bones serve as the fulcrum for the suspensory ligament and distal sesamoidean ligaments; structural failure predisposes to catastrophic breakdown — fetlock 'drop,' complete support limb failure, or fracture under athletic loading. This is distinct from navicular disease or DDFT pathology, which are secondary events. The bilateral involvement and advanced bony changes make return to high-level sport inadvisable.

Question 325: A 12-year-old Quarter Horse mare has progressive forelimb lameness with a history of repeated intra-articular coffin joint injections. Radiographs now show marked remodeling of the coffin joint. The MOST appropriate next diagnostic step is:

MRI of the foot to evaluate soft tissue and bone detail (Correct answer)
Radiographs of the opposite forelimb for comparison only
Ultrasound of the superficial digital flexor tendon
Repeat palmar digital nerve block

Correct answer: MRI of the foot to evaluate soft tissue and bone detail

MRI provides superior detail of both bony and soft tissue structures within the hoof capsule, allowing comprehensive evaluation of all coffin joint components when standard diagnostics have been inconclusive.

Question 326: A veterinarian is designing a Johne's disease (paratuberculosis) test-and-cull program for a 500-cow closed dairy herd. The herd-level prevalence is estimated at 8%. The diagnostic lab offers two ELISA tests: Test A (sensitivity 45%, specificity 99%) and Test B (sensitivity 28%, specificity 99.8%). The producer's primary goal is to eliminate all infected animals without culling excessive false-positives. Which testing strategy is most appropriate?

Use Test A as a screen, then confirm positives with Test B in series, to maximize both sensitivity and specificity (Correct answer)
Use Test B alone annually, because its higher specificity minimizes false-positive culls at this prevalence
Use fecal PCR as the primary test rather than ELISA, because ELISA sensitivity is inadequate below 10% prevalence
Use Test A alone annually, because its higher sensitivity identifies more infected animals per test cycle

Correct answer: Use Test A as a screen, then confirm positives with Test B in series, to maximize both sensitivity and specificity

At 8% prevalence, even a 99% specific test yields a positive predictive value (PPV) of approximately 82% for Test A and 97% for Test B when used alone. However, Test A's sensitivity (45%) catches more true positives per annual round. Using Test A as a screen (higher sensitivity captures more infected animals) and Test B as a confirmatory test in series (very high specificity eliminates most false positives) optimizes the program: sensitivity of the series is limited by Test A (acceptable), but specificity approaches Test B's 99.8%, making PPV very high and preventing unnecessary culls. Fecal PCR is valuable but not superior in all low-prevalence settings and is more expensive per sample; it is not 'always preferred' below 10% prevalence. The series testing strategy is the standard of practice for Johne's control programs.

Question 327: A 2-year-old indoor cat is presented to the emergency clinic with acute onset of vomiting, lethargy, and anorexia. The owner recently received a floral arrangement containing lilies. On physical examination, the cat is dehydrated and has painful kidneys on palpation. Bloodwork reveals severe azotemia. Which of the following is the most critical initial treatment for this suspected toxicity?

Intravenous fluid diuresis (Correct answer)
N-acetylcysteine administration
Administration of activated charcoal and a cathartic
Peritoneal dialysis

Correct answer: Intravenous fluid diuresis

Ingestion of any part of a lily plant (Lilium or Hemerocallis species) can cause severe, acute renal failure in cats. The primary mechanism is acute tubular necrosis. The cornerstone of treatment is aggressive intravenous fluid therapy to support renal perfusion, promote diuresis, and flush out the unknown nephrotoxin. While decontamination with activated charcoal is useful if ingestion was very recent, fluid therapy is the most critical life-saving intervention once clinical signs have developed. N-acetylcysteine is the antidote for acetaminophen toxicity, and peritoneal dialysis is reserved for anuric patients unresponsive to fluid therapy.

Question 328: Which of the following organisms is most frequently present in feline pyometra?

Staphylococcus aureus
Pseudomonas aeruginosa
Escherichia coli (Correct answer)
Streptococcus pyogenes

Correct answer: Escherichia coli

Escherichia coli (E. coli) is by far the most common bacterial isolate found in cases of feline pyometra, as well as canine pyometra. This bacterium typically ascends from the lower reproductive tract or urinary tract into the uterus, especially under the influence of progesterone, which makes the uterus more susceptible to infection.

Question 329: Which perineural block is required to desensitize the entire foot including the coronary band?

Low 4-point nerve block (palmar metacarpal + palmar digital)
High palmar (high 2-point) nerve block
Abaxial sesamoid nerve block (Correct answer)
Palmar digital nerve block

Correct answer: Abaxial sesamoid nerve block

An abaxial sesamoid nerve block desensitizes the entire foot including the coronary band by blocking the medial and lateral palmar digital nerves at the level of the proximal sesamoid bones.

Question 330: A 10-year-old domestic shorthair cat is being managed for hyperthyroidism with methimazole. Two weeks after starting therapy, the owner reports the cat is now eating less, has facial pruritus, and has developed excoriations around the face and neck. Blood work shows: BUN 58 mg/dL, creatinine 3.1 mg/dL, and phosphorus 6.8 mg/dL — values that were within normal limits prior to treatment. Which is the best next step?

Discontinue methimazole, switch to radioiodine therapy immediately to avoid further renal damage
Continue methimazole at the current dose and initiate anti-pruritic therapy for presumed idiopathic facial pruritus
Add benazepril and phosphorus binders; continue methimazole unchanged as azotemia is expected post-treatment
Discontinue methimazole temporarily, re-evaluate renal values, and consider dose reduction or alternative therapy based on clinical and lab reassessment (Correct answer)

Correct answer: Discontinue methimazole temporarily, re-evaluate renal values, and consider dose reduction or alternative therapy based on clinical and lab reassessment

This cat has two concurrent problems: methimazole-induced facial pruritus (a known idiosyncratic adverse effect in ~2% of cats, typically within the first 4 weeks) and unmasked chronic kidney disease (CKD). Hyperthyroidism raises GFR, masking underlying CKD; successful treatment lowers GFR and reveals pre-existing renal disease. The facial pruritus with excoriations is a cutaneous drug reaction requiring methimazole discontinuation. After stopping methimazole and allowing thyroid status to normalize, renal values should be reassessed. If CKD is confirmed, the risk-benefit of treating hyperthyroidism must be individualized — sometimes a lower target T4 or alternative therapy (radioiodine at a lower dose) is chosen. Continuing methimazole despite a drug reaction would be inappropriate.

Question 331: When evaluating a horse for subtle hindlimb lameness, which surface is MOST useful for accentuating the gait abnormality?

Firm, level asphalt surface
Grass pasture
Rubber-matted stall aisle
Soft, deep sand arena (Correct answer)

Correct answer: Soft, deep sand arena

A soft, deep surface increases concussion and proprioceptive demands on the hindlimb, accentuating subtle lameness signs that may not be visible on a firmer surface.

Question 332: A 3-year-old intact male cat presents with acute onset of pelvic limb paralysis, cold limbs below the stifle, absent femoral pulses bilaterally, and cyanotic nail beds. The most likely diagnosis is:

Traumatic spinal cord injury with T3-L3 myelopathy
Botulism with flaccid tetraplegia
Fibrocartilaginous embolism (FCE) of the thoracolumbar spinal cord
Aortic thromboembolism (ATE) secondary to hypertrophic cardiomyopathy (Correct answer)

Correct answer: Aortic thromboembolism (ATE) secondary to hypertrophic cardiomyopathy

Aortic thromboembolism in cats classically presents as the 'SAD' triad: Sudden onset, Asymmetric or bilateral pelvic limb paresis/paralysis, and Devastating pain. Cold, paralyzed limbs with absent femoral pulses and cyanotic nail beds (ischemia distal to the thrombus at the aortic trifurcation) are pathognomonic. Most cases have underlying hypertrophic cardiomyopathy. FCE is painless; spinal trauma has a history of injury.

Question 333: A 5-year-old FeLV-positive cat presents with a rapidly growing sublumbar mass. Fine-needle aspirate reveals a monomorphic population of large lymphocytes with prominent nucleoli and scant cytoplasm. Immunophenotyping shows CD3-negative, CD20-positive cells. Which statement about this neoplasm's relationship to FeLV is MOST accurate?

FeLV envelope glycoprotein gp70 directly transforms B-lymphocytes through binding to the thiamine transporter receptor
This B-cell lymphoma likely arose independently of FeLV; FeLV-associated lymphomas are almost exclusively T-cell in immunophenotype (Correct answer)
FeLV proviral integration near c-myc via insertional mutagenesis is the primary oncogenic mechanism for this B-cell phenotype
Reverse transcriptase error during FeLV replication generates B-cell-tropic recombinant proviruses in somatic tissue

Correct answer: This B-cell lymphoma likely arose independently of FeLV; FeLV-associated lymphomas are almost exclusively T-cell in immunophenotype

FeLV-associated lymphomas are overwhelmingly T-cell in origin (>90%), typically thymic/mediastinal lymphoma in young cats. B-cell lymphomas, such as this sublumbar presentation, are generally NOT FeLV-associated and likely arose through FeLV-independent mechanisms (e.g., chronic antigenic stimulation, Helicobacter-associated alimentary lymphoma). The co-occurrence with FeLV positivity is incidental in this case. Understanding immunophenotype-retrovirus associations is critical for prognosis and etiology — FeLV-positive T-cell lymphomas carry a particularly poor prognosis. The FeLV receptor is the thiamine transporter (THTR1), but this does not directly transform B-cells.

Question 334: On ultrasound of the urinary bladder, a dependent hyperechoic layer with acoustic shadowing that moves when the patient is repositioned most likely represents:

Bladder wall thickening
Blood clots
Transitional cell carcinoma
Uroliths (bladder stones) (Correct answer)

Correct answer: Uroliths (bladder stones)

Uroliths are hyperechoic foci with acoustic shadowing that are gravity-dependent and shift position when the patient moves, distinguishing them from wall masses.

Question 335: A 7-year-old German Shepherd presents with bloody diarrhea and a PCV of 10%. Smear shows anemia with marked polychromasia and many erythrocyte fragments (schistocytes). Which condition is most likely?

Heinz body anemia
Microangiopathic hemolytic anemia associated with DIC (Correct answer)
Immune-mediated hemolytic anemia
Iron deficiency anemia

Correct answer: Microangiopathic hemolytic anemia associated with DIC

Schistocytes (erythrocyte fragments) result from mechanical shearing in fibrin strands during DIC, causing microangiopathic hemolytic anemia.

Question 336: A 5-year-old dog presents with acute vomiting and abdominal pain. Abdominal radiographs reveal a segment of small intestine that is severely dilated with gas, proximal to a segment of normal-caliber, empty-appearing small intestine. What is this radiographic finding, often referred to as 'two populations of bowel,' most indicative of?

Pancreatitis
Functional ileus
Gastroenteritis
Mechanical obstruction (Correct answer)

Correct answer: Mechanical obstruction

The presence of two distinct populations of bowel (one severely dilated and one normal or empty) is a classic radiographic sign of a complete or high-grade mechanical obstruction. The intestine proximal to the blockage becomes distended with gas and fluid, while the intestine distal to the obstruction remains empty. Functional ileus and gastroenteritis typically cause a more generalized, mild to moderate dilation of the intestines without a clear transition point.

Question 337: A 7-year-old horse undergoing colic surgery develops hypotension (MAP 45 mmHg) unresponsive to IV fluid boluses. The anesthetist adds dobutamine at 3 mcg/kg/min with minimal improvement. Which pharmacologic intervention is MOST appropriate as the next step?

Add norepinephrine at 0.1–0.5 mcg/kg/min (Correct answer)
Increase dobutamine to 10 mcg/kg/min
Administer phenylephrine at 1–2 mcg/kg/min
Switch to vasopressin at 0.5 mU/kg/min

Correct answer: Add norepinephrine at 0.1–0.5 mcg/kg/min

Inhalant anesthesia (isoflurane/sevoflurane) in horses causes significant vasodilation and myocardial depression. When dobutamine (a β1/β2 agonist that increases cardiac output but causes vasodilation) is insufficient, norepinephrine is the drug of choice because it provides both α1-mediated vasoconstriction (increases SVR) and β1 inotropic support. Phenylephrine is a pure α1 agonist that raises SVR but can cause reflex bradycardia and reduced cardiac output—problematic in an already-compromised patient. Vasopressin can be used in refractory cases but is not typically a second-line agent. Escalating dobutamine alone will worsen vasodilation.

Question 338: A 7-year-old intact male Cavalier King Charles Spaniel presents with a 3-week history of progressive exercise intolerance and a grade IV/VI left apical systolic murmur. Thoracic radiographs reveal moderate left atrial enlargement with pulmonary venous distension but no overt edema. Per EPIC trial criteria, which treatment is most appropriate at this time?

Furosemide 2 mg/kg PO BID
Spironolactone 2 mg/kg PO SID
Pimobendan 0.25–0.3 mg/kg PO BID (Correct answer)
Enalapril 0.5 mg/kg PO BID

Correct answer: Pimobendan 0.25–0.3 mg/kg PO BID

The EPIC trial demonstrated that pimobendan initiated in the preclinical (Stage B2) phase of myxomatous mitral valve disease — defined by cardiomegaly on radiographs or echocardiography (LVIDDN ≥1.7 or vertebral heart score ≥10.5) — significantly delayed onset of CHF by a median of 15 months. Furosemide is reserved for overt heart failure (Stage C/D). ACE inhibitors and spironolactone are not indicated as monotherapy in B2 per current ACVIM guidelines post-EPIC.

Question 339: An 8-year-old Arabian endurance horse undergoes elective arthroscopy of the left carpal joints. During closure, the surgeon notes excessive hemorrhage from the dorsal aspect of the antebrachiocarpal joint. Which vessel, if lacerated during carpal arthroscopy via the standard dorsolateral or dorsomedial portals, is the most common source of significant intraoperative hemorrhage and what is the recommended immediate management?

Medial palmar vein; tourniquet application proximal to the carpus
Accessory cephalic vein; oversew the arthroscopic portal with a horizontal mattress suture
Cephalic vein; apply digital pressure followed by ligation if bleeding persists post-lavage
Dorsal carpal branch of the radial artery; controlled lavage with epinephrine-containing saline and direct cautery (Correct answer)

Correct answer: Dorsal carpal branch of the radial artery; controlled lavage with epinephrine-containing saline and direct cautery

The dorsal carpal branch of the radial artery crosses the dorsal aspect of the carpus and is at risk during portal placement or instrument manipulation in equine carpal arthroscopy. Significant hemorrhage from arterial origin can obscure visualization and complicate closure. Initial management includes copious joint lavage to clear the field, followed by direct electrocautery of the vessel if it can be visualized arthroscopically. Epinephrine in irrigation fluid is used as an adjunct to promote vasoconstriction. The cephalic and accessory cephalic veins are also at risk but produce lower-pressure venous bleeding more readily managed with pressure alone.

Question 340: A veterinarian is establishing a herd health program for a 500-cow dairy. Which parameter best defines 'failure of passive transfer' (FPT) in dairy calves?

Serum IgG <10 g/L measured at 24-48 hours of age (Correct answer)
Total serum protein <5.0 g/dL measured at 24-48 hours of age
Serum IgG <5 g/L measured within 6 hours of birth
Serum IgG <10 g/L measured at 1-2 weeks of age

Correct answer: Serum IgG <10 g/L measured at 24-48 hours of age

FPT is defined as serum IgG <10 g/L (or serum total protein <5.2 g/dL as a surrogate) measured at 24-48 hours of age, after the gut closes to macromolecular absorption.

Question 341: On CT of the nasal cavity in a dog with nasal discharge, which finding most strongly suggests fungal rhinitis (Aspergillus) rather than nasal neoplasia?

Mass with smooth margins crossing the midline
Fluid-filled nasal cavity with intact turbinates
Periosteal reaction along the frontal bones
Turbinate destruction with preserved nasal septum (Correct answer)

Correct answer: Turbinate destruction with preserved nasal septum

Aspergillus rhinitis typically causes extensive turbinate lysis/destruction while often leaving the nasal septum relatively intact, unlike neoplasia which often crosses the midline.

Question 342: A veterinarian working for a state health department is asked to evaluate a One Health surveillance system for Brucella melitensis in small ruminants. Which epidemiological measure best quantifies the probability that an animal testing positive by ELISA truly has brucellosis when the true prevalence in the population is 1%?

Sensitivity
Negative predictive value
Specificity
Positive predictive value (Correct answer)

Correct answer: Positive predictive value

Positive predictive value (PPV) is the probability that a test-positive animal is truly infected and is critically dependent on the prevalence of disease in the tested population. At low prevalence (1%), even a highly specific test will yield a low PPV, generating many false positives. Sensitivity measures the test's ability to correctly identify true positives; specificity measures correct identification of true negatives. Neither sensitivity nor specificity alone accounts for disease prevalence, making PPV the correct measure in this clinical and public health decision-making context.

Question 343: When using buprenorphine in cats, which route of administration achieves good bioavailability due to the cat's naturally alkaline oral pH?

Intravenous
Transmucosal (sublingual/buccal) (Correct answer)
Intramuscular
Subcutaneous

Correct answer: Transmucosal (sublingual/buccal)

The alkaline oral pH of cats promotes ionization of buprenorphine at mucosal surfaces, giving transmucosal administration ~100% bioavailability.

Question 344: A dairy producer utilizes a timed artificial insemination (TAI) protocol that includes Ovsynch. Which hormone is administered to cause luteolysis, or regression of the corpus luteum, thereby allowing the cow to return to estrus?

Gonadotropin-releasing hormone (GnRH)
Prostaglandin F2α (PGF2α) (Correct answer)
Progesterone
Oxytocin

Correct answer: Prostaglandin F2α (PGF2α)

Prostaglandin F2α (PGF2α) is the hormone responsible for causing luteolysis, which is the breakdown of the corpus luteum (CL). In synchronization protocols like Ovsynch, PGF2α is given when a mature CL is expected to be present, causing a drop in progesterone and allowing a new follicular wave to progress towards ovulation. GnRH is used to cause ovulation or start a new follicular wave, while progesterone (e.g., in a CIDR) is used to prevent estrus.

Question 345: On a ventrodorsal thoracic radiograph of a 6-year-old DSH cat with acute respiratory distress, you observe symmetric bilateral perihilar interstitial-to-alveolar infiltrates that become more alveolar at the lung periphery, with air bronchograms visible in the caudal lung lobes. The cardiac silhouette is within normal limits (VHS 7.2). Pleural effusion is absent. Which diagnosis best explains this radiographic pattern, and what is the most critical next diagnostic step?

Cardiogenic pulmonary edema; echocardiography to detect occult hypertrophic cardiomyopathy with normal cardiac size (Correct answer)
Feline bronchopneumonia (bacterial); transtracheal wash for cytology and culture
Non-cardiogenic pulmonary edema (e.g., neurogenic or post-obstructive); measure systolic blood pressure and assess for underlying cause
Pulmonary lymphoma; thoracic CT with contrast for mediastinal lymph node assessment

Correct answer: Cardiogenic pulmonary edema; echocardiography to detect occult hypertrophic cardiomyopathy with normal cardiac size

This is a high-level discriminator: cats with hypertrophic cardiomyopathy (HCM) frequently develop cardiogenic pulmonary edema WITHOUT radiographic cardiomegaly, because the hypertrophied ventricle maintains near-normal external dimensions while left atrial pressure rises acutely. A VHS of 7.2 is within the feline reference range (≤8.0), but HCM can still produce fulminant pulmonary edema before the cardiac silhouette enlarges. The perihilar-to-peripheral alveolar pattern with air bronchograms in cats classically represents cardiogenic edema, which in cats distributes differently than in dogs (less perihilar-predominant). Echocardiography is the critical next step to detect left atrial enlargement, diastolic dysfunction, or outflow obstruction. Non-cardiogenic edema is possible but less common with this symmetric perihilar distribution. Lymphoma typically produces a patchy or nodular interstitial pattern with mediastinal involvement.

Question 346: A 2-year-old intact female sugar glider (Petaurus breviceps) presents with a 1 cm, firm, non-painful mass on the dorsal midline of the head. The owner reports the mass appeared over 2 weeks. On exam, the animal is bright and alert with no neurologic signs. Cytology of a fine-needle aspirate reveals cells with abundant pale cytoplasm, round nuclei, and prominent nucleoli in a proteinaceous background. What is the most likely diagnosis?

Abscess secondary to conspecific bite wound
Lymphosarcoma with cutaneous metastasis
Dermatofibrosarcoma of the scalp secondary to repetitive self-trauma
Scent gland adenocarcinoma arising from the frontofrontal gland (Correct answer)

Correct answer: Scent gland adenocarcinoma arising from the frontofrontal gland

Male sugar gliders have a prominent frontofrontal (forehead) scent gland, but females can develop neoplasia of the same glandular tissue. Adenocarcinoma of the frontofrontal scent gland presents as a rapidly growing firm mass on the dorsal midline of the head. Cytology typically reveals epithelial cells with abundant pale cytoplasm and prominent nucleoli in a proteinaceous background consistent with glandular secretory tissue gone malignant. Dermatofibrosarcoma and lymphoma are less likely without inflammatory history or systemic signs. An abscess would typically show degenerate neutrophils and bacteria.

Question 347: A cow presents with acute right-sided abomasal displacement progressing to volvulus (RDA/RAV) in a freshly calved dairy cow. Which finding on physical exam is most consistent with this diagnosis?

High-pitched ping over a large area on the right side between ribs 9-12, with signs of toxemia and tachycardia (Correct answer)
Bilateral pings with fluid splashing sounds in the lower abdomen
Left-sided ping in the paralumbar fossa on simultaneous auscultation and percussion
Left-sided rumen atony with no ping detected

Correct answer: High-pitched ping over a large area on the right side between ribs 9-12, with signs of toxemia and tachycardia

Right abomasal volvulus produces a large-area right-sided ping (ribs 9-12), signs of severe toxemia, tachycardia, and rapid cardiovascular deterioration due to venous outflow obstruction.

Question 348: A 3-year-old German Shepherd Dog has progressive pelvic limb ataxia. MRI reveals an intramedullary T2-hyperintense lesion at L4 that does not contrast-enhance. The most likely diagnosis is:

Degenerative myelopathy
Intervertebral disc herniation
Fibrocartilaginous embolism (Correct answer)
Neoplasia (ependymoma)

Correct answer: Fibrocartilaginous embolism

Fibrocartilaginous embolism (FCE) typically appears as an intramedullary T2 hyperintensity without contrast enhancement, in young to middle-aged large breed dogs with acute onset.

Question 349: A rabbit is brought in with GI stasis. Which analgesic is safest to use in rabbits?

Ibuprofen
Acetaminophen
Meloxicam (Correct answer)
Aspirin

Correct answer: Meloxicam

Meloxicam is the preferred NSAID in rabbits and is commonly used for pain management due to its established safety profile in this species.

Question 350: Grass tetany (hypomagnesemic tetany) in beef cattle grazing lush spring pastures is best prevented by supplementing which mineral?

Magnesium oxide in mineral mix (Correct answer)
Sodium bicarbonate free-choice
Zinc sulfate boluses
Calcium carbonate in water

Correct answer: Magnesium oxide in mineral mix

Grass tetany results from hypomagnesemia; magnesium oxide in a palatable mineral mix is the standard prevention because magnesium has no adequate body reserve.

Question 351: Which reproductive technology is used to synchronize estrus in beef heifers and cows to facilitate fixed-time artificial insemination (FTAI) without heat detection?

Ovsynch or Select Synch protocols combining GnRH, progesterone (CIDR), and prostaglandin F2α (Correct answer)
Human chorionic gonadotropin (hCG) injection alone
Gonadotropin-releasing hormone (GnRH) injection alone
Melengestrol acetate (MGA) in feed for 14 days without any hormonal synchronization

Correct answer: Ovsynch or Select Synch protocols combining GnRH, progesterone (CIDR), and prostaglandin F2α

The 7-day CO-Synch+CIDR or Ovsynch protocols combining GnRH, a CIDR insert, and prostaglandin F2α synchronize follicular wave and luteal regression to enable fixed-time AI without heat detection.

Question 352: Weakness, despair, lethargy, ptyalism, and posterior paresis are symptoms that a 5-year-old ferret exhibits. The patient's owner reports that these symptoms frequently appear every morning before feeding and typically subside after the meal. The symptoms have recently gotten worse and lasted longer. Which of the subsequent diagnoses is most likely?

Insulinoma (Correct answer)
Adrenal cortical neoplasia
Lymphoma
Pancreatic exocrine adenocarcinoma

Correct answer: Insulinoma

The ferret's symptoms of weakness, despair, lethargy, ptyalism, and posterior paresis, which frequently appear before feeding and resolve after a meal, are classic signs of hypoglycemia. This pattern is highly characteristic of an insulinoma, a tumor of the pancreatic beta cells that secretes excessive insulin, leading to dangerously low blood glucose levels. The worsening and prolonged duration of symptoms indicate disease progression.

Question 353: Which Doppler modality provides a color-coded two-dimensional map of blood flow direction and velocity within a vessel or cardiac chamber?

Color flow Doppler (Correct answer)
Continuous wave Doppler
Power Doppler
Pulsed wave Doppler

Correct answer: Color flow Doppler

Color flow Doppler superimposes a color-coded map of mean flow velocity and direction over the B-mode image, using red/blue by convention for flow toward/away from the transducer.

Question 354: Which of the following is the preferred site for intravenous catheter placement in a rabbit?

Marginal ear vein (Correct answer)
Jugular vein
Lateral saphenous vein
Cephalic vein

Correct answer: Marginal ear vein

The marginal ear vein is the most accessible and commonly used IV catheter site in rabbits due to its visibility and ease of access.

Question 355: Which dietary modification is considered most critical in slowing the progression of chronic kidney disease (CKD) in cats?

Grain-free formulation
Increased high-quality protein
Increased sodium to encourage drinking
Restricted phosphorus (Correct answer)

Correct answer: Restricted phosphorus

Restricting dietary phosphorus is a cornerstone of managing feline CKD and has been shown to slow the progression of the disease. While moderate protein restriction is also part of therapeutic renal diets, phosphorus restriction is considered more critical for slowing progression. Excessive sodium restriction is not recommended, and increasing protein is contraindicated in later stages. Grain-free formulations have no proven benefit for CKD.

Question 356: During evaluation of a 9-year-old Andalusian with chronic bilateral forelimb lameness, distal limb flexion tests are strongly positive. MRI of the foot reveals a core lesion of the deep digital flexor tendon (DDFT) within the navicular bursa. Intra-bursal analgesia eliminates 90% of lameness bilaterally. Conservative management has failed after 8 months. Which surgical option directly addresses the pathological tension on the DDFT core lesion while preserving limb function?

Navicular suspensory ligament desmotomy via a palmar approach
Inferior check ligament desmotomy (accessory ligament of the DDFT) (Correct answer)
Coffin joint arthrodesis
Palmar digital neurectomy at the level of the proximal sesamoid bones

Correct answer: Inferior check ligament desmotomy (accessory ligament of the DDFT)

Inferior check ligament (accessory ligament of the DDFT) desmotomy reduces tension on the DDFT by eliminating the static tethering effect of the accessory ligament, allowing the DDFT to bear reduced load and facilitating healing of the core lesion. It is the preferred surgical option when MRI confirms DDFT pathology within the navicular bursa. Palmar digital neurectomy provides analgesia but does not address the biomechanical cause and carries risks of catastrophic tendon rupture.

Question 357: A 7-year-old Thoroughbred presents with acute-onset, severe left forelimb lameness following a race. Radiographs reveal a complete, non-displaced sagittal fracture of the proximal phalanx. Intraoperative lag screw fixation is planned. Which cortex should the lag screw thread engage to achieve interfragmentary compression?

The near cortex only, leaving the far cortex unthreaded
Both cortices with equal thread engagement to distribute load
The far cortex only, with the near cortex overdrilled to gliding hole diameter (Correct answer)
The far cortex with a washer placed under the screw head at the near cortex

Correct answer: The far cortex only, with the near cortex overdrilled to gliding hole diameter

Lag screw technique requires overdrilling the near (glide) cortex to the outer thread diameter so it does not engage, while the thread bites only the far cortex. As the screw head seats against the near cortex, it pulls the far fragment toward the head, generating interfragmentary compression. Engaging both cortices or the near cortex alone negates the compression mechanism.

Question 358: A 6-month-old female intact pig (Sus scrofa domesticus) raised as a pet presents with acute onset of paddling, opisthotonus, and salivation. The owner reports feeding table scraps including salted pork rinds and leftover soup. On exam the pig is non-febrile but disoriented. CSF tap shows increased protein with no organisms on Gram stain. Which diagnosis best explains this presentation?

Pseudorabies (Aujeszky's disease)
Mulberry heart disease (vitamin E/selenium deficiency)
Streptococcus suis meningitis
Salt poisoning / water deprivation encephalopathy (Correct answer)

Correct answer: Salt poisoning / water deprivation encephalopathy

Salt poisoning (sodium ion toxicosis) in pigs occurs classically when animals with water deprivation are suddenly allowed free water intake, OR when fed high-sodium diets without adequate water access. The CSF findings of elevated protein with no organisms, combined with the high-sodium diet history (salted pork rinds, soup), point strongly to this diagnosis. The classic histopathologic finding is eosinophilic meningoencephalitis with perivascular cuffing. Streptococcus suis would typically show CSF neutrophilia and organisms. Pseudorabies causes intense pruritus ('mad itch') and is reportable. Mulberry heart disease presents with sudden death, not CNS signs.

Question 359: An equine practitioner is treating a horse with endotoxemia and considers using polymyxin B for lipopolysaccharide neutralization. The horse also has acute kidney injury (creatinine 4.8 mg/dL). Which statement most accurately reflects the pharmacological risk in this scenario?

Polymyxin B is primarily hepatically metabolized; renal dysfunction does not affect its safety profile
Renal impairment increases polymyxin B protein binding, paradoxically reducing free drug toxicity
Polymyxin B nephrotoxicity is mediated exclusively through prostaglandin inhibition and is reversible with NSAIDs
Polymyxin B causes nephrotoxicity via tubular cell membrane disruption and accumulates with renal impairment, compounding existing injury (Correct answer)

Correct answer: Polymyxin B causes nephrotoxicity via tubular cell membrane disruption and accumulates with renal impairment, compounding existing injury

Polymyxin B is nephrotoxic due to its cationic detergent-like mechanism, which disrupts renal proximal tubular cell membranes. The drug undergoes renal elimination, and in horses with pre-existing acute kidney injury, reduced GFR leads to drug accumulation, markedly amplifying tubular toxicity. Use in patients with renal dysfunction is controversial; if used, very low doses (1,000–2,000 IU/kg IV) with aggressive fluid support and close renal monitoring are essential. The LPS-neutralizing benefit must be carefully weighed against the risk of worsening renal failure.

Question 360: A dog with a confirmed MDR1 (ABCB1) mutation (homozygous mutant) requires antiparasitic treatment for generalized demodicosis. Which drug combination poses the GREATEST risk of neurotoxicity in this patient?

Ivermectin + ketoconazole (Correct answer)
Milbemycin oxime + spinosad (Trifexis)
Doramectin + doxycycline
Selamectin + lufenuron

Correct answer: Ivermectin + ketoconazole

Ivermectin is a P-glycoprotein (P-gp) substrate; in MDR1-mutant dogs, reduced P-gp function allows accumulation of ivermectin in the CNS. Ketoconazole is a potent CYP3A4 and P-glycoprotein inhibitor. Co-administration of ketoconazole with ivermectin in a P-gp-deficient dog compounds the risk dramatically: ivermectin is already not being effluxed from the CNS, and ketoconazole further inhibits any residual P-gp activity and slows ivermectin hepatic metabolism. This combination has caused fatal neurotoxicity. Milbemycin + spinosad is approved for use in MDR1-mutant dogs at label doses. Selamectin has a wide safety margin even in MDR1-mutant dogs. Doramectin carries risk in MDR1 dogs, but the combination with doxycycline does not add a pharmacokinetic interaction that amplifies CNS accumulation.

NAVLE (North American Veterinary Licensing Exam)

The NAVLE (North American Veterinary Licensing Exam) exam validates essential knowledge and skills required for certification or licensure in this field.

360

Questions

420 min

Time Limit

65%

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Sources & references

Exam facts on this page (fees, format, dates, passing scores) are checked against these official sources; the date is our last check. Editorial policy

canadianveterinarians.net — Retake policy · verified Oct 2026
icva.net — Eligibility, fees, test delivery, exam format, passing score, retake policy, score release, late registration · verified Oct 2026