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

Question 1: A cat with hypertrophic cardiomyopathy requires anesthesia. Which inhalant anesthetic is generally preferred for its cardiovascular stability in cats with cardiac disease?

Halothane
Desflurane
Sevoflurane (Correct answer)
Isoflurane

Correct answer: Sevoflurane

Sevoflurane has the least negative cardiovascular effects and most rapid induction/recovery among currently available inhalants, making it preferred in feline cardiac patients.

Question 2: 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?

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

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

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

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 4: 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?

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

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 5: Equine degenerative joint disease of the proximal interphalangeal joint (high ringbone) is BEST confirmed with:

Thermography of the lower limb
Ultrasonography of the pastern
Lateromedial and dorsopalmar radiographs of the pastern (Correct answer)
Intra-articular anesthesia of the coffin joint

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 6: 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:

CT angiography of the thorax with IV contrast after stabilization via pericardiocentesis (Correct answer)
Radiographic measurement of the vertebral heart scale (VHS) to differentiate effusion from cardiomegaly
Repeat echocardiography in 48 hours following pericardiocentesis to assess for mass lesion
Contrast-enhanced ultrasound (CEUS) of the right auricular appendage after pericardiocentesis

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 7: A dairy producer wants to monitor transition cow health. Which single blood test best predicts subclinical ketosis in fresh cows?

Serum beta-hydroxybutyrate (BHB) ≥1.2 mmol/L (Correct answer)
Blood glucose <2.5 mmol/L
Serum NEFA >0.4 mEq/L at dry-off only
Urine acetone dipstick color change

Correct answer: Serum beta-hydroxybutyrate (BHB) ≥1.2 mmol/L

Serum BHB ≥1.2 mmol/L (1.0–1.4 mmol/L threshold range) measured in the first 2 weeks postpartum is the gold standard for diagnosing subclinical ketosis.

Question 8: 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?

Lymphangiectasia
Inflammatory bowel disease
Small intestinal bacterial overgrowth (SIBO) / dysbiosis (Correct answer)
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 9: Among commonly used local anesthetics in veterinary medicine, which agent provides the LONGEST duration of nerve block?

Lidocaine
Mepivacaine
Procaine
Bupivacaine (Correct answer)

Correct answer: Bupivacaine

Bupivacaine has the longest duration of action among common local anesthetics (4–8 hours for nerve blocks) due to its high protein binding and lipid solubility, making it ideal for postoperative pain management.

Question 10: On abdominal radiographs, which finding is MOST consistent with a congenital portosystemic shunt in a young dog?

Hepatomegaly with ascites
Splenomegaly with portal vein dilation
Microhepatica (small liver) with renomegaly (Correct answer)
Normal liver size with splenic mineralization

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 11: 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?

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

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 12: A veterinarian prescribes enrofloxacin 5 mg/kg IV once daily for a 6-year-old cat with bacteremia. On day 3, the owner calls reporting the cat is bumping into objects and appears disoriented. Fundic examination reveals multifocal areas of retinal degeneration. What pharmacokinetic property of fluoroquinolones in cats most directly explains this toxicity?

Enrofloxacin's metabolic conversion to ciprofloxacin is prolonged in cats, producing toxic peak plasma levels
Cats have a high volume of distribution for enrofloxacin, concentrating it in ocular tissues at doses safe in other species
Cats lack sufficient glucuronidation capacity, causing enrofloxacin to accumulate in retinal photoreceptors
Cats have reduced hepatic CYP1A2 activity, leading to accumulation of the parent compound (Correct answer)

Correct answer: Cats have reduced hepatic CYP1A2 activity, leading to accumulation of the parent compound

Cats have markedly reduced hepatic CYP1A2 (cytochrome P450 1A2) activity compared to dogs and humans. Enrofloxacin is primarily metabolized by CYP1A2 to ciprofloxacin. With impaired metabolism, the parent compound (enrofloxacin) accumulates to high plasma concentrations. Enrofloxacin — more so than ciprofloxacin — is directly retinotoxic in cats, causing acute retinal degeneration and blindness, especially at doses ≥5 mg/kg/day IV. The AVMA-recommended feline dose is ≤2.5 mg/kg/day to reduce this risk. Glucuronidation deficiency in cats is real but pertains to other drug classes (e.g., acetaminophen, aspirin), not fluoroquinolone toxicity.

Question 13: 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
Ivermectin toxicity; Intralipid emulsion
Permethrin toxicity; Methocarbamol (Correct answer)
Organophosphate toxicity; Atropine

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 14: A cat with chronic vomiting undergoes endoscopic biopsy showing diffuse infiltration of small lymphocytes in the lamina propria. PARR testing confirms clonality. Which diagnosis is confirmed?

Inflammatory bowel disease
Large cell lymphoma
Mast cell tumor
Small cell lymphoma (Correct answer)

Correct answer: Small cell lymphoma

Clonal small lymphocyte infiltration confirmed by PCR for antigen receptor rearrangement (PARR) distinguishes small cell lymphoma from IBD, which is polyclonal.

Question 15: A cat receiving phenobarbital for seizure management develops a sudden increase in seizure frequency despite adequate serum levels. Which mechanism best explains this phenomenon?

GABA receptor downregulation develops with chronic phenobarbital use, reducing drug efficacy (Correct answer)
Cats develop anti-phenobarbital antibodies after prolonged exposure
Phenobarbital accumulates in adipose tissue and redistributes unpredictably
Phenobarbital induces its own metabolism via CYP450 induction, lowering effective blood levels over time

Correct answer: GABA receptor downregulation develops with chronic phenobarbital use, reducing drug efficacy

Chronic barbiturate use can cause GABA-A receptor downregulation and tolerance, reducing seizure threshold despite unchanged serum drug concentrations.

Question 16: A 5-year-old male neutered Dachshund presents with acute onset severe abdominal pain, hematemesis, and collapse. PCV is 16% with adequate total protein (6.2 g/dL). Abdominal radiographs show a mild loss of serosal detail. Coagulation panel reveals: PT 28 sec (ref 7–12), PTT 98 sec (ref 60–90), fibrinogen 80 mg/dL (ref 150–400), d-dimers markedly elevated. Platelet count is 40,000/µL. Which of the following best explains this coagulopathy pattern?

Platelet dysfunction from aspirin ingestion with secondary hypofibrinogenemia
Vitamin K antagonist rodenticide toxicity causing factor II, VII, IX, X deficiency
Disseminated intravascular coagulation (DIC) secondary to a systemic disease process (Correct answer)
Inherited factor VIII deficiency (Hemophilia A) with concurrent thrombocytopenia

Correct answer: Disseminated intravascular coagulation (DIC) secondary to a systemic disease process

The combination of prolonged PT and PTT, thrombocytopenia, markedly elevated d-dimers, and critically low fibrinogen defines DIC (both the procoagulant and fibrinolytic phases). The consumption of clotting factors AND platelets combined with d-dimer elevation (cross-linked fibrin degradation products) is the hallmark. Rodenticide toxicity causes prolonged PT (extrinsic pathway factor VII is shortest half-life) but does NOT cause thrombocytopenia or elevated d-dimers or hypofibrinogenemia. Hemophilia A causes isolated PTT prolongation. Aspirin causes platelet dysfunction (prolonged closure time/buccal mucosal bleeding time) but not this global consumptive coagulopathy. The acute abdomen with hematemesis suggests an underlying trigger (splenic mass rupture, sepsis, or neoplasia) driving the DIC.

Question 17: 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 meningioma
Syringomyelia
Intramedullary astrocytoma
Spinal cord infarction (fibrocartilaginous embolism) (Correct answer)

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 18: During a routine laparotomy in a 3-year-old male French Bulldog for suspected intestinal foreign body, you discover a 4 cm segment of jejunum that is dark purple, non-peristaltic, and fails to pink up after 10 minutes of warm saline lavage and vascular assessment. The mesenteric vasculature appears intact. You resect the segment. Intraoperatively, what is the MOST critical technical consideration unique to intestinal anastomosis in brachycephalic dogs compared to mesocephalic breeds?

Stapled anastomosis is contraindicated in French Bulldogs due to documented staple-line failure related to breed-specific tissue fragility
Brachycephalic dogs require a larger luminal diameter anastomosis due to higher intraluminal pressures from aerophagia
The mesenteric border must be closed with interrupted sutures rather than continuous pattern to prevent ischemia in short mesenteries
End-to-end anastomosis carries higher dehiscence risk in brachycephalic dogs secondary to hypoxemia-related impaired wound healing (Correct answer)

Correct answer: End-to-end anastomosis carries higher dehiscence risk in brachycephalic dogs secondary to hypoxemia-related impaired wound healing

Brachycephalic dogs are predisposed to chronic intermittent hypoxemia due to upper airway obstruction (stenotic nares, elongated soft palate, hypoplastic trachea). Tissue hypoxia impairs collagen synthesis and wound healing, increasing the risk of anastomotic dehiscence. This is a recognized anesthetic and surgical risk factor specific to the breed conformation. While aerophagia does occur in brachycephalic dogs, it does not necessitate a larger anastomosis diameter. The mesenteric border closure and staple contraindication claims are not evidence-based breed-specific recommendations. Recognition of this hypoxemia-wound healing axis is essential for perioperative planning in these patients.

Question 19: 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 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
It most commonly represents hemorrhage around the lesion and warrants evaluation for a fungal or vascular etiology (Correct answer)

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 20: On orthogonal radiographs of a long bone, periosteal new bone with a 'sunburst' pattern is MOST characteristic of:

Hypertrophic osteopathy
Primary bone tumor (osteosarcoma) (Correct answer)
Septic osteomyelitis
Nutritional secondary hyperparathyroidism

Correct answer: Primary bone tumor (osteosarcoma)

A sunburst or spiculated periosteal reaction radiating perpendicular to the cortex is a classic aggressive pattern associated with osteosarcoma.

Question 21: Which internal parasite of cattle causes 'bottle jaw' (submandibular edema) due to hypoproteinemia?

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

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 22: 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?

Anechoic cavities within the mass representing blood-filled sinusoids
Hyperechoic peripheral rim representing compressed splenic parenchyma
Absence of internal Doppler signal within the cavities
Simultaneous detection of a hypoechoic hepatic nodule with similar internal architecture (Correct answer)

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 23: 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
Neurectomy of the tibial nerve
Intra-articular corticosteroids into the affected low-motion joints (Correct answer)
Arthroscopic joint lavage of the tarsocrural joint

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 24: A ferret presents for adrenalectomy. Which induction agent combination is most commonly used in ferrets for short procedures?

Tiletamine-zolazepam IM
Alfaxalone and diazepam IM
Propofol alone IV
Ketamine and midazolam IM (Correct answer)

Correct answer: Ketamine and midazolam IM

Ketamine combined with midazolam (or diazepam) given IM is a practical and commonly used induction protocol in ferrets, providing smooth anesthesia.

Question 25: 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?

Urine glucose strips
Serial blood glucose curve
Fructosamine concentration
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 26: 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?

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

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 27: Feline panleukopenia virus (FPV) primarily targets which tissue due to its requirement for rapidly dividing cells?

Intestinal crypt epithelium (Correct answer)
Hepatocytes
Renal tubular epithelium
Pulmonary alveolar cells

Correct answer: Intestinal crypt epithelium

FPV targets rapidly dividing intestinal crypt cells, leading to villous collapse, malabsorption, and severe hemorrhagic enteritis.

Question 28: A herd of cattle in the Texas panhandle develops polioencephalomalacia (PEM). The most common cause in feedlot cattle on high-sulfur diets is deficiency or antagonism of which vitamin?

Vitamin E
Niacin
Vitamin A
Thiamine (Vitamin B1) (Correct answer)

Correct answer: Thiamine (Vitamin B1)

High dietary sulfur promotes ruminal H2S production, which inhibits thiamine-dependent enzymes and causes cerebrocortical necrosis (polioencephalomalacia).

Question 29: 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?

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

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

Pleural fissure lines at the lung margins
Loss of diaphragmatic outline with abdominal organs in the thorax (Correct answer)
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 31: 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 preferentially shunt acetaminophen through the sulfation pathway, producing toxic sulfate conjugates
Cats have enhanced CYP2E1 activity that produces excessive NAPQI from acetaminophen
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)

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 32: In a feedlot outbreak of thromboembolism (liver abscesses leading to caudal vena cava thrombosis), which organism is most commonly isolated from liver abscesses in cattle?

Trueperella pyogenes
Clostridium perfringens
Fusobacterium necrophorum (Correct answer)
Bacteroides melaninogenicus

Correct answer: Fusobacterium necrophorum

Fusobacterium necrophorum is the primary pathogen in bovine liver abscesses, originating from rumenitis caused by high-concentrate diets.

Question 33: A Siamese cat presents with recurrent upper respiratory signs, chronic nasal discharge, and sneezing since kittenhood. Rhinoscopy reveals mucosal proliferation and turbinate destruction. Which diagnosis is most likely?

Cryptococcus neoformans rhinitis
Chronic rhinosinusitis secondary to herpesvirus-1 (FHV-1) (Correct answer)
Aspergillus rhinosinusitis
Nasal lymphoma

Correct answer: Chronic rhinosinusitis secondary to herpesvirus-1 (FHV-1)

Chronic rhinosinusitis with turbinate destruction in young cats with a history of repeated upper respiratory infections is most commonly a sequela of early FHV-1 infection causing permanent mucosal damage.

Question 34: 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 safe because the reduction factor exceeds the initial infectious burden, yielding a negative log-risk (Correct answer)
The product is unsafe because any bovine-derived material from a BSE-positive country must be rejected regardless of processing
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 35: The Hazard Analysis Critical Control Point (HACCP) system was originally developed to ensure food safety for which population?

Hospitalized immunocompromised patients
Military personnel in field operations
Commercial airline passengers
NASA astronauts (Correct answer)

Correct answer: NASA astronauts

HACCP was originally developed by NASA and Pillsbury in the 1960s to ensure food safety for astronauts in space missions.

Question 36: In nuclear scintigraphy used in veterinary medicine, which radiopharmaceutical is most commonly used for bone scanning in dogs?

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

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 37: Which dietary management strategy implemented during the final 2-3 weeks of the dry period is most effective for preventing periparturient hypocalcemia (milk fever) in dairy cows?

Maximizing dietary potassium to improve rumen function.
Feeding a diet high in calcium to 'prime' the system.
Feeding a diet with a negative Dietary Cation-Anion Difference (DCAD). (Correct answer)
Supplementing with high levels of intravenous calcium.

Correct answer: Feeding a diet with a negative Dietary Cation-Anion Difference (DCAD).

Feeding a diet with a negative Dietary Cation-Anion Difference (DCAD), also known as an acidogenic diet, is the most effective nutritional strategy to prevent milk fever. This diet induces a mild metabolic acidosis, which improves the cow's ability to mobilize calcium from bone and absorb it from the gut in response to parathyroid hormone (PTH) when the massive demand for calcium begins at calving. Feeding high calcium pre-calving or high potassium actually increases the risk of milk fever. IV calcium is a treatment, not a preventative feeding strategy.

Question 38: On a lateral thoracic radiograph of a dog, which structure should be used to assess left atrial enlargement?

Displacement of the trachea ventrally at the carina
Increased sternal contact of the cardiac silhouette
Dorsal elevation of the left mainstem bronchus (Correct answer)
Widening of the right cardiac border

Correct answer: Dorsal elevation of the left mainstem bronchus

Left atrial enlargement causes dorsal elevation and splaying of the left mainstem bronchus (carina angle >60°) on lateral radiographs.

Question 39: A veterinarian is conducting a pre-breeding soundness exam (BSE) on a herd bull. According to the Society for Theriogenology minimum standards, what minimum total motility percentage is required for a 'satisfactory' classification?

25% progressive motility with normal morphology >70%
30% progressively motile sperm (Correct answer)
60% morphologically normal sperm
50% total motility

Correct answer: 30% progressively motile sperm

The SFT BSE minimum requires ≥30% progressively motile sperm and ≥70% morphologically normal sperm for a satisfactory potential breeder classification.

Question 40: 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
Ceftiofur intrauterine infusion is effective because third-generation cephalosporins have broad-spectrum gram-negative coverage including Mycoplasma
Intrauterine infusion of oxytetracycline is the treatment of choice because Mycoplasma lacks a cell wall and oxytetracycline penetrates uterine secretions well
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 41: 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 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
Administer yohimbine IV to fully reverse both detomidine and butorphanol
Administer atipamezole IV to selectively reverse detomidine, accepting residual opioid sedation (Correct answer)

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 42: A cat with confirmed FeLV infection is most likely to develop which neoplastic condition?

Hepatocellular carcinoma
Multicentric lymphoma (Correct answer)
Mammary adenocarcinoma
Mast cell tumor

Correct answer: Multicentric lymphoma

FeLV strongly predisposes cats to multicentric lymphoma, particularly T-cell lymphoma in young cats.

Question 43: A cat is presented with a nasal mass and skin nodules; cytology reveals large encapsulated yeast with narrow-based budding. What is the most likely diagnosis?

Blastomycosis
Cryptococcosis (Correct answer)
Sporotrichosis
Histoplasmosis

Correct answer: Cryptococcosis

Cryptococcus neoformans/gattii appears as large encapsulated yeasts with narrow-based budding on cytology and commonly causes nasal and skin lesions in cats.

Question 44: A 10-year-old castrated male mixed-breed dog presents for evaluation of a 3-month history of regurgitation, weight loss, and occasional aspiration pneumonia. Cervical radiographs and fluoroscopic swallowing study confirm cricopharyngeal achalasia-like dysphagia with normal esophageal motility. EMG of the cricopharyngeal muscle shows spontaneous fibrillation potentials and positive sharp waves. Serology for acetylcholine receptor antibodies is negative. Which diagnostic step is MOST likely to reveal a treatable underlying systemic cause for this dog's condition?

Thoracic CT for anterior mediastinal mass
Muscle biopsy of the temporalis for inflammatory polymyositis (Correct answer)
Repetitive nerve stimulation study for a decremental response indicating myasthenia gravis
Serum thyroxine (T4) and TSH measurement for hypothyroidism

Correct answer: Muscle biopsy of the temporalis for inflammatory polymyositis

Acquired cricopharyngeal dysfunction with EMG evidence of spontaneous activity (fibrillation potentials, positive sharp waves) indicates active muscle denervation or myopathy rather than a pure neuromuscular junction disorder. In an older dog with dysphagia and muscle EMG changes, inflammatory polymyositis — particularly masticatory muscle myositis (MMM) or a generalized immune-mediated myopathy — is a key treatable cause. Muscle biopsy (temporalis, masseter, or limb muscle) with type 2M fiber immunostaining can confirm MMM. Seronegative MG is possible but the normal esophageal motility and EMG fibrillations make a pure NMJ disorder less likely. Hypothyroidism rarely causes cricopharyngeal dysfunction as a primary presentation.

Question 45: Which ultrasound artifact appears as hyperechoic lines parallel to a curved reflective surface, such as the near wall of a cystic structure?

Reverberation (Correct answer)
Mirror artifact
Shadowing
Enhancement

Correct answer: Reverberation

Reverberation artifacts appear as repeating hyperechoic lines at regular intervals deep to a highly reflective surface due to the sound beam bouncing back and forth.

Question 46: A backyard chicken flock presents with sudden death, cyanosis of the comb and wattles, and neurological signs. Which disease should be the primary differential?

Marek's disease
Fowl pox
Newcastle disease (velogenic strain) (Correct answer)
Infectious bronchitis

Correct answer: Newcastle disease (velogenic strain)

Velogenic Newcastle disease causes acute high mortality with concurrent respiratory, nervous, and circulatory signs including cyanosis.

Question 47: Which radiographic finding is MOST consistent with pyloric outflow obstruction in a dog?

Retroperitoneal effusion with loss of serosal detail
Dilated small intestinal loops > 3x rib width
Markedly distended stomach with delayed gastric emptying (Correct answer)
Free peritoneal gas on the VD view

Correct answer: Markedly distended stomach with delayed gastric emptying

Pyloric obstruction causes gastric outflow failure, producing marked gastric distension with delayed or absent contrast passage on fluoroscopy.

Question 48: 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
Atropine and Pralidoxime (2-PAM) (Correct answer)
Vitamin K1 and Methocarbamol
Naloxone and Epinephrine

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 49: A 7-year-old German Shepherd presents with progressive, non-painful pelvic limb ataxia and weakness over 12 months. The dog is ambulatory but shows proprioceptive deficits bilaterally. Spinal radiographs are normal. CSF is normal. Which diagnosis is most consistent with this presentation?

Lumbosacral stenosis (cauda equina syndrome)
Fibrocartilaginous embolism (FCE)
Degenerative myelopathy (DM) (Correct answer)
Meningomyelitis due to Neospora caninum

Correct answer: Degenerative myelopathy (DM)

Degenerative myelopathy (DM) in German Shepherds is a progressive, non-painful, symmetric upper motor neuron disease of late middle-age to older dogs, with normal imaging and CSF. It is associated with the SOD1 gene mutation. FCE is acute and often asymmetric. Lumbosacral stenosis causes pain and lower motor neuron signs. Neospora causes a painful, ascending LMN polyradiculoneuritis.

Question 50: During anesthesia, a dog develops frequent premature ventricular contractions (PVCs) visible on ECG. What is the FIRST-LINE pharmacologic treatment?

Epinephrine IV bolus
Lidocaine IV bolus (Correct answer)
Dopamine CRI
Atropine IV

Correct answer: Lidocaine IV bolus

Intravenous lidocaine is the first-line antiarrhythmic for ventricular arrhythmias (PVCs, ventricular tachycardia) in anesthetized dogs due to its rapid onset and favorable cardiac profile.

Question 51: A beef cow herd experiences an outbreak of abortion storms affecting 30% of pregnant cows. PCR testing confirms Neospora caninum. What is the primary route of transmission in cattle?

Venereal transmission from infected bulls
Tick vector transmission
Ingestion of oocysts from dog feces (horizontal)
Transplacental (vertical) transmission from dam to fetus (Correct answer)

Correct answer: Transplacental (vertical) transmission from dam to fetus

Neospora caninum is perpetuated in beef herds primarily by transplacental transmission; congenitally infected calves become the next generation of chronically infected dams.

Question 52: 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?

Vancomycin 7.5 mg/kg IV TID with therapeutic drug monitoring
Chloramphenicol 50 mg/kg PO QID
Enrofloxacin 5 mg/kg IV once daily (Correct answer)
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 53: A veterinarian is assessing a feedlot for bovine respiratory disease (BRD). Which scoring system is most widely used to objectively evaluate respiratory signs in individual cattle at the pen level?

FAMACHA scoring system
California Mastitis Test (CMT) adaptation for BRD
Body condition scoring (BCS)
Bovine Respiratory Disease Scoring System (BRDS) by McGuirk (Correct answer)

Correct answer: Bovine Respiratory Disease Scoring System (BRDS) by McGuirk

The McGuirk Bovine Respiratory Disease Scoring System evaluates rectal temperature, nasal discharge, eye discharge, ear position, and head carriage to provide an objective BRD score for pull decisions.

Question 54: 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:

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

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 55: A dairy herd has a transition cow period disorder rate of 25% for clinical ketosis. Which nutritional management strategy is most effective at reducing periparturient ketosis?

Feeding propylene glycol as a preventive drench in the close-up dry period (Correct answer)
Increasing body condition score to 4.0 or higher at dry-off
Implementing a negative DCAD (Dietary Cation-Anion Difference) diet prepartum
Feeding high-grain diet 6 weeks before calving

Correct answer: Feeding propylene glycol as a preventive drench in the close-up dry period

Propylene glycol is a glucogenic precursor that, when drenched preventively in the close-up period or early postpartum, reduces the incidence of clinical ketosis by supporting hepatic gluconeogenesis.

Question 56: A 1-year-old male cat from a multi-cat household presents with a distended abdomen, fever, and lethargy. Abdominocentesis yields a viscous, straw-colored fluid with a high protein content. Which simple, in-house test can be performed on the fluid to strongly support a diagnosis of effusive Feline Infectious Peritonitis (FIP)?

Fluid cytology
Rivalta's test (Correct answer)
Fluid bacterial culture and sensitivity
Serum coronavirus antibody titer

Correct answer: Rivalta's test

The Rivalta's test is a simple and affordable test that involves adding a drop of the effusion fluid to a tube of distilled water and acetic acid. A positive result (the drop retains its shape) is caused by the high protein and fibrin content typical of FIP effusions and has a high positive predictive value for FIP. While not definitive, it is a strong supportive indicator. Coronavirus titers are often non-diagnostic as many cats are exposed to feline coronavirus without developing FIP. Cytology typically shows non-specific pyogranulomatous inflammation, and bacterial culture will be negative.

Question 57: Which feline coronavirus (FCoV) mutation is classically associated with the transition from enteric infection to feline infectious peritonitis (FIP)?

Nucleocapsid gene frameshift
7b gene duplication
Spike protein S1 domain deletion
3c gene loss-of-function mutation (Correct answer)

Correct answer: 3c gene loss-of-function mutation

Loss-of-function mutations in the 3c gene of feline enteric coronavirus are associated with the shift to macrophage tropism and development of FIP.

Question 58: A food inspector observes condensation dripping from overhead pipes onto exposed ready-to-eat food contact surfaces. This represents a violation of which food safety principle?

Sanitation and hygienic design (environmental sanitation) (Correct answer)
Supplier verification
Temperature control for safety
Allergen labeling requirements

Correct answer: Sanitation and hygienic design (environmental sanitation)

Condensation dripping onto food contact surfaces represents an environmental sanitation and hygienic facility design failure, a prerequisite program violation.

Question 59: Guinea pigs are unable to synthesize vitamin C endogenously. What is the recommended daily dietary requirement?

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

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 60: 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 <5 g/L measured within 6 hours of birth
Serum IgG <10 g/L measured at 1-2 weeks of age
Total serum protein <5.0 g/dL measured at 24-48 hours of age
Serum IgG <10 g/L measured at 24-48 hours of age (Correct answer)

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 61: A positive response to a distal limb flexion test in a horse is most useful for localizing pain to which general anatomical area?

Stifle and tarsus
Elbow and shoulder
Carpus and proximal metacarpal region
Metacarpophalangeal joint and structures distal to it (Correct answer)

Correct answer: Metacarpophalangeal joint and structures distal to it

The distal limb flexion test specifically applies pressure to the joints and associated soft tissues of the fetlock, pastern, and coffin joint. A positive response (an increase in lameness after the hold) suggests a pain source within this region. While not perfectly specific, it effectively rules out primary pain from more proximal structures like the carpus, stifle, or shoulder, which are not significantly stressed by this particular test.

Question 62: A pig farm reports sudden death in 3-week-old piglets with gross necropsy findings of fibrinous polyserositis, arthritis, and meningitis. The most likely causative agent is:

Haemophilus parasuis (Glässer's disease) (Correct answer)
Actinobacillus pleuropneumoniae
Streptococcus suis type 2
Mycoplasma hyorhinis

Correct answer: Haemophilus parasuis (Glässer's disease)

Haemophilus parasuis causes Glässer's disease in young pigs, characterized by fibrinous polyserositis (peritonitis, pleuritis, pericarditis), arthritis, and meningitis at 3–8 weeks of age.

Question 63: A flock of sheep presents with sudden deaths in 2-to-6-week-old lambs that were thriving until 24 hours prior. Necropsy reveals hemorrhagic abomasal and intestinal lesions with gas in the intestinal lumen. Gram-positive rods are cultured. The most appropriate preventive strategy for next year's lamb crop is:

Vaccinate lambs at birth with Clostridium novyi type B bacterin
Vaccinate ewes with Clostridium perfringens types C and D toxoid 4–6 weeks before lambing (Correct answer)
Feed sodium bicarbonate free-choice to buffer rumen pH
Administer prophylactic penicillin G to all lambs at birth

Correct answer: Vaccinate ewes with Clostridium perfringens types C and D toxoid 4–6 weeks before lambing

Overeating disease (pulpy kidney) caused by Clostridium perfringens type D and enterotoxemia type C are the primary clostridial diseases of young lambs. Vaccinating ewes 4–6 weeks pre-lambing ensures high colostral antibody titers that passively protect newborn lambs. Antibiotic prophylaxis at birth is not practical or regulatory-appropriate for herd prevention.

Question 64: 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?

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

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 65: Which reproductive technology is used to synchronize estrus in beef heifers and cows to facilitate fixed-time artificial insemination (FTAI) without heat detection?

Melengestrol acetate (MGA) in feed for 14 days without any hormonal synchronization
Human chorionic gonadotropin (hCG) injection alone
Gonadotropin-releasing hormone (GnRH) injection alone
Ovsynch or Select Synch protocols combining GnRH, progesterone (CIDR), and prostaglandin F2α (Correct answer)

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 66: 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?

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.
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)
FIP develops exclusively in cats with concurrent FeLV or FIV co-infection, which suppresses regulatory T-cell responses and permits macrophage invasion.
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.

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 67: A 9-year-old, obese, male neutered domestic shorthair is diagnosed with diabetes mellitus. Which insulin type, when combined with a low-carbohydrate diet, offers the highest probability of achieving diabetic remission in a newly diagnosed cat?

NPH
Regular insulin
Vetsulin (Lente)
Glargine (Correct answer)

Correct answer: Glargine

Glargine insulin, a long-acting insulin analog, has been shown to result in better glycemic control and a higher probability of remission in newly diagnosed diabetic cats compared to other insulins like PZI or Lente (Vetsulin). NPH has a short duration of action in cats, and regular insulin is used for emergencies like DKA, not long-term management.

Question 68: A herd of stocker cattle develops red-water disease (bacillary hemoglobinuria). Which organism and predisposing factor is responsible?

Clostridium haemolyticum, liver fluke migration (Correct answer)
Clostridium septicum, skin wounds in wet conditions
Clostridium perfringens type C, high-grain diet
Clostridium novyi type A, wound contamination

Correct answer: Clostridium haemolyticum, liver fluke migration

Bacillary hemoglobinuria is caused by C. haemolyticum (C. novyi type D), which proliferates in anaerobic zones created by migrating Fasciola hepatica liver flukes.

Question 69: Cunean bursitis in horses with bone spavin is associated with inflammation of which structure?

Calcaneal bursa
Bursa beneath the cunean (medial) branch of the cranial tibial tendon (Correct answer)
Navicular bursa of the hind foot
Bicipital bursa of the shoulder

Correct answer: Bursa beneath the cunean (medial) branch of the cranial tibial tendon

Cunean bursitis involves the bursa located beneath the cunean branch of the cranial tibial tendon as it crosses the medial aspect of the hock, often concurrent with bone spavin.

Question 70: Which federal agency is responsible for the inspection of meat and poultry products under the Federal Meat Inspection Act?

CDC
FDA
USDA FSIS (Correct answer)
USDA APHIS

Correct answer: USDA FSIS

The USDA Food Safety and Inspection Service (FSIS) is mandated to inspect meat, poultry, and egg products under federal law.

Question 71: A 6-year-old Standardbred pacer develops progressive bilateral hindlimb ataxia and weakness that worsens going downhill. Cervical radiographs show vertebral canal stenosis at C4-C5. What is the most likely diagnosis?

Stringhalt
Equine protozoal myeloencephalitis (EPM)
Equine herpesvirus myeloencephalopathy
Cervical vertebral stenotic myelopathy (Wobbler syndrome) (Correct answer)

Correct answer: Cervical vertebral stenotic myelopathy (Wobbler syndrome)

Cervical vertebral stenotic myelopathy (Wobbler syndrome) presents with progressive spinal cord compression causing symmetric ataxia and weakness, confirmed by vertebral canal stenosis on radiographs.

Question 72: A cat with confirmed hypertrophic cardiomyopathy (HCM) and left atrial enlargement (LA:Ao ratio 1.7) is asymptomatic and has no pleural effusion. Which of the following treatment decisions is BEST supported by current evidence-based feline cardiology guidelines?

Initiate furosemide prophylactically to prevent future congestive heart failure
Initiate clopidogrel to reduce the risk of arterial thromboembolism given the left atrial enlargement (Correct answer)
Initiate atenolol to reduce dynamic left ventricular outflow tract obstruction and slow heart rate
Initiate an ACE inhibitor to reduce left ventricular hypertrophy and remodeling

Correct answer: Initiate clopidogrel to reduce the risk of arterial thromboembolism given the left atrial enlargement

The FATCAT study and current consensus guidelines recommend clopidogrel over aspirin for cats with HCM and left atrial enlargement, as LA enlargement is the strongest predictor of arterial thromboembolism (ATE) risk in cats. Clopidogrel significantly reduces recurrence of ATE in cats that have experienced a prior event, and is widely extrapolated for primary prevention in high-risk cats with marked LA dilation. Atenolol may be used for dynamic LVOTO but is not universally indicated for all HCM cats. Furosemide is reserved for overt CHF. ACE inhibitors have not been shown to benefit pre-clinical HCM cats in controlled feline studies.

Question 73: A 2-year-old male intact German Shepherd presents with a 3-week history of mucopurulent nasal discharge unilateral to the left nostril, sneezing, and mild epistaxis. Rhinoscopy reveals a pale, irregular mucosal lesion. Biopsy shows pyogranulomatous inflammation with broad, pauciseptate hyphae with right-angle branching on GMS stain. Which organism is MOST likely responsible, and what is the MOST appropriate initial antifungal therapy?

Pythium insidiosum — itraconazole + terbinafine combination
Aspergillus fumigatus — topical clotrimazole infusion via trephination
Conidiobolus coronatus — itraconazole monotherapy (Correct answer)
Rhinosporidium seeberi — surgical debulking with no antifungal indicated

Correct answer: Conidiobolus coronatus — itraconazole monotherapy

Broad, pauciseptate hyphae with right-angle branching on GMS stain in a dog with nasal/facial disease is characteristic of zygomycetes, specifically the Entomophthoromycota order. Conidiobolus coronatus (formerly Entomophthora coronata) causes rhinofacial conidiobolomycosis — pyogranulomatous rhinitis with broad hyphae that are difficult to culture. Aspergillus produces narrower, septate hyphae with acute-angle branching. Pythium is an oomycete (not a true fungus) presenting as GI/subcutaneous disease, and its hyphae are similar but the clinical presentation differs. Rhinosporidium produces sporangia, not hyphae. Itraconazole is the recommended first-line treatment for Conidiobolus, though prognosis is guarded.

Question 74: Which class of drugs can cause crystalluria and urinary obstruction in dogs, particularly in acidic urine?

Tetracyclines
Sulfonamides (Correct answer)
Aminoglycosides
Fluoroquinolones

Correct answer: Sulfonamides

Sulfonamides can precipitate in acidic urine and form crystals, potentially causing crystalluria, hematuria, and renal tubular obstruction.

Question 75: 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?

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

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 76: 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:

Ringbone (high)
Sesamoiditis
Fetlock synovitis (Correct answer)
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 77: When evaluating a horse for subtle hindlimb lameness, which surface is MOST useful for accentuating the gait abnormality?

Firm, level asphalt surface
Soft, deep sand arena (Correct answer)
Rubber-matted stall aisle
Grass pasture

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 78: 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)
Frequent high-protein, low-carbohydrate meals alone are sufficient medical management for insulinoma without pharmacologic intervention
Prednisone at 0.5–1 mg/kg PO BID is the preferred first-line medical management for insulinoma in ferrets
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 79: 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:

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

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 80: Which principle of disease prevention is represented by routine vaccination of dogs against rabies in the US?

Secondary prevention through early detection
Quaternary prevention
Primary prevention by reducing exposure and susceptibility (Correct answer)
Tertiary prevention

Correct answer: Primary prevention by reducing exposure and susceptibility

Routine rabies vaccination is a primary prevention strategy that reduces the reservoir of infection and prevents the disease from occurring.

Question 81: On thoracic radiographs of a 4-year-old DSH cat, you identify a soft tissue opacity in the cranial mediastinum that causes dorsal displacement of the trachea and is associated with pleural effusion. Ultrasonography reveals a cystic structure with internal echogenic debris. Which diagnosis is MOST consistent with these findings?

Cranial mediastinal lymphoma
Ectopic thyroid carcinoma
Thymoma
Branchial cyst (Correct answer)

Correct answer: Branchial cyst

Branchial (or thymic) cysts are uncommon but produce a cranial mediastinal cystic mass with internal debris on ultrasound — a key differentiating feature. Lymphoma is the most common cranial mediastinal mass in cats but is typically solid (not cystic) on ultrasound and rarely shows the cystic-with-debris pattern. Thymoma can have cystic components but tends to be more heterogeneously solid. The purely cystic appearance with debris is the hallmark of a branchial/thymic retention cyst. This distinction is critical because management differs markedly.

Question 82: 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?

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

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 83: Feline lower urinary tract disease (FLUTD) in a young male cat is most commonly attributable to which condition?

Idiopathic feline interstitial cystitis (FIC) (Correct answer)
Urolithiasis (struvite or oxalate)
Bacterial urinary tract infection
Urethral neoplasia

Correct answer: Idiopathic feline interstitial cystitis (FIC)

Idiopathic feline interstitial cystitis (FIC) accounts for approximately 55–65% of FLUTD cases in young cats, and bacterial UTI is rare in cats under 10 years.

Question 84: A 6-year-old bearded dragon (Pogona vitticeps) presents with anorexia, lethargy, and swollen limbs. Radiographs show lytic bone lesions and periosteal proliferation. Bloodwork reveals marked heterophilia and a PCV of 18%. Cytology of a fine-needle aspirate from a swollen limb reveals large, round organisms with a clear halo and a basophilic nucleus consistent with yeast. Which diagnosis and treatment is most appropriate?

Basidiobolus ranarum infection — amphotericin B and potassium iodide
Disseminated Devriesea agamarum infection — enrofloxacin and supportive care
Disseminated Ophidiomyces ophiodiicola — voriconazole monotherapy
Chrysosporium anamorph of Nannizziopsis vriesii (CANV) infection — itraconazole and surgical debridement (Correct answer)

Correct answer: Chrysosporium anamorph of Nannizziopsis vriesii (CANV) infection — itraconazole and surgical debridement

CANV (Chrysosporium anamorph of Nannizziopsis vriesii) is a primary fungal pathogen of agamid lizards, including bearded dragons, causing deep mycosis with lytic bone lesions, skin ulceration, and systemic dissemination. The large round yeast with a clear halo on cytology is characteristic. Treatment requires long-term itraconazole combined with aggressive surgical debridement of affected tissue. Devriesea agamarum is a bacterial pathogen. Ophidiomyces is a snake fungal disease. Basidiobolus causes GI infections in reptiles but has a different clinical presentation.

Question 85: A 7-year-old spayed female cat presents with polyuria, polydipsia, and a palpable ventral neck mass. T4 is markedly elevated. Which treatment option is considered curative?

Methimazole administered daily
Dietary iodine restriction
Thyroidectomy only when bilateral
Radioactive iodine (I-131) therapy (Correct answer)

Correct answer: Radioactive iodine (I-131) therapy

Radioactive iodine (I-131) is the treatment of choice for feline hyperthyroidism as it selectively destroys hyperfunctional thyroid tissue and is considered curative with a single dose.

Question 86: 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?

Babesiosis
Von Willebrand's disease
Zinc toxicity
Immune-Mediated Hemolytic Anemia (IMHA) (Correct answer)

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 87: A state veterinarian receives a report of a cluster of human cases of hemolytic uremic syndrome (HUS) in a rural county. Epidemiological investigation links the cases to a small farm that sells raw milk and allows petting zoo visits. Which of the following zoonotic transmission pathways is MOST likely responsible, and what is the primary regulatory authority responsible for interstate commerce of the implicated product?

Aerosol transmission of Campylobacter jejuni; USDA-FSIS under the Federal Meat Inspection Act
Fecal-oral transmission of Escherichia coli O157:H7 via raw milk; FDA under the Grade A Pasteurized Milk Ordinance (PMO) (Correct answer)
Vector-borne transmission of Cryptosporidium parvum; EPA under the Safe Drinking Water Act
Direct contact transmission of Salmonella Typhimurium; CDC under the Public Health Service Act

Correct answer: Fecal-oral transmission of Escherichia coli O157:H7 via raw milk; FDA under the Grade A Pasteurized Milk Ordinance (PMO)

E. coli O157:H7 is the classic cause of HUS, particularly in children, and raw milk is a well-documented vehicle. The FDA regulates interstate raw milk commerce under the PMO (21 CFR Part 1240.61 prohibits interstate sale of raw milk for direct human consumption). The fecal-oral route from cattle reservoirs through unpasteurized milk is the primary pathway in this scenario. Campylobacter causes gastroenteritis but rarely HUS. Cryptosporidium is waterborne and causes diarrhea, not typically HUS. USDA-FSIS covers meat/poultry, not dairy.

Question 88: In a feedlot, the recommended withdrawal time before slaughter must be observed when using which antibiotic for treatment of bovine respiratory disease?

Tulathromycin (Correct answer)
Vitamin A injection
Balanced electrolyte solution
Flunixin meglumine

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 89: In llamas, the most typical source of bony facial tumors is

Tooth root abscess (Correct answer)
Facial bone fracture
Ossifying fibroma
Osteomyelitis

Correct answer: Tooth root abscess

In llamas, tooth root abscesses are a very common cause of bony facial tumors or swellings. The infection and inflammation associated with an abscess can lead to significant osteomyelitis and reactive bone proliferation in the surrounding facial bones. This presents as a firm, bony mass, making tooth root abscesses the most frequent etiology for such lesions in this species.

Question 90: Gabapentin is increasingly used in veterinary patients for chronic and neuropathic pain. What is its primary mechanism of action?

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

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 91: Which dietary modification is considered most critical in slowing the progression of chronic kidney disease (CKD) in cats?

Grain-free formulation
Restricted phosphorus (Correct answer)
Increased sodium to encourage drinking
Increased high-quality protein

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 92: On MRI, T2-weighted sequences are MOST useful for identifying:

Calcified lesions
Fluid-filled structures and edema (Correct answer)
Cortical bone detail
Gas within tissues

Correct answer: Fluid-filled structures and edema

T2-weighted MRI sequences produce high signal (bright) from fluid, making them ideal for identifying edema, effusions, and fluid-filled structures.

Question 93: A 7-year-old FIV-positive cat is being treated for Cryptococcus neoformans meningoencephalitis with fluconazole. After 8 weeks, the cat shows neurological deterioration despite antigen titers decreasing. What is the MOST likely explanation for this paradoxical worsening?

Immune reconstitution inflammatory syndrome (IRIS) triggered by partial immune recovery on antifungal therapy (Correct answer)
Fluconazole resistance has developed and liposomal amphotericin B should be substituted immediately
Secondary Toxoplasma gondii co-infection causing immune-mediated encephalitis
Cerebral cryptococcoma formation requiring surgical debulking

Correct answer: Immune reconstitution inflammatory syndrome (IRIS) triggered by partial immune recovery on antifungal therapy

Immune reconstitution inflammatory syndrome (IRIS) is recognized in FIV-positive cats undergoing antifungal treatment, analogous to HIV patients. As antifungal therapy reduces fungal burden, even partial immune recovery in an FIV-affected cat can trigger a dysregulated inflammatory response to residual fungal antigens in the CNS, causing paradoxical worsening despite falling titers. This is managed with short-course immunomodulation (prednisolone), not antifungal escalation. Fluconazole resistance is rare in Cryptococcus and would present with rising titers, not falling ones.

Question 94: A 7-year-old cat presents with a history of chronic vomiting, diarrhea, and weight loss. Bloodwork reveals a low serum cobalamin (Vitamin B12) level. Concurrent inflammation of the intestine, pancreas, and biliary tract is suspected. What is this condition called?

Exocrine pancreatic insufficiency (EPI)
Lymphocytic-plasmacytic enteritis
Triaditis (Correct answer)
Feline Infectious Peritonitis (FIP)

Correct answer: Triaditis

Feline triaditis is the concurrent inflammation of the pancreas (pancreatitis), biliary tract (cholangitis), and small intestine (inflammatory bowel disease). This combination of conditions is common in cats and often leads to malabsorption, resulting in clinical signs like vomiting, weight loss, and hypocobalaminemia due to impaired intestinal absorption. While the other conditions can cause similar signs, 'triaditis' specifically refers to the inflammation of these three associated organs.

Question 95: Which anesthetic agent is considered safest for induction in chelonians due to minimal cardiovascular depression?

Propofol
Alfaxalone (Correct answer)
Ketamine alone
Tiletamine-zolazepam

Correct answer: Alfaxalone

Alfaxalone provides smooth induction with less cardiovascular and respiratory depression compared to propofol and is preferred in chelonians.

Question 96: Kinematic gait analysis of a Warmblood dressage horse reveals a decreased protraction arc of the right forelimb with a shortened cranial phase of the stride but a normal caudal phase. Flexion tests are equivocal. Diagnostic analgesia of the coffin and pastern joints is negative. Which anatomical structure's pathology BEST explains decreased protraction with preserved caudal phase?

Subscapular bursitis limiting scapulohumeral joint extension
Medial palmar intercarpal ligament desmitis restricting carpal flexion
Infraspinatus muscle contracture limiting shoulder abduction and cranial advancement (Correct answer)
Superficial digital flexor tendon adhesion at the fetlock annular ligament

Correct answer: Infraspinatus muscle contracture limiting shoulder abduction and cranial advancement

Infraspinatus muscle contracture or fibrotic myopathy produces a characteristic limitation of shoulder abduction and external rotation, mechanically restricting cranial limb advancement (protraction). Because the caudal phase depends primarily on the stay apparatus and caudal muscle groups — which are unaffected — the stride has a normal push-off but a clipped cranial arc. This is distinct from elbow or carpal lesions and from foot pain. Diagnosis is confirmed by palpation of a firm, fibrous infraspinatus body, asymmetric shoulder abduction, and circumduction gait. It is an under-recognized cause of 'subtle' forelimb gait asymmetry in sport horses.

Question 97: 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?

Abdominal ultrasound
Low-dose dexamethasone suppression test
ACTH stimulation test (Correct answer)
Endogenous ACTH concentration

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 98: 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
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
High-dose dexamethasone suppression test (HDDST) to confirm PDH vs. ADH

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 99: On thoracic radiographs of a dog, which cardiac silhouette finding is most consistent with left atrial enlargement?

Rounding of the right heart border
Loss of the caudal waist on the ventrodorsal view
Elevation of the trachea at the carina (Correct answer)
Increased sternal contact length

Correct answer: Elevation of the trachea at the carina

Left atrial enlargement causes dorsal displacement and elevation of the trachea at the carina (mainstem bronchi splaying) on lateral radiographs.

Question 100: 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
Quarantine Zone → Protection Zone → Surveillance Zone → Free Zone; wildlife surveillance targets migratory birds as the primary maintenance host of FMD virus
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)
Infected Premises → Buffer Zone → Control Area → Surveillance Zone; wildlife surveillance is required solely to comply with OIE notification standards

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 101: A chinchilla presents with drooling, difficulty eating, and sharp molar spurs on oral exam. This condition is best described as:

Cheek pouch impaction
Slobbers (dental malocclusion) (Correct answer)
Stomatitis
Oral candidiasis

Correct answer: Slobbers (dental malocclusion)

Dental malocclusion in chinchillas, commonly called 'slobbers,' results from molar spurs that lacerate the tongue and cause hypersalivation.

Question 102: Which breed is most predisposed to developing dilated cardiomyopathy (DCM) and typically presents with atrial fibrillation as its most common arrhythmia?

Doberman Pinscher
Cavalier King Charles Spaniel
Boxer
Irish Wolfhound (Correct answer)

Correct answer: Irish Wolfhound

Irish Wolfhounds have a very high prevalence of DCM and, due to their large atrial mass, are particularly prone to atrial fibrillation as a complicating arrhythmia.

Question 103: Malignant hyperthermia is a rare, life-threatening complication of anesthesia. Which drug is the treatment of choice?

Acepromazine
Dantrolene (Correct answer)
Diazepam
Propranolol

Correct answer: Dantrolene

Dantrolene sodium blocks calcium release from the sarcoplasmic reticulum, directly treating the uncontrolled skeletal muscle hypermetabolism characteristic of malignant hyperthermia.

Question 104: 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)
Switch to vasopressin at 0.5 mU/kg/min
Increase dobutamine to 10 mcg/kg/min
Administer phenylephrine at 1–2 mcg/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 105: 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?

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

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 106: The 3-day history of moderate to severe episodes of left-sided epistaxis in a male fjord pony, 19, is evaluated. The pony is quiet, attentive, and receptive when presented. The rectal temperature was 101 degrees Fahrenheit, the heart rate is 60, and the respiration rate is 40. The total protein level is 6.5 g/dL, and the hematocrit is 31%. Airflow through each nostril is not especially restricted, and there is no sign of damage or swelling over the head's sinus area. Which of the following diagnostic procedures will give the most accurate results to support an assumed diagnosis?

Thoracic ultrasonography
Endoscopic examination (Correct answer)
Transtracheal aspiration
Head/Thorax radiography

Correct answer: Endoscopic examination

The pony's history of recurrent, unilateral epistaxis without obvious external trauma or swelling suggests a lesion within the nasal passages, paranasal sinuses, or guttural pouches. Endoscopic examination (rhinoscopy and guttural pouch endoscopy) is the most accurate diagnostic procedure to directly visualize these structures, identify the source of bleeding (e.g., fungal plaques, ethmoid hematoma, tumor), and guide further treatment.

Question 107: 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?

Ammonium Urate (Correct answer)
Struvite (Magnesium Ammonium Phosphate)
Calcium Oxalate Monohydrate
Silica

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 108: A beef producer reports that 20% of his cows are losing calves due to abortion in the second trimester. Fluorescent antibody testing of aborted fetal tissues confirms Neospora caninum. What is the most likely source of infection in this cow-calf herd?

Vertical transmission from infected cows to fetuses only
Ingestion of feed or water contaminated with dog feces containing oocysts (Correct answer)
Contact with infected bulls during breeding
Contact with infected deer at the fence line

Correct answer: Ingestion of feed or water contaminated with dog feces containing oocysts

Dogs are the definitive host for Neospora caninum and shed oocysts in feces; cattle are infected by ingesting contaminated feed or water, making canine fecal contamination the primary horizontal transmission route.

Question 109: Which finding on plain thoracic radiographs is MOST suggestive of a cranial mediastinal mass in a cat?

Pleural fissure lines
Caudal mediastinal widening
Loss of the cranial cardiac border and elevation of the trachea (Correct answer)
Perihilar alveolar pattern

Correct answer: Loss of the cranial cardiac border and elevation of the trachea

Cranial mediastinal masses obscure the cranial cardiac silhouette and displace the trachea dorsally or laterally, a common presentation in cats with lymphoma.

Question 110: During arthroscopic surgery of the equine tarsocrural joint, the surgeon inadvertently penetrates the medial plantar pouch and instrument access is compromised. Which anatomical landmark best describes the communication (or lack thereof) between the tarsocrural joint and the proximal intertarsal joint in most horses, and what is its clinical implication for analgesia?

A consistent communication exists dorsally, so tarsocrural analgesia reliably desensitizes the proximal intertarsal joint
No consistent communication exists; analgesia of the tarsocrural joint does not reliably desensitize the proximal intertarsal joint (Correct answer)
The joints communicate via the tarsal sheath, making tarsal sheath injection equivalent to both joint injections
Communication is present only in horses under 3 years of age through the tarsal canal

Correct answer: No consistent communication exists; analgesia of the tarsocrural joint does not reliably desensitize the proximal intertarsal joint

The tarsocrural joint and proximal intertarsal joint do NOT consistently communicate in adult horses. While communication may occasionally be present, it cannot be relied upon clinically. This is why diagnostic analgesia must be performed separately for each joint when localizing lameness to the hock region. Failure to appreciate this anatomy leads to misinterpretation of nerve block results, particularly when differentiating tarsocrural pathology from bone spavin (distal intertarsal/tarsometatarsal involvement).

Question 111: 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?

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
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

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 112: A 4-year-old ferret presents with muscle wasting, hindlimb weakness, and hypoglycemia (blood glucose 40 mg/dL) that resolves with dextrose. The most likely diagnosis is:

Lymphoma
Adrenal gland disease
Insulinoma (Correct answer)
Aleutian disease

Correct answer: Insulinoma

Insulinoma is the most common pancreatic tumor in ferrets over 3 years old and classically causes fasting hypoglycemia, weakness, and neurological signs relieved by glucose administration.

Question 113: A 9-year-old spayed female Cocker Spaniel presents with progressive exercise intolerance, a 3/6 left apical systolic murmur, and radiographic evidence of left atrial enlargement without pulmonary edema. Echocardiography confirms myxomatous mitral valve disease (MMVD) with a left atrial-to-aortic root ratio (LA:Ao) of 1.7. Which management decision is most consistent with current ACVIM consensus guidelines for this patient?

Recheck echocardiography in 6 months; initiate pimobendan only if LA:Ao ≥ 1.7 persists at that recheck
Begin furosemide prophylactically to prevent fluid accumulation
Begin enalapril immediately to reduce cardiac remodeling
Begin pimobendan immediately to delay onset of congestive heart failure (Correct answer)

Correct answer: Begin pimobendan immediately to delay onset of congestive heart failure

Per the 2019 ACVIM consensus guidelines for MMVD (EPIC trial criteria), dogs in Stage B2 — defined as radiographic cardiomegaly OR LA:Ao ≥ 1.7 on echo — should be started on pimobendan to delay onset of CHF. An LA:Ao of 1.7 meets the echocardiographic threshold for Stage B2, making pimobendan initiation appropriate now. Enalapril was not shown to significantly delay CHF onset in Stage B dogs in the SVEP trial. Furosemide is reserved for Stage C (active CHF) and should not be used prophylactically.

Question 114: A beef operation loses 3 cows to sudden death with no premonitory signs. Necropsy reveals a 'paint-brush' hemorrhage pattern on the heart and rapid bloat. Which clostridial disease is most likely?

Black disease (Clostridium novyi type B)
Blackleg (Clostridium chauvoei) (Correct answer)
Enterotoxemia type D (Clostridium perfringens)
Malignant edema (Clostridium septicum)

Correct answer: Blackleg (Clostridium chauvoei)

Blackleg (C. chauvoei) classically affects young cattle 6–24 months, causing myonecrosis with rapid death and characteristic crepitant swellings and myocardial hemorrhage.

Question 115: Which reproductive toxin produced by endophyte-infected tall fescue grass causes 'summer slump' and reduced pregnancy rates in beef cows?

Deoxynivalenol
Zearalenone
Ergovaline (Correct answer)
Fumonisin B1

Correct answer: Ergovaline

Ergovaline from the Neotyphodium coenophialum endophyte causes vasoconstriction, hyperthermia, and poor reproductive performance in cattle grazing infected fescue.

Question 116: 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
Culling infected bulls and resting infected cows for 90+ days to allow self-clearance (Correct answer)
Systemic metronidazole treatment of all infected bulls
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 117: A cat anesthetized with isoflurane develops bradycardia (HR 70 bpm). What is the MOST appropriate first step before administering any drug?

Administer atropine IV immediately
Lighten anesthetic depth and reassess all parameters (Correct answer)
Begin a dopamine CRI
Increase the oxygen flow rate

Correct answer: Lighten anesthetic depth and reassess all parameters

Before administering any drug, the appropriate first response is to lighten anesthetic depth and assess all parameters, as anesthetic-induced vagal tone and excessive depth are common reversible causes of bradycardia.

Question 118: 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?

Medial and lateral palmar metacarpal nerves (Correct answer)
Medial and lateral cutaneous antebrachial nerves
Axillary and musculocutaneous nerves
Deep and superficial branches of the radial nerve

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 119: A cat presents with corneal sequestrum and chronic ocular discharge. Which herpesvirus is most commonly implicated in this condition?

Feline herpesvirus-1 (Correct answer)
Feline leukemia virus
Feline immunodeficiency virus
Feline calicivirus

Correct answer: Feline herpesvirus-1

Feline herpesvirus-1 (FHV-1) is strongly associated with corneal sequestrum formation due to chronic corneal inflammation and ulceration.

Question 120: Which finding on effusion fluid analysis is most consistent with FIP rather than cardiac or neoplastic effusion?

Hemorrhagic effusion with numerous erythrocytes
Straw-colored viscous exudate with protein >35 g/L and low cell count (Correct answer)
Transudate with protein <25 g/L
Exudate with low protein and low cell count

Correct answer: Straw-colored viscous exudate with protein >35 g/L and low cell count

FIP effusion is typically a viscous, straw-colored exudate with high protein (>35 g/L) but surprisingly low cell counts, yielding a high Rivalta test result.

Question 121: 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 can be used safely in cats at doses 50% lower than those used in dogs with aggressive IV fluid diuresis
Cisplatin toxicity in cats manifests primarily as nephrotoxicity and peripheral neuropathy, identical to other species
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 122: 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:

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

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 123: A draft horse presents with chronic bilateral hindlimb swelling below the hock and painful, progressive lameness. The skin over the palmar pastern region is thickened with exudative crusts. What condition is most likely responsible for the lameness in addition to skin disease?

Thrombophlebitis of the digital veins
Pastern dermatitis (scratches) with secondary pastern cellulitis and possible pastern joint involvement (Correct answer)
Pemphigus foliaceus
Lymphangitis secondary to Corynebacterium pseudotuberculosis

Correct answer: Pastern dermatitis (scratches) with secondary pastern cellulitis and possible pastern joint involvement

Chronic pastern dermatitis (scratches/mud fever) in draft horses can progress to cellulitis and occasionally involve the pastern joint or digital flexor tendon sheath, causing significant lameness.

Question 124: 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?

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

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 125: A beef cow herd in the northern Great Plains experiences a cluster of late-term abortions in January. Fetuses are autolyzed, placentas are retained, and Brucella testing is negative. PCR on placental tissue detects Neospora caninum. Which epidemiological pattern would most strongly support vertical (transplacental) rather than horizontal (postnatal oral) transmission as the dominant route in this herd?

Outbreak resolution after removing dogs and coyotes from the property
Abortions occurring in cows of all parities clustered temporally around a single feed source change
Abortion rate significantly higher in daughters of seropositive dams compared to daughters of seronegative dams, regardless of exposure to definitive hosts (Correct answer)
Seroprevalence highest in heifers purchased from a single sale barn the prior autumn

Correct answer: Abortion rate significantly higher in daughters of seropositive dams compared to daughters of seronegative dams, regardless of exposure to definitive hosts

Neospora caninum is transmitted both vertically (cow to calf in utero) and horizontally (ingestion of oocysts shed by definitive hosts — canids). The hallmark of vertical transmission dominance is a familial clustering pattern: daughters of seropositive dams have dramatically higher seroprevalence and abortion risk independent of canid exposure. This dam-to-offspring clustering across generations is the epidemiological fingerprint of congenital transmission. Temporal clustering around a feed change or purchase event would suggest horizontal exposure, and removal of definitive hosts would reduce horizontal but not vertical risk.

Question 126: Pinkeye (Infectious Bovine Keratoconjunctivitis) in a cow herd is most commonly caused by which organism?

Mycoplasma bovis
Listeria monocytogenes
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 127: A 6-month-old intact female Border Collie is presented with a 2-week history of progressive hindlimb ataxia, hypermetria, and intention tremors. The puppy was purchased from a farm where the dam was fed a selenium-deficient diet during gestation. Cerebrospinal fluid analysis is unremarkable. Which diagnosis is most consistent with these findings?

Canine distemper virus–induced cerebellar hypoplasia
Neuroaxonal dystrophy (NAD) specific to Border Collies (Correct answer)
Hereditary ataxia due to RAB3GAP1 mutation
Neonatal selenium deficiency–related cerebellar hypoplasia

Correct answer: Neuroaxonal dystrophy (NAD) specific to Border Collies

Neuroaxonal dystrophy (NAD) is a hereditary neurodegenerative condition recognized in Border Collies caused by mutations in the PLA2G6 gene. It presents in young dogs (typically 2–6 months) with progressive cerebellar signs including ataxia, hypermetria, and intention tremors. CSF is often normal. While selenium deficiency can cause white muscle disease (skeletal and cardiac muscle necrosis) in young animals, it does not cause cerebellar hypoplasia in dogs. Canine distemper causes cerebellar hypoplasia in neonatal infection but would typically have other systemic signs. The breed-specific hereditary condition is the most accurate diagnosis here.

Question 128: A veterinarian recommends a Selective Dry Cow Therapy (SDCT) program instead of blanket dry cow therapy. What is the PRIMARY advantage of SDCT?

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

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

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

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 130: A 3-year-old Thoroughbred filly sustained a non-displaced condylar fracture of the third metacarpus during a race. What is the recommended surgical treatment to allow return to racing?

Condylar resection
Stall rest with a full limb cast for 12 weeks
Robert Jones bandage and controlled exercise
Internal fixation with cortical lag screws placed perpendicular to the fracture line (Correct answer)

Correct answer: Internal fixation with cortical lag screws placed perpendicular to the fracture line

Non-displaced condylar fractures of the third metacarpus are best managed with internal fixation using cortical lag screws to provide interfragmentary compression and allow earlier return to training.

Question 131: Scrapie is a prion disease of sheep. Which characteristic most accurately describes the diagnostic approach in suspect live animals?

Cerebrospinal fluid analysis showing 14-3-3 protein elevation
Immunohistochemistry of lymphoid tissue (rectal biopsy or third eyelid) for PrPSc accumulation (Correct answer)
PCR of blood for scrapie prion RNA
Serum ELISA for PrPSc antibodies

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 132: A dairy manager reports a sudden increase in the herd's bulk tank somatic cell count (SCC). The majority of cows appear clinically normal. What is the most effective and practical initial step to identify the individual cows contributing to the high SCC?

Immediately treat all lactating cows with a broad-spectrum intramammary antibiotic.
Perform a California Mastitis Test (CMT) on milk from all lactating cows. (Correct answer)
Cull all cows with a previous history of clinical mastitis.
Culture a milk sample from the bulk tank to identify the causative pathogen.

Correct answer: Perform a California Mastitis Test (CMT) on milk from all lactating cows.

The California Mastitis Test (CMT) is a rapid, cow-side test that provides a semi-quantitative estimate of the SCC for individual cows (or quarters), allowing for the quick identification of animals with subclinical mastitis. While bulk tank culture identifies pathogens, it doesn't pinpoint the infected cows. Treating the whole herd is not cost-effective and is poor antimicrobial stewardship. Culling is a drastic measure used for chronically infected cows, not as an initial diagnostic step.

Question 133: A group of yearling beef cattle on pasture for the first time during late summer exhibit profuse watery diarrhea, poor growth, and submandibular edema ('bottle jaw'). Which of the following is the most likely diagnosis?

Bovine Viral Diarrhea Virus (BVDV)
Type I Ostertagiasis (Correct answer)
Johne's Disease
Coccidiosis

Correct answer: Type I Ostertagiasis

This clinical presentation is classic for Type I Ostertagiasis, caused by a heavy burden of the brown stomach worm, Ostertagia ostertagi. The parasites cause a protein-losing enteropathy, leading to hypoalbuminemia, which results in submandibular edema ('bottle jaw') and diarrhea. This typically affects young cattle in their first grazing season. Johne's disease typically affects older cattle, and while coccidiosis causes diarrhea, severe bottle jaw is less common.

Question 134: During arthroscopic surgery of the tarsocrural joint in a horse, you identify an osteochondral fragment at the distal intermediate ridge of the tibia (DIRT lesion). Intraoperatively you notice the synovial membrane is markedly hypertrophied and there is significant fibrillation of the adjacent cartilage beyond the fragment margin. Which prognostic factor most significantly worsens the long-term athletic outcome after fragment removal in this scenario?

Duration of lameness prior to surgery
Size of the original osteochondral fragment
Presence of concurrent cartilage fibrillation extending beyond the lesion (Correct answer)
Patient age at time of surgery

Correct answer: Presence of concurrent cartilage fibrillation extending beyond the lesion

While fragment size and age are considered, extensive cartilage fibrillation beyond the OCD lesion margin indicates generalized articular cartilage degeneration that will progress independently of fragment removal. This diffuse cartilage damage is the strongest negative prognostic indicator for return to full athletic function, as fragment removal alone cannot address the surrounding degenerative process.

Question 135: What is the most typical cause of dystocia and egg binding in caged birds?

Oviduct damage
Obesity
Hypocalcemia (Correct answer)
Genetic predisposition

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 136: 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
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
Mycotoxin contamination from clostridial overgrowth in poorly fermented silage directly suppressing lymphocyte proliferation

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 137: 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?

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

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 138: During exploratory laparotomy for colic, the surgeon identifies a section of small intestine that is dark purple-black in color with no palpable pulse in the mesenteric vasculature after 10 minutes of warm saline lavage. What is the appropriate surgical decision?

Apply topical papaverine to improve perfusion
Replace the intestine and close; reassess in 24 hours
Pack the abdomen and stage the surgery
Perform resection and anastomosis of the non-viable segment (Correct answer)

Correct answer: Perform resection and anastomosis of the non-viable segment

Non-viable intestine (no color change, no mesenteric pulse after warming) must be resected with end-to-end or side-to-side anastomosis to prevent endotoxemia and peritonitis.

Question 139: A 9-year-old Golden Retriever is diagnosed with protein-losing nephropathy. UPC ratio is 4.8. Which antihypertensive class is considered first-line therapy to reduce proteinuria?

ACE inhibitors (Correct answer)
Loop diuretics
Calcium channel blockers
Beta-blockers

Correct answer: ACE inhibitors

ACE inhibitors (e.g., enalapril, benazepril) reduce glomerular capillary pressure and proteinuria and are first-line therapy for PLN.

Question 140: A 9-year-old male neutered Golden Retriever presents with progressive forelimb lameness. Radiographs of the shoulder reveal a 'moth-eaten' lytic lesion of the proximal humerus with periosteal reaction and cortical destruction. What is the most likely diagnosis and treatment?

Osteochondrosis dissecans; arthroscopic debridement
Septic osteomyelitis; long-term antibiotics
Osteosarcoma; limb amputation with adjuvant carboplatin chemotherapy (Correct answer)
Hypertrophic osteodystrophy; supportive care

Correct answer: Osteosarcoma; limb amputation with adjuvant carboplatin chemotherapy

Osteosarcoma most commonly affects the proximal humerus in large breeds; amputation combined with carboplatin or doxorubicin chemotherapy provides the best median survival.

Question 141: A beef producer has a 3% calf crop loss from scours annually. To calculate the cost of a calf scours prevention program, which parameter is NOT included in the basic cost-benefit analysis?

Cost of the vaccine program
Value of calves saved
Labor costs for treatment
Breed of the dam (Correct answer)

Correct answer: Breed of the dam

Dam breed is not a direct economic variable in a cost-benefit analysis of a vaccination program; the relevant inputs are vaccine cost, calf value, morbidity/mortality rates, and treatment costs.

Question 142: Under the 21 CFR Part 117 Preventive Controls rule, which of the following is classified as a 'process control'?

Supplier verification for incoming ingredients
Employee hygiene training records
Environmental monitoring for Listeria
Cooking step that kills pathogens to a safe level (Correct answer)

Correct answer: Cooking step that kills pathogens to a safe level

A process control is a procedure such as cooking that applies a lethal treatment to eliminate or reduce a biological hazard to an acceptable level.

Question 143: Which anatomical site is preferred for intramuscular injections in birds?

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

Correct answer: Pectoral muscle

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

Question 144: A 12-year-old cat diagnosed with hyperthyroidism is started on oral methimazole. Within the first three weeks of treatment, the owner reports the cat is scratching its face and neck incessantly, causing excoriations. Which of the following is the most appropriate action?

Decrease the dose of methimazole by half and recheck in one week.
Switch to the transdermal formulation of methimazole.
Add a glucocorticoid to the treatment regimen to control the pruritus.
Discontinue methimazole and discuss alternative treatments like radioiodine (I-131) therapy. (Correct answer)

Correct answer: Discontinue methimazole and discuss alternative treatments like radioiodine (I-131) therapy.

Severe facial pruritus and excoriation is an uncommon but serious idiosyncratic adverse reaction to methimazole in cats. It is considered an immunologic reaction and will not resolve by lowering the dose and is likely to recur with any formulation of the drug, including transdermal. The appropriate response is to stop the drug immediately and manage the pruritus. An alternative therapy for hyperthyroidism, such as radioiodine (I-131) or a prescription diet, must be chosen as the cat cannot tolerate methimazole.

Question 145: Which of the following is the recommended first-line treatment for lead toxicosis in birds?

Succimer (DMSA)
Dimercaprol (BAL)
D-Penicillamine
Calcium EDTA (Correct answer)

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 146: During colic surgery, you identify a large colon displacement in which the left dorsal colon is displaced laterally under the spleen and nephrosplenic ligament. What is this condition called and what is the initial non-surgical treatment?

Right dorsal displacement; phenylephrine and rolling
Cecal volvulus; nasogastric decompression
Right dorsal displacement; heparin therapy
Left dorsal displacement (nephrosplenic entrapment); phenylephrine and rolling (Correct answer)

Correct answer: Left dorsal displacement (nephrosplenic entrapment); phenylephrine and rolling

Nephrosplenic (left dorsal) displacement involves the colon entrapped over the nephrosplenic ligament and can often be corrected non-surgically using phenylephrine to contract the spleen combined with controlled rolling under general anesthesia.

Question 147: Xylitol ingestion in cats compared to dogs is best described as:

More dangerous, causing acute renal failure in addition to hypoglycemia
Equally dangerous, causing hypoglycemia and hepatic failure
Non-toxic; cats do not absorb xylitol from the GI tract
Less understood; cats appear more resistant to xylitol-induced hypoglycemia than dogs (Correct answer)

Correct answer: Less understood; cats appear more resistant to xylitol-induced hypoglycemia than dogs

Current evidence suggests cats are less susceptible to xylitol-induced hypoglycemia than dogs, though caution is still warranted and monitoring is recommended.

Question 148: Which vaccination protocol is most appropriate for preventing clostridial diseases (blackleg, malignant edema) in beef calves?

Two doses 3-4 weeks apart starting at 2-3 months of age with annual boosters (Correct answer)
Single dose at weaning only
Passive transfer via colostrum is sufficient without active vaccination
Monthly intranasal vaccine starting at birth

Correct answer: Two doses 3-4 weeks apart starting at 2-3 months of age with annual boosters

Clostridial vaccines require a primary series of two doses 3-4 weeks apart to achieve protective immunity, with annual boosters to maintain protection.

Question 149: Botulism outbreaks associated with commercially processed foods typically involve which form of Clostridium botulinum toxin production?

Iatrogenic botulism from therapeutic injections
Preformed toxin ingestion from improperly processed low-acid canned foods (Correct answer)
Wound botulism from contaminated soil
Intestinal toxicoinfection in infants consuming spores

Correct answer: Preformed toxin ingestion from improperly processed low-acid canned foods

Foodborne botulism typically results from ingestion of preformed toxin in low-acid, anaerobic environments created by improper canning processes.

Question 150: Amlodipine is the first-line treatment for systemic hypertension in cats. What is its primary mechanism of action?

Alpha-adrenergic receptor antagonism
Calcium channel blockade (Correct answer)
Beta-adrenergic receptor blockade
Angiotensin-converting enzyme (ACE) inhibition

Correct answer: Calcium channel blockade

Amlodipine is a dihydropyridine calcium channel blocker. Its primary effect is to block the influx of calcium into vascular smooth muscle cells, which leads to peripheral vasodilation and a subsequent decrease in systemic blood pressure. ACE inhibitors (like benazepril), beta-blockers (like atenolol), and alpha-antagonists (like prazosin) are other classes of antihypertensive drugs with different mechanisms of action.

Question 151: A 5-year-old cat with severe Mycoplasma haemofelis infection requires aggressive antibiotic therapy. The attending clinician wants to use enrofloxacin. Which of the following statements most accurately describes the risk-benefit consideration for enrofloxacin in this patient?

Young cats under 1 year are uniquely susceptible due to incomplete retinal development, while adult cats tolerate standard doses safely
Enrofloxacin-induced retinopathy in cats is fully reversible if the drug is discontinued within 48 hours of the first visual deficit
Enrofloxacin causes retinal degeneration in a dose-independent fashion; even a single dose at any concentration poses equal risk
Retinal toxicity risk is substantially increased at doses exceeding 5 mg/kg/day; lesions typically occur within days and are irreversible (Correct answer)

Correct answer: Retinal toxicity risk is substantially increased at doses exceeding 5 mg/kg/day; lesions typically occur within days and are irreversible

Enrofloxacin causes acute retinal degeneration (cone-rod degeneration leading to blindness) in cats in a dose-dependent manner. The FDA label restricts enrofloxacin in cats to a maximum of 5 mg/kg/day for this reason. Toxicity can occur within days of high-dose use and the photoreceptor damage is generally irreversible — vision loss is permanent once significant retinal degeneration has occurred. Lower doses are associated with acceptable risk, making dose precision critical. Doxycycline is frequently preferred for Mycoplasma haemofelis to avoid this risk.

Question 152: A shelter cat is diagnosed with feline panleukopenia. What is the minimum isolation period recommended after clinical recovery to prevent spread to susceptible cats?

At least 4 weeks (Correct answer)
72 hours
6 months
24 hours

Correct answer: At least 4 weeks

Cats recovering from FPV can shed virus in feces for up to 6 weeks; a minimum isolation period of 4 weeks post-recovery is recommended in shelter settings.

Question 153: Which clinical sign most distinguishes feline metaldehyde (slug bait) toxicity from other tremorgenic toxicoses?

Hyperthermia is the predominant presenting sign
Cats display continuous violent muscle tremors that are difficult to control (Correct answer)
Mydriasis and tachycardia are the first signs
Signs are worsened by sensory stimulation

Correct answer: Cats display continuous violent muscle tremors that are difficult to control

Metaldehyde causes severe, relentless muscle tremors due to GABA inhibition; signs are often refractory to benzodiazepines alone.

Question 154: 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
Peripheral neuropathy
Hepatotoxicity
Facial pruritus and excoriation (Correct answer)

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 155: 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?

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

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 156: 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 diffuse, unstructured interstitial pattern with prominent pulmonary veins.
A patchy alveolar pattern concentrated in the cranioventral lung lobes.
A prominent bronchial pattern, characterized by 'doughnuts' and 'tramlines', with evidence of lung hyperinflation. (Correct answer)
Enlarged, tortuous pulmonary arteries and right-sided cardiomegaly.

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 157: During a contrast-enhanced CT of the abdomen in a 9-year-old Golden Retriever, a hepatic lesion shows marked arterial phase enhancement followed by rapid 'washout' (hypoattenuation relative to liver parenchyma in the portal venous phase). What is the MOST likely diagnosis?

Biliary cystadenoma
Hepatocellular carcinoma (HCC) (Correct answer)
Nodular hyperplasia
Hepatic cavernous hemangioma

Correct answer: Hepatocellular carcinoma (HCC)

The 'arterial enhancement followed by portal venous phase washout' pattern is the hallmark of hepatocellular carcinoma on contrast CT, reflecting the lesion's dependence on arterial blood supply and rapid contrast clearance. Hemangiomas classically show peripheral nodular enhancement that fills in centripetally (similar to human hemangiomas). Nodular hyperplasia typically appears iso- or hypoattenuating without dramatic washout. Biliary cystadenomas are cystic or multilocular and do not enhance in this arterial-dominant pattern. This washout sign carries high specificity for HCC in dogs.

Question 158: A bird (psittacine) presents with a bacterial infection. Which antibiotic class should be avoided due to risk of fatal dysbiosis?

Aminoglycosides
Fluoroquinolones
Beta-lactams
Lincosamides and macrolides at high doses (Correct answer)

Correct answer: Lincosamides and macrolides at high doses

Lincosamides (e.g., clindamycin) and certain macrolides can cause fatal disruption of the GI microbiome in birds, similar to the antibiotic-associated enterocolitis seen in other species.

Question 159: Feline leukemia virus (FeLV) is classified into subtypes based on host range. Which subtype is associated with the most rapid disease progression and immunosuppression?

FeLV-C
FeLV-A
FeLV-B
FeLV-T (Correct answer)

Correct answer: FeLV-T

FeLV-T is highly pathogenic, targets T lymphocytes directly causing profound lymphopenia and accelerated immunodeficiency.

Question 160: Which radiographic view is most useful for evaluating the dens (odontoid process) of the axis (C2) in a dog for atlantoaxial instability?

Oblique cervical
Lateral cervical with flexion
Lateral cervical with extension
Open-mouth ventrodorsal (Correct answer)

Correct answer: Open-mouth ventrodorsal

The open-mouth ventrodorsal view projects the dens through the mouth and allows direct visualization of the atlantoaxial articulation and dens morphology.

Question 161: 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%?

Specificity
Sensitivity
Negative predictive value
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 162: 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?

Mineralization within the soft tissue opacity of the liver.
Generalized loss of serosal detail throughout the entire abdomen.
Focal loss of serosal detail and increased soft tissue opacity in the right cranial abdomen. (Correct answer)
A gas-filled and distended gallbladder (emphysematous cholecystitis).

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 163: Which vaccine-preventable feline disease is caused by a parvovirus and requires only biannual boosters in adult cats after the initial series?

Feline calicivirus
Feline panleukopenia (Correct answer)
Feline herpesvirus-1
Feline leukemia virus

Correct answer: Feline panleukopenia

Feline panleukopenia virus (FPV) vaccines provide long-lasting immunity; AAFP guidelines recommend triennial or less frequent boosters in low-risk adult cats after initial series.

Question 164: A 9-year-old cat with chronic kidney disease (CKD, IRIS Stage 3) and osteoarthritis requires long-term analgesia. Buprenorphine has provided insufficient pain control. Which analgesic option presents the HIGHEST risk of acute-on-chronic kidney injury in this patient and should be strictly avoided?

Low-dose ketamine CRI (0.1–0.2 mg/kg/hr) during hospitalization
Robenacoxib 1 mg/kg PO q24h for ≤3 days
Gabapentin 5 mg/kg PO q12h
Meloxicam 0.1 mg/kg PO q24h as long-term maintenance (Correct answer)

Correct answer: Meloxicam 0.1 mg/kg PO q24h as long-term maintenance

NSAIDs inhibit prostaglandin synthesis via COX enzymes. Prostaglandins are critical for maintaining afferent arteriolar dilation and glomerular filtration pressure in cats with CKD, where compensatory renal hemodynamics are already stressed. Long-term meloxicam use in CKD cats (especially IRIS Stage 3–4) poses a high risk of further reducing GFR and precipitating acute decompensation. While robenacoxib is also an NSAID, the short-course limitation (≤3 days) and its preferential local tissue distribution reduce systemic renal risk in CKD compared to chronic meloxicam. Gabapentin is renally excreted but is generally considered safe with dose adjustment in CKD, and low-dose ketamine CRI does not depend on prostaglandin-mediated renal perfusion. Chronic NSAID use in IRIS Stage 3+ CKD is contraindicated in cats.

Question 165: A cow at 60 days postpartum has been anestrus. Body condition score is 2/5. Progesterone profiles confirm ovarian inactivity. The primary cause is most likely:

Persistent corpus luteum
Subclinical mastitis causing hormonal disruption
Ovarian cyst formation
Negative energy balance suppressing the hypothalamic-pituitary axis (Correct answer)

Correct answer: Negative energy balance suppressing the hypothalamic-pituitary axis

Postpartum anestrus in cattle is most commonly caused by negative energy balance, which suppresses GnRH pulsatility and LH release, preventing follicular maturation and ovulation.

Question 166: During anesthesia of a horse, you notice the mean arterial pressure drops to 55 mmHg. After adjusting vaporizer settings, which drug is most appropriate to improve cardiac output?

Dobutamine (Correct answer)
Atropine
Epinephrine
Vasopressin

Correct answer: Dobutamine

Dobutamine is a positive inotrope that increases cardiac output and improves perfusion pressure in anesthetized horses with inhalant-induced hypotension.

Question 167: A red-eared slider turtle is found floating at the surface of the water and unable to dive. Radiographs show increased opacity in the caudal lung fields. The most likely diagnosis is:

Bladder calculi
Hepatic lipidosis
Gastrointestinal obstruction
Pneumonia (Correct answer)

Correct answer: Pneumonia

Pneumonia in aquatic turtles causes asymmetric buoyancy and inability to dive; radiographic consolidation in the lung fields confirms the diagnosis.

Question 168: Which form of feline upper respiratory infection is most likely to cause chronic rhinosinusitis as a sequela following acute infection?

Chlamydia felis infection
Feline calicivirus infection
Feline herpesvirus-1 infection (Correct answer)
Bordetella bronchiseptica infection

Correct answer: Feline herpesvirus-1 infection

FHV-1 establishes latency in the trigeminal ganglion and can cause turbinate destruction leading to chronic rhinosinusitis after reactivation episodes.

Question 169: A dog with dilated cardiomyopathy is started on digoxin. Which electrolyte abnormality increases the risk of digoxin toxicity?

Hyperkalemia
Hypercalcemia
Hypokalemia (Correct answer)
Hypernatremia

Correct answer: Hypokalemia

Hypokalemia potentiates digoxin toxicity because potassium and digoxin compete for the same binding site on Na+/K+-ATPase; low potassium increases digoxin binding and effect.

Question 170: 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)
Transitional cell carcinoma
Ectopic ureter
Urethral sphincter mechanism incompetence

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 171: A dog receiving long-term phenobarbital therapy for epilepsy requires treatment with metronidazole for anaerobic infection. The metronidazole dose used is 60 mg/kg/day (an inadvertent overdose). Three days later the dog shows acute onset vertical nystagmus, intention tremors, and ataxia. What is the MOST accurate explanation for why phenobarbital may have worsened the neurotoxicity risk in this case?

Phenobarbital competes with metronidazole at GABA-A receptors, paradoxically disinhibiting cerebellar circuits
Phenobarbital upregulates CYP450 enzymes, accelerating metronidazole metabolism to its toxic hydroxyl metabolite
Phenobarbital depletes hepatic glutathione stores, impairing metronidazole detoxification
Phenobarbital induces hepatic CYP450 enzymes, reducing metronidazole clearance and elevating plasma concentrations (Correct answer)

Correct answer: Phenobarbital induces hepatic CYP450 enzymes, reducing metronidazole clearance and elevating plasma concentrations

Phenobarbital is a potent inducer of hepatic cytochrome P450 enzymes (particularly CYP2B and CYP3A). Paradoxically, while enzyme induction generally accelerates drug metabolism, metronidazole's primary metabolic pathway through CYP2C/3A becomes saturated or altered in the context of enzyme induction, and critically, some studies indicate phenobarbital reduces metronidazole clearance in dogs, raising plasma levels. Metronidazole neurotoxicity (cerebellar signs — nystagmus, ataxia, intention tremors) is concentration-dependent. While the overdose is the primary driver here, concurrent CYP450 induction by phenobarbital can paradoxically impair metronidazole clearance rather than enhance it in dogs, worsening accumulation. The safe dose of metronidazole in dogs on phenobarbital is ≤30 mg/kg/day.

Question 172: 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?

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

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 173: Which inhalant anesthetic is associated with the GREATEST cardiovascular depression and sensitization of the myocardium to catecholamine-induced arrhythmias?

Desflurane
Isoflurane
Sevoflurane
Halothane (Correct answer)

Correct answer: Halothane

Halothane causes significant myocardial depression, decreased cardiac output, and sensitizes the heart to catecholamine-induced arrhythmias, making it the most cardiotoxic of the inhalants; it is rarely used in modern veterinary practice for this reason.

Question 174: A 6-year-old Labrador is undergoing a splenectomy under isoflurane anesthesia. The end-tidal CO2 rises to 65 mmHg. What is the most appropriate initial intervention?

Increase respiratory rate on the ventilator (Correct answer)
Increase fresh gas flow rate
Switch to sevoflurane
Administer sodium bicarbonate IV

Correct answer: Increase respiratory rate on the ventilator

Increasing the ventilator rate will increase minute ventilation and eliminate the excess CO2, correcting the hypercapnia.

Question 175: 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 hypointense lesion in the dorsal columns
T1 hyperintense intramedullary lesion
T2 hyperintense fluid-filled cavity within the spinal cord (Correct answer)

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 176: 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?

Cervical disc disease
Brachial plexus avulsion (Correct answer)
Radial nerve paralysis
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 177: A pet cockatiel presents with nasal discharge, sneezing, and conjunctivitis. Which organism is the most likely causative agent?

Chlamydia psittaci (Correct answer)
Pasteurella multocida
Aspergillus fumigatus
Mycobacterium avium

Correct answer: Chlamydia psittaci

Chlamydia psittaci causes psittacosis (avian chlamydiosis), which commonly presents with respiratory signs and conjunctivitis in psittacine birds.

Question 178: A 4-year-old domestic shorthair cat presents with a 3-week history of progressive neurological signs including head tremors, cerebellar ataxia, and vertical nystagmus. The owner recently moved from the Ohio River Valley. CSF analysis shows eosinophilic pleocytosis. Serum Cryptococcus antigen is negative. Which organism is the most likely causative agent?

Blastomyces dermatitidis (Correct answer)
Toxoplasma gondii
Coccidioides immitis
Cuterebra sp. (aberrant larval migration)

Correct answer: Blastomyces dermatitidis

Blastomyces dermatitidis is endemic to the Ohio and Mississippi River Valleys and can cause CNS blastomycosis in cats, presenting with granulomatous meningoencephalitis and eosinophilic pleocytosis. The geographic history is a critical clue. While Toxoplasma is common in cats, it typically causes mixed or neutrophilic pleocytosis and is not geographically restricted. Cuterebra larval migration is possible but does not fit as neatly with the endemic area history. Coccidioides is southwestern U.S., not the Ohio Valley.

Question 179: An outbreak of West Nile Virus neurological disease is detected in horses in a county. What is the primary public health concern for veterinarians to communicate?

Infected horses serve as sentinel animals indicating high mosquito transmission activity in the area (Correct answer)
Horses can directly transmit the virus to humans through contact
Culling infected horses will eliminate the outbreak
Horse vaccination will reduce human infection rates

Correct answer: Infected horses serve as sentinel animals indicating high mosquito transmission activity in the area

Horses are dead-end hosts and cannot transmit WNV to humans, but equine cases signal active arboviral transmission by mosquitoes in the area.

Question 180: 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 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
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)

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 181: An 8-year-old Dachshund presents with acute onset of severe back pain and inability to ambulate. MRI confirms acute thoracolumbar IVDD at T12-13. Deep pain perception is absent. Within what time frame should surgical decompression ideally occur to maximize neurological recovery?

Within 6 hours
Within 4 hours
Within 48 hours (Correct answer)
Within 24 hours

Correct answer: Within 48 hours

Surgical decompression within 48 hours of loss of deep pain perception is associated with the best neurological outcomes in acute IVDD.

Question 182: 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?

N-acetylcysteine administration
Intravenous fluid diuresis (Correct answer)
Peritoneal dialysis
Administration of activated charcoal and a cathartic

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 183: 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 184: Intra-articular injection of which substance is used as a visco-supplementation therapy to improve synovial fluid quality in horses with joint disease?

Polysulfated glycosaminoglycan (Adequan)
Platelet-rich plasma (PRP)
Hyaluronic acid (sodium hyaluronate) (Correct answer)
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 185: Which opioid is most appropriate for epidural administration in dogs to provide extended postoperative analgesia with minimal motor blockade?

Morphine (Correct answer)
Meperidine
Butorphanol
Fentanyl

Correct answer: Morphine

Preservative-free morphine administered epidurally provides long-duration analgesia (12–24 hours) with minimal motor effects due to its hydrophilicity.

Question 186: On abdominal radiographs, retroperitoneal effusion is BEST identified by:

Loss of renal and sublumbar muscle detail with preserved peritoneal serosal detail (Correct answer)
Displacement of the colon ventrally
Gas accumulation dorsal to the kidneys
Loss of all serosal detail including the bladder and intestines

Correct answer: Loss of renal and sublumbar muscle detail with preserved peritoneal serosal detail

Retroperitoneal effusion selectively obliterates retroperitoneal structures (kidneys, sublumbar muscles) while intraperitoneal serosal detail (bladder, gut) may remain visible.

Question 187: There is currently no viable treatment for FIP that can extend life.

False (Correct answer)
True

Correct answer: False

This statement is false because recent advancements in veterinary medicine have led to the development of antiviral drugs, such as GS-441524 and remdesivir. These treatments have shown remarkable efficacy in treating FIP, can significantly extend life, and often lead to a cure, revolutionizing the prognosis for cats with FIP.

Question 188: 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?

95.0% (Correct answer)
90.9%
85.0%
91.7%

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 189: 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 negative-sense, segmented RNA virus in the family Orthomyxoviridae that causes secondary demyelination of enteric nerves
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 double-stranded DNA virus in the family Herpesviridae that induces T-cell lymphoma in the myenteric plexus

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 190: A cat is diagnosed with feline infectious peritonitis (FIP). Which antiviral drug has shown efficacy and received conditional FDA approval for this disease?

Oseltamivir
Interferon omega
Famciclovir
GS-441524 (Correct answer)

Correct answer: GS-441524

GS-441524, an adenosine nucleoside analog, inhibits feline coronavirus RNA-dependent RNA polymerase and has conditional FDA approval as Mutian/brand equivalents for FIP.

Question 191: A 3-year-old Quarter Horse presents with right forelimb lameness localized to the foot by perineural anesthesia. MRI (low-field standing unit) shows a hyperintense T2 signal lesion within the lateral lobe of the deep digital flexor tendon (DDFT) at the level of the navicular bone, with a corresponding hypointense T1 signal. The navicular bone shows focal subchondral signal loss on T1 at the flexor cortex. Which combination of lesions is present?

DDFT insertional desmopathy with collateral sesamoidean ligament enthesopathy
Navicular bursitis with secondary DDFT surface fibrillation (no intrinsic tendon lesion)
DDFT core lesion (longitudinal split tear) with navicular bone flexor cortex erosion (Correct answer)
Impar ligament desmitis with reactive navicular bone marrow edema

Correct answer: DDFT core lesion (longitudinal split tear) with navicular bone flexor cortex erosion

Hyperintense T2 / hypointense T1 signal within the DDFT substance indicates a fluid-filled cleft consistent with a longitudinal split tear (core lesion). This is distinct from surface fibrillation, which would show signal change only at the tendon margin without intrinsic disruption. The focal subchondral T1 hypointensity at the navicular flexor cortex indicates bone erosion or fibrocartilage loss — a recognized sequela of chronic DDFT pathology compressing the navicular bone. Navicular bursitis alone would show bursal distension with signal change in the bursal recess, not intrinsic tendon signal. Impar ligament desmitis produces signal change at the palmar distal navicular-P3 interface.

Question 192: Which fluoroquinolone antibiotic is most associated with acute retinal degeneration and blindness in cats when used at high doses?

Enrofloxacin (Correct answer)
Pradofloxacin
Marbofloxacin
Orbifloxacin

Correct answer: Enrofloxacin

Enrofloxacin at doses above 5 mg/kg/day causes retinal degeneration in cats due to accumulation in the retinal pigment epithelium.

Question 193: During a TPLO in a dog, the surgeon requests addition of an NSAID for multimodal analgesia. The dog has received acepromazine and morphine as premedication. Which consideration is most important before administering carprofen?

Carprofen must be given at least 2 hours before morphine to avoid drug interaction
Carprofen is contraindicated with morphine due to serotonin syndrome risk
NSAIDs are contraindicated with acepromazine due to additive CNS depression
Confirm the dog has normal renal perfusion before NSAID administration (Correct answer)

Correct answer: Confirm the dog has normal renal perfusion before NSAID administration

NSAIDs inhibit prostaglandin-mediated afferent arteriolar dilation in the kidney; adequate renal perfusion must be confirmed before perioperative NSAID use to prevent acute kidney injury.

Question 194: 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 195: In a cow-calf operation managing johne's disease (paratuberculosis), a producer asks about the MAP (Mycobacterium avium subsp. paratuberculosis) fecal PCR sensitivity in different clinical stages of disease. You are designing a test-and-cull program and want to maximize detection of infectious animals before they show clinical signs. Which statement MOST accurately reflects the limitations of fecal PCR in this context?

Fecal PCR sensitivity is highest in late subclinical/early clinical animals but drops significantly in early subclinical animals due to intermittent low-level shedding (Correct answer)
A single negative fecal PCR in a seronegative animal rules out MAP infection with >98% specificity
Fecal PCR is unreliable in cattle under 24 months because passive fecal shedding of ingested MAP confounds results
Fecal PCR has >95% sensitivity in subclinical animals with low-level MAP shedding, making a single test sufficient for herd clearance

Correct answer: Fecal PCR sensitivity is highest in late subclinical/early clinical animals but drops significantly in early subclinical animals due to intermittent low-level shedding

MAP infection in cattle follows a long subclinical incubation (often 2–5 years) during which shedding is intermittent and at very low levels — below the detection threshold of fecal PCR. Sensitivity of a single fecal PCR in early subclinical animals is estimated at only 15–30%, rising to 50–70% in late subclinical/early clinical animals with heavier continuous shedding, and approaching 90%+ in clinically affected animals with protein-losing enteropathy. This is the critical limitation: test-and-cull programs based on a single fecal PCR will miss the majority of infected animals in the subclinical phase — exactly when you most want to detect them. Repeated annual testing over 3–5 years is required to achieve meaningful herd prevalence reduction. Passive shedding in young calves is a real concern for ELISA interpretation but less so for PCR at the clone level. Specificity of PCR is high (>99%) but sensitivity is the Achilles heel.

Question 196: 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
Palmar digital nerve block
Intra-articular distal interphalangeal joint block (Correct answer)
Abaxial sesamoid nerve block

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 197: Organophosphate toxicity in animals is treated with which combination of drugs?

Pralidoxime (2-PAM) alone
Physostigmine and diazepam
Atropine and pralidoxime (2-PAM) (Correct answer)
Naloxone and flumazenil

Correct answer: Atropine and pralidoxime (2-PAM)

Atropine blocks muscarinic signs of organophosphate toxicity while pralidoxime reactivates acetylcholinesterase if given early before 'aging' of the enzyme occurs.

Question 198: A lesion causing ipsilateral hemiparesis, ipsilateral facial paralysis (CN VII), and ipsilateral loss of the menace response with intact vision best localizes to which neuroanatomical site?

Ipsilateral brainstem (pons/medulla) (Correct answer)
Ipsilateral cerebellum (cerebellar hemisphere)
Contralateral cerebral cortex (forebrain)
Ipsilateral C1-C5 spinal cord segment

Correct answer: Ipsilateral brainstem (pons/medulla)

Cranial nerve VII (facial) nucleus is located in the pons. A lesion in the ipsilateral pons/medulla causes ipsilateral CN VII palsy (facial paralysis), ipsilateral hemiparesis (UMN, because corticospinal tracts haven't crossed yet at this level), and ipsilateral menace loss (cerebellar/pontine relay for menace). A forebrain lesion would cause contralateral deficits. Cerebellar lesions cause ataxia, not weakness or CN VII signs.

Question 199: 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?

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
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

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 200: A community outbreak of E. coli O157:H7 is traced to a petting zoo. The primary mode of transmission in this setting is:

Fecal-oral transmission through direct animal contact (Correct answer)
Airborne transmission from animal dander
Waterborne transmission from decorative ponds
Vectorborne transmission via insects in the zoo

Correct answer: Fecal-oral transmission through direct animal contact

E. coli O157:H7 is shed in the feces of ruminants and transmitted to humans via fecal-oral contact in petting zoo settings.

Question 201: Which NSAID is FDA-approved for long-term pain management in cats in the United States?

Grapiprant
Meloxicam
Ketoprofen
Robenacoxib (Correct answer)

Correct answer: Robenacoxib

Robenacoxib (Onsior) is the only NSAID approved for longer-term use in cats in the US; meloxicam is approved for single-dose injection only.

Question 202: In equine radiography, 'rotation' of the distal phalanx relative to the hoof wall is measured by which imaging technique?

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

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 203: A 5-year-old spayed female domestic shorthair cat presents with a 2-day history of open-mouth breathing and severe dyspnea. On auscultation, heart sounds are muffled ventrally and lung sounds are absent in the ventral thorax bilaterally. Thoracocentesis yields 180 mL of milky, white-opaque fluid from each hemithorax. Cytology shows small lymphocytes predominating with a triglyceride concentration greater than serum. What is the most likely underlying etiology in this cat?

Right-sided heart failure from hypertrophic cardiomyopathy
Diaphragmatic hernia with hepatic incarceration
Cardiac lymphoma causing thoracic duct obstruction
Idiopathic chylothorax (Correct answer)

Correct answer: Idiopathic chylothorax

Idiopathic chylothorax is the most common cause of chylothorax in cats (~50% of cases). While lymphoma and cardiac disease are differentials, lymphoma would typically show neoplastic lymphocytes on cytology, and HCM-associated chylothorax is relatively rare. The milky fluid with chylomicrons (triglycerides > serum triglycerides) and small lymphocyte predominance is classic chylothorax; without neoplastic cells and with a normal-appearing cardiac silhouette bilaterally, idiopathic etiology is most likely.

Question 204: Which statement most accurately describes the use of bisphosphonates (e.g., tiludronate) in equine lameness management?

They are first-line treatment for acute septic arthritis
They inhibit osteoclast activity and are approved for navicular syndrome and other bone remodeling disorders in horses (Correct answer)
They are contraindicated in horses under 4 years due to growth plate interference
They stimulate cartilage repair in osteoarthritic joints

Correct answer: They inhibit osteoclast activity and are approved for navicular syndrome and other bone remodeling disorders in horses

Tiludronate (Tildren) and clodronate (Osphos) are bisphosphonates approved in horses that inhibit osteoclast-mediated bone resorption and are indicated for navicular syndrome and other conditions with pathologic bone remodeling.

Question 205: Which local anesthetic has the highest risk of causing methemoglobinemia in cats?

Lidocaine
Bupivacaine
Benzocaine (Correct answer)
Ropivacaine

Correct answer: Benzocaine

Benzocaine, found in some topical sprays, rapidly induces methemoglobinemia in cats due to their limited ability to metabolize certain oxidizing agents.

Question 206: What is the significance of 'air bronchograms' on thoracic radiographs?

Air-filled bronchi are visible because surrounding alveoli are fluid-filled, indicating alveolar disease (Correct answer)
The bronchi contain fluid while the alveoli are normally aerated
Gas is present within the bronchial walls
Pleural air outlines the bronchi from the outside

Correct answer: Air-filled bronchi are visible because surrounding alveoli are fluid-filled, indicating alveolar disease

Air bronchograms occur when alveolar consolidation or fluid makes normally invisible air-filled bronchi visible by contrast.

Question 207: A 10-year-old Warmblood used for dressage presents with a 2/5 left forelimb lameness that resolves by over 90% following a palmar digital nerve block. Which of the following is the MOST likely source of the horse's pain?

Metacarpophalangeal (fetlock) joint
Navicular bursa (Correct answer)
Proximal suspensory ligament
Distal check ligament

Correct answer: Navicular bursa

The palmar digital nerve (PDN) block desensitizes the palmar third of the foot. This includes the navicular bone, navicular bursa, deep digital flexor tendon within the hoof capsule, the sole, frog, and palmar aspects of the coffin joint. The fetlock joint, proximal suspensory ligament, and distal check ligament are all located proximal to the area desensitized by a PDN block and would not be affected.

Question 208: A 12-year-old Miniature Schnauzer presents with hypercalcemia (Ca 14.2 mg/dL), weight loss, and peripheral lymphadenopathy. Which test is most useful to differentiate hypercalcemia of malignancy from primary hyperparathyroidism?

Ionized calcium
PTH and PTHrP assay (Correct answer)
Urinary calcium:creatinine ratio
Serum phosphorus

Correct answer: PTH and PTHrP assay

Measuring both PTH (elevated in hyperparathyroidism) and PTHrP (elevated in humoral hypercalcemia of malignancy) is the most direct way to distinguish these causes.

Question 209: Air sac mites (Sternostoma tracheacolum) most commonly cause respiratory disease in which group of birds?

Canaries and finches (Correct answer)
Psittacines (parrots)
Waterfowl
Domestic poultry

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 210: 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 depletes stores of vitamins K2 and K3, which cannot be replaced by K1 supplementation alone
Brodifacoum irreversibly alkylates the vitamin K epoxide reductase enzyme complex
Brodifacoum has a much shorter half-life than warfarin, requiring more frequent dosing
Brodifacoum undergoes extensive enterohepatic recirculation, maintaining toxic tissue concentrations long after ingestion (Correct answer)

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 211: 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?

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
Deep digital flexor tendon splitting via the palmar approach to decompress intrathecal pressure

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 212: 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?

A fructosamine of 285 µmol/L is diagnostic for hyperthyroidism-induced insulin resistance
The fructosamine is within normal range, suggesting stress hyperglycemia rather than DM (Correct answer)
The fructosamine confirms sustained hyperglycemia consistent with diabetes mellitus
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 213: When performing a dental nerve block using the infraorbital approach in a dog, which nerve is primarily desensitized?

Lingual nerve
Mental nerve
Inferior alveolar nerve
Maxillary nerve branches supplying upper premolars and incisors (Correct answer)

Correct answer: Maxillary nerve branches supplying upper premolars and incisors

The infraorbital nerve block desensitizes the upper incisors, canine, and premolars ipsilaterally by blocking the maxillary nerve at the infraorbital foramen.

Question 214: 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:

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

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 215: A 9-year-old cat presents with acute collapse, jugular distension, muffled heart sounds, and pulsus paradoxus. Echocardiography confirms pericardial effusion with right atrial collapse. Which etiology is most common for pericardial effusion causing tamponade in cats, and how does it differ from dogs?

Thymoma compressing cardiac structures; dogs more commonly develop mesothelioma
Lymphoma infiltrating the pericardium; dogs most commonly have right atrial hemangiosarcoma
Feline infectious peritonitis (FIP) causing exudative effusion; dogs more commonly have hemangiosarcoma (Correct answer)
Hypertrophic cardiomyopathy with congestive heart failure extending to pericardium; dogs primarily have idiopathic effusion

Correct answer: Feline infectious peritonitis (FIP) causing exudative effusion; dogs more commonly have hemangiosarcoma

In cats, FIP is the most common cause of pericardial effusion producing cardiac tamponade, causing an exudative high-protein effusion due to coronavirus-mediated vasculitis. In dogs, right atrial hemangiosarcoma and idiopathic pericardial effusion dominate. This species difference is clinically important because treatment, prognosis, and diagnostics differ substantially. FIP effusion in cats characteristically has high protein content (>3.5 g/dL) and a yellow, viscous appearance with Rivalta test positivity.

Question 216: Which ultrasound finding is most specific for portal hypertension in a dog?

Hepatic parenchymal hypoechogenicity
Decreased portal vein diameter
Acquired portosystemic shunting vessels (Correct answer)
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 217: On ultrasound, a dog's liver shows hyperechoic parenchyma compared to the spleen and falciform fat. This finding is most consistent with:

Hepatic congestion
Acute hepatitis
Hepatic lipidosis (Correct answer)
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 218: 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:

Radiographs of the opposite forelimb for comparison only
MRI of the foot to evaluate soft tissue and bone detail (Correct answer)
Repeat palmar digital nerve block
Ultrasound of the superficial digital flexor tendon

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 219: 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?

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

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 220: 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?

Dilated cardiomyopathy
Pericardial effusion
Restrictive cardiomyopathy
Hypertrophic cardiomyopathy (Correct answer)

Correct answer: Hypertrophic cardiomyopathy

Hyperthyroidism in cats most commonly causes hypertrophic cardiomyopathy due to the chronotropic and inotropic effects of excess thyroid hormone.

Question 221: 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?

Extracorporeal shock wave therapy (ESWT) targeted to the lumbosacral facet joints under ultrasound guidance (Correct answer)
Retirement from cutting, with consideration of mesotherapy along the thoracolumbar epaxial musculature
Sacroiliac joint arthrodesis via percutaneous implant placement
Computed tomography-guided chemical neurolysis of the dorsal sacral nerve roots

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 222: 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?

Pulmonary lymphoma; thoracic CT with contrast for mediastinal lymph node assessment
Feline bronchopneumonia (bacterial); transtracheal wash for cytology and culture
Cardiogenic pulmonary edema; echocardiography to detect occult hypertrophic cardiomyopathy with normal cardiac size (Correct answer)
Non-cardiogenic pulmonary edema (e.g., neurogenic or post-obstructive); measure systolic blood pressure and assess for underlying cause

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 223: A cattle producer wants to treat a cow with bacterial pneumonia. Which beta-lactam antibiotic has an approved long-acting formulation for cattle?

Penicillin G procaine
Amoxicillin
Ceftiofur (Correct answer)
Ampicillin

Correct answer: Ceftiofur

Ceftiofur (as ceftiofur crystalline free acid) has a long-acting formulation approved in cattle that provides therapeutic concentrations for several days.

Question 224: 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?

Deferasirox
Deferoxamine
EDTA
D-penicillamine (Correct answer)

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 225: A horse presents with sudden onset severe hindlimb lameness and a palpable defect in the middle gluteal muscle. The horse had been exercising at speed just before onset. What is the most likely diagnosis?

Sacroiliac subluxation
Exertional rhabdomyolysis with muscle tear (tying-up) (Correct answer)
Fibrotic myopathy of the semimembranosus
Femoral nerve paralysis

Correct answer: Exertional rhabdomyolysis with muscle tear (tying-up)

Acute muscle tear of the gluteal region with a palpable defect following high-intensity exercise is consistent with exertional rhabdomyolysis severe enough to cause myofibrillar disruption.

Question 226: A 9-year-old FIV-positive cat presents with a chronic, non-healing ulcer on the dorsal tongue. Cytology reveals large lymphoid cells. A biopsy confirms diffuse large B-cell lymphoma (DLBCL). Which of the following BEST characterizes the relationship between FIV and feline lymphoma development?

FIV encodes an oncoprotein (Tax) that directly transactivates proto-oncogenes in T lymphocytes, causing T-cell lymphoma as the predominant malignancy in FIV-infected cats.
FIV integrates its proviral DNA preferentially adjacent to the c-myc locus, causing insertional mutagenesis analogous to FeLV, making it a directly transforming retrovirus.
FIV-associated lymphoma is always of T-cell origin and occurs exclusively in cats with CD4:CD8 ratios below 0.5, making immunophenotyping unnecessary for prognostication.
FIV does not directly transform lymphocytes; rather, chronic immune dysregulation, persistent B-cell antigenic stimulation, and impaired immune surveillance create a permissive environment for spontaneous oncogenic mutations, most commonly yielding B-cell lymphomas in older FIV-infected cats. (Correct answer)

Correct answer: FIV does not directly transform lymphocytes; rather, chronic immune dysregulation, persistent B-cell antigenic stimulation, and impaired immune surveillance create a permissive environment for spontaneous oncogenic mutations, most commonly yielding B-cell lymphomas in older FIV-infected cats.

Unlike FeLV, FIV is not a directly transforming retrovirus—it lacks an oncogene and does not cause insertional mutagenesis at proto-oncogene loci. Instead, FIV-associated lymphomagenesis is indirect: chronic immune dysregulation, loss of tumor immunosurveillance, and persistent antigenic stimulation of B cells create conditions favorable for malignant transformation. Both B- and T-cell lymphomas occur in FIV-infected cats, with B-cell lymphomas (including DLBCL) becoming more prevalent in older cats. Tax is an HTLV-1/BLV oncoprotein, not an FIV protein. The CD4:CD8 ratio inversion is a feature of FIV disease progression but does not define lymphoma immunophenotype.

Question 227: A 6-month-old Labrador Retriever puppy presents for evaluation of exercise intolerance and a loud continuous 'machinery' murmur heard best at the left heart base. What is the most likely congenital defect?

Pulmonic stenosis
Patent ductus arteriosus (Correct answer)
Aortic stenosis
Ventricular septal defect

Correct answer: Patent ductus arteriosus

Patent ductus arteriosus produces the classic continuous 'machinery' murmur due to left-to-right shunting throughout the cardiac cycle via the unclosed ductus.

Question 228: 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 229: A cat tests positive for FeLV by ELISA antigen test. Which follow-up test best determines if the cat is persistently viremic vs. regressor?

IFA (immunofluorescence assay) on blood smear (Correct answer)
FeLV PCR on bone marrow
Repeat ELISA in 30 days
FeLV antibody titer

Correct answer: IFA (immunofluorescence assay) on blood smear

IFA detects FeLV p27 antigen within neutrophils and platelets; a positive IFA confirms progressive (persistent) viremia, whereas a negative IFA after a positive ELISA suggests a regressor or discordant result.

Question 230: A 5-year-old dog presents with peracute collapse, pale mucous membranes, and abdominal distension. FAST ultrasound reveals free abdominal fluid and a splenic mass. PCV is 18%. Which statement is most accurate regarding the splenic mass?

Fine needle aspirate is diagnostic in the majority of splenic masses
Splenectomy is contraindicated until coagulopathy is corrected
Approximately 50% of splenic masses in dogs are malignant (hemangiosarcoma) (Correct answer)
Most splenic masses in dogs are benign hematomas

Correct answer: Approximately 50% of splenic masses in dogs are malignant (hemangiosarcoma)

In dogs with splenic masses and hemoabdomen, approximately 50% are hemangiosarcoma (malignant), 25% are other malignancies, and only 25% are benign nodular hyperplasia or hematoma.

Question 231: Which program is used in the US to eradicate bovine tuberculosis caused by Mycobacterium bovis, and what is the testing method of choice for herd surveillance?

National Animal Health Monitoring System using PCR of nasal swabs
USDA Brucellosis Eradication Program using ELISA
Federal-State TB Eradication Program using the caudal fold tuberculin test (CFT) (Correct answer)
APHIS-VS program using whole blood interferon-gamma assay only

Correct answer: Federal-State TB Eradication Program using the caudal fold tuberculin test (CFT)

The US Federal-State TB Eradication Program uses the caudal fold test (CFT) for initial herd testing, with positive reactors confirmed by the comparative cervical tuberculin (CCT) test.

Question 232: Which parameter is most commonly monitored as a critical control point (CCP) during pasteurization of milk?

Fat content percentage
Time and temperature of heat treatment (Correct answer)
Coliform count before processing
pH of the final product

Correct answer: Time and temperature of heat treatment

Time and temperature are the critical control point parameters for pasteurization, as they determine whether pathogens are eliminated.

Question 233: A cat receiving repeated or prolonged propofol infusions is at risk for which unique hematologic complication?

Aplastic anemia
Thrombocytopenia
Disseminated intravascular coagulation
Heinz body anemia (Correct answer)

Correct answer: Heinz body anemia

Cats lack efficient glucuronidation and are sensitive to the phenolic compounds in propofol, which can cause oxidative damage to hemoglobin and formation of Heinz bodies, leading to hemolytic anemia.

Question 234: A 7-year-old Thoroughbred racehorse undergoes nuclear scintigraphy after a 4-week history of right hindlimb lameness. The scan shows intense increased radiopharmaceutical uptake (IRU) at the right tuber sacrale. Standing rectal palpation reveals mild asymmetry. Radiographs are normal. Which diagnosis BEST explains these findings, and what is the primary mechanism of injury?

Septic sacroiliac arthritis from hematogenous seeding
Sacroiliac joint desmopathy secondary to repetitive torsional loading during racing (Correct answer)
Stress fracture of the ilial wing from compressive axial loading
Supraspinous ligament desmopathy causing referred pain to the pelvis

Correct answer: Sacroiliac joint desmopathy secondary to repetitive torsional loading during racing

Sacroiliac joint desmopathy is the most common cause of intense IRU at the tuber sacrale in racehorses with hindlimb lameness and pelvic asymmetry. The SI joint undergoes repetitive torsional and shear forces during gallop and tight turns, causing ligamentous strain and enthesopathy without early radiographic changes. Scintigraphy is the most sensitive early modality. Stress fractures of the ilial wing would show IRU at a different site, and septic arthritis would typically present with systemic signs.

Question 235: A dog is prescribed phenobarbital for seizure control. Which of the following is the most important monitoring parameter for long-term therapy?

Complete blood count
Urinalysis
Serum electrolytes
Serum bile acids and liver enzymes (Correct answer)

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 236: 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?

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

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 237: Toxoplasma gondii infection in pregnant women is most commonly acquired in the US through:

Inhalation of aerosolized oocysts
Consumption of undercooked meat containing tissue cysts (Correct answer)
Direct contact with infected cats
Contaminated drinking water

Correct answer: Consumption of undercooked meat containing tissue cysts

In the US, most human T. gondii infections result from consuming undercooked meat containing bradyzoite tissue cysts.

Question 238: 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?

Accessory cephalic vein; oversew the arthroscopic portal with a horizontal mattress suture
Dorsal carpal branch of the radial artery; controlled lavage with epinephrine-containing saline and direct cautery (Correct answer)
Cephalic vein; apply digital pressure followed by ligation if bleeding persists post-lavage
Medial palmar vein; tourniquet application proximal to the carpus

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 239: A 7-year-old cat with hyperthyroidism is well-controlled on methimazole. The owner reports the cat has developed facial pruritus, excoriations, and a mild leukopenia on recent CBC. What is the MOST appropriate next step?

Discontinue methimazole immediately and transition to radioactive iodine (I-131) or surgical thyroidectomy after stabilization (Correct answer)
Reduce the methimazole dose by 50% and add prednisolone to manage the immune-mediated reaction
Switch to carbimazole, as it has a completely different adverse effect profile than methimazole
Continue methimazole and treat the pruritus symptomatically; leukopenia is expected and not clinically significant

Correct answer: Discontinue methimazole immediately and transition to radioactive iodine (I-131) or surgical thyroidectomy after stabilization

Facial pruritus/excoriations and hematologic abnormalities (leukopenia, thrombocytopenia, agranulocytosis) are recognized adverse effects of methimazole in cats, occurring in approximately 15–20% of treated cats. Agranulocytosis is the most life-threatening hematologic complication. When these reactions occur, methimazole must be discontinued — not dose-reduced — because rechallenge carries high risk of recurrence. Carbimazole is a prodrug that is converted to methimazole in vivo, so it carries the same adverse effect risk and is NOT a safe alternative. After methimazole withdrawal and patient stabilization, definitive therapy (radioactive iodine or surgical thyroidectomy) is the recommended path forward.

Question 240: Which biosecurity measure is most effective at preventing introduction of Johne's disease (paratuberculosis) into a closed beef herd?

Vaccinating all incoming animals with killed M. paratuberculosis vaccine
Quarantining new arrivals for 14 days in a separate pen
Purchasing animals from Johne's-tested herds and testing all additions (Correct answer)
Testing fecal samples from all animals annually with PCR

Correct answer: Purchasing animals from Johne's-tested herds and testing all additions

Because no test has 100% sensitivity for Johne's disease, purchasing from certified low-prevalence herds combined with pre-purchase testing provides the best risk reduction.

Question 241: A dog receives an overdose of acepromazine. Which statement about acepromazine reversal is correct?

Naloxone effectively reverses acepromazine sedation
Flumazenil fully reverses phenothiazine effects
Reversal can be achieved with atipamezole
There is no specific reversal agent; treatment is supportive (Correct answer)

Correct answer: There is no specific reversal agent; treatment is supportive

Acepromazine, a phenothiazine tranquilizer, has no specific reversal agent; management consists of supportive care including IV fluids and vasopressors for hypotension.

Question 242: A cat presents comatose after ingesting ethylene glycol. Which diagnostic finding would confirm ethylene glycol toxicity?

Elevated blood ammonia with hepatic encephalopathy
Presence of uric acid crystals in urine sediment
Hypocalcemia with prolonged QT interval on ECG
Calcium oxalate monohydrate crystalluria (Correct answer)

Correct answer: Calcium oxalate monohydrate crystalluria

Ethylene glycol is metabolized to oxalic acid, which combines with calcium to form calcium oxalate monohydrate crystals visible in urine sediment.

Question 243: A dog is diagnosed with leptospirosis after exposure to wildlife. Which organ system is MOST commonly affected, leading to the clinical presentation seen in acute leptospirosis?

Central nervous system
Renal and hepatic systems (Correct answer)
Musculoskeletal system
Respiratory system primarily

Correct answer: Renal and hepatic systems

Leptospira organisms have a particular tropism for renal tubular epithelium and hepatocytes, leading to acute kidney injury and hepatopathy as the dominant clinical syndrome.

Question 244: Which epidemiological measure best quantifies the additional risk of disease attributable to a specific exposure?

Odds ratio
Attributable risk (risk difference) (Correct answer)
Relative risk
Incidence rate

Correct answer: Attributable risk (risk difference)

Attributable risk (risk difference) measures the excess disease burden among the exposed group that is directly attributable to the exposure.

Question 245: 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?

Increase dietary roughage inclusion from 5% to 12% to buffer rumen pH
Switch from dry-rolled to high-moisture corn to slow starch fermentation rate
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 246: 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?

Feline calicivirus caused neonatal cerebellar hypoplasia by infecting ependymal cells of the fourth ventricle, leading to obstructive hydrocephalus and secondary cerebellar compression.
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 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)
Feline herpesvirus-1 caused meningoencephalitis in the neonatal period, selectively destroying Purkinje cells of the cerebellum and sparing cortical neurons.

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 247: 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 248: 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?

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

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 249: Which of the following conditions or interventions would DECREASE MAC (reduce the anesthetic requirement) of an inhalant agent?

Opioid premedication (Correct answer)
Hyperthermia
Hyperthyroidism
Chronic alcohol consumption

Correct answer: Opioid premedication

Opioid premedication provides MAC sparing by 20–40%, reducing the amount of inhalant required; hyperthermia, chronic alcohol use, and hyperthyroidism all increase MAC.

Question 250: Ketamine is commonly used as an induction agent, particularly in cats. What is its PRIMARY mechanism of anesthetic action?

Mu-opioid receptor agonism
GABA-A receptor potentiation
NMDA receptor antagonism (Correct answer)
Alpha-2 adrenergic 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 251: A veterinarian administers a drug that causes dose-dependent sinus bradycardia in a horse. Atropine is given but produces no improvement. Which drug class most likely caused this atropine-resistant bradycardia?

Alpha-2 adrenergic agonist (e.g., detomidine)
Cardiac glycoside (e.g., digoxin)
Calcium channel blocker (e.g., diltiazem) (Correct answer)
Opioid agonist (e.g., butorphanol)

Correct answer: Calcium channel blocker (e.g., diltiazem)

Calcium channel blockers such as diltiazem decrease SA node automaticity and AV node conduction by blocking L-type calcium channels — a mechanism entirely independent of muscarinic receptors. Atropine works by blocking vagal (parasympathetic) tone via muscarinic receptor antagonism. Because diltiazem's bradycardic effect does not rely on acetylcholine-mediated vagal input, atropine cannot reverse it. Alpha-2 agonists (e.g., detomidine) cause bradycardia primarily through increased vagal tone and are at least partially responsive to atropine. Opioids cause mild bradycardia that is vagally mediated and atropine-responsive. Digoxin toxicity may respond partially to atropine for its vagomimetic effects.

Question 252: Xylazine and dexmedetomidine produce sedation and analgesia through which primary mechanism of action?

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

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 253: A dog presents with acute epistaxis, petechiae on the gums, and prolonged bleeding after venipuncture. CBC reveals a platelet count of 8,000/μL. Coagulation times (PT and aPTT) are normal. What is the most likely diagnosis?

Immune-mediated thrombocytopenia (IMT) (Correct answer)
Disseminated intravascular coagulation
Rodenticide toxicosis
Von Willebrand disease

Correct answer: Immune-mediated thrombocytopenia (IMT)

IMT presents with severely low platelets causing mucosal bleeding and petechiae while PT and aPTT remain normal because coagulation factor function is intact.

Question 254: On a lateral skull radiograph of a rabbit, you observe bilateral tympanic bullae with significantly increased opacity and thickened walls. The petrous temporal bones appear sclerotic. This pattern is MOST consistent with:

Otitis media/interna with secondary bulla osteitis (Correct answer)
Thymoma with paraneoplastic vestibular syndrome
Cervical lymphoma compressing the vestibulocochlear nerve
Encephalitozoon cuniculi granulomatous encephalitis

Correct answer: Otitis media/interna with secondary bulla osteitis

In rabbits, bilateral tympanic bulla opacification with wall thickening and petrous bone sclerosis on skull radiographs is diagnostic of chronic otitis media/interna with bulla osteitis. Pasteurella multocida is the most common causative agent. This imaging triad—bulla opacity, bulla wall thickening, and petrosal sclerosis—represents chronic inflammatory and reactive bone change. Encephalitozoon cuniculi causes neurological signs but does not produce radiographic bulla changes. Thymoma is a thoracic disease. Cervical lymphoma would not produce intraosseous bulla changes visible radiographically.

Question 255: 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
Pyloromyotomy
Esophageal banding
Gastropexy (Correct answer)

Correct answer: Gastropexy

Gastropexy permanently affixes the stomach to the body wall and reduces GDV recurrence from ~70–80% to less than 5%.

Question 256: A 6-month-old intact male puppy presents with bilateral cryptorchidism confirmed on exam. What is the recommended course of action?

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

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

File a report with the CDC within 72 hours
Quarantine the dog for up to 6 months (Correct answer)
Vaccinate and release within 24 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 258: 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?

Paraneoplastic syndrome from a perianal adenocarcinoma causing hypercalcemia-induced nephrogenic diabetes insipidus
Concurrent benign prostatic hyperplasia compressing the urethra and leading to hydronephrosis
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

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 259: On a lateral thoracic radiograph of a dog, you note the cardiac silhouette contacts the sternum across more than 2.5 intercostal spaces. The trachea is elevated and the caudal vena cava is not visible. Which condition BEST explains this constellation of findings?

Cranial mediastinal mass with secondary pericardial effusion
Severe left atrial enlargement compressing the mainstem bronchus
Right-sided cardiomegaly with pleural effusion
Peritoneopericardial diaphragmatic hernia (PPDH) (Correct answer)

Correct answer: Peritoneopericardial diaphragmatic hernia (PPDH)

PPDH is characterized by an enlarged, often misshapen cardiac silhouette that contacts the sternum (sternal contact > 2.5 ICS on lateral view), dorsal tracheal elevation, loss of the diaphragmatic outline, and absence or obscuring of the caudal vena cava. Abdominal organs (omentum, small intestine, liver) within the pericardium create heterogeneous opacity within the cardiac silhouette. Right-sided cardiomegaly alone does not cause sternal contact to this degree or obscure the CVC. PPDH is the most common pericardial disorder in young dogs.

Question 260: 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
Clopidogrel
Furosemide (Correct answer)

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 261: 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?

Adrenal cortical neoplasia
Lymphoma
Pancreatic exocrine adenocarcinoma
Insulinoma (Correct answer)

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 262: Which of the following correctly describes 'first-pass metabolism'?

Hepatic metabolism that reduces bioavailability of orally administered drugs before reaching systemic circulation (Correct answer)
Drug elimination by the kidneys after IV administration
The initial drug distribution phase immediately after IV injection
Metabolism occurring in the GI lumen before absorption

Correct answer: Hepatic metabolism that reduces bioavailability of orally administered drugs before reaching systemic circulation

First-pass metabolism refers to the hepatic biotransformation of an orally administered drug as it passes through the portal circulation before reaching systemic circulation, reducing bioavailability.

Question 263: 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)
Initiate itraconazole therapy for fungal otitis and recheck in 4 weeks
Lance and flush the abscess under sedation using dilute chlorhexidine, followed by topical antibiotic ointment
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 264: On abdominal ultrasound, an anechoic structure with distal acoustic enhancement in the kidney is MOST consistent with:

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

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 265: Aminoglycoside antibiotics (e.g., gentamicin) should be used with extreme caution in patients with which condition?

Pulmonary disease
Hepatic disease
Renal insufficiency (Correct answer)
Cardiac arrhythmias

Correct answer: Renal insufficiency

Aminoglycosides are nephrotoxic and require renal elimination; pre-existing renal insufficiency greatly increases the risk of drug accumulation and toxicity.

Question 266: Which anesthetic protocol is most commonly associated with post-anesthetic myopathy in horses undergoing prolonged recumbency?

Regional nerve blocks prior to induction
Epidural analgesia with detomidine
Inhalant anesthesia with hypotension and poor padding (Correct answer)
Total intravenous anesthesia with ketamine-xylazine-guaifenesin

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 267: 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?

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

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

Desflurane (Correct answer)
Halothane
Isoflurane
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 269: Which drug is the antidote for acetaminophen toxicity in cats?

Atropine
N-acetylcysteine (NAC) (Correct answer)
Vitamin K1
Activated charcoal alone

Correct answer: N-acetylcysteine (NAC)

N-acetylcysteine replenishes glutathione stores, allowing detoxification of the toxic acetaminophen metabolite NAPQI and is the primary antidote for acetaminophen toxicity.

Question 270: 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?

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

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 271: 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 pattern is consistent with a congenital extrahepatic portosystemic shunt requiring surgical attenuation
This represents portal vein hypoplasia (microvascular dysplasia) with compensatory collateral formation
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 272: A bearded dragon is presented with a black beard, lethargy, and yellow-white caseous plugs in the intestine on necropsy. The causative agent is:

Cryptosporidium varanii
Entamoeba invadens (Correct answer)
Histomonas meleagridis
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 273: During a routine physical exam, a 4-month-old Bulldog puppy is noted to have a heart murmur. Echocardiography reveals obstruction of the right ventricular outflow tract and right ventricular hypertrophy. What is the definitive therapy?

Balloon valvuloplasty via cardiac catheterization (Correct answer)
Beta-blocker therapy alone
Open-heart surgical valvotomy
Pacemaker implantation

Correct answer: Balloon valvuloplasty via cardiac catheterization

Balloon valvuloplasty is the treatment of choice for pulmonic stenosis in dogs, providing effective relief of the outflow obstruction with low morbidity.

Question 274: An alpaca presents with progressive weight loss, bottle jaw, and anemia. Fecal flotation reveals strongyle-type eggs. Which anthelmintic class is most commonly used as first-line therapy in camelids with suspected Haemonchus?

Imidazothiazoles (e.g., levamisole)
Benzimidazoles (e.g., fenbendazole)
Salicylanilides (e.g., closantel)
Macrocyclic lactones (e.g., ivermectin) (Correct answer)

Correct answer: Macrocyclic lactones (e.g., ivermectin)

Macrocyclic lactones such as ivermectin are commonly used first-line in camelids for Haemonchus contortus, though resistance monitoring via fecal egg count reduction tests is recommended.

Question 275: 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?

Primary hypoparathyroidism
Eclampsia (puerperal tetany) (Correct answer)
Chronic renal failure
Vitamin D deficiency

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 276: A 2-year-old Thoroughbred colt has bilateral forelimb angular limb deformity (valgus) at the carpus identified at 4 months of age. Radiographs show the deformity originates at the distal radial physis. The foal is now presenting at 6 months without improvement. What surgical option should be considered?

Arthrodesis of the radiocarpal joint
Transphyseal bridging (screw and wire or staple) on the convex side (Correct answer)
Medial condylar resection of the distal radius
Periosteal stripping on the concave side of the deformity

Correct answer: Transphyseal bridging (screw and wire or staple) on the convex side

Transphyseal bridging on the convex (lateral) side of a carpal valgus deformity slows growth on that side, allowing the concave side to 'catch up' and correct the angular deformity.

Question 277: A sugar glider presents with self-mutilation of the scrotum and hindquarters. The most common underlying cause is:

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

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 278: 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?

Enterohepatic recirculation of phenobarbital decreases progressively with hepatic adaptation
Renal tubular secretion of phenobarbital increases with chronic exposure
Phenobarbital undergoes tachyphylaxis at GABA-A receptors over time
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 279: Which of the following birds is most susceptible to aspergillosis due to its natural habitat and immune characteristics?

Cockatiel
African grey parrot
Budgerigar
Gyrfalcon (Correct answer)

Correct answer: Gyrfalcon

Gyrfalcons and other Arctic raptors lack prior environmental exposure to Aspergillus and are highly immunologically naive, making them very susceptible.

Question 280: 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:

Age of the patient at time of surgery
Presence or absence of deep pain perception in the pelvic limbs (Correct answer)
Severity of disc extrusion on MRI (Grasso scale grade)
Duration of clinical signs before surgery

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 281: A 5-year-old Labrador Retriever is presented with acute collapse and hematemesis. On exam, the dog is tachycardic (HR 160 bpm), pale, and has a fluid wave on abdominal ballottement. PCV is 18%, total protein is 3.2 g/dL, and abdominal ultrasound reveals a large splenic mass with free abdominal fluid. After stabilization, a splenectomy is performed. Histopathology confirms splenic hemangiosarcoma. Which combination of prognostic factors is associated with the LONGEST median survival time post-splenectomy?

Stage III disease with adjuvant metronomic cyclophosphamide
Stage II disease with adjuvant vincristine, doxorubicin, and cyclophosphamide (VAC)
Stage I disease with no adjuvant therapy
Stage I disease with adjuvant doxorubicin chemotherapy (Correct answer)

Correct answer: Stage I disease with adjuvant doxorubicin chemotherapy

Splenic hemangiosarcoma staged as Stage I (tumor confined to spleen, no rupture, no metastasis) combined with adjuvant doxorubicin-based chemotherapy is associated with the longest median survival — approximately 4–6 months compared to 1–2 months with surgery alone. Stage II (ruptured or with regional spread) and Stage III (distant metastasis) carry significantly worse prognoses regardless of protocol. VAC has not consistently outperformed single-agent doxorubicin in canine HSA.

Question 282: Ultrasonography reveals a core lesion in the body of the superficial digital flexor tendon (SDFT) in a sport horse. The MOST appropriate initial treatment is:

Controlled rest with hand-walking rehabilitation program (Correct answer)
Immediate return to full work to promote collagen remodeling
Intravenous administration of bisphosphonates
Surgical splitting of the tendon

Correct answer: Controlled rest with hand-walking rehabilitation program

Core lesions of the SDFT require controlled rest and a graduated hand-walking rehabilitation program to allow fibrous repair while minimizing further damage.

Question 283: A cat with a suspected portosystemic shunt has an ammonia tolerance test performed. Which additional diagnostic best confirms intrahepatic vs. extrahepatic shunt location?

Abdominal ultrasound with Doppler
Serum bile acid pre/post prandial
Rectal portal scintigraphy
CT angiography (Correct answer)

Correct answer: CT angiography

CT angiography (computed tomographic angiography) provides precise anatomic delineation of shunt location and morphology, guiding surgical planning.

Question 284: On thoracic radiographs, a cat with hypertrophic cardiomyopathy (HCM) most commonly shows which cardiac silhouette shape on the VD view?

Valentine heart shape (biatrial enlargement) (Correct answer)
Normal silhouette despite severe disease
Globoid (round) silhouette
Right-sided enlargement with D-shape

Correct answer: Valentine heart shape (biatrial enlargement)

HCM in cats classically produces a 'valentine heart' shape on VD radiographs due to bilateral atrial enlargement, though some cats have relatively normal-appearing hearts.

Question 285: Which of the following is the gold standard post-exposure prophylaxis regimen for unvaccinated humans exposed to rabies?

Rabies vaccine series alone (days 0, 3, 7, 14)
Rabies vaccine series plus systemic antibiotics
Rabies immune globulin administered systemically with no vaccine
Rabies immune globulin at wound site plus vaccine series (days 0, 3, 7, 14) (Correct answer)

Correct answer: Rabies immune globulin at wound site plus vaccine series (days 0, 3, 7, 14)

PEP for unvaccinated individuals requires infiltration of rabies immune globulin at the wound plus a 4-dose vaccine series to provide immediate and long-term protection.

Question 286: 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)
Serum calcium measurement
Serum total protein
Packed cell volume (PCV)

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 287: A 3-year-old Labrador Retriever ingested approximately 6 mg/kg of acetaminophen 2 hours ago. It is asymptomatic. What is the most appropriate treatment?

Vitamin K1 administration
Induced emesis only
Activated charcoal alone
N-acetylcysteine and supportive care (Correct answer)

Correct answer: N-acetylcysteine and supportive care

N-acetylcysteine replenishes glutathione stores and is the antidote for acetaminophen toxicity; it should be combined with supportive care even in an asymptomatic patient presenting within 4 hours of ingestion.

Question 288: 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 reduced hepatic CYP450 enzyme activity, leading to slower phenobarbital clearance
Greyhounds have accelerated renal tubular secretion of phenobarbital, requiring higher doses to maintain therapeutic levels

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 289: Which flea and tick preventive acts as a selective antagonist of insect GABA-gated chloride channels?

Imidacloprid
Spinosad
Selamectin
Fipronil (Correct answer)

Correct answer: Fipronil

Fipronil selectively blocks GABA-gated chloride channels in insects and arachnids, causing CNS hyperexcitability and death; it has low affinity for mammalian receptors.

Question 290: A cat is presented for suspected oleander (Nerium oleander) ingestion. What is the primary mechanism of toxicity?

Inhibition of Na+/K+-ATPase causing cardiac glycoside toxidrome (Correct answer)
Cyanide-like inhibition of cellular cytochrome oxidase
Muscarinic cholinergic receptor agonism
Competitive inhibition of vitamin K epoxide reductase

Correct answer: Inhibition of Na+/K+-ATPase causing cardiac glycoside toxidrome

Oleandrin and neriine in oleander inhibit Na+/K+-ATPase, causing hyperkalemia, bradyarrhythmias, and AV block similar to digoxin toxicity.

Question 291: 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?

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

Correct answer: Pituitary-dependent hyperadrenocorticism

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

Question 292: Tyzzer's disease, an acute hepatic and enteric condition seen in small mammals (rabbits, rodents), is caused by which organism?

Lawsonia intracellularis
Clostridium piliforme (Correct answer)
Clostridium perfringens
Campylobacter jejuni

Correct answer: Clostridium piliforme

Clostridium piliforme (formerly Bacillus piliformis) is the obligate intracellular causative agent of Tyzzer's disease, producing acute hepatitis and enteritis.

Question 293: 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
Renal amyloid A deposition in glomeruli and medullary interstitium leading to nephrotic syndrome (Correct answer)
Tubular proteinuria from aminoglycoside nephrotoxicity used to treat febrile episodes
Immune-complex glomerulonephritis secondary to chronic interleukin-6 overproduction

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 294: A veterinary public health officer is reviewing a HACCP plan for a federally inspected poultry slaughter establishment. The establishment proposes a single critical control point (CCP) — post-chill chlorinated water immersion at 50 ppm — for Salmonella control. Which of the following is the most accurate assessment of this plan's adequacy under current USDA-FSIS regulations?

The plan is inadequate solely because FSIS prohibits chlorine concentrations above 20 ppm in immersion chillers under the Federal Food, Drug, and Cosmetic Act
The plan is adequate; 50 ppm chlorine post-chill is an FSIS-approved intervention that satisfies all Salmonella performance standards when properly monitored
The plan is inadequate; FSIS requires pathogen reduction performance standards for Salmonella that must be validated with microbial testing data, and a single post-chill intervention without upstream interventions (ante-mortem, scalding, defeathering CCPs) is unlikely to meet the Salmonella performance standard for broilers (Correct answer)
The plan is adequate but only if the establishment also maintains an antimicrobial resistance monitoring program under the National Antimicrobial Resistance Monitoring System (NARMS)

Correct answer: The plan is inadequate; FSIS requires pathogen reduction performance standards for Salmonella that must be validated with microbial testing data, and a single post-chill intervention without upstream interventions (ante-mortem, scalding, defeathering CCPs) is unlikely to meet the Salmonella performance standard for broilers

FSIS mandates Salmonella performance standards (9 CFR Part 381) requiring establishments to demonstrate through microbial sampling that their process consistently produces product meeting the standard. A HACCP plan must be validated — meaning the establishment must show the CCP actually achieves the food safety objective. A single post-chill CCP is generally insufficient because a multi-hurdle approach (scalding temperature, inside-outside bird washer, antimicrobial rinses at multiple points) is needed to achieve meaningful log reductions. FSIS allows chlorine up to 20 ppm in water that contacts carcasses for human consumption without rinsing, but chiller water at higher concentrations with rinsing is managed under different tolerances — the regulatory limit issue is real but secondary to the validation inadequacy. NARMS participation is voluntary.

Question 295: An 11-year-old Cocker Spaniel with mitral valve disease is now in CHF (NYHA functional class III). Which combination of drugs is considered standard of care per the ACVIM 2019 consensus guidelines for dogs with CHF?

Furosemide + pimobendan + enalapril (Correct answer)
Amlodipine + furosemide + atenolol
Furosemide + atenolol + digoxin
Pimobendan + digoxin + spironolactone

Correct answer: Furosemide + pimobendan + enalapril

The ACVIM 2019 consensus recommends furosemide, pimobendan, and an ACE inhibitor as the core triple therapy for dogs in CHF due to myxomatous mitral valve disease.

Question 296: 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?

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

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 297: On ultrasound of the urinary bladder, a non-shadowing, gravity-dependent echogenic material that shifts with patient repositioning is MOST consistent with:

Blood clot
Polypoid cystitis
Cystic calculi too small to shadow (sludge/crystalluria) (Correct answer)
Transitional cell carcinoma

Correct answer: Cystic calculi too small to shadow (sludge/crystalluria)

Fine echogenic material that is gravity-dependent and moves freely with repositioning but does not shadow is consistent with fine crystalluria or bladder sludge.

Question 298: Which antiviral drug has been shown to induce remission of FIP caused by FCoV mutation (FIPV) in clinical trials and is now widely used off-label?

GS-441524 (nucleoside analog) (Correct answer)
Famciclovir
Interferon-omega
Ribavirin

Correct answer: GS-441524 (nucleoside analog)

GS-441524, an adenosine nucleoside analog, inhibits FCoV replication and has shown >85% sustained remission rates in cats with wet and dry FIP in clinical studies.

Question 299: A 6-year-old bearded dragon (Pogona vitticeps) presents with bilateral periocular swelling, lethargy, and anorexia. Cytology of aspirated periocular material reveals caseous debris with heterophils. Culture yields Salmonella arizonae. Which of the following statements about treatment is MOST accurate?

Systemic fluoroquinolone therapy alone is curative because Salmonella arizonae is invariably susceptible and the caseous material resolves with antimicrobials
Chloramphenicol is the first-line agent because fluoroquinolones fail to penetrate reptilian ocular tissue
Surgical debridement of caseous exudate combined with systemic antimicrobials is required, as reptilian heterophilic pus does not liquefy and will not resolve with antibiotics alone (Correct answer)
Enrofloxacin is contraindicated in bearded dragons because it causes irreversible cartilage damage at therapeutic doses

Correct answer: Surgical debridement of caseous exudate combined with systemic antimicrobials is required, as reptilian heterophilic pus does not liquefy and will not resolve with antibiotics alone

Reptiles lack the enzymatic machinery to liquefy caseous (inspissated) pus as mammals do — their heterophils do not produce the proteases needed for liquefaction. Consequently, antibiotic therapy alone cannot eliminate the solid caseous mass; surgical debridement or curettage is mandatory to remove the inspissated material, followed by systemic antimicrobials based on culture and sensitivity. Enrofloxacin is routinely used in bearded dragons and is not contraindicated; cartilage concerns apply more to immature large-breed dogs.

Question 300: 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:

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

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 301: Which route of buprenorphine administration has been shown to achieve effective plasma concentrations in cats via the oral mucosa?

Transmucosally (OTM — oral transmucosal) (Correct answer)
Intranasal
Transdermal patch
Subcutaneous injection only

Correct answer: Transmucosally (OTM — oral transmucosal)

Buprenorphine is highly bioavailable when applied to the oral mucosa of cats (OTM) due to the alkaline feline oral pH facilitating absorption.

Question 302: Which of the following describes the classic gait abnormality associated with Australian stringhalt?

A short, choppy stride in the forelimbs, often described as 'walking on eggshells'.
Ataxia and paresis, most pronounced in the hindlimbs, that worsens with circling.
A spastic, involuntary hyperflexion of one or both hindlimbs during movement. (Correct answer)
A dragging of the toes of the hind feet, resulting in squared-off hoof wear.

Correct answer: A spastic, involuntary hyperflexion of one or both hindlimbs during movement.

Stringhalt is a neuromuscular condition characterized by an involuntary, spasmodic, and exaggerated upward flexion of one or both hindlimbs during the protraction phase of the stride. Australian stringhalt is a specific form, often seen in outbreaks, associated with the ingestion of toxic plants like Hypochaeris radicata (flatweed). The gait is often described as a jerking or snapping of the hindlimb up toward the abdomen.

Question 303: 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 304: 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 305: A 9-year-old warmblood mare shows intermittent right forelimb lameness that is consistently worse the day after competition and improves with rest. On evaluation, the horse exhibits a prominent 'head nod' lameness of 3/5 at the trot on a hard surface that reduces to 1/5 on a soft surface. Palmar digital nerve blocks are negative. Low 4-point blocks are negative. An abaxial sesamoid nerve block on the right forelimb abolishes the lameness. However, intrasynovial anesthesia of the metacarpophalangeal joint, the navicular bursa, and the distal interphalangeal joint are all negative. What anatomical structure, frequently underdiagnosed, should be the primary focus of further diagnostic workup?

The digital flexor tendon sheath, with particular attention to the proximal digital annular ligament and manica flexoria (Correct answer)
The ergot and associated fibrocartilage of the palmar fetlock
The distal sesamoidean impar ligament
The collateral ligaments of the proximal interphalangeal joint

Correct answer: The digital flexor tendon sheath, with particular attention to the proximal digital annular ligament and manica flexoria

When an abaxial sesamoid block is positive but all three major intrasynovial blocks (MCP joint, navicular bursa, DIP joint) are negative, the pain source is within the digital flexor tendon sheath (DFTS) or its associated structures. The DFTS was not blocked in this sequence. Within the sheath, the manica flexoria (the sleeve of SDFT that partially encircles the DDFT) and the proximal digital annular ligament are frequently overlooked sources of pathology — particularly in sport horses with repetitive athletic loading. The next step is intrasynovial analgesia of the DFTS itself, followed by high-field MRI or tenoscopy if positive. The other listed structures would have been blocked or at least partially desensitized by the negative blocks already performed.

Question 306: During a herd health visit to a 300-cow cow-calf operation, you review the spring vaccination protocol. Calves receive modified-live virus (MLV) BVDV vaccine at branding (approximately 3 months of age). Several producers in the region report that calves vaccinated with MLV-BVDV at this age occasionally fail to seroconvert. Which mechanism BEST explains this vaccine failure in the context of herd health?

Colostral maternal antibody interference neutralizing vaccine virus before an immune response is mounted (Correct answer)
BVDV Type 2 strains in the MLV vaccine are poorly immunogenic in calves under 6 months
CD8+ T-cell immaturity at 3 months of age prevents development of cytotoxic memory
Concurrent PI (persistently infected) calves shedding wild-type BVDV that overcompetes with vaccine virus

Correct answer: Colostral maternal antibody interference neutralizing vaccine virus before an immune response is mounted

Maternal antibody interference is the classic and most well-documented explanation for MLV-BVDV vaccine failure at branding age. Calves acquire passive immunity through colostrum, and maternally derived antibodies (MDA) to BVDV can persist for 3–6 months or longer depending on colostrum quality and dam titer. These MDAs neutralize the attenuated vaccine virus before the calf's own immune system can mount a primary response, resulting in seronegative calves despite vaccination. This is why some protocols recommend delaying BVDV vaccination until weaning (~6–7 months) or using killed vaccine initially. PI calves shedding high-titer wild-type BVDV can cause immunotolerance in herd-mates but do not mechanistically interfere with vaccine virus the same way MDA does.

Question 307: A cat presents with sedation, hypersalivation, and ataxia after grooming itself following topical permethrin application intended for dogs. What is the most appropriate treatment?

Give vitamin K1 orally
Bathe with mild dish soap and provide supportive care including muscle relaxants (Correct answer)
Administer atropine IV
Administer activated charcoal via nasogastric tube

Correct answer: Bathe with mild dish soap and provide supportive care including muscle relaxants

Permethrin toxicity in cats causes neurological signs; bathing removes the toxin and methocarbamol or diazepam controls tremors.

Question 308: A slaughter plant veterinarian observes a pig with depression, erythematous skin lesions, and sudden death in the pen. The most important zoonotic differential diagnosis to consider is:

Porcine reproductive and respiratory syndrome
Classical swine fever
Erysipelothrix rhusiopathiae infection (Correct answer)
Porcine circovirus disease

Correct answer: Erysipelothrix rhusiopathiae infection

Erysipelothrix rhusiopathiae causes erysipelas in swine and can cause erysipeloid in humans who handle infected carcasses.

Question 309: Which antifungal is the treatment of choice for feline cryptococcosis affecting the CNS?

Ketoconazole
Terbinafine
Fluconazole (Correct answer)
Amphotericin B alone

Correct answer: Fluconazole

Fluconazole achieves excellent CNS penetration and is the preferred long-term treatment for feline cryptococcal meningoencephalitis.

Question 310: 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?

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

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 311: A cat with cholangiohepatitis has a liver aspirate showing a neutrophilic infiltrate. Which organism should be cultured, and what is the most appropriate antibiotic class?

Toxoplasma gondii; clindamycin
Mycobacterium spp.; rifampicin
Enteric bacteria (E. coli, Enterococcus); fluoroquinolone or amoxicillin-clavulanate (Correct answer)
Cryptococcus neoformans; fluconazole

Correct answer: Enteric bacteria (E. coli, Enterococcus); fluoroquinolone or amoxicillin-clavulanate

Neutrophilic cholangitis is typically caused by ascending enteric bacteria; culture-guided treatment with fluoroquinolones or amoxicillin-clavulanate targets gram-negative and anaerobic organisms.

Question 312: A 5-year-old Thoroughbred racehorse has a complete transverse fracture of the proximal sesamoid bone following a race. Which statement best describes the prognosis for return to racing?

Excellent prognosis with internal fixation using lag screws
Guarded to poor prognosis; most horses are retired from racing after this injury (Correct answer)
Prognosis depends solely on which sesamoid (medial vs. lateral) is fractured
Good prognosis with 6 weeks of stall rest alone

Correct answer: Guarded to poor prognosis; most horses are retired from racing after this injury

Complete transverse fractures of the proximal sesamoid bone carry a guarded to poor prognosis for return to racing due to disruption of the suspensory apparatus and risk of fetlock hyperextension.

Question 313: Which perineural block is required to desensitize the entire foot including the coronary band?

Palmar digital nerve block
High palmar (high 2-point) nerve block
Abaxial sesamoid nerve block (Correct answer)
Low 4-point nerve block (palmar metacarpal + palmar digital)

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 314: 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?

Carbon dioxide absorption causing hypercarbia-induced vagal stimulation and intestinal hypomotility
Inadvertent ligation of the right uterine artery causing uterine ischemia and visceral pain
Pneumoperitoneum-induced mesenteric traction leading to ileus of the descending colon
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 315: A 14-year-old cat presents with progressive muscle wasting, pot-bellied appearance, fragile skin that tears with routine handling, bilaterally symmetric alopecia, and a non-suppressed low-dose dexamethasone suppression test (LDDST). Endogenous ACTH is undetectable. Which diagnosis and most appropriate next step are correct?

Ectopic ACTH syndrome from a thoracic mass; perform thoracic CT to identify the source
Adrenal-dependent hyperadrenocorticism (ADH) due to adrenocortical tumor; perform abdominal imaging to characterize the adrenal glands (Correct answer)
Pituitary-dependent hyperadrenocorticism (PDH); proceed to high-dose dexamethasone suppression test to confirm
Iatrogenic hyperadrenocorticism; detailed medication history and cessation of exogenous glucocorticoids

Correct answer: Adrenal-dependent hyperadrenocorticism (ADH) due to adrenocortical tumor; perform abdominal imaging to characterize the adrenal glands

Undetectable endogenous ACTH in a cat with confirmed hyperadrenocorticism (non-suppression on LDDST) indicates an ACTH-independent source of cortisol excess — pointing to a functional adrenocortical tumor (adrenal-dependent HAC). In pituitary-dependent disease, ACTH would be elevated or high-normal. In iatrogenic HAC, ACTH is also suppressed, but this is distinguished by history of exogenous steroid administration (not mentioned here). The next step is abdominal imaging (ultrasound or CT) to evaluate the adrenal glands for asymmetric enlargement, mass, or mineralization. Feline skin fragility syndrome (fragile skin) is a hallmark of feline HAC.

Question 316: 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?

Baermann technique to detect larvae in feces
Fecal Egg Count Reduction Test (FECRT) comparing pre- and post-treatment counts (Correct answer)
Larval development assay using pooled fecal cultures
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 317: 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?

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

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 318: Which finding on thoracic radiographs of a cat is MOST suggestive of hypertrophic cardiomyopathy (HCM)?

Valentine-shaped heart on VD view with left atrial enlargement (Correct answer)
Microcardia with retraction of lung lobes
Right-sided cardiomegaly with increased sternal contact
Globoid cardiac silhouette with loss of cardiac waist

Correct answer: Valentine-shaped heart on VD view with left atrial enlargement

HCM in cats classically produces a Valentine or bivalve-shaped cardiac silhouette on the VD view due to biatrial enlargement.

Question 319: 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?

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

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 320: 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 321: 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?

Granulomatous enteritis (multisystemic eosinophilic epitheliotropic disease)
Right dorsal colitis secondary to NSAID toxicity
Cyathostominosis (larval cyathostomiasis) with mucosal larval emergence (Correct answer)
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 322: In a beef herd vaccination program, Bovine Viral Diarrhea Virus (BVDV) Type 1 and Type 2 vaccines are used. Which cattle are most critical to vaccinate to prevent persistently infected (PI) calves from being born?

Newborn calves in the first week of life
Heifers and cows before breeding (Correct answer)
All bulls used for natural service
Weaned calves at 6-8 months of age

Correct answer: Heifers and cows before breeding

PI calves result from fetal infection with BVDV between days 40-125 of gestation; vaccinating cows and heifers before breeding prevents viremia during this critical window.

Question 323: 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?

Epinephrine (Correct answer)
Norepinephrine
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 324: During a routine splenectomy in a 6-year-old DSH cat for splenic mast cell tumor, the surgeon encounters unexpected difficulty controlling hemorrhage from the short gastric vessels. Intraoperatively, the cat develops a sudden drop in systolic BP to 55 mmHg, bradycardia (HR 48 bpm), and becomes unresponsive. Which drug combination is MOST appropriate as the FIRST intervention?

Atropine 0.04 mg/kg IV + epinephrine 0.01 mg/kg IV (Correct answer)
Vasopressin 0.4 units/kg IV + atropine 0.02 mg/kg IV
Dopamine CRI at 5 µg/kg/min
Epinephrine 0.01 mg/kg IV alone

Correct answer: Atropine 0.04 mg/kg IV + epinephrine 0.01 mg/kg IV

This presentation — profound hypotension + bradycardia + unresponsiveness during mast cell tumor manipulation — is consistent with a massive histamine/tryptase release event (anaphylaxis or mast cell degranulation crisis). The combination of hypotension AND bradycardia (rather than the reflex tachycardia of simple hemorrhage) with intraoperative mast cell tumor handling strongly implicates degranulation. Atropine addresses the vagotonic bradycardia, and epinephrine is the drug of choice for anaphylaxis — it reverses bronchospasm, causes vasoconstriction (α1), and positive chronotropy/inotropy (β1/β2). Vasopressin is a second-line vasopressor but does not address the bradycardia or anaphylactic mechanism. A dopamine CRI has too slow an onset in this acute crisis.

Question 325: Which statement about maropitant (Cerenia) use in cats is correct?

It is contraindicated in cats under 4 months of age
It works by blocking D2 dopamine receptors in the chemoreceptor trigger zone
It has no visceral analgesic properties in cats
It is approved at 1 mg/kg SC once daily for nausea prevention (Correct answer)

Correct answer: It is approved at 1 mg/kg SC once daily for nausea prevention

Maropitant is approved at 1 mg/kg SC in cats for nausea and vomiting; it blocks NK1 receptors and also provides visceral analgesia.

Question 326: Which MRI sequence best demonstrates hemorrhage of varying ages due to its sensitivity to paramagnetic effects of blood breakdown products?

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

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 327: A 5-year-old Beagle is presented with an acute abdomen and radiographs reveal a markedly distended stomach with gas and a 'double bubble' appearance. Which surgical procedure is performed to prevent recurrence after gastric decompression?

Fundoplication
Gastrectomy
Pyloroplasty
Gastropexy (Correct answer)

Correct answer: Gastropexy

Gastropexy permanently adheres the stomach to the right abdominal wall, preventing future rotation and recurrence of gastric dilatation-volvulus (GDV).

Question 328: A 'string of pearls' sign on abdominal radiographs of a cat refers to:

Small gas bubbles trapped between intestinal folds indicating ileus (Correct answer)
Multiple uroliths in the ureter
Gas within the portal vasculature
Mineralization of lymph nodes in the mesentery

Correct answer: Small gas bubbles trapped between intestinal folds indicating ileus

The 'string of pearls' sign describes small gas bubbles trapped between the valvulae conniventes in paralytic ileus, indicating functional obstruction.

Question 329: 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?

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

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 330: 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?

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

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 331: A dog is receiving a fentanyl CRI at 5 mcg/kg/hr intraoperatively. Signs of opioid-induced bradycardia appear. Which drug reverses fentanyl's cardiovascular effects with the least effect on analgesia?

Naloxone full dose IV
Glycopyrrolate IV to treat bradycardia without reversing opioid (Correct answer)
Flumazenil IV
Atipamezole IV

Correct answer: Glycopyrrolate IV to treat bradycardia without reversing opioid

Glycopyrrolate treats opioid-induced bradycardia by blocking vagal tone without reversing analgesia, unlike naloxone which would eliminate pain control.

Question 332: Which surveillance system in the US monitors antimicrobial resistance in zoonotic enteric pathogens from humans, animals, and retail meat?

NAHMS
APHIS VS
NARMS (Correct answer)
FSIS HACCP

Correct answer: NARMS

The National Antimicrobial Resistance Monitoring System (NARMS) tracks resistance trends across the human-animal-food interface.

Question 333: A dairy manager is concerned about a rising bulk tank somatic cell count (SCC). Which of the following is the most effective and direct on-farm screening tool to identify individual cows with subclinical mastitis?

Teat end scoring
California Mastitis Test (CMT) (Correct answer)
Bulk tank culture
Direct microscopic somatic cell count (DMSCC)

Correct answer: California Mastitis Test (CMT)

The California Mastitis Test (CMT) is a simple, cow-side test that provides a semi-quantitative estimate of the SCC in milk from individual quarters, allowing for rapid identification of subclinical mastitis. Bulk tank culture identifies pathogens present in the herd's milk but does not pinpoint individual infected cows. Teat end scoring assesses the risk of infection but does not diagnose existing mastitis. DMSCC is a precise laboratory test, not a rapid on-farm screening tool for individual animals.

Question 334: 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:

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

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 335: 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?

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)
Lycorine alkaloids found in Lilium species competitively inhibit renal organic anion transporters, causing tubular toxin accumulation
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

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 336: A rancher reports abortions in 8% of his beef cows in the last trimester. Brucella abortus is confirmed. Which test is used for the official US brucellosis eradication program to test individual cattle?

PCR of milk
ELISA only
Card test (Rose Bengal plate test) (Correct answer)
Complement fixation test

Correct answer: Card test (Rose Bengal plate test)

The card (Rose Bengal) test is the approved screening test in the US brucellosis eradication program, with positive reactors confirmed by the buffered acidified plate antigen (BAPA) or fluorescent polarization assay.

Question 337: Which test best differentiates a vaccinated cat from a truly FeLV-infected cat when using a standard ELISA?

The ELISA detects p27 antigen which vaccines do not induce (Correct answer)
Western blot for gp70 antigen
Virus isolation in culture
PCR for proviral DNA

Correct answer: The ELISA detects p27 antigen which vaccines do not induce

FeLV ELISA tests detect the p27 core antigen released by replicating virus, not antibody, so vaccination does not produce a positive result.

Question 338: 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 339: A kitten born to a queen with Toxoplasma gondii primary infection during pregnancy is most at risk for which clinical outcome?

Fading kitten syndrome with hepatic necrosis (Correct answer)
Development of mucosal immunity only
Persistent asymptomatic shedding of oocysts
Skin granulomas at birth

Correct answer: Fading kitten syndrome with hepatic necrosis

Congenitally infected kittens develop severe disseminated toxoplasmosis with hepatic necrosis, often presenting as fading kittens.

Question 340: A green iguana is presented with metabolic bone disease. Which nutritional deficiency is most commonly responsible?

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

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 341: 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?

Renal tubular dysfunction secondary to hypercortisolism causing a Fanconi-like syndrome (Correct answer)
Primary renal glucosuria due to SGLT2 transporter mutation
Occult postprandial hyperglycemia exceeding the renal threshold transiently
Concurrent diabetes mellitus with stress-induced blood glucose normalization at time of sampling

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

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 343: 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?

Idiosyncratic acute hepatic necrosis unique to cats receiving oral benzodiazepines, unrelated to dose or duration (Correct answer)
Type B hypersensitivity reaction triggered by benzodiazepine ring oxidation products in genetically susceptible cats
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

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 344: A dog is diagnosed with immune-mediated hemolytic anemia (IMHA). Which finding on the CBC is most specific for confirming immune-mediated destruction?

Thrombocytopenia
Macrocytosis and polychromasia
Spherocytosis on blood smear (Correct answer)
Neutrophilia with a left shift

Correct answer: Spherocytosis on blood smear

Spherocytes, which lack the normal biconcave shape due to partial phagocytosis of antibody-coated membrane by macrophages, are the most specific morphologic finding for IMHA.

Question 345: 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:

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

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 346: A 5-year-old Border Collie is evaluated for progressive ataxia and seizures. MRI of the brain (1.5T) shows bilateral, symmetrical T2 hyperintensity in the thalamus and caudate nucleus with no mass effect and no contrast enhancement. CSF analysis is normal. Which condition is MOST consistent with these MRI findings?

Granulomatous meningoencephalitis (GME)
Neospora caninum encephalomyelitis
Cerebral infarction (ischemic stroke)
Thiamine (vitamin B1) deficiency encephalopathy (Correct answer)

Correct answer: Thiamine (vitamin B1) deficiency encephalopathy

Bilateral symmetrical T2 hyperintensity restricted to the thalamus and basal ganglia (caudate nucleus) without contrast enhancement or mass effect is the classic MRI signature of thiamine deficiency encephalopathy in dogs (and cats). This mirrors the Wernicke's encephalopathy pattern seen in humans. GME typically shows contrast-enhancing, asymmetric multifocal lesions. Neospora lesions are usually multifocal and may enhance. Cerebral infarction causes unilateral, vascular-territory distribution lesions. The bilateral symmetry and selective thalamic/basal ganglia involvement are the key discriminating features.

Question 347: An 8-year-old Cocker Spaniel presents with a chronic cough, exercise intolerance, and a loud left apical systolic murmur (grade V/VI). Thoracic radiographs show pulmonary venous congestion. Which drug is indicated to reduce preload in this patient?

Amlodipine
Furosemide (Correct answer)
Digoxin
Atenolol

Correct answer: Furosemide

Furosemide, a loop diuretic, reduces preload by promoting sodium and water excretion, relieving pulmonary venous congestion in congestive heart failure.

Question 348: 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?

Ectopic ureter with secondary hydronephrosis and hydroureter
Peritoneal inclusion cyst secondary to prior abdominal surgery
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 349: You are managing a cat that ingested topical permethrin flea spray (concentrated dog formulation) 90 minutes ago. The cat is tremoring severely. After decontamination with dish soap, which treatment combination is MOST appropriate for controlling permethrin-induced tremors in this cat?

Atropine IV to block muscarinic hyperstimulation, followed by pralidoxime
Methocarbamol IV combined with diazepam; avoid pyrethroid-specific antidotes (Correct answer)
Cyproheptadine PO or per rectum combined with methocarbamol IV
Lipid emulsion therapy (ILE) as sole treatment, given permethrin's high lipophilicity

Correct answer: Methocarbamol IV combined with diazepam; avoid pyrethroid-specific antidotes

Permethrin toxicosis in cats causes sodium channel dysfunction leading to repetitive neuronal firing, manifesting as tremors and seizures. The treatment of choice for tremor control is methocarbamol (a muscle relaxant; 44–220 mg/kg IV slowly to effect) combined with diazepam or other benzodiazepines for CNS sedation and seizure control. There is no specific antidote. Atropine + pralidoxime is the antidote regimen for organophosphate/carbamate toxicity (which acts via AChE inhibition), not pyrethroids. Cyproheptadine (a serotonin antagonist) is used for serotonin syndrome, not permethrin toxicosis. IVLipid emulsion can be a useful adjunct in severe refractory cases but is not the primary or sole treatment.

Question 350: A veterinary public health team is conducting a quantitative microbial risk assessment (QMRA) for Listeria monocytogenes in ready-to-eat (RTE) deli meat distributed through retail delis. They calculate a mean dose-response risk of 1.4 × 10⁻⁸ per serving for the general population. However, the immunocompromised subpopulation has a dose-response slope 100-fold higher. If the immunocompromised population consumes an estimated 3 servings per week over 52 weeks, what is the approximate annual risk per person in this subpopulation, and does it exceed the USDA FSIS negligible risk benchmark of 1 × 10⁻⁶ per year?

Annual risk ≈ 1.4 × 10⁻⁶; exceeds the benchmark but only marginally
Annual risk ≈ 2.2 × 10⁻⁴; exceeds the benchmark by ~220-fold
Annual risk ≈ 2.2 × 10⁻⁴; exceeds the benchmark by ~220-fold (Correct answer)
Annual risk ≈ 7.3 × 10⁻⁵; exceeds the benchmark by ~73-fold

Correct answer: Annual risk ≈ 2.2 × 10⁻⁴; exceeds the benchmark by ~220-fold

For the immunocompromised subpopulation, the per-serving risk is 100 × 1.4 × 10⁻⁸ = 1.4 × 10⁻⁶ per serving. Over 3 servings/week × 52 weeks = 156 servings/year, the annual risk (using the independent events approximation: 1 − (1 − p)ⁿ ≈ n × p for small p) is approximately 156 × 1.4 × 10⁻⁶ ≈ 2.18 × 10⁻⁴. This exceeds the USDA FSIS negligible risk benchmark of 1 × 10⁻⁶/year by approximately 218-fold, confirming that standard population-level risk estimates dramatically underestimate risk in high-susceptibility subpopulations and underscoring why Listeria control in RTE facilities targets a zero-tolerance standard for ready-to-eat environments.

Question 351: A cat anesthetized with ketamine/diazepam develops prolonged apnea after induction. Which characteristic of ketamine best explains this risk?

Ketamine inhibits NMDA receptors in the brainstem
Ketamine stimulates mu-opioid receptors
Ketamine increases upper airway secretions causing obstruction
Ketamine causes dose-dependent respiratory depression at high doses (Correct answer)

Correct answer: Ketamine causes dose-dependent respiratory depression at high doses

While ketamine is generally considered a respiratory-sparing agent, high or rapidly administered doses can cause dose-dependent apnea in cats.

Question 352: 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?

Hansen Type I intervertebral disc extrusion with foraminal migration (Correct answer)
Degenerative lumbosacral stenosis with foraminal osteophytosis
Synovial cyst arising from the articular facet joint
Nerve sheath tumor of the L7 nerve root

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 353: 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?

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

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 354: 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 355: 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?

Mandatory 30-day quarantine of all affected cattle
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

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 356: 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
Mechanical obstruction (Correct answer)
Gastroenteritis

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 357: In nuclear scintigraphy, a 'cold spot' on a thyroid scan in a dog MOST likely represents:

Ectopic thyroid tissue
Normal thyroid tissue
Nonfunctional or necrotic tissue within the thyroid (Correct answer)
Hyperfunctional adenoma

Correct answer: Nonfunctional or necrotic tissue within the thyroid

A cold (photopenic) area on thyroid scintigraphy indicates reduced radionuclide uptake, consistent with nonfunctional, necrotic, or cystic tissue.

Question 358: A cat presents with bilateral anterior uveitis. FIP testing is negative. Which other infectious agent should be high on the differential list?

Toxoplasma gondii (Correct answer)
Feline parvovirus
Feline panleukopenia virus
Feline calicivirus

Correct answer: Toxoplasma gondii

Toxoplasma gondii is a leading cause of feline uveitis and should be tested via serology when FIP is ruled out.

Question 359: A beef producer wants to improve weaning weights and post-weaning growth. Which management practice during the preconditioning period (45-60 days post-weaning) has the GREATEST impact on feedlot health outcomes?

Administering growth implants immediately at weaning
Providing ad libitum grain access from birth
Completing vaccination series, weaning, castration, and dehorning at least 45 days before sale (Correct answer)
Keeping calves on the cow for 9 months before weaning

Correct answer: Completing vaccination series, weaning, castration, and dehorning at least 45 days before sale

Preconditioning programs that complete the BRD vaccination series, castration, and dehorning at least 45 days before sale reduce feedlot morbidity and mortality by allowing stress recovery and vaccine immune response maturation.

Question 360: 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.

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

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420 min

Time Limit

65%

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