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

Question 1: A cat presents with pleural effusion. On thoracic radiographs, which finding best differentiates pleural effusion from pulmonary consolidation?

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

Correct answer: Retraction of lung lobes from the thoracic wall

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

Question 2: According to USDA-APHIS regulations, which of the following diseases requires IMMEDIATE notification by an accredited veterinarian to state or federal animal health officials if suspected?

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

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

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

Question 3: During a shelter outbreak investigation, 6 of 12 adult cats develop severe erosive stomatitis, limb edema, and pneumonia over 10 days with 2 fatalities. Kittens in the same ward are largely unaffected. Feline calicivirus (FCV) PCR is positive. Which strain characteristic BEST explains this outbreak pattern?

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

Correct answer: A recombinant FCV strain with enhanced tropism for endothelial cells causing virulent systemic FCV (VS-FCV)

Virulent systemic FCV (VS-FCV), also called hemorrhagic fever FCV, is characterized by endotheliotropism causing facial and limb edema, hemorrhagic diatheses, high fever, and mortality rates up to 67% in adult cats. Critically, VS-FCV preferentially affects adults because maternal antibodies from queens (who lack VS-FCV immunity) do NOT protect kittens against this antigenically distinct strain — however, adult cats with prior FCV immunity can still succumb because VS-FCV escapes neutralization by antibodies generated against classical FCV strains. The mortality pattern skewing toward adults is a hallmark of VS-FCV outbreaks.

Question 4: A 6-year-old Standardbred pacer presents with an acute onset Grade 4/5 right forelimb lameness after a race. On examination there is moderate fetlock effusion, periarticular swelling, and pain on deep palpation of the lateral proximal sesamoid bone. Radiographs reveal a mid-body, sagittal fracture of the lateral proximal sesamoid bone without articular involvement. The horse is otherwise systemically healthy. Which treatment offers the BEST prognosis for return to racing performance in this specific fracture configuration?

Conservative management with box rest, support bandaging, and NSAIDs for 6–12 months
Neurectomy of the palmar digital nerve to provide long-term pain control and allow return to work
Sesamoidectomy of the lateral proximal sesamoid bone to prevent non-union
Lag screw fixation with a 4.5 mm cortical screw placed perpendicular to the fracture plane under general anesthesia (Correct answer)

Correct answer: Lag screw fixation with a 4.5 mm cortical screw placed perpendicular to the fracture plane under general anesthesia

Mid-body sagittal fractures of the proximal sesamoid bone that do not involve the articular surface and are not comminuted carry the best prognosis when treated with lag screw fixation. The lag screw creates interfragmentary compression that promotes primary bone healing and restores the structural integrity of the sesamoid bone, which is essential for resuming the biomechanical demands of racing. Conservative management alone has poor outcomes for racing soundness. Sesamoidectomy is reserved for apical or basal fractures. Neurectomy treats pain but does not address the structural problem and carries welfare concerns for performance horses.

Question 5: 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
Trimethoprim-sulfamethoxazole 30 mg/kg PO BID
Enrofloxacin 5 mg/kg IV once daily (Correct answer)
Chloramphenicol 50 mg/kg PO QID

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

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

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

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

Question 7: A cat is prescribed methimazole for hyperthyroidism. Which adverse effect is most commonly reported in the first 1–3 months of therapy?

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

Radiographs of the pastern
MRI of the foot
Low 4-point nerve block
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 9: A USDA veterinarian performing post-mortem inspection on a steer carcass finds multiple, well-demarcated, caseous abscesses in the lungs and associated mediastinal lymph nodes. What is the correct disposition for this carcass?

Condemn the entire carcass. (Correct answer)
Pass for human consumption after trimming affected parts.
Condemn the thoracic organs and pass the rest of the carcass.
Pass for cooking only.

Correct answer: Condemn the entire carcass.

The lesions described (caseous necrosis/granulomas in lungs and associated lymph nodes) are classic for bovine tuberculosis (*Mycobacterium bovis*). According to USDA regulations, evidence of generalized tuberculosis, which includes extensive lesions in the thoracic cavity, requires condemnation of the entire carcass due to its significant zoonotic potential and systemic nature.

Question 10: In the context of zoonotic disease epidemiology, which of the following pathogens is correctly classified as an obligate maintenance host situation, where humans are ONLY incidental (dead-end) hosts and contribute negligibly to transmission cycles?

Mycobacterium tuberculosis var. bovis in a region with active cattle-to-human spillover and human-to-human transmission documented
Rabies virus in an enzootic raccoon-variant region
Yersinia pestis during a sylvatic plague epizootic in prairie dogs (Correct answer)
Influenza A (H1N1) pdm09 during the 2009 pandemic

Correct answer: Yersinia pestis during a sylvatic plague epizootic in prairie dogs

During sylvatic plague epizootics in prairie dog colonies, Yersinia pestis cycles entirely within wild rodent populations via flea vectors. Humans who become infected (via flea bite or handling infected animals) are true dead-end hosts — they do not sustain or amplify the transmission cycle back into the rodent reservoir or among other humans (pneumonic plague is rare and requires close contact). In contrast, M. bovis can involve human-to-human transmission in high-burden settings, rabies variants can occasionally cycle in human communities with dog-mediated rabies, and influenza H1N1 became a fully sustained human pandemic pathogen.

Question 11: Which of the following antiparasitic drugs has a narrow margin of safety and is associated with severe neurotoxicity in dog breeds with the ABCB1 (formerly MDR1) gene mutation, such as Collies and Australian Shepherds?

Ivermectin (Correct answer)
Praziquantel
Selamectin
Fipronil

Correct answer: Ivermectin

Ivermectin, a macrocyclic lactone, can cause severe neurotoxicity in dogs with the ABCB1/MDR1 gene mutation. This mutation results in a defective P-glycoprotein pump, which is responsible for transporting certain drugs out of the central nervous system. Without a functional pump, ivermectin accumulates in the brain, leading to signs like ataxia, tremors, blindness, and coma.

Question 12: Foot rot (Fusobacterium necrophorum infection) is common in beef feedlots. Which environmental management change has the greatest impact on reducing foot rot incidence?

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

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

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

Question 13: A 12-year-old Warmblood sport horse presents with a 6-month history of intermittent right forelimb lameness that worsens after collected work. Radiographs reveal subchondral cystic lesions in the medial femoral condyle. Intra-articular anesthesia of the femoropatellar joint abolishes 70% of the lameness, but the stifle shows no significant synovial effusion. Which surgical treatment has demonstrated the best long-term outcomes for large (>15 mm diameter) subchondral cystic lesions of the medial femoral condyle in sport horses?

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

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

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

Question 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?

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

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

Correct answer: Transarterial coil embolization of the affected artery

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

Question 16: 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
Radial nerve paralysis
Brachial plexus avulsion (Correct answer)
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 17: Polioencephalomalacia in adult cattle most commonly results from which underlying cause, distinct from the thiamine deficiency seen in sheep and young ruminants?

Vitamin A deficiency causing increased CSF pressure
Sodium ion toxicosis (salt poisoning) following water deprivation
Molybdenum toxicity causing copper depletion
High dietary sulfur intake causing hydrogen sulfide (H2S) neurotoxicity (Correct answer)

Correct answer: High dietary sulfur intake causing hydrogen sulfide (H2S) neurotoxicity

In adult cattle, PEM is increasingly associated with high dietary sulfur (from distillers grains, gypsum water, or sulfur supplements), which promotes rumen production of hydrogen sulfide — a neurotoxin that causes cortical necrosis. While thiamine deficiency also occurs in cattle, high-sulfur PEM is the emerging predominant cause and is sulfur-diet-associated rather than thiaminase-related. Sodium toxicosis causes cerebral edema/herniation rather than laminar cortical necrosis.

Question 18: 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?

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

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 19: 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?

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

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 20: A 1,200-head Holstein dairy uses a voluntary waiting period (VWP) of 50 days. Herd records show mean days to first service = 58 days, mean days open = 145 days, and 12-month rolling culling rate = 32%. The herd veterinarian proposes shortening the VWP to 35 days. Which of the following accurately predicts the PRIMARY unintended consequence of this change in a high-producing herd averaging 95 lbs/cow/day at peak?

Mastitis incidence will increase due to immunosuppression associated with early resumption of luteal activity
First-service conception rate will decline because insemination will more frequently occur before complete uterine involution and during peak negative energy balance (Correct answer)
Culling rate will increase because shortened inter-calving intervals reduce productive life
Milk yield in the subsequent lactation will decrease because early rebreeding reduces the length of the current lactation

Correct answer: First-service conception rate will decline because insemination will more frequently occur before complete uterine involution and during peak negative energy balance

In high-producing dairy cows, the nadir of negative energy balance (NEB) typically occurs between 10–14 days in milk, but NEB persists and substantially impairs reproductive function through ~50–60 DIM. Shortening the VWP to 35 days means many cows will be inseminated while still in NEB, with incomplete uterine involution, suboptimal progesterone profiles, and impaired embryo survival. Research consistently shows that conception rates at early first service in high-producers are 8–15 percentage points lower than services at 50–60 DIM. Additionally, uterine involution is not complete in many cows before 40–45 DIM. The net result is more services per conception and no improvement in days open, negating the intended benefit.

Question 21: During isoflurane anesthesia in a cat undergoing a perineal urethrostomy, end-tidal CO₂ rises to 65 mmHg despite a respiratory rate of 16 breaths/min and tidal volume appearing normal. Oxygen saturation (SpO₂) is 99%. Which is the MOST likely cause?

Exhausted CO₂ absorbent in a circle rebreathing system (Correct answer)
Increased dead space due to a kinked endotracheal tube
Esophageal intubation causing rebreathing of expired gases
Malignant hyperthermia triggered by isoflurane exposure

Correct answer: Exhausted CO₂ absorbent in a circle rebreathing system

Exhausted CO₂ absorbent (e.g., soda lime or barium hydroxide lime that is spent) allows exhaled CO₂ to re-enter the inspiratory limb of a circle breathing system, causing progressive hypercapnia. SpO₂ remains high because oxygen supplementation compensates, making the diagnosis subtle. Esophageal intubation would show absent CO₂ waveform initially or very low ETCO₂, not elevated. Malignant hyperthermia is extremely rare in cats and would present with rapidly escalating hyperthermia, tachycardia, muscle rigidity, and metabolic acidosis—not isolated ETCO₂ elevation. A kinked ETT would reduce tidal volume and cause increased airway pressure, not isolated hypercapnia with normal SpO₂ and visible normal breathing.

Question 22: 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?

Enlarged, tortuous pulmonary arteries and right-sided cardiomegaly.
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)
A diffuse, unstructured interstitial pattern with prominent pulmonary veins.

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

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

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 24: During abdominal ultrasound, the normal feline adrenal gland has which characteristic appearance?

Elongated hyperechoic structure parallel to the aorta, 15-20mm length
Oval homogeneous hyperechoic structure, 5-10mm length
Round anechoic structure adjacent to the kidney, 3-5mm diameter
Bilobed hypoechoic structure with a hyperechoic medulla, less than 4.3mm width (Correct answer)

Correct answer: Bilobed hypoechoic structure with a hyperechoic medulla, less than 4.3mm width

Normal feline adrenal glands are bilobed (peanut-shaped) with a hypoechoic cortex and hyperechoic medulla, measuring less than 4.3mm in width.

Question 25: 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?

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

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 26: A 5-year-old intact male Cocker Spaniel presents with acute vomiting, fever, and a painful cranial abdomen. Serum lipase is markedly elevated. Which dietary fat level is most appropriate during recovery?

High fat (>25% DM)
Low fat (<10% DM) (Correct answer)
Fat-free diet
Moderate fat (15-20% DM)

Correct answer: Low fat (<10% DM)

Dogs recovering from pancreatitis should receive a low-fat diet (<10% DM) to minimize pancreatic stimulation and reduce recurrence risk.

Question 27: 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 toxic glycoside tuliposide A is activated in the renal cortex and alkylates mitochondrial DNA of tubular cells
Lily stamen pollen contains calcium oxalate crystals that deposit in renal tubules and cause obstructive nephropathy
Lycorine alkaloids found in Lilium species competitively inhibit renal organic anion transporters, causing tubular toxin accumulation
The nephrotoxic principle causes direct proximal tubular epithelial cell death via a mechanism not yet fully elucidated at the molecular level, with no known antidote (Correct answer)

Correct answer: The nephrotoxic principle causes direct proximal tubular epithelial cell death via a mechanism not yet fully elucidated at the molecular level, with no known antidote

True lily nephrotoxicity (Lilium and Hemerocallis species) in cats is a well-documented but mechanistically incompletely understood toxidrome. The toxic principle causes acute, severe proximal tubular necrosis, but the exact molecular mechanism has not been definitively identified in peer-reviewed literature. There is no antidote — treatment is aggressive IV fluid diuresis initiated within hours of exposure, before renal injury is established. Calcium oxalate crystals causing obstructive nephropathy are associated with Oxalis and Araceae species (e.g., Philodendron, Dieffenbachia), not true lilies. Lycorine is found in Narcissus/Amaryllidaceae; tuliposide A is found in Tulipa. Cats are uniquely and exquisitely sensitive to Lilium/Hemerocallis; dogs are not.

Question 28: On CT of the abdomen with IV contrast, hepatic nodules that are hyperattenuating in the arterial phase and isoattenuating in the portal venous phase are MOST suggestive of:

Biliary cystadenoma
Hepatic cysts
Hepatic abscess
Hepatocellular carcinoma (Correct answer)

Correct answer: Hepatocellular carcinoma

Hepatocellular carcinoma is typically hypervascular, showing arterial phase enhancement that washes out to isoattenuation in the portal venous phase.

Question 29: A ferret presents with episodic weakness, ptyalism, pawing at the mouth, and hypoglycemia (BG 42 mg/dL) that resolves with dextrose. Abdominal ultrasound reveals a 1.2 cm hypoechoic pancreatic nodule. Intraoperative exploration reveals a solitary mass in the left limb of the pancreas with no visible metastasis. Which of the following perioperative management strategies carries the GREATEST risk of iatrogenic harm in this patient?

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

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

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

Question 30: 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?

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

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 31: 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)
A sole depth ≥5 mm after rotation carries a favorable prognosis; corrective shoeing alone is sufficient treatment
Venography is contraindicated in chronic laminitis cases with rotation due to risk of increased lamellar ischemia
Coffin bone rotation beyond 10 degrees is an absolute indication for euthanasia regardless of sole depth

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

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

Question 32: In equine foot radiography, which landmark is used to assess the position of the navicular bone relative to the distal phalanx?

Dorsal cortex width of the middle phalanx
Solar margin of the coffin bone on dorsopalmar view
Angle of the coronary band to the hoof wall
Palmar angle of the distal phalanx relative to the ground surface (Correct answer)

Correct answer: Palmar angle of the distal phalanx relative to the ground surface

The palmar angle of P3 on lateral foot radiographs is used to assess navicular bone position and the degree of podotrochlear pathology.

Question 33: Propylene glycol is present in some semi-moist cat foods and medications. Why is it contraindicated in cats?

It is directly nephrotoxic through oxalate crystal deposition
It causes acute pancreatitis due to lipase inhibition
It causes Heinz body formation and hemolytic anemia in cats (Correct answer)
It causes hypernatremia by drawing water from red blood cells

Correct answer: It causes Heinz body formation and hemolytic anemia in cats

Cats are uniquely susceptible to propylene glycol-induced Heinz body hemolytic anemia because their hemoglobin contains eight SH groups versus four in dogs.

Question 34: 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?

Pyloromyotomy
Gastropexy (Correct answer)
Splenectomy in all cases
Esophageal banding

Correct answer: Gastropexy

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

Question 35: A 12-year-old Quarter Horse mare has progressive forelimb lameness with a history of repeated intra-articular coffin joint injections. Radiographs now show marked remodeling of the coffin joint. The MOST appropriate next diagnostic step is:

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

Correct answer: MRI of the foot to evaluate soft tissue and bone detail

MRI provides superior detail of both bony and soft tissue structures within the hoof capsule, allowing comprehensive evaluation of all coffin joint components when standard diagnostics have been inconclusive.

Question 36: 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?

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

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 37: 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
Meloxicam 0.1 mg/kg PO q24h as long-term maintenance (Correct answer)
Robenacoxib 1 mg/kg PO q24h for ≤3 days
Gabapentin 5 mg/kg PO q12h

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 38: During evaluation of a 9-year-old Andalusian with chronic bilateral forelimb lameness, distal limb flexion tests are strongly positive. MRI of the foot reveals a core lesion of the deep digital flexor tendon (DDFT) within the navicular bursa. Intra-bursal analgesia eliminates 90% of lameness bilaterally. Conservative management has failed after 8 months. Which surgical option directly addresses the pathological tension on the DDFT core lesion while preserving limb function?

Palmar digital neurectomy at the level of the proximal sesamoid bones
Inferior check ligament desmotomy (accessory ligament of the DDFT) (Correct answer)
Navicular suspensory ligament desmotomy via a palmar approach
Coffin joint arthrodesis

Correct answer: Inferior check ligament desmotomy (accessory ligament of the DDFT)

Inferior check ligament (accessory ligament of the DDFT) desmotomy reduces tension on the DDFT by eliminating the static tethering effect of the accessory ligament, allowing the DDFT to bear reduced load and facilitating healing of the core lesion. It is the preferred surgical option when MRI confirms DDFT pathology within the navicular bursa. Palmar digital neurectomy provides analgesia but does not address the biomechanical cause and carries risks of catastrophic tendon rupture.

Question 39: On thoracic auscultation of an 8-year-old Cavalier King Charles Spaniel, you hear a grade IV/VI left apical systolic heart murmur. Echocardiography shows myxomatous mitral valve disease with moderate left atrial enlargement (LA:Ao ratio 1.7). Which ACVIM staging is most appropriate?

Stage C
Stage B1
Stage B2 (Correct answer)
Stage A

Correct answer: Stage B2

Stage B2 MMVD is defined by cardiac remodeling (LA:Ao ≥1.6 or normalized left ventricular internal diameter in diastole >1.7) without clinical signs of heart failure.

Question 40: A veterinarian is called to a swine operation to investigate an outbreak of high fever, anorexia, and vesicular lesions on the snouts and coronary bands of multiple pigs. What is the most critical and immediate first action for the veterinarian to take?

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

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

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

Question 41: Which of the following is the most critical component of a biosecurity program to prevent the introduction of infectious diseases into a closed beef cow-calf herd?

Testing and quarantining all newly purchased animals. (Correct answer)
Requiring all visitors to wear disposable plastic boots.
Vaccinating the resident herd for all common regional diseases.
Maintaining a double-fenced perimeter to prevent nose-to-nose contact.

Correct answer: Testing and quarantining all newly purchased animals.

The introduction of new animals poses the highest risk for introducing new pathogens into an established herd. A strict protocol of testing for key diseases and quarantining new animals for a minimum of 30 days is the most critical biosecurity measure. This allows for observation, acclimatization, and re-testing before commingling. While other measures like visitor protocols and boundary fences are important parts of a comprehensive biosecurity plan, they are secondary to managing the risk from new animal introductions.

Question 42: A 7-year-old intact male Boxer with a known history of dilated cardiomyopathy requires anesthesia for a splenic mass removal. Which induction protocol is MOST appropriate to minimize myocardial depression while providing adequate anesthesia depth?

Ketamine 5 mg/kg IV with diazepam 0.5 mg/kg IV combination
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
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 43: A beef cow has been in second-stage labor for 90 minutes with no calf produced. Vaginal examination reveals a calf in dorsal longitudinal presentation with both forelimbs retained. Which corrective manipulation should be performed?

Administer oxytocin 20 IU IV to increase uterine contractions
Repel the head, extend and cup each forelimb in turn, then reposition in anterior presentation before applying traction (Correct answer)
Perform fetotomy of the head to relieve obstruction
Apply traction immediately to the visible head to deliver the calf

Correct answer: Repel the head, extend and cup each forelimb in turn, then reposition in anterior presentation before applying traction

Retained forelimbs (head-only presentation) must be corrected before traction to avoid traumatic brachial plexus injury and uterine laceration. The calf is repelled cranially (pushed back into the uterus) to create space, each forelimb is cupped and brought into extension one at a time, then traction is applied with the calf in normal anterior presentation. Traction on the head alone risks elbow lock and maternal injury.

Question 44: 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?

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

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 45: A 3-year-old intact male cat presents with acute onset of pelvic limb paralysis, cold limbs below the stifle, absent femoral pulses bilaterally, and cyanotic nail beds. The most likely diagnosis is:

Fibrocartilaginous embolism (FCE) of the thoracolumbar spinal cord
Traumatic spinal cord injury with T3-L3 myelopathy
Aortic thromboembolism (ATE) secondary to hypertrophic cardiomyopathy (Correct answer)
Botulism with flaccid tetraplegia

Correct answer: Aortic thromboembolism (ATE) secondary to hypertrophic cardiomyopathy

Aortic thromboembolism in cats classically presents as the 'SAD' triad: Sudden onset, Asymmetric or bilateral pelvic limb paresis/paralysis, and Devastating pain. Cold, paralyzed limbs with absent femoral pulses and cyanotic nail beds (ischemia distal to the thrombus at the aortic trifurcation) are pathognomonic. Most cases have underlying hypertrophic cardiomyopathy. FCE is painless; spinal trauma has a history of injury.

Question 46: Which of the following reproductive strategies describes the boa constrictor?

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

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

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

Question 47: 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
Serum electrolytes
Urinalysis
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 48: A 7-year-old male castrated Persian cat presents with episodic vomiting, weight loss, and small-intestinal diarrhea. Jejunal biopsy reveals lymphocytic-plasmacytic infiltration with villous blunting. Serum folate is elevated and cobalamin is severely low. Which statement best explains the cobalamin deficiency in this patient?

Hepatic failure impairing cobalamin storage and enterohepatic recirculation
Bacterial overgrowth consuming cobalamin before ileal absorption can occur
Cobalamin malabsorption due to loss of ileal cubilin/amnionless receptors from mucosal disease (Correct answer)
Exocrine pancreatic insufficiency causing absent intrinsic factor production

Correct answer: Cobalamin malabsorption due to loss of ileal cubilin/amnionless receptors from mucosal disease

In cats, intrinsic factor is produced by the pancreas but cobalamin absorption occurs via cubilin/amnionless receptor complexes in the ileum. Diffuse small intestinal mucosal disease (as seen here with IBD/lymphoma) damages ileal absorptive receptors, causing cobalamin malabsorption despite normal pancreatic IF production. Elevated folate suggests proximal small intestinal bacterial overgrowth or intact proximal mucosa with bacteria producing folate. EPI would cause both low folate and low cobalamin. Severe ileal mucosal loss is the direct mechanism here.

Question 49: 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)
Fetlock synovitis (Correct answer)
Extensor tendon laceration
Sesamoiditis

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 50: A veterinarian is designing a Johne's disease (paratuberculosis) test-and-cull program for a 500-cow closed dairy herd. The herd-level prevalence is estimated at 8%. The diagnostic lab offers two ELISA tests: Test A (sensitivity 45%, specificity 99%) and Test B (sensitivity 28%, specificity 99.8%). The producer's primary goal is to eliminate all infected animals without culling excessive false-positives. Which testing strategy is most appropriate?

Use Test B alone annually, because its higher specificity minimizes false-positive culls at this prevalence
Use fecal PCR as the primary test rather than ELISA, because ELISA sensitivity is inadequate below 10% prevalence
Use Test A as a screen, then confirm positives with Test B in series, to maximize both sensitivity and specificity (Correct answer)
Use Test A alone annually, because its higher sensitivity identifies more infected animals per test cycle

Correct answer: Use Test A as a screen, then confirm positives with Test B in series, to maximize both sensitivity and specificity

At 8% prevalence, even a 99% specific test yields a positive predictive value (PPV) of approximately 82% for Test A and 97% for Test B when used alone. However, Test A's sensitivity (45%) catches more true positives per annual round. Using Test A as a screen (higher sensitivity captures more infected animals) and Test B as a confirmatory test in series (very high specificity eliminates most false positives) optimizes the program: sensitivity of the series is limited by Test A (acceptable), but specificity approaches Test B's 99.8%, making PPV very high and preventing unnecessary culls. Fecal PCR is valuable but not superior in all low-prevalence settings and is more expensive per sample; it is not 'always preferred' below 10% prevalence. The series testing strategy is the standard of practice for Johne's control programs.

Question 51: A 9-year-old spayed female Labrador Retriever presents with a 4-month history of progressive rear limb weakness. The owner reports the dog can walk but stumbles, especially on slippery floors, and has difficulty rising. On neurologic exam, you observe proprioceptive deficits in both pelvic limbs (worse on the right), preserved but slightly diminished patellar reflexes bilaterally, and normal perineal reflex and anal tone. MRI of the thoracolumbar spine is unremarkable. Which diagnosis best explains this constellation of findings?

Lumbosacral stenosis (cauda equina syndrome)
Myasthenia gravis (focal form)
Degenerative myelopathy (Correct answer)
Fibrocartilaginous embolism at T12-T13

Correct answer: Degenerative myelopathy

Degenerative myelopathy (DM) classically presents as a slowly progressive, non-painful upper motor neuron (UMN) spastic paraparesis in older large-breed dogs (especially Labradors, GSDs, and Boxers), with proprioceptive ataxia and no sensory deficits. A critical diagnostic clue is that MRI is normal early in the disease — DM is a clinical and genetic diagnosis (SOD1 mutation) confirmed histopathologically. FCE would present acutely, not over 4 months. Cauda equina syndrome causes hyporeflexia, tail and perineal deficits, and lumbosacral pain. Focal MG causes megaesophagus/regurgitation, not proprioceptive deficits.

Question 52: A bird (psittacine) presents with a bacterial infection. Which antibiotic class should be avoided due to risk of fatal dysbiosis?

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

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 53: 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
Enlarged globoid cardiac silhouette without pleural effusion (Correct answer)
Discontinuity of the diaphragmatic line
Gas-filled bowel loops in the pleural space

Correct answer: Enlarged globoid cardiac silhouette without pleural effusion

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

Question 54: A cat is presented for evaluation of recurrent upper respiratory signs and oral ulcerations. FHV-1 PCR is positive on conjunctival swab. Which of the following statements about feline herpesvirus-1 pathophysiology is MOST accurate?

Latency is established exclusively in trigeminal ganglia, and reactivation consistently produces clinical disease
The virus establishes persistent viremia, making antigen testing on serum the preferred diagnostic method
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)

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 55: A cat's thoracic CT shows a pulmonary mass with a 'halo sign' (ground-glass opacity surrounding a solid nodule). This finding in cats is most associated with:

Fungal pneumonia (cryptococcosis) (Correct answer)
Feline asthma
Primary lung adenocarcinoma
Pulmonary lymphoma

Correct answer: Fungal pneumonia (cryptococcosis)

The CT halo sign represents hemorrhage or inflammatory infiltrate surrounding a fungal nodule and is classically associated with angioinvasive fungal infections including Cryptococcus in cats.

Question 56: A 7-year-old intact female ferret (Mustela putorius furo) presents with bilateral symmetric alopecia starting at the tail base, a 20% body weight loss over 2 months, a palpable cranial abdominal mass, and a blood glucose of 38 mg/dL. Which combination of conditions MOST likely explains this presentation, and what is the underlying endocrine interrelationship?

Adrenal neoplasia causing androgen excess and concurrent insulinoma; adrenal androgens may promote pancreatic beta-cell hyperplasia (Correct answer)
Ovarian remnant syndrome causing estrogen-mediated alopecia and concurrent hepatic lipidosis with hypoglycemia
Primary hypothyroidism causing alopecia and cold intolerance with secondary insulinoma from reduced hepatic glucose output
Hyperadrenocorticism causing insulin resistance and secondary reactive hypoglycemia with concurrent lymphoma

Correct answer: Adrenal neoplasia causing androgen excess and concurrent insulinoma; adrenal androgens may promote pancreatic beta-cell hyperplasia

This ferret has classic 'ferret adrenal disease' (hyperandrogenism from adrenocortical neoplasia or hyperplasia) presenting with tail-base alopecia and concurrent insulinoma (pancreatic beta-cell tumor). In North American domestic ferrets, adrenal disease and insulinoma co-occur at rates significantly above chance — estimated at 30–50% concurrent presentation. Research suggests adrenal androgens, particularly androstenedione, may have a trophic effect on pancreatic islet cells, promoting beta-cell hyperplasia and neoplasia. The hypoglycemia (38 mg/dL) with the abdominal mass and weight loss confirms insulinoma alongside the adrenal signs.

Question 57: A 12-year-old Thoroughbred mare undergoes an emergency exploratory celiotomy for a large colon volvulus. Which of the following is the most common post-operative complication that can significantly impact morbidity and mortality in the immediate post-surgical period?

Post-operative ileus (POI) (Correct answer)
Incisional infection
Adhesion formation
Laminitis

Correct answer: Post-operative ileus (POI)

Post-operative ileus (POI), characterized by a lack of normal intestinal motility, is a very common and serious complication following equine colic surgery, particularly after procedures involving the small intestine or significant large colon manipulation. It can lead to gastric reflux, pain, and endotoxemia, and is a leading cause of post-operative death or euthanasia. While incisional infections, laminitis, and adhesions are also significant complications, POI is a more immediate and frequent life-threatening concern in the first few days post-surgery.

Question 58: 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?

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

Correct answer: Vestibulovaginal stenosis (vaginal stricture)

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

Question 59: 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 60: A beef cattle producer wishes to use a medicated feed containing chlortetracycline to control an active anaplasmosis infection. What must a veterinarian provide to legally authorize the producer to obtain and use this feed?

A signed letter on clinic letterhead describing the intended use.
A valid Veterinary Feed Directive (VFD) order. (Correct answer)
A standard prescription on a state-approved script pad.
Verbal authorization communicated directly to the feed mill.

Correct answer: A valid Veterinary Feed Directive (VFD) order.

The FDA classifies chlortetracycline as a medically important antimicrobial. Its use in or on animal feed is regulated under the Veterinary Feed Directive (VFD) final rule. To legally purchase and administer this medicated feed, the producer must have a valid VFD order issued by a licensed veterinarian with whom they have an established veterinarian-client-patient relationship (VCPR).

Question 61: A green iguana is presented with metabolic bone disease. Which nutritional deficiency is most commonly responsible?

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

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

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

Question 62: When using a whole-herd approach to control bovine respiratory disease (BRD) in a stocker operation, what does the term 'pull rate' refer to?

Number of cattle shipped per week to slaughter
Proportion of animals vaccinated at arrival processing
Rate at which calves are pulled from the pasture for processing
Percentage of animals removed from the pen for individual treatment due to BRD signs (Correct answer)

Correct answer: Percentage of animals removed from the pen for individual treatment due to BRD signs

Pull rate measures the proportion of cattle identified and pulled from pens for individual BRD treatment, serving as a key performance indicator of disease prevalence and health management efficacy.

Question 63: 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?

Ectopic thyroid carcinoma
Thymoma
Cranial mediastinal lymphoma
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 64: How would you handle FIP with ocular involvement?

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

Correct answer: Topical steroids and atropine

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

Question 65: A 4-year-old Labrador Retriever is presented for acute vomiting and hematemesis 36 hours after accidental ingestion of ibuprofen. BUN is 85 mg/dL, creatinine is 6.2 mg/dL, and urinalysis shows glucosuria with isosthenuria. Renal biopsy reveals necrosis of the medullary thick ascending limb. Which mechanism BEST explains this specific distribution of renal injury?

Direct tubular toxicity of ibuprofen metabolites concentrated in the cortical proximal tubules
Inhibition of thromboxane A2 causing glomerular thrombosis
Inhibition of prostaglandin-mediated vasodilation in the renal medulla leading to hypoxic necrosis (Correct answer)
Systemic hypoperfusion causing cortical ischemia

Correct answer: Inhibition of prostaglandin-mediated vasodilation in the renal medulla leading to hypoxic necrosis

NSAIDs inhibit cyclooxygenase, blocking prostaglandin synthesis. In the renal medulla, prostaglandins (particularly PGE2 and PGI2) are critical for maintaining vasodilation against the high medullary osmotic gradient and countercurrent vasoconstrictive environment. The medullary thick ascending limb (mTAL) is metabolically active yet receives relatively hypoxic blood, making it uniquely dependent on prostaglandin-mediated vasodilation. NSAID inhibition causes vasoconstriction and medullary ischemia, selectively damaging the mTAL. This differs from the cortical proximal tubule injury seen with aminoglycosides.

Question 66: Which scoring system is validated for assessing acute pain in cats in the postoperative period?

Colorado State University Feline Acute Pain Scale (Correct answer)
Glasgow Composite Measure Pain Scale – Short Form (CMPS-SF)
Numeric Rating Scale (NRS) only
UNESP-Botucatu Multidimensional Composite Pain Scale

Correct answer: Colorado State University Feline Acute Pain Scale

The Colorado State University Feline Acute Pain Scale is a validated, species-specific tool widely used in clinical settings to assess acute pain in cats.

Question 67: 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
Carpus and proximal metacarpal region
Elbow and shoulder
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 68: A 9-year-old cat with a 6-month history of recurrent upper respiratory signs, bilateral corneal sequestra, and chronic gingivostomatitis has positive FHV-1 PCR on conjunctival swab. The owner asks about antiviral therapy. Which statement regarding famciclovir use in cats is MOST accurate?

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

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

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

Question 69: A geriatric cat with known HCM develops signs of congestive heart failure with pulmonary edema. Which diuretic is the cornerstone of initial CHF management?

Furosemide (Correct answer)
Spironolactone
Torsemide
Hydrochlorothiazide

Correct answer: Furosemide

Furosemide (a loop diuretic) is the cornerstone of acute and chronic CHF management in cats with HCM-associated pulmonary edema.

Question 70: A horse with forelimb lameness has a positive response to hoof testers over the medial heel region. After palmar digital nerve block the lameness is only partially improved. The MOST appropriate next step is:

Apply a bar shoe and reassess in 6 weeks
Repeat the palmar digital block with a higher volume
Perform an intra-articular coffin joint block (Correct answer)
Block the navicular bursa directly

Correct answer: Perform an intra-articular coffin joint block

When a palmar digital block provides only partial improvement, an intra-articular coffin joint block helps determine whether the DIP joint is contributing to the residual lameness.

Question 71: A 9-year-old Paint Horse gelding presents with a 3-month history of weight loss, fever of unknown origin, and a firm, non-painful enlargement in the inguinal region. Aspiration reveals thick, greenish pus. What is the most likely diagnosis?

Ulcerative lymphangitis (Corynebacterium pseudotuberculosis abscess) (Correct answer)
Squamous cell carcinoma of the inguinal lymph node
Strangles (Streptococcus equi subsp. equi) abscessation
Inguinal hernia strangulation

Correct answer: Ulcerative lymphangitis (Corynebacterium pseudotuberculosis abscess)

Corynebacterium pseudotuberculosis causes caseous lymphadenitis (pigeon fever) with characteristic thick, greenish pus in firm subcutaneous or inguinal abscesses, often with systemic signs.

Question 72: On abdominal radiographs, a 'string of pearls' gas pattern within the bowel wall is most suggestive of which condition?

Ileus
Foreign body obstruction
Intussusception
Pneumatosis intestinalis (Correct answer)

Correct answer: Pneumatosis intestinalis

Pneumatosis intestinalis (gas within the intestinal wall) produces a 'string of pearls' or bubbly gas pattern and is associated with intestinal necrosis or ischemia.

Question 73: Cats develop more severe Heinz body hemolytic anemia from propylene glycol exposure than dogs given equivalent doses. Which mechanistic explanation best accounts for this species difference?

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

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

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

Question 74: 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?

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

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 75: A 7-year-old intact male Golden Retriever presents with a 3-week history of progressive tetraparesis, bilateral pelvic limb weakness, and marked muscle wasting. MRI reveals an intradural-extramedullary mass at T3. CSF analysis shows albuminocytologic dissociation. Histopathology of the mass is most consistent with which diagnosis?

Nephroblastoma
Meningioma
Peripheral nerve sheath tumor (Correct answer)
Spinal cord astrocytoma

Correct answer: Peripheral nerve sheath tumor

Peripheral nerve sheath tumors (PNSTs) are the most common intradural-extramedullary spinal tumors in dogs, particularly large breeds. They arise from Schwann cells or perineural fibroblasts, and CSF frequently shows albuminocytologic dissociation (elevated protein without significant pleocytosis) due to blood-brain barrier disruption adjacent to the mass. Meningiomas are more common in the intracranial compartment in dogs. Nephroblastomas are typically intramedullary and occur in young dogs (usually <3 years) at T10–L2. Astrocytomas are intramedullary.

Question 76: What is the gold standard diagnostic test for confirming wet (effusive) FIP?

Effusion fluid RT-PCR for FCoV with immunostaining of macrophages (Correct answer)
Serum coronavirus antibody titer >1:3200
Abdominal ultrasound showing mesenteric lymphadenopathy
Complete blood count showing lymphopenia

Correct answer: Effusion fluid RT-PCR for FCoV with immunostaining of macrophages

Immunostaining for FCoV antigen within macrophages in effusion fluid or tissue biopsy is the gold standard for definitive FIP diagnosis.

Question 77: Which feline coronavirus (FCoV) mutation is classically associated with the transition from enteric infection to feline infectious peritonitis (FIP)?

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

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 78: A cat on long-term phenobarbital for seizure control is started on chloramphenicol for a resistant infection. Two weeks later the owner reports markedly increased sedation and ataxia with no dose change of phenobarbital. What is the most likely pharmacokinetic explanation?

Chloramphenicol inhibits hepatic cytochrome P450 enzymes, reducing phenobarbital clearance and raising its serum concentration (Correct answer)
Chloramphenicol directly potentiates GABA-A receptor activity, synergizing with phenobarbital
Chloramphenicol induces P-glycoprotein, increasing CNS penetration of phenobarbital
Chloramphenicol competes with phenobarbital for plasma protein binding, increasing free phenobarbital fraction

Correct answer: Chloramphenicol inhibits hepatic cytochrome P450 enzymes, reducing phenobarbital clearance and raising its serum concentration

Chloramphenicol is a potent inhibitor of hepatic cytochrome P450 enzymes (particularly CYP2B and CYP3A isoforms) in cats. Phenobarbital is primarily metabolized by these hepatic CYP enzymes. When chloramphenicol inhibits phenobarbital's metabolism, clearance decreases and phenobarbital plasma concentrations rise significantly — often into toxic ranges — despite no change in dose. This is a clinically important drug interaction in feline practice. Phenobarbital monitoring (serum levels) is mandatory when adding chloramphenicol, and dose reduction is frequently required.

Question 79: In nuclear scintigraphy used in veterinary medicine, which radiopharmaceutical is most commonly used for bone scanning in dogs?

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

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 80: Which antiparasitic drug has a narrow safety margin in cats and can cause mydriasis, ataxia, tremors, and death if overdosed, particularly in debilitated individuals?

Fenbendazole
Selamectin
Praziquantel
Ivermectin (Correct answer)

Correct answer: Ivermectin

Ivermectin toxicity in cats causes CNS signs by enhancing GABA-mediated inhibition; cats lack MDR1 mutation but are still sensitive to overdose.

Question 81: A 9-year-old cat presents with pleural effusion. Thoracocentesis yields a fluid with total protein 5.2 g/dL, nucleated cell count 4,200 cells/µL (predominantly non-degenerate neutrophils and macrophages), and a cholesterol-to-triglyceride ratio less than 1. Fluid triglycerides are 320 mg/dL. What is the MOST likely diagnosis?

Feline infectious peritonitis (FIP) with pleural involvement
Pyothorax secondary to migrating foreign body
Chylothorax (Correct answer)
Cardiac-origin transudative pleural effusion

Correct answer: Chylothorax

Chylothorax is characterized by a milky, triglyceride-rich effusion. The hallmark diagnostic criteria include pleural fluid triglycerides exceeding serum triglycerides (and typically >100 mg/dL) and a cholesterol-to-triglyceride ratio less than 1. Cytology typically shows small lymphocytes and non-degenerate neutrophils/macrophages, consistent with this case. FIP effusions are typically high-protein exudates but with lower cell counts and a higher cholesterol:triglyceride ratio. Pyothorax produces a septic exudate with degenerate neutrophils and intracellular bacteria. A pure transudate would have low protein and low cellularity.

Question 82: Nuclear scintigraphy (bone scan) in equine lameness is particularly valuable for identifying:

Soft tissue injuries with low bone involvement
Nerve compression along the digital sheath
Areas of increased bone remodeling before radiographic changes appear (Correct answer)
Joint effusion and synovial inflammation

Correct answer: Areas of increased bone remodeling before radiographic changes appear

Bone scintigraphy detects areas of increased osteoblastic activity and bone remodeling that may precede visible radiographic changes, making it useful for early stress fractures and occult bone pain.

Question 83: A veterinarian discharges a post-obstructed cat with buprenorphine prescribed for sublingual (oral transmucosal) administration at home. She explains to the owner that this route achieves good bioavailability in cats but would not work nearly as well if given the same way to a dog. Which physiological property of cats most directly explains this species difference in sublingual buprenorphine absorption?

Cats have a significantly higher density of mu-opioid receptors in the buccal mucosa, enabling receptor-mediated transcytosis of buprenorphine
The alkaline salivary pH in cats (~8.5–9.0) maintains buprenorphine predominantly in its non-ionized, lipid-soluble form, facilitating passive mucosal absorption (Correct answer)
Feline sublingual vasculature bypasses hepatic first-pass metabolism via direct lymphatic drainage into the thoracic duct
Cats express lower levels of P-glycoprotein efflux pumps in oral epithelium, reducing active buprenorphine efflux back into the oral cavity

Correct answer: The alkaline salivary pH in cats (~8.5–9.0) maintains buprenorphine predominantly in its non-ionized, lipid-soluble form, facilitating passive mucosal absorption

Cats have an alkaline oral/salivary pH of approximately 8.5–9.0, which is close to buprenorphine's pKa (~8.24). At this pH, a substantial proportion of buprenorphine molecules are in the non-ionized, lipid-soluble form that readily crosses lipid bilayer membranes — achieving approximately 38–53% bioavailability via the oral transmucosal route. In dogs, the more acidic oral pH (~7.5) shifts the equilibrium toward the ionized, water-soluble form that poorly penetrates mucosa, making sublingual administration ineffective. This is a key pharmacokinetic reason why OTM buprenorphine is a practical analgesic route in cats but not dogs.

Question 84: 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 toxicity in cats manifests primarily as nephrotoxicity and peripheral neuropathy, identical to other species
Cisplatin can be used safely in cats at doses 50% lower than those used in dogs with aggressive IV fluid diuresis
Cisplatin is safe in cats when combined with ondansetron pretreatment to blunt the acute cytokine-mediated response
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 85: A 3-year-old indoor cat presents with pleural effusion, hyperglobulinemia (total protein 10.2 g/dL), and a pleural fluid albumin-to-globulin ratio of 0.3. FIP coronavirus PCR on the effusion is positive. Which additional finding would MOST strongly support effusive FIP over other causes of pleural effusion?

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

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

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

Question 86: A 7-year-old Warmblood show jumper presents with intermittent right forelimb lameness that worsens after flexion of the distal limb. Radiographs reveal subchondral bone cysts in the medial femoral condyle. Intra-articular analgesia of the femoropatellar joint provides 70% improvement. Which treatment approach has demonstrated the highest long-term success rate for return to athletic function in horses with large (>15 mm) medial femoral condyle cysts?

Subchondral bone grafting via arthroscopy
Systemic bisphosphonate therapy combined with rest
Conservative management with intra-articular hyaluronic acid every 60 days
Arthroscopic debridement with intralesional corticosteroid injection (Correct answer)

Correct answer: Arthroscopic debridement with intralesional corticosteroid injection

Arthroscopic debridement combined with intralesional corticosteroid injection (typically triamcinolone acetonide) into the cyst lining is the gold-standard surgical treatment for large medial femoral condyle cysts. This technique disrupts the fibrous cyst lining that maintains the cystic cavity and delivers high local concentrations of corticosteroid, which reduces the inflammatory mediators driving bone resorption. Studies show return-to-athletic-function rates of 60–75% with this approach, superior to conservative management or bone grafting alone for cysts >15 mm.

Question 87: Which Salmonella serotype is most commonly associated with poultry products and represents the leading cause of salmonellosis in the US?

Salmonella Dublin
Salmonella Enteritidis (Correct answer)
Salmonella Choleraesuis
Salmonella Typhi

Correct answer: Salmonella Enteritidis

Salmonella Enteritidis is the most common serotype linked to poultry and eggs and is a major cause of human foodborne illness in the US.

Question 88: During a PRRS (Porcine Reproductive and Respiratory Syndrome) outbreak investigation, a veterinary epidemiologist calculates a basic reproduction number (R₀) of 3.8 for the index swine production system. The system achieves 70% sow vaccination coverage with a vaccine that has 60% efficacy against transmission. What is the approximate effective reproduction number (Rₑ) after vaccination, and does it cross the epidemic threshold?

Rₑ ≈ 1.5; above threshold — epidemic continues
Rₑ ≈ 2.2; above threshold — epidemic continues (Correct answer)
Rₑ ≈ 0.9; below threshold — epidemic controlled
Rₑ ≈ 1.1; above threshold — epidemic continues

Correct answer: Rₑ ≈ 2.2; above threshold — epidemic continues

The effective reproduction number after vaccination is calculated as Rₑ = R₀ × (1 − vaccine efficacy × coverage) = 3.8 × (1 − 0.60 × 0.70) = 3.8 × (1 − 0.42) = 3.8 × 0.58 ≈ 2.2. Since Rₑ > 1, the epidemic threshold has not been crossed and transmission will continue, though at a reduced rate. To achieve herd immunity (Rₑ < 1), the product of efficacy × coverage would need to exceed 1 − 1/R₀ = 1 − 1/3.8 ≈ 0.74 (74%), meaning either higher coverage or a more efficacious vaccine is required.

Question 89: A 7-year-old jersey cow is examined for an irregular pelvic gait that began in the right hind leg a month ago but has already spread to the left limb. She mated with a bull last month, the dairy farmer mentions. The cow can move her pelvic limbs forward, but she does it with a dorsally buckled metatarsophalangeal joint and an excessively flexed (dropping) tarsus. On all of the surfaces of the pelvic limbs, pain perception was normal. Anal tone and tail function were both normal. Which of the following nerves' malfunction is the cause of these physical examination results?

Obturator nerve
Sciatic nerve
Tibial nerve (Correct answer)
Peroneal nerve

Correct answer: Tibial nerve

The described gait abnormalities – dorsally buckled metatarsophalangeal joint and an excessively flexed (dropping) tarsus – are characteristic signs of tibial nerve dysfunction. The tibial nerve innervates muscles responsible for hock extension and digital flexion. Damage to this nerve results in the inability to extend the hock and flex the digits, leading to the observed 'dropped hock' and buckled toe appearance.

Question 90: A 7-year-old intact female Boxer presents with polyuria, polydipsia, and a serum sodium of 157 mEq/L. She is not pregnant. Endogenous ACTH stimulation test is normal. Which diagnosis is most consistent with these findings?

Primary hyperaldosteronism
Diestrus-associated acromegaly or progesterone-induced GH excess (Correct answer)
Diabetes insipidus
Hyperadrenocorticism

Correct answer: Diestrus-associated acromegaly or progesterone-induced GH excess

Progesterone during diestrus stimulates mammary GH secretion in intact females, causing insulin resistance, PU/PD, and hypernatremia (acromegaly-like syndrome).

Question 91: 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?

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

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 92: Which fluoroquinolone is known to cause retinal degeneration in cats, particularly at high doses?

Enrofloxacin (Correct answer)
Ciprofloxacin
Pradofloxacin
Marbofloxacin

Correct answer: Enrofloxacin

Enrofloxacin at high doses has been associated with acute retinal degeneration and blindness in cats, and dosing must be carefully limited in this species.

Question 93: A 12-year-old Hanoverian mare develops acute severe lameness 48 hours after a routine intra-articular corticosteroid injection in the stifle. The joint is severely swollen, warm, and painful. Synoviocentesis is performed. Which synovial fluid finding would most strongly indicate post-injection septic arthritis rather than a corticosteroid flare?

WBC of 3,000/μL with 60% mononuclear cells
WBC of 60,000/μL with 95% neutrophils and positive bacterial culture (Correct answer)
Xanthochromic fluid with red blood cells
Slightly elevated protein with no change in cell count

Correct answer: WBC of 60,000/μL with 95% neutrophils and positive bacterial culture

Post-injection septic arthritis is confirmed by markedly elevated WBC (>30,000/μL) with predominantly neutrophils and positive bacterial culture, distinguishing it from a transient corticosteroid flare.

Question 94: A cat rescue organization routinely tests all cats for FeLV and FIV using a point-of-care ELISA combo test. A 2-year-old cat tests FIV antibody-positive. The organization plans to euthanize the cat per their protocol. The attending veterinarian recommends Western blot confirmatory testing. Which scenario would produce the MOST clinically significant false-positive FIV ELISA result and thus most strongly justify confirmatory testing?

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

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

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

Question 95: Chlamydia felis infection in cats primarily affects which organ system?

Urinary tract causing cystitis
Conjunctiva causing persistent unilateral then bilateral conjunctivitis (Correct answer)
Gastrointestinal tract causing vomiting and diarrhea
Respiratory tract causing severe pneumonia

Correct answer: Conjunctiva causing persistent unilateral then bilateral conjunctivitis

Chlamydia felis is an obligate intracellular pathogen that primarily causes chronic conjunctivitis, often beginning unilaterally before becoming bilateral.

Question 96: Which drug is used to treat hyperthyroidism in cats by blocking thyroid hormone synthesis?

Levothyroxine
Methimazole (Correct answer)
Radioactive iodine (I-131)
Propranolol

Correct answer: Methimazole

Methimazole inhibits thyroid peroxidase, thereby blocking the synthesis of thyroid hormones and is the most common medical management for feline hyperthyroidism.

Question 97: 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 98: A 5-year-old intact female Boxer presents for abdominal radiographs due to acute vomiting. Radiographs reveal a markedly distended, gas-filled stomach with a soft tissue band ('shelf sign') in the mid-gastric region and the pylorus positioned to the left of midline on the VD projection. A small amount of free peritoneal gas is also noted. Which combination of conditions does this radiographic constellation represent?

Simple gastric dilatation with concurrent pneumoperitoneum from recent abdominocentesis
Hiatal hernia with secondary pneumoperitoneum
Gastric dilatation-volvulus (GDV) with gastric perforation (Correct answer)
Gastric foreign body with pyloric obstruction and diaphragmatic hernia

Correct answer: Gastric dilatation-volvulus (GDV) with gastric perforation

The combination of marked gastric gas distension, a 'shelf sign' (also called the 'double bubble' or compartmentalization created by torsion of the gastric wall), and pyloric displacement to the LEFT of midline on the VD view is pathognomonic for GDV. In GDV, the pylorus rotates clockwise (viewed from the patient's caudal aspect) to end up cranial and to the left. The presence of free peritoneal gas (pneumoperitoneum) indicates gastric rupture/perforation, which is a grave complication confirming the need for immediate surgical intervention. This constellation—GDV + perforation—carries the worst prognosis.

Question 99: 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?

Iron deficiency anemia
Immune-mediated hemolytic anemia
Heinz body anemia
Microangiopathic hemolytic anemia associated with DIC (Correct answer)

Correct answer: Microangiopathic hemolytic anemia associated with DIC

Schistocytes (erythrocyte fragments) result from mechanical shearing in fibrin strands during DIC, causing microangiopathic hemolytic anemia.

Question 100: A 6-year-old warmblood gelding has MRI findings consistent with a deep digital flexor tendon (DDFT) lesion within the hoof capsule. Which treatment has shown the most promise for core lesions of the DDFT in the foot?

Deep digital flexor tenotomy
Palmar digital neurectomy alone
Full-limb casting for 6 months
Intralesional injection of platelet-rich plasma (PRP) combined with corrective shoeing (Correct answer)

Correct answer: Intralesional injection of platelet-rich plasma (PRP) combined with corrective shoeing

Intralesional PRP combined with corrective shoeing (heel elevation and/or egg bar shoe) is the current evidence-based approach for DDFT core lesions within the foot.

Question 101: A horse with chronic forelimb lameness shows 'pointing' at rest — standing with the affected limb extended cranially. This posture is MOST commonly associated with:

Laminitis
Extensor tendon injury
Coffin joint arthritis
Navicular syndrome (Correct answer)

Correct answer: Navicular syndrome

Pointing at rest is a classic postural sign of navicular syndrome, as the horse reduces weight on the heel to relieve pressure on the navicular apparatus.

Question 102: Which of the following is the recommended nutritional strategy to prevent osteochondrosis dissecans (OCD) in fast-growing market pigs?

Ensuring Ca:P ratio of approximately 1.2:1 with adequate vitamin D and controlled growth rate (Correct answer)
Supplementing vitamin E and selenium to prevent oxidative cartilage damage
High-calcium, low-phosphorus diet to maximize bone density
Restricting dietary lysine to slow growth rate

Correct answer: Ensuring Ca:P ratio of approximately 1.2:1 with adequate vitamin D and controlled growth rate

OCD in pigs is a developmental orthopedic disease linked to rapid growth, genetic selection for leanness, and mineral imbalances. A Ca:P ratio near 1.2:1 with adequate vitamin D3 and avoiding excess growth rate are the primary preventive strategies. Extreme calcium restriction or excess both impair endochondral ossification.

Question 103: A 3-year-old intact male cat tests FIV-positive. What is the most reliable route of transmission for this virus?

Vertical transmission via placenta
Fomite contact
Bite wounds (Correct answer)
Shared food bowls

Correct answer: Bite wounds

FIV is most efficiently transmitted through bite wounds because high viral loads are present in saliva.

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?

Administer phenylephrine at 1–2 mcg/kg/min
Increase dobutamine to 10 mcg/kg/min
Add norepinephrine at 0.1–0.5 mcg/kg/min (Correct answer)
Switch to vasopressin at 0.5 mU/kg/min

Correct answer: Add norepinephrine at 0.1–0.5 mcg/kg/min

Inhalant anesthesia (isoflurane/sevoflurane) in horses causes significant vasodilation and myocardial depression. When dobutamine (a β1/β2 agonist that increases cardiac output but causes vasodilation) is insufficient, norepinephrine is the drug of choice because it provides both α1-mediated vasoconstriction (increases SVR) and β1 inotropic support. Phenylephrine is a pure α1 agonist that raises SVR but can cause reflex bradycardia and reduced cardiac output—problematic in an already-compromised patient. Vasopressin can be used in refractory cases but is not typically a second-line agent. Escalating dobutamine alone will worsen vasodilation.

Question 105: Toxoplasma gondii infection in pregnant women is most commonly acquired in the US through:

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

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

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

Correct answer: Thymic lymphoma

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

Question 107: On thoracic radiographs of a dog, you notice the cardiac silhouette occupies more than 75% of the thoracic width on the VD view. What does this most likely indicate?

Pleural effusion
Pneumothorax
Pulmonary consolidation
Cardiomegaly (Correct answer)

Correct answer: Cardiomegaly

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

Question 108: A horse presents with chronic forelimb lameness localized to the coffin joint. Radiographs show marked osteolysis and periarticular new bone formation. Synoviocentesis yields thick, turbid fluid with 85,000 WBC/μL (>90% neutrophils) and a glucose concentration much lower than serum. What is the next most critical step?

Perform through-and-through joint lavage and systemic antimicrobials (Correct answer)
Perform arthroscopic debridement under general anesthesia immediately without lavage
Initiate systemic corticosteroids
Repeat radiographs in 2 weeks

Correct answer: Perform through-and-through joint lavage and systemic antimicrobials

Septic arthritis requires immediate joint lavage (through-and-through or arthroscopic) combined with systemic and intra-articular antimicrobials to remove bacteria and inflammatory mediators.

Question 109: 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?

Atenolol
Digoxin
Furosemide (Correct answer)
Amlodipine

Correct answer: Furosemide

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

Question 110: 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
Vector-borne transmission of Cryptosporidium parvum; EPA under the Safe Drinking Water Act
Fecal-oral transmission of Escherichia coli O157:H7 via raw milk; FDA under the Grade A Pasteurized Milk Ordinance (PMO) (Correct answer)
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 111: A 2-year-old intact female sugar glider (Petaurus breviceps) presents with a 1 cm, firm, non-painful mass on the dorsal midline of the head. The owner reports the mass appeared over 2 weeks. On exam, the animal is bright and alert with no neurologic signs. Cytology of a fine-needle aspirate reveals cells with abundant pale cytoplasm, round nuclei, and prominent nucleoli in a proteinaceous background. What is the most likely diagnosis?

Lymphosarcoma with cutaneous metastasis
Scent gland adenocarcinoma arising from the frontofrontal gland (Correct answer)
Dermatofibrosarcoma of the scalp secondary to repetitive self-trauma
Abscess secondary to conspecific bite wound

Correct answer: Scent gland adenocarcinoma arising from the frontofrontal gland

Male sugar gliders have a prominent frontofrontal (forehead) scent gland, but females can develop neoplasia of the same glandular tissue. Adenocarcinoma of the frontofrontal scent gland presents as a rapidly growing firm mass on the dorsal midline of the head. Cytology typically reveals epithelial cells with abundant pale cytoplasm and prominent nucleoli in a proteinaceous background consistent with glandular secretory tissue gone malignant. Dermatofibrosarcoma and lymphoma are less likely without inflammatory history or systemic signs. An abscess would typically show degenerate neutrophils and bacteria.

Question 112: A pet cockatiel presents with nasal discharge, sneezing, and conjunctivitis. Which organism is the most likely causative agent?

Pasteurella multocida
Chlamydia psittaci (Correct answer)
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 113: A dairy producer utilizes a timed artificial insemination (TAI) protocol that includes Ovsynch. Which hormone is administered to cause luteolysis, or regression of the corpus luteum, thereby allowing the cow to return to estrus?

Oxytocin
Gonadotropin-releasing hormone (GnRH)
Prostaglandin F2α (PGF2α) (Correct answer)
Progesterone

Correct answer: Prostaglandin F2α (PGF2α)

Prostaglandin F2α (PGF2α) is the hormone responsible for causing luteolysis, which is the breakdown of the corpus luteum (CL). In synchronization protocols like Ovsynch, PGF2α is given when a mature CL is expected to be present, causing a drop in progesterone and allowing a new follicular wave to progress towards ovulation. GnRH is used to cause ovulation or start a new follicular wave, while progesterone (e.g., in a CIDR) is used to prevent estrus.

Question 114: 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?

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

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

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

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 116: Anaplasmosis in cattle is transmitted primarily by which vector in the US?

Haematobia irritans horn flies
Dermacentor andersoni and Dermacentor variabilis ticks (Correct answer)
Aedes aegypti mosquitoes
Stomoxys calcitrans stable flies

Correct answer: Dermacentor andersoni and Dermacentor variabilis ticks

Anaplasma marginale is transmitted by Dermacentor tick species in the US, though mechanical transmission by biting flies and blood-contaminated instruments also occurs.

Question 117: During recovery from general anesthesia following orthopedic surgery, a horse makes multiple violent attempts to stand and sustains a fracture of the contralateral limb. This type of complication is best prevented by which approach?

Using an assisted recovery system (head/tail ropes) with quiet, padded recovery stall (Correct answer)
Administering acepromazine immediately post-surgery
Placing the horse in dorsal recumbency during recovery
Prolonging anesthesia until the horse is fully awake

Correct answer: Using an assisted recovery system (head/tail ropes) with quiet, padded recovery stall

Assisted recovery using head and tail ropes in a well-padded, quiet stall helps guide the horse to a controlled, coordinated standing position, minimizing the risk of fractures and post-anesthetic myopathy.

Question 118: A 3-year-old intact female Cocker Spaniel is presented with a fever, mucopurulent vaginal discharge, PU/PD, and leukocytosis. Abdominal ultrasound confirms uterine distension. What is the definitive treatment?

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

Correct answer: Ovariohysterectomy

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

Question 119: Which MRI finding is characteristic of syringomyelia (syrinx) in a Cavalier King Charles Spaniel with Chiari-like malformation?

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

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 120: Acetaminophen (paracetamol) toxicity in cats primarily causes which two clinical findings?

Methemoglobinemia and hepatic necrosis (Correct answer)
Acute renal failure and hypertension
Coagulopathy and thrombocytopenia
Hypocalcemia and seizures

Correct answer: Methemoglobinemia and hepatic necrosis

Cats lack sufficient glucuronyl transferase to conjugate acetaminophen, leading to methemoglobinemia (muddy mucous membranes) and hepatic necrosis.

Question 121: A veterinarian wants to use tramadol for postoperative analgesia in a cat. Which metabolic difference limits tramadol's efficacy in cats compared to humans?

Cats rapidly glucuronidate tramadol into an inactive metabolite
Cats over-express mu-opioid receptors, making them hypersensitive to tramadol
Cats have reduced CYP2D6 activity and produce very little O-desmethyltramadol (M1), the active opioid metabolite (Correct answer)
Cats excrete tramadol unchanged in bile, reducing systemic exposure

Correct answer: Cats have reduced CYP2D6 activity and produce very little O-desmethyltramadol (M1), the active opioid metabolite

Cats have low CYP2D6 activity and generate minimal M1 metabolite, so tramadol's analgesic effect via opioid receptors is substantially reduced.

Question 122: 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?

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

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 123: Which of the following is the most critical control point for eliminating Bovine Viral Diarrhea Virus (BVDV) from a beef cow-calf herd?

Identifying and removing persistently infected (PI) animals. (Correct answer)
Implementing a comprehensive fly and vector control program.
Vaccinating all adult animals annually with a modified-live virus (MLV) vaccine.
Treating all clinically ill animals with supportive care and antibiotics.

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

Persistently infected (PI) animals are the primary reservoir and source of BVDV shedding within a herd. They become infected in utero and shed the virus throughout their lives. While vaccination is a key part of prevention, it may not be fully effective in the face of the massive viral load shed by a PI animal. Therefore, the most critical step for eradication is to test for, identify, and remove these PI animals from the population.

Question 124: A cow presents with acute right-sided abomasal displacement progressing to volvulus (RDA/RAV) in a freshly calved dairy cow. Which finding on physical exam is most consistent with this diagnosis?

Bilateral pings with fluid splashing sounds in the lower abdomen
High-pitched ping over a large area on the right side between ribs 9-12, with signs of toxemia and tachycardia (Correct answer)
Left-sided ping in the paralumbar fossa on simultaneous auscultation and percussion
Left-sided rumen atony with no ping detected

Correct answer: High-pitched ping over a large area on the right side between ribs 9-12, with signs of toxemia and tachycardia

Right abomasal volvulus produces a large-area right-sided ping (ribs 9-12), signs of severe toxemia, tachycardia, and rapid cardiovascular deterioration due to venous outflow obstruction.

Question 125: A 12-year-old Warmblood dressage horse presents with a 6-month history of progressive hindlimb ataxia and symmetric weakness. Cervical radiographs show dynamic stenosis at C3-C4. Myelography confirms spinal cord compression only during neck flexion. The owners request surgical intervention. Which procedure is most appropriate?

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

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

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

Question 126: On thoracic radiographs of a dog, which cardiac silhouette finding is most consistent with left atrial enlargement?

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

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 127: Which of the following best describes the pharmacokinetic term 'volume of distribution' (Vd)?

A theoretical volume relating plasma drug concentration to total drug in the body (Correct answer)
The time for plasma drug concentration to decrease by 50%
The fraction of an oral dose reaching systemic circulation
The rate at which a drug is eliminated from the body

Correct answer: A theoretical volume relating plasma drug concentration to total drug in the body

Volume of distribution is a theoretical volume that relates the total amount of drug in the body to the concentration measured in plasma.

Question 128: A 9-year-old Labrador Retriever is diagnosed with stage 3 chronic kidney disease (IRIS). Serum phosphorus is 6.8 mg/dL. Which intervention is most important to slow CKD progression?

Sodium restriction alone
Increased protein supplementation
Phosphate restriction and phosphate binders (Correct answer)
IV fluid diuresis three times weekly

Correct answer: Phosphate restriction and phosphate binders

Phosphate restriction through diet and phosphate binders reduces renal mineralization and is one of the most evidence-based strategies to slow CKD progression.

Question 129: A lateral skull radiograph of an 8-month-old Boxer shows a multilocular, expansile radiolucent lesion of the mandible with a 'soap bubble' internal architecture and cortical thinning without periosteal reaction. The lesion is centered on the mandibular premolar region. Which diagnosis is most consistent, and what additional imaging modality would best characterize the lesion before surgery?

Canine acanthomatous ameloblastoma; CT with bone algorithm for cortical integrity and tooth root involvement (Correct answer)
Dentigerous cyst; dental radiographs only are sufficient for definitive characterization
Osteosarcoma of the mandible; nuclear scintigraphy to detect skip metastases
Multilobular tumor of bone (MLO); MRI for soft-tissue extension into the masticatory muscles

Correct answer: Canine acanthomatous ameloblastoma; CT with bone algorithm for cortical integrity and tooth root involvement

Canine acanthomatous ameloblastoma (CAA, formerly adamantinoma) classically presents in young to middle-aged dogs — particularly Boxers — as an expansile, multilocular 'soap bubble' radiolucent mandibular lesion. Unlike osteosarcoma, CAA is locally invasive but rarely metastasizes; its hallmark is bone invasion without distant spread. CT with a bone algorithm is the standard pre-surgical modality because it precisely delineates cortical penetration, tooth root resorption, and the true extent of bone involvement — critical for planning marginal vs. segmental mandibulectomy. Dentigerous cysts are unilocular pericoronal lucencies, not multilocular. MLO (multilobular osteochondrosarcoma) typically affects the calvarium or hard palate with a 'popcorn' mineralized matrix, not a purely radiolucent jaw lesion.

Question 130: A 3-year-old intact female rabbit is anesthetized for an ovariohysterectomy. Forty minutes into maintenance on 2.5% isoflurane, the rabbit becomes apneic with no response to a sternal rub. SpO2 drops to 82%. Which factor is MOST responsible for this rabbit's increased anesthetic risk compared to dogs and cats?

Rabbits have obligate nasal breathing and a relatively small thoracic cavity with diaphragm-dependent ventilation (Correct answer)
Rabbits lack µ-opioid receptors, making premedication protocols less effective
Rabbits metabolize inhalant agents 3× faster due to their high surface-area-to-volume ratio
Rabbits have a higher requirement for isoflurane (MAC ~2.05%) than most domestic species

Correct answer: Rabbits have obligate nasal breathing and a relatively small thoracic cavity with diaphragm-dependent ventilation

Rabbits are obligate nasal breathers with a diaphragm-dependent respiratory pattern and a relatively large abdominal visceral mass that restricts diaphragmatic excursion in dorsal recumbency. They have a narrow thoracic cavity relative to body size, poor respiratory reserve, and a highly sensitive respiratory center that is easily depressed by inhalants. These anatomical features make apnea common at surgical planes of anesthesia and make ventilatory support mandatory. The rabbit MAC for isoflurane (~2.05%) is indeed slightly higher than in dogs (~1.28%) and cats (~1.63%), but this alone doesn't cause apnea at 2.5%. Rabbits do have µ-opioid receptors. While high metabolic rate is real, it does not cause apnea.

Question 131: A 7-year-old Thoroughbred mare undergoes emergency celiotomy for small colon impaction. The surgeon identifies a mesenteric rent through which small intestine has passed and become strangulated. After reducing the hernia and assessing the intestine, the surgeon should:

Close the mesenteric rent with simple interrupted sutures after intestinal assessment (Correct answer)
Perform a bypass anastomosis without closing the rent
Pack the rent with omentum and close the abdomen
Leave the mesenteric rent open to prevent recurrence

Correct answer: Close the mesenteric rent with simple interrupted sutures after intestinal assessment

Mesenteric rents must be closed after reducing the herniated intestine to prevent recurrence of internal herniation and strangulation.

Question 132: Which of the following birds is most susceptible to aspergillosis due to its natural habitat and immune characteristics?

Gyrfalcon (Correct answer)
Budgerigar
African grey parrot
Cockatiel

Correct answer: Gyrfalcon

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

Question 133: A 3-year-old Quarter Horse mare is given detomidine (20 µg/kg IV) and butorphanol (0.02 mg/kg IV) for standing sedation during a laceration repair. Thirty minutes later the mare becomes ataxic and recumbent. The veterinarian decides to partially reverse the sedation. Which reversal strategy is MOST pharmacologically precise?

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

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

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

Question 134: A 4-year-old spayed DSH with phenobarbital-refractory epilepsy is started on potassium bromide (KBr) as add-on therapy. Eight weeks later she presents with progressive coughing, expiratory dyspnea, and eosinophilia (1,800 cells/µL). Thoracic radiographs reveal a diffuse bronchial-interstitial pattern. The most likely diagnosis is:

Aspiration pneumonia secondary to postictal laryngeal dysfunction
Potassium bromide–induced eosinophilic bronchopneumopathy (Correct answer)
Feline idiopathic asthma triggered by bromide-induced mast cell degranulation
Secondary bacterial pneumonia from phenobarbital-induced immunosuppression

Correct answer: Potassium bromide–induced eosinophilic bronchopneumopathy

Potassium bromide causes eosinophilic bronchopneumopathy (EBP) in cats — a serious, species-specific adverse effect not observed in dogs. Clinical signs include coughing, dyspnea, and radiographic interstitial infiltrates with peripheral eosinophilia, typically developing weeks to months after initiation. This is distinct from feline asthma and resolves with KBr discontinuation. Because of this risk, KBr is generally avoided in cats; phenobarbital, levetiracetam, or zonisamide are preferred antiepileptic agents in this species.

Question 135: A cat with confirmed FeLV infection is most likely to develop which neoplastic condition?

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

Correct answer: Multicentric lymphoma

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

Question 136: 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?

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

Correct answer: Fusobacterium necrophorum

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

Question 137: On a 500-cow dairy, the conception rate to first service drops from 42% to 28% over 3 months. Which herd-level factor should be investigated first?

Milk production records from 6 months ago
Heat detection efficiency and estrus expression (Correct answer)
Bull fertility in the herd sire
BVD vaccination status of heifers only

Correct answer: Heat detection efficiency and estrus expression

In AI-based dairies, poor heat detection is the most common cause of declining first-service conception rates, as undetected or wrongly timed AI submissions drive down the metric.

Question 138: Which preanesthetic agent is CONTRAINDICATED in patients with suspected splenic masses because it causes splenic engorgement and sequestration of red blood cells?

Dexmedetomidine
Butorphanol
Midazolam
Acepromazine (Correct answer)

Correct answer: Acepromazine

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

Question 139: A cat with suspected exocrine pancreatic insufficiency (EPI) should have which test performed to confirm the diagnosis?

Serum lipase
Serum amylase
Fecal fat staining
Feline trypsin-like immunoreactivity (fTLI) (Correct answer)

Correct answer: Feline trypsin-like immunoreactivity (fTLI)

Feline TLI (fTLI) below 8 µg/L confirms EPI in cats by measuring pancreatic exocrine secretion capacity; EPI is rare in cats but fTLI is the diagnostic gold standard.

Question 140: Which anesthetic agent is considered safest for induction in chelonians due to minimal cardiovascular depression?

Alfaxalone (Correct answer)
Propofol
Tiletamine-zolazepam
Ketamine alone

Correct answer: Alfaxalone

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

Question 141: Feline infectious peritonitis (FIP) wet form is characterized by accumulation of effusion. Which laboratory finding is most consistent with FIP effusion?

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

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

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

Question 142: Which statement about the use of doxycycline in cats is most accurate?

Liquid or food must accompany doxycycline administration to prevent esophageal stricture (Correct answer)
Doxycycline is contraindicated in cats under 6 months due to bone growth plate damage
Subcutaneous injection of doxycycline is preferred over oral administration
Cats require twice the canine mg/kg dose due to faster hepatic clearance

Correct answer: Liquid or food must accompany doxycycline administration to prevent esophageal stricture

Doxycycline pills lodged in the feline esophagus cause chemical strictures; always follow tablets with food or water, or use liquid formulations.

Question 143: 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 144: Feline calicivirus virulent systemic strain (VS-FCV) outbreaks are characterized by which distinctive clinical sign NOT typical of classic FCV?

Conjunctivitis
Subcutaneous edema and facial swelling (Correct answer)
Sneezing
Oral ulceration

Correct answer: Subcutaneous edema and facial swelling

VS-FCV causes severe systemic disease including facial and limb edema, skin ulceration, and high mortality, distinguishing it from classical FCV.

Question 145: 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?

Permethrin toxicity; Methocarbamol (Correct answer)
Ethylene glycol toxicity; Fomepizole
Ivermectin toxicity; Intralipid emulsion
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 146: A 5-year-old Siberian Husky is presented with zinc toxicosis after ingesting pennies minted after 1982. Which hematologic finding best explains the hemolysis observed?

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

Correct answer: Heinz body formation from oxidative RBC damage

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

Question 147: A 5-year-old spayed female Cavalier King Charles Spaniel with known mitral valve disease (ACVIM Stage C1) is being managed medically. She is currently on pimobendan and enalapril. The owner reports a new 2-day onset of weakness and exercise intolerance. ECG shows a sustained wide-complex tachycardia at 280 bpm with a left bundle branch block morphology. What is the MOST appropriate IMMEDIATE pharmacologic intervention?

IV diltiazem at 0.25 mg/kg over 2 minutes
IV digoxin at 0.0055 mg/kg slow push
IV lidocaine bolus at 2 mg/kg followed by CRI at 50–80 µg/kg/min (Correct answer)
Oral sotalol loading dose

Correct answer: IV lidocaine bolus at 2 mg/kg followed by CRI at 50–80 µg/kg/min

A sustained wide-complex tachycardia at 280 bpm with LBBB morphology in a dog most likely represents ventricular tachycardia (VT) originating from the right ventricular outflow tract or interventricular septum. In a hemodynamically compromised patient (weakness), immediate intervention is required. IV lidocaine is the first-line agent for acute VT in dogs — it is a class IB sodium channel blocker with rapid onset and short duration, given as a bolus followed by CRI. Diltiazem is appropriate for supraventricular tachycardias (SVT) and could be dangerous in VT by causing further hemodynamic compromise without slowing the rate. Oral sotalol is too slow in onset for acute management. Digoxin's positive inotropic and AV-nodal slowing effects are not indicated in acute VT and can be proarrhythmic.

Question 148: A 5-year-old male Dalmatian presents with recurrent urinary tract infections and struvite uroliths. Urate crystals are also identified on urinalysis. Which metabolic defect predisposes Dalmatians to urate urolithiasis?

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

Correct answer: Reduced hepatic conversion of uric acid to allantoin

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

Question 149: 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 150: Pinkeye (Infectious Bovine Keratoconjunctivitis) in a cow herd is most commonly caused by which organism?

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

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 151: 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?

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

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 152: A 5-year-old Holstein cow has not shown estrus 60 days postpartum. Rectal palpation reveals a corpus luteum (CL) on one ovary with no other abnormalities. Which treatment protocol is most appropriate to initiate cyclicity?

Administer prostaglandin F2α (PGF2α) to lyse the CL and allow return to estrus (Correct answer)
Administer GnRH to stimulate follicle-stimulating hormone release
Administer estradiol cypionate to induce a standing heat
Begin a progesterone-releasing intravaginal device (PRID) for 14 days

Correct answer: Administer prostaglandin F2α (PGF2α) to lyse the CL and allow return to estrus

A persistent CL causing anestrus is treated with prostaglandin F2α (dinoprost or cloprostenol), which causes luteolysis — regression of the CL, progesterone levels drop, and the cow returns to estrus within 2–5 days. GnRH induces ovulation of the dominant follicle but does not address a persistent CL. PRIDs are used for synchronization, not CL regression.

Question 153: A veterinarian performs an abdominal ultrasound on a dog with acute vomiting and anorexia. Which finding is most specific for a mechanical small intestinal obstruction?

Hyperechoic mesenteric fat is noted surrounding the entire small bowel.
The intestinal wall is diffusely thickened with preserved layering.
Peristaltic waves are increased to 6-7 contractions per minute throughout the small intestine.
A segment of intestine is severely dilated with fluid (>1.6 times the diameter of the aorta) proximal to a distinct transition point. (Correct answer)

Correct answer: A segment of intestine is severely dilated with fluid (>1.6 times the diameter of the aorta) proximal to a distinct transition point.

The most reliable ultrasonographic sign of a mechanical small intestinal obstruction is segmental dilation of the intestine proximal to the obstruction. A commonly used objective criterion is a small intestinal diameter greater than 1.6 times the diameter of the aorta. Other signs include a visible foreign body, plication, or intussusception.

Question 154: Which of the following best describes the primary mechanism by which non-steroidal anti-inflammatory drugs (NSAIDs) can induce acute kidney injury in a cat that is dehydrated or hypotensive?

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

Correct answer: Inhibition of prostaglandin-mediated renal vasodilation

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

Question 155: A dairy producer wants to monitor transition cow health. Which single blood test best predicts subclinical ketosis in fresh cows?

Serum NEFA >0.4 mEq/L at dry-off only
Blood glucose <2.5 mmol/L
Serum beta-hydroxybutyrate (BHB) ≥1.2 mmol/L (Correct answer)
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 156: Which ultrasonographic finding is MOST consistent with gastric dilatation-volvulus (GDV) versus simple dilatation in a dog?

Uniform gastric distension with fluid content
Compartmentalization of the stomach into two gas-filled regions on the right lateral view (Correct answer)
Inability to obtain gastric images due to gas artifact
Thickening of the gastric wall with loss of wall layering

Correct answer: Compartmentalization of the stomach into two gas-filled regions on the right lateral view

GDV causes the stomach to rotate, creating a compartmentalized 'double bubble' appearance, whereas simple dilatation shows uniform distension.

Question 157: Amlodipine is the first-line treatment for systemic hypertension in cats. What is its primary mechanism of action?

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

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 158: What is the primary mechanism by which ivermectin kills parasites?

Inhibits acetylcholinesterase
Disrupts parasite cell membrane integrity
Blocks tubulin polymerization
Potentiates glutamate-gated chloride channels causing paralysis (Correct answer)

Correct answer: Potentiates glutamate-gated chloride channels causing paralysis

Ivermectin potentiates glutamate-gated chloride channels in invertebrate nerve and muscle cells, causing hyperpolarization, paralysis, and death of the parasite.

Question 159: Which breed is most predisposed to developing dilated cardiomyopathy (DCM) and typically presents with atrial fibrillation as its most common arrhythmia?

Cavalier King Charles Spaniel
Doberman Pinscher
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 160: 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
Immune-Mediated Hemolytic Anemia (IMHA) (Correct answer)
Zinc toxicity
Von Willebrand's disease

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 161: FIP has no known treatment.

False
True (Correct answer)

Correct answer: True

Historically, Feline Infectious Peritonitis (FIP) was considered an untreatable and universally fatal disease. While new antiviral drugs have emerged, at the time this question was likely formulated, there was no widely recognized or approved 'cure' or treatment. The statement reflects the historical understanding and the challenge of FIP treatment.

Question 162: Transmissible Gastroenteritis (TGE) and Porcine Epidemic Diarrhea (PED) cause clinically identical disease but differ in one key epidemiological feature. Which statement correctly distinguishes them?

TGE is caused by a coronavirus while PED is caused by a rotavirus
Both are coronaviruses, but TGE has largely been displaced in North America by PEDV since its 2013 emergence (Correct answer)
PED virus does not infect adult swine, while TGE virus affects all ages equally
TGE causes bloody diarrhea while PED causes watery white diarrhea with no blood

Correct answer: Both are coronaviruses, but TGE has largely been displaced in North America by PEDV since its 2013 emergence

Both TGE virus and PEDV (Porcine Epidemic Diarrhea Virus) are alpha-coronaviruses causing watery diarrhea with high mortality in neonates. A key epidemiological point: PEDV emerged explosively in North America in 2013 and has largely replaced TGE as the dominant enteric coronavirus. Both affect all ages, but neonatal mortality is highest. PED is not a rotavirus.

Question 163: A 15-year-old Quarter Horse gelding has a chronic, non-healing wound over the lateral aspect of the pastern with a fistulous tract. Probing reveals contact with bone. Radiographs show cortical lysis of the lateral proximal phalanx. What is the definitive treatment?

Surgical debridement and sequestrum removal (Correct answer)
Cast application for 8 weeks
Long-term systemic penicillin without debridement
Intra-articular antibiotic perfusion only

Correct answer: Surgical debridement and sequestrum removal

Sequestrum formation requires surgical removal of the devitalized bone fragment combined with debridement of the surrounding infected tissue to allow healing.

Question 164: Osteochondrosis dissecans (OCD) in horses most commonly affects which joint when presenting as tarsal lameness in young Thoroughbreds?

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

Correct answer: Tarsocrural (tibiotarsal) joint

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

Question 165: A cat with chronic diarrhea is found to shed feline coronavirus on fecal PCR. The cat is otherwise healthy. What is the most appropriate management?

Monitor clinically; most cats clear enteric FCoV shedding without developing FIP (Correct answer)
Isolate permanently from all other cats
Administer prednisolone to prevent FIP development
Immediately begin GS-441524 treatment

Correct answer: Monitor clinically; most cats clear enteric FCoV shedding without developing FIP

Most cats shed enteric FCoV transiently without progressing to FIP; monitoring clinical status is appropriate rather than immediate treatment.

Question 166: A 6-year-old DSH cat with hyperthyroidism is started on methimazole. Two weeks later, the owner reports the cat is scratching its face intensely and has developed facial excoriations. Which statement BEST explains the pathophysiology and recommended management?

Methimazole causes dose-dependent peripheral neuropathy; reduce the dose by 50% and monitor for resolution
Methimazole-induced hypothyroidism has unmasked latent feline hyperesthesia syndrome; adjust thyroid hormone levels with levothyroxine supplementation
Facial pruritus is a known idiosyncratic drug reaction in cats, likely immune-mediated; discontinue methimazole and consider carbimazole or alternative definitive therapy (Correct answer)
This represents a Type II hypersensitivity reaction to methimazole; switch to radioactive iodine (I-131) therapy

Correct answer: Facial pruritus is a known idiosyncratic drug reaction in cats, likely immune-mediated; discontinue methimazole and consider carbimazole or alternative definitive therapy

Facial pruritus and self-excoriation is a well-documented idiosyncratic adverse effect of methimazole in cats, occurring in approximately 2–3% of treated cats, typically within the first 1–3 months of therapy. The mechanism is thought to be immune-mediated. This reaction is an indication to discontinue methimazole immediately, as continued use can lead to more severe reactions including hepatotoxicity, thrombocytopenia, or agranulocytosis. Carbimazole (a prodrug of methimazole) should theoretically cross-react, so definitive therapy with I-131, surgical thyroidectomy, or a prescription iodine-restricted diet (Hill's y/d) is preferred. This is not a dose-dependent effect and dose reduction is inadequate management.

Question 167: A herd of 120 commercial beef cows has a pregnancy rate of 78% after a 63-day breeding season using natural service at a 1:25 bull-to-cow ratio. Breeding soundness evaluations (BSE) were performed on all bulls 45 days before turnout and all passed. Cow body condition averaged 5.5/9 at breeding. Progesterone assays on 20 randomly selected non-pregnant cows at preg-check reveal 14 of 20 have luteal-phase progesterone levels (>1 ng/mL). What is the MOST likely diagnosis for the reproductive failure in these cows?

Subclinical BVDV infection causing early embryonic death after fertilization
Repeat breeding syndrome secondary to uterine subclinical endometritis from prior calving
Embryonic loss between days 16–45 of gestation after normal conception (Correct answer)
Inadequate bull power with libido or musculoskeletal limitations undetected by BSE

Correct answer: Embryonic loss between days 16–45 of gestation after normal conception

The key finding is that 14/20 non-pregnant cows (70%) have luteal-phase progesterone at preg-check, indicating they were cycling and had been bred (they are in a luteal phase cycle, not anestrus), yet failed to maintain pregnancy. BSE-passed bulls in adequate numbers with cycling cows of good BCS points toward the problem occurring AFTER fertilization — early embryonic or fetal loss between days 16–45, after maternal recognition of pregnancy would have been expected but before the conceptus reached a size detectable at preg-check. BVDV is plausible but would require more evidence. Subclinical endometritis could cause repeat breeding but would more typically present with cows that cycle back quickly without sustained luteal activity. The high proportion with active corpora lutea suggests conception occurred but embryos were lost before or around preg-check, and they've cycled back.

Question 168: A 320-cow spring-calving beef herd experiences a 22% calf scours rate in calves aged 3–10 days, with 6 deaths. ELISA fecal antigen testing of 12 affected calves yields: Cryptosporidium parvum positive in 10/12, rotavirus positive in 5/12, and coronavirus positive in 2/12. Bulk colostrum Brix refractometer readings average 18%. Which management interpretation is MOST accurate?

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

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

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

Question 169: 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)
Bilateral navicular bursitis
Equine protozoal myeloencephalitis (EPM)
Bilateral coffin joint sepsis

Correct answer: Laminitis

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

Question 170: A Labrador retriever aged 7 is examined for developing foreleg lameness that has been present for about two months. Physical examination reveals a noticeable soft tissue bulge around the carpus, and palpating this region causes severe pain. Radiographs of the afflicted area show significant cortical bone loss and lysis of the distal radius. Osteoblasts with many mitotic patterns, peculiar nuclei, and very basophilic cytoplasm are visible in a needle biopsy. What type of medication is the most suitable if the owner decides to have an amputation?

Prednisone
Azathioprine
Vincristine
Cisplatin (Correct answer)

Correct answer: Cisplatin

The clinical signs and biopsy results (cortical bone loss, lysis, atypical osteoblasts) are highly suggestive of osteosarcoma, an aggressive bone tumor. For appendicular osteosarcoma, amputation is often followed by chemotherapy to delay metastasis and improve survival. Cisplatin is a commonly used and effective chemotherapeutic agent for canine osteosarcoma, making it the most suitable medication post-amputation.

Question 171: 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?

Renal tubular secretion of phenobarbital increases with chronic exposure
Phenobarbital undergoes tachyphylaxis at GABA-A receptors over time
Enterohepatic recirculation of phenobarbital decreases progressively with hepatic adaptation
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 172: 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?

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

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 173: 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 positive-sense, single-stranded RNA virus in the family Coronaviridae that primarily damages proventricular smooth muscle
It is a negative-sense, single-stranded RNA virus in the family Bornaviridae that targets glial cells and neurons of the enteric and central nervous systems (Correct answer)
It is a negative-sense, segmented RNA virus in the family Orthomyxoviridae that causes secondary demyelination of enteric nerves
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 174: An 8-year-old Arabian mare undergoes ovariectomy via flank laparotomy. On post-op day 2, she develops acute abdominal pain and pyrexia. Abdominocentesis reveals yellow-tinged fluid with a total protein of 4.5 g/dL and WBC of 90,000 cells/μL. What is the most likely complication?

Cecal impaction
Incisional seroma
Normal post-operative peritoneal response
Peritonitis secondary to intestinal contamination or pedicle infection (Correct answer)

Correct answer: Peritonitis secondary to intestinal contamination or pedicle infection

Markedly elevated peritoneal fluid protein and WBC with fever and pain indicate septic peritonitis, a serious complication of flank ovariectomy typically due to contamination or pedicle infection.

Question 175: A 10-year-old intact female dog presents with vaginal discharge, PU/PD, and leukocytosis with a left shift. Radiographs show a fluid-filled uterus. Which finding would support a closed-cervix pyometra over an open-cervix pyometra?

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

Correct answer: More severe azotemia and toxemia

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

Question 176: 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)
Implementing a negative DCAD (Dietary Cation-Anion Difference) diet prepartum
Increasing body condition score to 4.0 or higher at dry-off
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 177: 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)
Arachnoid diverticulum
Meningioma (Correct answer)
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 178: What type of virus is FIP?

Pestivirus
Coronavirus (Correct answer)
Adenovirus
Herpesvirus

Correct answer: Coronavirus

Feline Infectious Peritonitis (FIP) is caused by a mutated form of the Feline Coronavirus (FCoV). While FCoV itself is common and usually causes mild or asymptomatic enteric disease, certain mutations can lead to the development of the severe, systemic disease known as FIP.

Question 179: Which of the following is a primary therapeutic goal in the management of a dog with chronic kidney disease (CKD) and proteinuria?

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

Correct answer: Controlling systemic hypertension and reducing phosphorus intake

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

Question 180: A 10-year-old Labrador Retriever is being managed for degenerative joint disease with long-term meloxicam. The owner reports the dog has developed polyuria and polydipsia over the past 6 weeks. Serum creatinine is 2.4 mg/dL (baseline 1.0 mg/dL), BUN 52 mg/dL, phosphorus 6.8 mg/dL, and urine specific gravity 1.014. Blood pressure is 178/112 mmHg. Which combination of interventions is most appropriate as the FIRST priority?

Discontinue meloxicam, initiate amlodipine, and recheck creatinine in 2 weeks before starting additional therapies
Discontinue meloxicam, initiate amlodipine, begin phosphate binder therapy, and start subcutaneous fluids (Correct answer)
Reduce meloxicam dose by 50%, initiate enalapril, and restrict dietary protein
Continue meloxicam with renal-protective dose, initiate benazepril, and begin phosphate restriction

Correct answer: Discontinue meloxicam, initiate amlodipine, begin phosphate binder therapy, and start subcutaneous fluids

This dog has IRIS Stage 2–3 CKD with concurrent hypertension and hyperphosphatemia. The NSAID must be discontinued immediately as it contributes to renal vasoconstriction and worsening CKD. Hypertension at this level (>160 mmHg systolic) requires immediate treatment with amlodipine (first-line antihypertensive in dogs). Hyperphosphatemia above 6 mg/dL in CKD warrants phosphate binder initiation. Subcutaneous fluids support renal perfusion. Waiting to address hypertension or hyperphosphatemia would allow ongoing target organ damage.

Question 181: A 6-year-old Arabian endurance horse presents with acute right forelimb lameness of 4 days' duration following a 100-mile ride. The horse is grade 4/5 lame, resents flexion of the fetlock, and has a marked digital pulse. Radiographs are unremarkable. MRI reveals a complete palmar annular ligament desmitis with concurrent proximal digital annular ligament thickening and significant fluid accumulation within the digital flexor tendon sheath (DFTS). After conservative management fails at 6 weeks, you plan a surgical intervention. Which procedure is MOST appropriate to address the primary compressive pathology?

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

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 182: Coxiella burnetii (Q fever agent) is classified as a Category B bioterrorism agent. Which animal reservoir is the primary source of human infection?

Dogs and cats
Domestic ruminants (cattle, sheep, goats) (Correct answer)
Wild rodents
Wild birds

Correct answer: Domestic ruminants (cattle, sheep, goats)

Cattle, sheep, and goats are the primary reservoirs; parturient materials (placenta, birth fluids) contain extremely high concentrations of C. burnetii.

Question 183: A cat colony manager reports that 4 of 20 colony cats have died with signs of acute vomiting, hemorrhagic diarrhea, and profound leukopenia (WBC 400 cells/µL). The colony was vaccinated against feline panleukopenia virus (FPV) 3 years ago with an inactivated vaccine. Necropsy reveals villous blunting with crypt necrosis. Which scenario MOST plausibly explains vaccine failure in this outbreak?

Canine parvovirus type 2c (CPV-2c) infection, which is not cross-neutralized by antibodies induced by FPV inactivated vaccines
Waning humoral immunity below protective thresholds after 3 years combined with a high environmental viral load (Correct answer)
Antigenic drift in circulating FPV strains rendering the inactivated vaccine antigenically mismatched
Cold-chain failure during vaccine storage causing loss of adjuvant efficacy without affecting antigen content

Correct answer: Waning humoral immunity below protective thresholds after 3 years combined with a high environmental viral load

Inactivated FPV vaccines in cats provide shorter duration of immunity than modified live vaccines — protective titers may wane below threshold levels by 2–3 years in some individuals, particularly in colony settings where annual or triennial boosters may be inconsistent. FPV is environmentally hardy (survives years in fomites), so high environmental pressure combined with waned immunity is the most plausible explanation. CPV-2c does infect cats and causes panleukopenia-like disease, but antibodies from FPV vaccines DO cross-neutralize CPV-2 variants due to high antigenic homology (>98% capsid similarity). FPV shows no significant antigenic drift. Cold-chain failure would affect antigen integrity more than adjuvant.

Question 184: 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 leukemia virus
Feline herpesvirus-1

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 185: A 3-year-old Beagle presents with seizures and a serum ammonia of 280 µmol/L. Abdominal ultrasound reveals a single extrahepatic portosystemic shunt. Which amino acid supplementation is MOST important in this patient's management?

Branched-chain amino acids
Taurine
Methionine
Arginine (Correct answer)

Correct answer: Arginine

Arginine is essential for the urea cycle; dogs with PSS may develop arginine deficiency, worsening hyperammonemia, so supplementation is important.

Question 186: A 9-year-old Quarter Horse barrel racing horse presents with bilateral hindlimb lameness worse on the right. Intra-articular analgesia of both distal tarsal joints resolves the lameness 70%. Radiographs show periarticular osteophytes at the centrodistal and tarsometatarsal joints bilaterally but no joint space narrowing. What is the MOST appropriate next step in management, and why?

Repeated intra-articular methylprednisolone acetate injections every 4–6 weeks indefinitely
Computed tomography-guided chemical arthrodesis with sodium monoiodoacetate to accelerate fusion of the affected joints (Correct answer)
Surgical cunean tenectomy to decompress the medial branch of the deep peroneal nerve
Extracorporeal shock wave therapy targeting the dorsomedial aspect of the tarsus to stimulate osteophyte remodeling

Correct answer: Computed tomography-guided chemical arthrodesis with sodium monoiodoacetate to accelerate fusion of the affected joints

CT-guided chemical arthrodesis using sodium monoiodoacetate (or alcohol) is an advanced technique used to accelerate the natural fusion of the distal tarsal joints (centrodistal and tarsometatarsal), which are the joints involved in bone spavin. These joints have minimal range of motion and are better pain-free when fused. When conservative corticosteroid management is insufficient or short-lived, and radiographic changes confirm bone spavin, chemical arthrodesis provides a definitive solution. Repeated methylprednisolone is not appropriate as a long-term sole strategy and may accelerate cartilage degradation. Cunean tenectomy is an older, rarely indicated procedure.

Question 187: An 11-year-old Andalusian dressage horse presents with progressive bilateral forelimb 'pottery' gait, stumbling, and a short, stabbing stance phase. Nerve blocks are unhelpful. Radiographs show extensive remodeling and irregular sclerosis of both proximal sesamoid bones with fragmentation at the base. Which long-term structural consequence makes the prognosis for return to full work GUARDED to POOR?

Secondary navicular bone remodeling from altered weight-bearing biomechanics
Chronic deep digital flexor tendon core lesion from altered fetlock alignment
Progressive failure of the suspensory apparatus with risk of catastrophic fetlock breakdown due to compromised sesamoid bone structural integrity (Correct answer)
Bilateral coffin joint synovitis from compensatory toe-first landing

Correct answer: Progressive failure of the suspensory apparatus with risk of catastrophic fetlock breakdown due to compromised sesamoid bone structural integrity

Chronic sesamoiditis with fragmentation and sclerosis represents advanced degenerative disease of the proximal sesamoid bones, which are critical structural components of the suspensory apparatus. The sesamoid bones serve as the fulcrum for the suspensory ligament and distal sesamoidean ligaments; structural failure predisposes to catastrophic breakdown — fetlock 'drop,' complete support limb failure, or fracture under athletic loading. This is distinct from navicular disease or DDFT pathology, which are secondary events. The bilateral involvement and advanced bony changes make return to high-level sport inadvisable.

Question 188: Lily (Lilium spp.) ingestion in cats primarily targets which organ system?

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

Correct answer: Renal system

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

Question 189: A 'string of pearls' sign on abdominal radiographs of a cat refers to:

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

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

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

Correct answer: The glandular stomach that secretes HCl and pepsin

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

Question 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?

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

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

Flumazenil
Naloxone
Atipamezole (Correct answer)
Neostigmine

Correct answer: Atipamezole

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

Question 193: A cat diagnosed with nasal lymphoma has disease confined to the nasal cavity. Which treatment modality offers the best local control and median survival?

Radiation therapy alone (Correct answer)
Systemic chemotherapy alone
Rhinotomy and debulking
Intranasal corticosteroids

Correct answer: Radiation therapy alone

Radiation therapy is the treatment of choice for nasal lymphoma in cats, providing excellent local control with median survival times of 18–24 months.

Question 194: 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
Joint lavage and systemic broad-spectrum antibiotics (Correct answer)
Application of a cast and long-term NSAID administration
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 195: 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?

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
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
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

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

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

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

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

Question 197: A 4-year-old male intact Labrador Retriever is presented for acute collapse. ECG shows a ventricular rate of 280 bpm with wide, bizarre QRS complexes and no discernible P waves. Blood pressure is 60/40 mmHg. The dog ate a large meal 3 hours ago and the owner notes intermittent exercise intolerance for 2 months. Cardiac troponin I is markedly elevated. What is the MOST likely underlying diagnosis driving this arrhythmia?

Dilated cardiomyopathy with secondary ventricular tachycardia
Gastric dilatation-volvulus with vagally-mediated arrhythmia
Arrhythmogenic right ventricular cardiomyopathy (ARVC) (Correct answer)
Hypokalemia-induced ventricular tachycardia following dietary indiscretion

Correct answer: Arrhythmogenic right ventricular cardiomyopathy (ARVC)

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a heritable cardiomyopathy particularly prevalent in Boxers but also documented in Labrador Retrievers. It is characterized by fibrofatty replacement of right ventricular myocardium and a propensity for sustained ventricular tachycardia and sudden death, often without concurrent structural dilation. The elevated troponin I reflects myocardial injury, the history of exercise intolerance suggests a chronic underlying process, and the arrhythmia morphology is consistent with a right ventricular origin. Dilated cardiomyopathy typically shows systolic dysfunction on echo; GDV arrhythmias are usually less organized; hypokalemia alone rarely causes rates this high with this degree of hemodynamic compromise.

Question 198: On ultrasound of the urinary bladder, a dependent hyperechoic layer with acoustic shadowing that moves when the patient is repositioned most likely represents:

Uroliths (bladder stones) (Correct answer)
Transitional cell carcinoma
Bladder wall thickening
Blood clots

Correct answer: Uroliths (bladder stones)

Uroliths are hyperechoic foci with acoustic shadowing that are gravity-dependent and shift position when the patient moves, distinguishing them from wall masses.

Question 199: Which drug class is contraindicated in cats with urethral obstruction due to risk of worsening urethral tone?

Benzodiazepines
Opioid agonists (Correct answer)
Alpha-1 adrenergic antagonists
Non-depolarizing neuromuscular blockers

Correct answer: Opioid agonists

Pure opioid agonists (e.g., morphine) increase urethral sphincter tone in cats and can worsen urinary obstruction.

Question 200: 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?

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
Excellent prognosis with internal fixation using lag screws
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 201: Which antibiotic classes are contraindicated in rabbits due to the risk of fatal clostridial enterotoxemia?

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

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

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

Question 202: A horse develops laminitis after prolonged use of which drug class?

Aminoglycosides
Opioids
Corticosteroids (Correct answer)
Tetracyclines

Correct answer: Corticosteroids

Prolonged corticosteroid use in horses can lead to laminitis due to alterations in digital blood flow and carbohydrate metabolism.

Question 203: A 10-year-old cat dies of renal failure. Necropsy shows bilaterally small, pale, irregularly pitted kidneys. Histology reveals tubular atrophy, interstitial fibrosis, glomerulosclerosis, and lymphoplasmacytic interstitial infiltrate. The most accurate pathologic diagnosis is:

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

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

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

Question 204: On thoracic radiographs, a cat with hypertrophic cardiomyopathy (HCM) most commonly shows which cardiac silhouette shape on the VD view?

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

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

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

Correct answer: Single-layer simple interrupted appositional pattern

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

Question 206: Which class of drugs can cause crystalluria and urinary obstruction in dogs, particularly in acidic urine?

Fluoroquinolones
Tetracyclines
Aminoglycosides
Sulfonamides (Correct answer)

Correct answer: Sulfonamides

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

Question 207: A 7-year-old Great Dane presents with acute, non-productive retching, hypersalivation, and a distended, tympanic abdomen. A right lateral abdominal radiograph is taken. Which radiographic finding is most pathognomonic for gastric dilatation-volvulus (GDV)?

Displacement of the small intestines to the right cranial abdomen.
The presence of gravel or foreign material within the gastric lumen.
Severe gaseous distention of the entire stomach with a normal pyloric position.
A soft tissue opacity compartmentalizing the gas-filled stomach, creating a 'double bubble' appearance. (Correct answer)

Correct answer: A soft tissue opacity compartmentalizing the gas-filled stomach, creating a 'double bubble' appearance.

The classic radiographic sign for GDV on a right lateral view is the compartmentalization of the stomach by a soft tissue band, which is the pylorus folding over the fundus. This creates what is often described as a 'double bubble', 'Smurf hat', or 'Popeye arm' appearance and is pathognomonic for the condition.

Question 208: Which opioid is most appropriate for epidural administration in dogs to provide extended postoperative analgesia with minimal motor blockade?

Butorphanol
Fentanyl
Meperidine
Morphine (Correct answer)

Correct answer: Morphine

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

Question 209: A green iguana presents with dysecdysis (retained shed). What is the safest and most appropriate initial treatment?

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

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

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

Question 210: A 4-week-old foal presents with a carpal valgus deformity of the right forelimb. The deviation is moderate and has not improved with stall rest and corrective hoof trimming. What is the most appropriate next step in managing this case to achieve a successful outcome?

Recommend euthanasia due to a poor prognosis for athletic function.
Perform periosteal stripping on the medial aspect of the distal radius. (Correct answer)
Continue conservative management as the growth plates will close soon.
Perform transphyseal bridging on the medial aspect of the distal radius.

Correct answer: Perform periosteal stripping on the medial aspect of the distal radius.

For a moderate carpal valgus (knock-kneed) deformity in a 4- to 6-week-old foal that is not responding to conservative therapy, periosteal stripping (also called a hemicircumferential periosteal transection and elevation) on the concave side (medial aspect) of the limb is the appropriate surgical intervention. This procedure is thought to accelerate growth on the slower-growing side of the physis. Transphyseal bridging is used on the convex (lateral) side to slow growth and is typically reserved for more severe deformities or older foals. Continuing conservative management is inappropriate as the optimal window for surgical correction is during rapid growth.

Question 211: Which ultrasound finding is most specific for portal hypertension in a dog?

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

Correct answer: Acquired portosystemic shunting vessels

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

Question 212: A beef herd in the southeastern US has calves born with contracted tendons, cleft palate, and arthrogryposis. The dam grazed lupine between days 40–70 of gestation. Which teratogen is responsible?

Swainsonine (locoweed)
Veratrum californicum alkaloids
Nitrates from sudan grass
Anagyrine (quinolizidine alkaloid in lupine) (Correct answer)

Correct answer: Anagyrine (quinolizidine alkaloid in lupine)

Anagyrine in lupine species causes crooked calf disease (arthrogryposis and cleft palate) when dams graze lupine between days 40 and 70 of gestation.

Question 213: A horse presents with acute colic, nasogastric reflux >2 L, absent borborygmi on the right side, and tachycardia of 68 bpm. What is the most likely diagnosis?

Cecal impaction
Large colon displacement to the right (right dorsal displacement)
Duodenitis-proximal jejunitis (Correct answer)
Simple large colon impaction

Correct answer: Duodenitis-proximal jejunitis

Large volumes of nasogastric reflux (>2 L) combined with absent right-sided borborygmi, severe tachycardia, and acute pain are classic for duodenitis-proximal jejunitis (anterior enteritis).

Question 214: A horse presents with a positive flexion test of the distal limb and lameness that is abolished by a palmar digital nerve block. Which structure is MOST likely affected?

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

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 215: 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?

Aspergillus fumigatus — topical clotrimazole infusion via trephination
Conidiobolus coronatus — itraconazole monotherapy (Correct answer)
Pythium insidiosum — itraconazole + terbinafine combination
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 216: Which principle of disease prevention is represented by routine vaccination of dogs against rabies in the US?

Secondary prevention through early detection
Primary prevention by reducing exposure and susceptibility (Correct answer)
Quaternary prevention
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 217: 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?

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

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 218: A 10-year-old male neutered Cavalier King Charles Spaniel with known myxomatous mitral valve disease (MMVD) stage C1 (compensated heart failure on furosemide, enalapril, and pimobendan) presents for re-evaluation. Recent echocardiography shows LA:Ao of 2.1 and fractional shortening of 18%. The owner reports increased resting respiratory rate of 42 breaths/min over the past week. Thoracic radiographs confirm pulmonary venous congestion without alveolar edema. Serum creatinine is 2.4 mg/dL (up from 1.6 mg/dL at last visit 6 weeks ago). BUN is 58 mg/dL. What is the MOST appropriate immediate management adjustment?

Discontinue enalapril to protect renal function and optimize diuretic dose
Increase furosemide dose by 50% and recheck electrolytes and renal values in 5–7 days (Correct answer)
Add amlodipine 0.1 mg/kg/day to reduce afterload and improve forward output
Add spironolactone 2 mg/kg/day and recheck in 2 weeks without changing current furosemide dose

Correct answer: Increase furosemide dose by 50% and recheck electrolytes and renal values in 5–7 days

This dog is showing early decompensation evidenced by elevated resting respiratory rate and pulmonary venous congestion on radiographs despite current therapy, indicating insufficient diuresis. Increasing furosemide dose by 50% is the appropriate first step to address the fluid overload, with close monitoring of renal values and electrolytes in 5–7 days given the concurrent rise in creatinine—likely due to reduced forward perfusion from poor cardiac output. Discontinuing the ACE inhibitor (enalapril) is contraindicated in heart failure management as it provides vital neurohormonal blockade and is nephroprotective in this setting. Adding spironolactone without increasing the loop diuretic is unlikely to adequately address the active fluid accumulation. Amlodipine is not a first-line agent for MMVD-CHF without concurrent systemic hypertension; it would not address the primary issue of volume overload.

Question 219: Which of the following is the most accurate description of a 'chip fracture' at the dorsal aspect of the proximal interphalangeal joint in a performance horse?

A traumatic fracture of the extensor process of the distal phalanx
An osteochondral fragment typically arising from the dorsal proximal rim of the middle phalanx (Correct answer)
A stress fracture of the palmar cortex of the middle phalanx
A subchondral cystic lesion within the proximal interphalangeal joint

Correct answer: An osteochondral fragment typically arising from the dorsal proximal rim of the middle phalanx

Dorsal chip fractures at the pastern joint are osteochondral fragments typically arising from the dorsal proximal rim of the middle phalanx, removed arthroscopically.

Question 220: A 2-year-old intact male dog presents with acute scrotal swelling, fever, and pain. Orchitis is suspected. What is the most appropriate initial management?

Cold hydrotherapy and NSAIDs only
Aspiration of the testis for culture
Antibiotics alone and recheck in 2 weeks
Castration and broad-spectrum antibiotics (Correct answer)

Correct answer: Castration and broad-spectrum antibiotics

Castration combined with broad-spectrum antibiotics is recommended for bacterial orchitis to eliminate the infection source, prevent abscess formation, and avoid systemic sepsis.

Question 221: 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:

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

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 222: A dairy herd has a transition cow program. Which serum calcium concentration defines subclinical hypocalcemia (milk fever) in periparturient cows?

<1.4 mmol/L (5.5 mg/dL) with clinical signs
<2.5 mmol/L (10 mg/dL) within 7 days of calving
<1.0 mmol/L (4.0 mg/dL) with recumbency
<2.0 mmol/L (8.0 mg/dL) without clinical signs (Correct answer)

Correct answer: <2.0 mmol/L (8.0 mg/dL) without clinical signs

Subclinical hypocalcemia is defined as serum calcium <2.0 mmol/L (8.0 mg/dL) without overt clinical signs, and it predisposes cows to other periparturient disorders including metritis, displaced abomasum, and ketosis.

Question 223: 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)
Intravenous administration of bisphosphonates
Surgical splitting of the tendon
Immediate return to full work to promote collagen remodeling

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 224: 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 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)
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 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-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.

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 225: Which of the following medications is a potent, broad-spectrum antiemetic that functions by antagonizing neurokinin-1 (NK-1) receptors in the central vomiting center?

Maropitant (Correct answer)
Ondansetron
Metoclopramide
Famotidine

Correct answer: Maropitant

Maropitant is a neurokinin-1 (NK-1) receptor antagonist. It works by blocking the binding of Substance P, a key neurotransmitter in the emetic pathway, at NK-1 receptors located in the vomiting center and the chemoreceptor trigger zone. This mechanism makes it highly effective against vomiting from both central and peripheral stimuli. Ondansetron is a serotonin (5-HT3) antagonist, metoclopramide is primarily a dopamine (D2) antagonist, and famotidine is an H2-receptor antagonist used to reduce stomach acid.

Question 226: 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?

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

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

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

Correct answer: Surgical stabilization of the atlantoaxial joint

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

Question 228: 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?

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

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 229: A nursery pig presents with acute onset of polyarthritis, meningitis, and sudden death. Gram-positive cocci in pairs and short chains are isolated from CSF. What is the most likely causative organism?

Erysipelothrix rhusiopathiae
Streptococcus suis serotype 2 (Correct answer)
Mycoplasma hyorhinis
Haemophilus parasuis

Correct answer: Streptococcus suis serotype 2

Streptococcus suis serotype 2 is a leading cause of meningitis, polyarthritis, and septicemia in nursery and weanling pigs. It is a Gram-positive coccus in pairs/short chains. Erysipelothrix is Gram-positive but rod-shaped; Haemophilus parasuis (Glässer's disease) is Gram-negative; Mycoplasma lacks a cell wall.

Question 230: A German Shepherd presents with chronic intermittent diarrhea, weight loss, and a serum cobalamin level of 85 ng/L (reference: 251-908). Serum folate is markedly elevated. What is the most likely diagnosis?

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

Correct answer: Small intestinal bacterial overgrowth

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

Question 231: A wildlife rehabilitator presents a great horned owl with severe lead toxicosis (blood lead 95 µg/dL). The bird is ataxic and unable to fly. Chelation therapy with CaNa2EDTA is initiated. Which of the following adverse effects is of GREATEST concern with aggressive CaNa2EDTA chelation in raptors specifically?

Nephrotoxicity exacerbated by dehydration, leading to acute tubular necrosis (Correct answer)
Thiamine depletion causing peripheral neuropathy indistinguishable from lead toxicosis
Hemolytic anemia from erythrocyte membrane oxidation in avian nucleated red blood cells
Hypocalcemia due to chelation of ionized calcium, causing tetanic seizures

Correct answer: Nephrotoxicity exacerbated by dehydration, leading to acute tubular necrosis

CaNa2EDTA chelation carries significant risk of nephrotoxicity in raptors, especially when birds are debilitated and potentially dehydrated. The drug is eliminated renally and at high doses causes acute tubular necrosis; this risk is amplified by the reduced renal perfusion common in compromised birds. While the calcium form (CaNa2EDTA rather than Na2EDTA) mitigates hypocalcemia risk, renal damage remains the primary dose-limiting toxicity. Adequate hydration must be maintained and renal values monitored throughout chelation. Thiamine depletion is associated with fish-eating birds and mercury toxicosis, not EDTA chelation.

Question 232: A 7-year-old male intact Golden Retriever presents with a firm, painless swelling at the base of the tail. Cytology reveals sheets of round cells with prominent nucleoli and vacuolated cytoplasm. What is the most likely diagnosis?

Perianal adenocarcinoma
Perianal adenoma
Mast cell tumor
Anal sac adenocarcinoma (Correct answer)

Correct answer: Anal sac adenocarcinoma

Anal sac adenocarcinoma presents as a firm mass in the anal sac region and cytology shows epithelial cells with malignant features; it is not hormone-dependent unlike perianal adenomas.

Question 233: A 15-year-old Hanoverian dressage horse is evaluated for progressive bilateral hindlimb weakness and hindlimb lameness. The horse exhibits a characteristic 'goose-stepping' gait, excessive hip drop bilaterally, and difficulty backing. Intra-articular analgesia of the sacroiliac joints dramatically improves the lameness score from 3/5 to 1/5. Which diagnostic imaging modality is considered gold standard for confirming sacroiliac joint pathology in the horse, and what finding would confirm active joint disease?

Radiography demonstrating subchondral sclerosis and periarticular osteophyte formation
CT myelography showing nerve root compression at the lumbosacral junction
Nuclear scintigraphy showing bilaterally increased IRU at the sacroiliac joints; subchondral uptake pattern
Transrectal ultrasonography revealing hypoechoic joint margins and loss of normal joint contour (Correct answer)

Correct answer: Transrectal ultrasonography revealing hypoechoic joint margins and loss of normal joint contour

Transrectal ultrasonography (TRUS) is considered the gold standard for imaging the sacroiliac joint in horses because it allows direct visualization of the ventral joint margin, synovium, and surrounding structures with high resolution. Findings confirming active SI joint disease include hypoechoic (thickened/inflamed) joint capsule, loss of normal smooth joint contour, and irregularity of the subchondral surfaces. Nuclear scintigraphy is useful but less specific — it reflects bone remodeling activity, not active synovitis. Standard radiography cannot adequately image the SI joint due to overlying structures. CT myelography evaluates spinal cord compression, not SI joint pathology.

Question 234: On MRI, T2-weighted sequences are MOST useful for identifying:

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

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 235: What is the most reliable and practical method for assessing failure of passive transfer (FPT) in a 2-day-old calf on-farm?

Visual assessment of calf vigor and suckle reflex
Radial immunodiffusion (RID) assay
Zinc sulfate turbidity test
Serum total protein measurement via refractometer (Correct answer)

Correct answer: Serum total protein measurement via refractometer

Measuring serum total protein (STP) with a refractometer is a widely used, practical, and reliable on-farm method to estimate passive immunity status. In neonatal calves, immunoglobulins (primarily IgG) make up a large portion of serum proteins, so there is a strong correlation between STP and serum IgG levels. While RID is the gold standard for directly measuring IgG, it is a laboratory test and not practical for immediate, on-farm assessment. Visual assessment is unreliable, and the zinc sulfate turbidity test is an older, less accurate method.

Question 236: During a herd health visit to a 600-cow feedlot, you identify a pen of 150 steers (day 14 on feed) with a 9% morbidity rate. Pulled animals show biphasic fever, nasal discharge, and decreased rumination. At necropsy of a non-responder, you find cranioventral pulmonary consolidation, fibrinous pleuritis, and isolation of Mannheimia haemolytica serotype 1. The owner's current protocol uses metaphylaxis with tulathromycin on arrival. Which finding is MOST consistent with a failure of metaphylactic protocol rather than a true treatment failure?

Fibrinous pleuritis indicates a chronic infection predating arrival that metaphylaxis cannot address
The majority of morbidity cases are occurring between days 10–21 post-arrival, suggesting the 96-hour effective plasma concentration window of tulathromycin was exceeded before challenge (Correct answer)
A 9% morbidity rate is within acceptable limits for a high-risk pen and does not indicate protocol failure
M. haemolytica serotype 1 is intrinsically resistant to tulathromycin, indicating a wrong drug selection

Correct answer: The majority of morbidity cases are occurring between days 10–21 post-arrival, suggesting the 96-hour effective plasma concentration window of tulathromycin was exceeded before challenge

Tulathromycin achieves concentrations above the MIC for M. haemolytica in lung tissue for approximately 96 hours (4 days) post-injection, though tissue concentrations remain elevated longer. However, protection against clinical BRD is generally considered most effective for the first 10–14 days post-treatment. Morbidity clustering at days 10–21 indicates the window of metaphylactic protection has passed before the peak of viral/bacterial challenge — a pharmacokinetic/epidemiological timing mismatch. M. haemolytica serotype 1 retains susceptibility to macrolides including tulathromycin in most North American feedlot populations. Fibrinous pleuritis in a necropsy animal likely reflects disease progression in that individual, not herd-wide chronicity. A 9% rate in a high-risk pen is above acceptable thresholds (typically <5–8% depending on risk classification).

Question 237: Which inhalant anesthetic is associated with the GREATEST cardiovascular depression and sensitization of the myocardium to catecholamine-induced arrhythmias?

Halothane (Correct answer)
Desflurane
Sevoflurane
Isoflurane

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

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

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

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

Question 239: On CT of the nasal cavity in a dog with nasal discharge, which finding most strongly suggests fungal rhinitis (Aspergillus) rather than nasal neoplasia?

Fluid-filled nasal cavity with intact turbinates
Periosteal reaction along the frontal bones
Turbinate destruction with preserved nasal septum (Correct answer)
Mass with smooth margins crossing the midline

Correct answer: Turbinate destruction with preserved nasal septum

Aspergillus rhinitis typically causes extensive turbinate lysis/destruction while often leaving the nasal septum relatively intact, unlike neoplasia which often crosses the midline.

Question 240: An 8-year-old Cavalier King Charles Spaniel undergoes brain MRI for evaluation of vestibular signs and progressive cerebellar ataxia. Sagittal T2-weighted images reveal caudal displacement of the cerebellar vermis through the foramen magnum with effacement of the cisterna magna. There is no hydrocephalus. Additionally, a longitudinal fluid-filled cavity is identified within the cervical spinal cord parenchyma that is isointense to CSF on all sequences. Which TWO conditions are being described together?

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

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

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

Question 241: A 4-year-old spayed female cat with hypertrophic cardiomyopathy (HCM) requires anesthesia for a perineal urethrostomy. Which of the following induction protocols would be MOST appropriate to maintain cardiac output while avoiding tachycardia and excessive vasodilation?

Alfaxalone (2 mg/kg IV) + butorphanol (0.2 mg/kg IV)
Propofol (4 mg/kg IV) + fentanyl (2 mcg/kg IV)
Ketamine (5 mg/kg IM) + midazolam (0.2 mg/kg IM)
Etomidate (1–2 mg/kg IV) + midazolam (0.2 mg/kg IV) (Correct answer)

Correct answer: Etomidate (1–2 mg/kg IV) + midazolam (0.2 mg/kg IV)

Etomidate is the preferred induction agent in patients with compromised cardiac function because it provides the most cardiovascular stability of any injectable induction agent — minimal effects on heart rate, contractility, and systemic vascular resistance. Midazolam reduces the myoclonus associated with etomidate. Propofol causes vasodilation and can cause hypotension. Ketamine increases heart rate and sympathetic tone, which is detrimental in HCM where diastolic filling is already impaired. Alfaxalone, while moderate, has more hemodynamic effects than etomidate in cats with significant cardiac disease.

Question 242: Which anatomical site is preferred for intramuscular injections in birds?

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

Correct answer: Pectoral muscle

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

Question 243: A cat presents with a 3-week history of weight loss, icterus, and anorexia. Abdominal ultrasound reveals a diffusely hyperechoic liver. Cytology of a fine-needle aspirate shows >50% of hepatocytes containing large cytoplasmic lipid vacuoles. Serum ALT is 3× ULN; ALP is only mildly elevated. Which statement about this condition is most accurate?

Aggressive nutritional support via feeding tube is a cornerstone of treatment, as anorexia perpetuates the condition (Correct answer)
This condition is primary and self-limiting; supportive care with fluid therapy alone is curative
The mildly elevated ALP confirms biliary cirrhosis as the underlying cause rather than lipidosis
ALP is markedly elevated in this condition because feline ALP has a short half-life, making marked elevation impossible

Correct answer: Aggressive nutritional support via feeding tube is a cornerstone of treatment, as anorexia perpetuates the condition

This is hepatic lipidosis (HL), the most common hepatopathy in cats. Unlike dogs, cats have low hepatic ALP activity and a short isoenzyme half-life, so ALP elevation is often mild even in severe HL — making option A partially true but not the most clinically useful statement. The critical management principle is that HL is driven by continued anorexia and negative energy balance; aggressive nutritional support (esophagostomy or gastrostomy tube) is essential to reverse hepatocyte lipid accumulation. HL is not self-limiting without intervention, and mild ALP does not distinguish HL from biliary disease by itself.

Question 244: A veterinary technician performing a loco-regional block for feline dental extractions inadvertently injects bupivacaine 0.5% at a total dose of 4 mg/kg. Within 10 minutes the cat develops ventricular tachycardia refractory to lidocaine administration. Which treatment is MOST likely to restore sinus rhythm?

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

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

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

Question 245: A veterinarian is performing a complete blood count on a red-tailed hawk (Buteo jamaicensis) and notices large, round, pale-staining intracytoplasmic inclusions within erythrocytes, affecting approximately 15% of cells. The bird is mildly lethargic but otherwise clinically stable. Which of the following is the MOST accurate statement regarding this finding?

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

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

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

Question 246: 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?

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)
Brachycephalic dogs require a larger luminal diameter anastomosis due to higher intraluminal pressures from aerophagia
Stapled anastomosis is contraindicated in French Bulldogs due to documented staple-line failure related to breed-specific tissue fragility

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 247: A state veterinarian is investigating a cluster of human Salmonella Heidelberg cases linked to a poultry processing facility. Whole-genome sequencing (WGS) reveals the human isolates match a strain found in broilers from Farm A, but the processing plant draws from 14 farms. Which epidemiological concept best explains why WGS alone is insufficient to establish regulatory action against Farm A without additional trace-back data?

Berkson's bias introduced by hospitalized case selection
The difference between statistical association and attributable source under legal burden-of-proof standards
Misclassification of exposure due to cross-contamination during slaughter (Correct answer)
The ecological fallacy arising from aggregating farm-level data

Correct answer: Misclassification of exposure due to cross-contamination during slaughter

Cross-contamination during slaughter is the critical confounder. A single processing line can transfer a strain from one farm's flock to carcasses originating from other farms, meaning WGS identity between human cases and Farm A broilers could reflect contamination at the plant rather than Farm A as the true reservoir. Without lot-specific trace-back confirming the matched carcasses came exclusively from Farm A and were not co-mingled on the same line, regulatory action targeting that farm specifically is scientifically unsupported. The other options describe real biases but are not the primary mechanistic explanation in a multi-farm slaughter scenario.

Question 248: 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?

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

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 249: 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)
Excretory urogram
Negative contrast cystogram

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

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

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

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

Question 251: A 4-year-old Boxer presents with episodic syncope. ECG reveals a wide, bizarre QRS complex occurring at a rate of 180 bpm with no preceding P waves. What is the most likely diagnosis?

Second-degree AV block
Supraventricular tachycardia with aberrant conduction
Ventricular tachycardia (Correct answer)
Atrial fibrillation

Correct answer: Ventricular tachycardia

Wide bizarre QRS complexes with no preceding P waves at a rapid rate are characteristic of ventricular tachycardia, common in Boxers with ARVC.

Question 252: A 6-year-old intact male English Bulldog is scheduled for soft palate resection. During inhalant anesthesia with isoflurane, the patient develops a ventricular bigeminy rhythm. Which of the following inhalant agents, if used instead, would have posed the GREATEST risk for sensitizing the myocardium to catecholamine-induced arrhythmias in this patient?

Isoflurane
Halothane (Correct answer)
Desflurane
Sevoflurane

Correct answer: Halothane

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

Question 253: During a herd health visit to a 600-cow commercial beef operation, you identify a 4% prevalence of footrot (Fusobacterium necrophorum / Trueperella pyogenes) over the past 60 days despite routine zinc sulfate footbathing. Environmental assessment reveals persistently saturated soil near the water tanks. The producer asks about strategic use of long-acting oxytetracycline (LA-OTC) as a herd-level preventive. Under which circumstance is this practice MOST appropriately justified?

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

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

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

Question 254: A 4-year-old Siberian Husky presents with PU/PD. Water deprivation test shows urine osmolality of 180 mOsm/kg after 12 hours. After desmopressin administration, urine osmolality rises to 650 mOsm/kg. What is the diagnosis?

Chronic renal failure
Central diabetes insipidus (Correct answer)
Nephrogenic diabetes insipidus
Primary (psychogenic) polydipsia

Correct answer: Central diabetes insipidus

A robust response to exogenous ADH (desmopressin) indicates intact renal tubular response, confirming central (hypothalamic/pituitary) diabetes insipidus.

Question 255: A 10-year-old spayed female Cocker Spaniel presents with a 2-month history of progressive exercise intolerance, ascites, and jugular venous distension. Echocardiography reveals a thickened, immobile tricuspid valve with moderate tricuspid regurgitation, a mildly dilated right atrium, and paradoxical septal motion. The left heart is structurally normal. B-type natriuretic peptide (BNP) is markedly elevated. Which echocardiographic finding is MOST pathognomonic for tricuspid valve dysplasia (TVD) rather than acquired myxomatous tricuspid degeneration (secondary to right-sided CHF)?

Paradoxical interventricular septal motion indicating right ventricular volume overload
Right atrial enlargement disproportionate to the degree of tricuspid regurgitation
Tricuspid valve leaflets that are thickened, shortened, and tethered to the ventricular wall with abnormal chordae tendineae insertion (Correct answer)
Moderate-to-severe tricuspid regurgitation on color Doppler imaging

Correct answer: Tricuspid valve leaflets that are thickened, shortened, and tethered to the ventricular wall with abnormal chordae tendineae insertion

Tricuspid valve dysplasia (TVD) is a congenital malformation characterized by structural abnormalities of the valve apparatus itself: shortened, thickened, or dysplastic leaflets; direct attachment (tethering) of leaflet tissue to the papillary muscles or ventricular wall; malformed or absent chordae tendineae; and abnormal papillary muscle architecture. These anatomical features are distinguishable on echocardiography from acquired myxomatous degeneration, which causes nodular thickening at the leaflet tips and prolapse without tethering. Paradoxical septal motion, tricuspid regurgitation by Doppler, and right atrial enlargement can all occur in either condition and are therefore not pathognomonic. The tethering/dysplastic valve apparatus is specific to TVD.

Question 256: A rabbit undergoing ovariohysterectomy shows bradycardia (HR 120 bpm) under isoflurane. What is the most likely cause and initial treatment?

Hyperthermia — apply cooling
Anesthetic overdose — reduce vaporizer setting (Correct answer)
Vagal stimulation — administer atropine IV
Hyperkalemia — administer calcium gluconate

Correct answer: Anesthetic overdose — reduce vaporizer setting

Reducing the isoflurane vaporizer setting addresses anesthetic-induced bradycardia by decreasing myocardial depression from excessive anesthetic depth.

Question 257: Which antifungal is the treatment of choice for feline cryptococcosis affecting the CNS?

Terbinafine
Fluconazole (Correct answer)
Ketoconazole
Amphotericin B alone

Correct answer: Fluconazole

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

Question 258: A dog presents with acute onset of right-sided head tilt, nystagmus with the fast phase to the left, and rolling. MRI is normal. The most likely diagnosis is:

Otitis interna
Brainstem neoplasia
Cerebellar stroke
Idiopathic vestibular syndrome (Correct answer)

Correct answer: Idiopathic vestibular syndrome

Idiopathic (geriatric) vestibular syndrome presents with acute severe peripheral vestibular signs and a normal MRI, and typically resolves spontaneously within 72 hours to 2 weeks.

Question 259: A cat is diagnosed with feline infectious peritonitis (FIP). Which antiviral drug has shown efficacy and received conditional FDA approval for this disease?

Famciclovir
Interferon omega
Oseltamivir
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 260: 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:

Aleutian disease
Lymphoma
Adrenal gland disease
Insulinoma (Correct answer)

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

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

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 262: On abdominal radiographs, which finding is MOST consistent with uroabdomen (uroperitoneum) in a dog?

Loss of serosal detail with retrograde urethrogram showing contrast extravasation (Correct answer)
Mineralized density within the bladder lumen
Dilation of the ureters on excretory urogram
Increased opacity of the retroperitoneal space only

Correct answer: Loss of serosal detail with retrograde urethrogram showing contrast extravasation

Uroabdomen presents as loss of intraperitoneal serosal detail (due to urine effusion); a retrograde urethrogram or cystogram confirms contrast extravasation at the rupture site.

Question 263: A 12-year-old cat with well-regulated hyperthyroidism (post-radioiodine therapy, now euthyroid) develops azotemia (creatinine 3.1 mg/dL, BUN 58 mg/dL). Prior to treatment, renal parameters were within normal limits. What is the MOST likely explanation for this finding?

Post-treatment hypothyroidism caused renal vasoconstriction and acute ischemic injury
Radioiodine therapy caused direct nephrotoxicity to the renal tubules
Hyperthyroidism increased GFR and masked pre-existing chronic kidney disease; euthyroidism unmasked it (Correct answer)
Concurrent pyelonephritis developed secondary to immune suppression from the hyperthyroid state

Correct answer: Hyperthyroidism increased GFR and masked pre-existing chronic kidney disease; euthyroidism unmasked it

Hyperthyroidism increases cardiac output and renal blood flow, artificially elevating GFR and masking underlying CKD by keeping creatinine and BUN within normal limits. Once hyperthyroidism is treated and the cat becomes euthyroid, GFR normalizes (or decreases), and pre-existing CKD is 'unmasked.' This is a well-recognized phenomenon in feline medicine and is why a post-treatment renal function decline does not necessarily indicate a treatment complication. Radioiodine is not directly nephrotoxic, and acute ischemic injury from mild post-treatment hypothyroidism is not a recognized complication.

Question 264: 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?

Chronic rhinosinusitis secondary to herpesvirus-1 (FHV-1) (Correct answer)
Cryptococcus neoformans rhinitis
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 265: 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?

Bulk tank culture
Teat end scoring
California Mastitis Test (CMT) (Correct answer)
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 266: A 7-year-old intact male Golden Retriever presents with progressive exercise intolerance, muffled heart sounds, and jugular venous distension. Echocardiography reveals a large pericardial effusion. Cytology of the pericardial fluid shows hemorrhagic fluid with no neoplastic cells identified. Which of the following is the MOST likely underlying etiology?

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

Correct answer: Hemangiosarcoma of the right atrium

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

Question 267: When calculating the economic impact of mastitis in a dairy herd, which production loss component is typically the largest?

Veterinary labor and diagnostic fees
Antibiotic treatment costs
Reduced milk production (discarded milk + production drop) (Correct answer)
Premature culling costs

Correct answer: Reduced milk production (discarded milk + production drop)

Reduced milk yield accounts for approximately 60–70% of total mastitis costs; clinical and subclinical cases each cow produces significantly less milk throughout the lactation.

Question 268: 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?

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

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 269: A beef cow-calf operation has a 15% calf mortality rate in the first 30 days of life. Which intervention has the greatest impact on reducing neonatal calf mortality?

Vaccination of calves at birth against BRD pathogens
Providing supplemental selenium at birth
Prophylactic antibiotic treatment at birth
Ensuring adequate colostrum intake within 6 hours of birth (Correct answer)

Correct answer: Ensuring adequate colostrum intake within 6 hours of birth

Adequate colostrum intake (at least 10% of body weight within 6 hours) provides passive immunity and is the single most impactful intervention for reducing neonatal calf mortality.

Question 270: A 9-year-old dog with a meningioma is receiving mannitol (0.5 g/kg IV) preoperatively to reduce intracranial pressure (ICP). Which of the following anesthetic agents would be the MOST appropriate choice for induction to avoid exacerbating elevated ICP?

Tiletamine-zolazepam (2 mg/kg IV)
Ketamine (5 mg/kg IV)
Propofol (4 mg/kg IV, titrated slowly) (Correct answer)
Alfaxalone (3 mg/kg IV bolus)

Correct answer: Propofol (4 mg/kg IV, titrated slowly)

Propofol reduces cerebral metabolic rate of oxygen consumption (CMRO2), cerebral blood flow, and ICP, making it the preferred induction agent in patients with elevated ICP. It should be titrated slowly to avoid hypotension, which would reduce cerebral perfusion pressure. Ketamine and tiletamine-zolazepam are contraindicated in patients with elevated ICP because they increase cerebral blood flow and ICP. Alfaxalone at a large bolus dose can cause cardiovascular depression and, unlike propofol, does not have the same well-established cerebroprotective profile in this context.

Question 271: A cockatiel presents with symmetrical feather loss over the head and neck, with pin feathers that appear hemorrhagic and dystrophic. The most appropriate diagnostic test is:

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

Correct answer: PCR for Psittacine Beak and Feather Disease virus

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

Question 272: When performing an arthroscopic procedure on the equine tarsocrural (tibiotarsal) joint, the surgeon must be aware that the dorsolateral portal is placed just lateral to which tendon?

Long digital extensor tendon (Correct answer)
Lateral digital extensor tendon
Cranial tibial tendon
Peroneus tertius tendon

Correct answer: Long digital extensor tendon

The dorsolateral portal of the tarsocrural joint is placed lateral to the long digital extensor tendon, which serves as the key anatomical landmark to avoid during portal placement.

Question 273: What is the recommended minimum colostrum quality (Brix refractometer reading) indicating adequate IgG concentration for feeding to neonatal calves?

≥22% Brix (Correct answer)
≥30% Brix
≥15% Brix
≥10% Brix

Correct answer: ≥22% Brix

A Brix refractometer reading of ≥22% correlates with IgG concentrations ≥50 g/L, which is the threshold for high-quality colostrum suitable for feeding neonatal calves.

Question 274: Xylazine and dexmedetomidine produce sedation and analgesia through which primary mechanism of action?

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

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 275: On abdominal radiographs, retroperitoneal effusion is BEST identified by:

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

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 276: A producer wants to reduce the risk of hardware disease (traumatic reticuloperitonitis) in his dairy herd. What is the most cost-effective preventive measure?

Administering rumen magnets to all cows (Correct answer)
Installing metal detectors on TMR feeders only
Vaccinating with Clostridium perfringens toxoid
Feeding chopped hay to slow rumen contractions

Correct answer: Administering rumen magnets to all cows

A permanent ceramic or bar magnet placed in the reticulum captures ingested ferrous metal objects, preventing them from penetrating the reticulum wall.

Question 277: During an arthroscopic surgery of the equine tarsocrural joint, you inadvertently lacerate the medial branch of the deep peroneal nerve. Which immediate postoperative complication is most specifically associated with this iatrogenic injury in the horse?

Denervation atrophy of the extensor digitorum longus muscle
Loss of sensation over the dorsal metatarsus with no motor deficit (Correct answer)
Persistent swelling of the dorsomedial tarsocrural joint pouch due to impaired lymphatic drainage
Inability to extend the digit, resulting in knuckling at the fetlock

Correct answer: Loss of sensation over the dorsal metatarsus with no motor deficit

The medial branch of the deep peroneal (fibular) nerve in the horse is primarily sensory to the dorsal metatarsus and dorsal fetlock region. Damage to this branch produces analgesia/hypoalgesia of the dorsal metatarsus without meaningful motor loss, since the motor contributions to the digital extensors arise from the main trunk more proximally. Knuckling at the fetlock results from damage to the extensor branches of the peroneal nerve much more proximally, or from true extensor muscle denervation — not from the medial branch at the tarsocrural level. Lymphatic effects are not attributable to this nerve.

Question 278: A 10 kg dog receives a constant rate infusion of lidocaine at 50 µg/kg/min for ventricular arrhythmia management post-cardiac surgery. After 8 hours, the dog develops muscle tremors and seizures. Serum lidocaine concentration is 8 µg/mL (toxic range >6 µg/mL in dogs). Which factor most likely contributed to lidocaine accumulation in this patient?

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

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

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

Question 279: Which radiographic view is most useful for evaluating the dens (odontoid process) of the axis (C2) in a dog for atlantoaxial instability?

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

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 280: 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?

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

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 281: 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 282: Which surveillance system in the US monitors antimicrobial resistance in zoonotic enteric pathogens from humans, animals, and retail meat?

NAHMS
FSIS HACCP
NARMS (Correct answer)
APHIS VS

Correct answer: NARMS

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

Question 283: An equine practitioner is treating a horse with endotoxemia and considers using polymyxin B for lipopolysaccharide neutralization. The horse also has acute kidney injury (creatinine 4.8 mg/dL). Which statement most accurately reflects the pharmacological risk in this scenario?

Polymyxin B is primarily hepatically metabolized; renal dysfunction does not affect its safety profile
Renal impairment increases polymyxin B protein binding, paradoxically reducing free drug toxicity
Polymyxin B nephrotoxicity is mediated exclusively through prostaglandin inhibition and is reversible with NSAIDs
Polymyxin B causes nephrotoxicity via tubular cell membrane disruption and accumulates with renal impairment, compounding existing injury (Correct answer)

Correct answer: Polymyxin B causes nephrotoxicity via tubular cell membrane disruption and accumulates with renal impairment, compounding existing injury

Polymyxin B is nephrotoxic due to its cationic detergent-like mechanism, which disrupts renal proximal tubular cell membranes. The drug undergoes renal elimination, and in horses with pre-existing acute kidney injury, reduced GFR leads to drug accumulation, markedly amplifying tubular toxicity. Use in patients with renal dysfunction is controversial; if used, very low doses (1,000–2,000 IU/kg IV) with aggressive fluid support and close renal monitoring are essential. The LPS-neutralizing benefit must be carefully weighed against the risk of worsening renal failure.

Question 284: A warmblood dressage horse presents with bilateral hindlimb toe-dragging and a shuffling gait. Neurological examination reveals hindlimb ataxia. The MOST important differential diagnosis to rule out first is:

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

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 285: A 4-year-old Quarter Horse shows reluctance to extend the left forelimb fully when walking. On observation, there is a characteristic 'catching' of the hindlimb with the hoof dragging during protraction. Which condition best explains the hindlimb gait abnormality?

Stringhalt (Australian stringhalt)
Upward fixation of the patella
Fibrotic myopathy of the semitendinosus/semimembranosus (Correct answer)
Shivers

Correct answer: Fibrotic myopathy of the semitendinosus/semimembranosus

Fibrotic myopathy following injury to the caudal thigh muscles causes a characteristic mechanical gait with a sudden caudal 'flip' of the foot during the cranial phase of the stride.

Question 286: 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 induces hepatic CYP450 enzymes, reducing metronidazole clearance and elevating plasma concentrations (Correct answer)
Phenobarbital depletes hepatic glutathione stores, impairing metronidazole detoxification

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 287: Postweaning multisystemic wasting syndrome (PMWS) associated with Porcine Circovirus type 2 (PCV2) is diagnosed in a 6-week-old pig. Which histologic lesion in lymph nodes is considered pathognomonic?

Lymphoid depletion with histiocytic replacement and intracytoplasmic basophilic inclusion bodies (Correct answer)
Lymphocytic vasculitis with fibrinoid necrosis
Granulomatous lymphadenitis with central caseation
Lymphoid hyperplasia with germinal center formation

Correct answer: Lymphoid depletion with histiocytic replacement and intracytoplasmic basophilic inclusion bodies

PCV2-associated PMWS characteristically produces lymphoid depletion with replacement by histiocytes/macrophages that contain intracytoplasmic basophilic inclusion bodies (viral antigen). This combination is considered pathognomonic. Lymphoid hyperplasia is the opposite of what occurs.

Question 288: 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?

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

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 289: 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?

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
Pulmonary lymphoma; thoracic CT with contrast for mediastinal lymph node assessment

Correct answer: Cardiogenic pulmonary edema; echocardiography to detect occult hypertrophic cardiomyopathy with normal cardiac size

This is a high-level discriminator: cats with hypertrophic cardiomyopathy (HCM) frequently develop cardiogenic pulmonary edema WITHOUT radiographic cardiomegaly, because the hypertrophied ventricle maintains near-normal external dimensions while left atrial pressure rises acutely. A VHS of 7.2 is within the feline reference range (≤8.0), but HCM can still produce fulminant pulmonary edema before the cardiac silhouette enlarges. The perihilar-to-peripheral alveolar pattern with air bronchograms in cats classically represents cardiogenic edema, which in cats distributes differently than in dogs (less perihilar-predominant). Echocardiography is the critical next step to detect left atrial enlargement, diastolic dysfunction, or outflow obstruction. Non-cardiogenic edema is possible but less common with this symmetric perihilar distribution. Lymphoma typically produces a patchy or nodular interstitial pattern with mediastinal involvement.

Question 290: A 10-year-old DSH cat presents with polyuria, polydipsia, and a serum fructosamine of 285 µmol/L (reference: 190–365). Blood glucose is 14.2 mmol/L. Which interpretation is most accurate?

The fructosamine is within normal range, suggesting stress hyperglycemia rather than DM (Correct answer)
The fructosamine confirms sustained hyperglycemia consistent with diabetes mellitus
A fructosamine of 285 µmol/L is diagnostic for hyperthyroidism-induced insulin resistance
Fructosamine is unreliable in cats with concurrent hemolytic anemia and should be repeated

Correct answer: The fructosamine is within normal range, suggesting stress hyperglycemia rather than DM

Feline fructosamine reflects average glycemic control over 1–3 weeks. A value of 285 µmol/L falls within the normal reference range (190–365 µmol/L), indicating the hyperglycemia is likely transient (stress-induced) rather than sustained DM. Stress hyperglycemia is common in cats; fructosamine helps differentiate it from true DM. A fructosamine >400 µmol/L typically confirms DM. The other options misapply the reference values or attribute the finding incorrectly.

Question 291: Which epidemiological measure best quantifies the additional risk of disease attributable to a specific exposure?

Odds ratio
Relative risk
Attributable risk (risk difference) (Correct answer)
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 292: 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 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)
Brodifacoum irreversibly alkylates the vitamin K epoxide reductase enzyme complex
Brodifacoum depletes stores of vitamins K2 and K3, which cannot be replaced by K1 supplementation alone

Correct answer: Brodifacoum undergoes extensive enterohepatic recirculation, maintaining toxic tissue concentrations long after ingestion

Brodifacoum is a long-acting anticoagulant rodenticide with extensive enterohepatic recirculation and high lipophilicity, resulting in a plasma half-life of weeks to months in companion animals. This prolonged tissue retention means that even after a single ingestion, the drug continues to inhibit vitamin K epoxide reductase for an extended period. Treatment with vitamin K1 must continue until all brodifacoum is eliminated, typically 3–6 weeks, verified by PT/aPTT testing 48–72 hours after cessation.

Question 293: A 3-year-old intact male ferret presents with insulinoma-related hypoglycemia. The clinician elects to use diazoxide as medical management. Which mechanism of action makes diazoxide appropriate for this condition?

It opens ATP-sensitive potassium channels in pancreatic beta cells, hyperpolarizing the membrane and inhibiting insulin release (Correct answer)
It stimulates hepatic glycogenolysis via glucagon receptor agonism, raising blood glucose independent of insulin
It competitively inhibits glucokinase in beta cells, reducing glucose-stimulated insulin secretion
It blocks GLUT-2 transporters in beta cells, preventing glucose sensing and suppressing insulin secretion

Correct answer: It opens ATP-sensitive potassium channels in pancreatic beta cells, hyperpolarizing the membrane and inhibiting insulin release

Diazoxide acts by opening ATP-sensitive potassium channels (K-ATP channels) in pancreatic beta cells. This hyperpolarizes the cell membrane, preventing calcium influx through voltage-gated calcium channels, and thereby inhibiting insulin exocytosis. This directly counteracts the excessive autonomous insulin secretion from insulinoma cells. In contrast, sulfonylureas (like glipizide) close these same K-ATP channels, stimulating insulin release — making them contraindicated in insulinoma. Glucokinase inhibition, GLUT-2 blockade, or glucagon receptor agonism are not diazoxide's mechanisms.

Question 294: 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 reduced hepatic CYP1A2 activity, leading to accumulation of the parent compound (Correct answer)
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

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 295: 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)
Enhancement
Mirror artifact
Shadowing

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 296: A 4-year-old beef cow presents with a history of chronic, profuse, watery diarrhea and significant weight loss over several months despite maintaining a normal appetite. On rectal palpation, the rectal mucosa feels thickened and corrugated. What is the most likely causative agent?

Salmonella enterica serovar Typhimurium
Mycobacterium avium subsp. paratuberculosis (Correct answer)
Eimeria spp.
Bovine Viral Diarrhea Virus (BVDV)

Correct answer: Mycobacterium avium subsp. paratuberculosis

This classic presentation of chronic 'pipestream' diarrhea, severe weight loss with a good appetite ('wasting disease'), and thickened intestinal walls is pathognomonic for Johne's disease, caused by Mycobacterium avium subsp. paratuberculosis (MAP). While Salmonella and BVDV can cause diarrhea, the chronicity, good appetite, and specific rectal finding are highly suggestive of Johne's. Coccidiosis (Eimeria) is typically a disease of younger animals.

Question 297: 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?

Enrofloxacin is contraindicated in bearded dragons because it causes irreversible cartilage damage at therapeutic doses
Chloramphenicol is the first-line agent because fluoroquinolones fail to penetrate reptilian ocular tissue
Systemic fluoroquinolone therapy alone is curative because Salmonella arizonae is invariably susceptible and the caseous material resolves with antimicrobials
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)

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 298: During a pre-purchase exam of a 5-year-old Quarter Horse, grade 3/5 left forelimb lameness is localized to the foot with a palmar digital nerve block. Radiographs reveal navicular bone erosions and synovial invaginations. The diagnosis is:

Distal phalanx fracture
Laminitis with rotation
Navicular syndrome (palmar foot pain) (Correct answer)
Pedal osteitis

Correct answer: Navicular syndrome (palmar foot pain)

Navicular syndrome is characterized by palmar foot pain, positive response to palmar digital nerve block, and radiographic changes including synovial fossae and flexor cortex erosions of the navicular bone.

Question 299: A 9-year-old Quarter Horse cutting horse presents with a 4-month history of bilateral hindlimb stiffness that is worse in the morning and improves with exercise. The horse shows a characteristic 'goose-stepping' gait. Intra-articular anesthesia of the distal intertarsal and tarsometatarsal joints produces marked improvement. Medical management has failed over 6 months. Chemical arthrodesis with sodium monoiodoacetate (MIA) is elected. Which of the following correctly describes the mechanism of action of sodium monoiodoacetate in inducing arthrodesis?

It directly stimulates osteoblastic activity at subchondral bone, promoting bridging osteophyte formation across the joint space
It chelates calcium ions within the synovial fluid, precipitating calcium monoiodoacetate crystals that mechanically abrade cartilage
It activates the complement cascade within the joint, inducing a sterile neutrophilic arthritis that ablates the synovial membrane
It inhibits glycolysis in chondrocytes by alkylating sulfhydryl groups of glyceraldehyde-3-phosphate dehydrogenase, causing chondrocyte death and cartilage destruction (Correct answer)

Correct answer: It inhibits glycolysis in chondrocytes by alkylating sulfhydryl groups of glyceraldehyde-3-phosphate dehydrogenase, causing chondrocyte death and cartilage destruction

Sodium monoiodoacetate (MIA) is a chondrotoxic agent that alkylates (irreversibly inhibits) the sulfhydryl group of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a key enzyme in glycolysis. Since articular cartilage relies almost entirely on anaerobic glycolysis for energy, this inhibition causes rapid chondrocyte death, cartilage matrix degradation, and subsequent subchondral bone-to-bone apposition — eventually leading to bony fusion. MIA does not primarily stimulate osteoblasts directly, does not chelate calcium, and does not work via complement activation.

Question 300: A beef producer asks about strategies to reduce the use of medically important antimicrobials in the feedlot. Which intervention is the best alternative for reducing bovine respiratory disease (BRD) morbidity?

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

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

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

Question 301: A llama is treated with flunixin meglumine IV at the bovine label dose for 5 consecutive days for GI pain. Which adverse effect is MOST likely due to the species-specific pharmacokinetic difference compared to cattle?

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

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

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

Question 302: An 8-month-old kitten presents with intention tremors of the head, broad-based stance, hypermetria, and falling toward the right. The neurologic examination is otherwise normal with no weakness. Which region of the nervous system is affected?

Right side of the cerebellum (Correct answer)
Right vestibular apparatus (peripheral)
Right C1-C5 spinal cord segment
Right cerebral hemisphere (forebrain)

Correct answer: Right side of the cerebellum

Intention tremors, hypermetria, and broad-based stance without weakness are signs of cerebellar disease. Falling/rolling ipsilaterally (toward the lesion side) with a unilateral cerebellar lesion reflects ipsilateral cerebellar hemispheric dysfunction (cerebellum has ipsilateral control). Forebrain lesions cause contralateral deficits with normal gait quality. Peripheral vestibular disease causes head tilt and nystagmus without hypermetria or intention tremor.

Question 303: A 7-month-old DSH kitten presents with acute onset of corneal ulceration, periocular alopecia with facial dermatitis, and sneezing. Fluorescein staining reveals a classic dendritic (branching) corneal ulcer. Treatment with topical idoxuridine is initiated. Three weeks later, despite apparent resolution of acute signs, the owner reports persistent squinting and a new corneal opacity in the same eye. Slit-lamp examination reveals stromal vascularization and haze without epithelial staining. What is the MOST likely mechanism and appropriate management?

The stromal opacity represents immune-mediated keratitis (eosinophilic or stromal keratitis) driven by viral antigen persistence or recurrent subclinical reactivation; treatment should include topical corticosteroids (used cautiously) combined with antiviral prophylaxis such as topical cidofovir. (Correct answer)
Topical idoxuridine resistance has developed, and switching to topical trifluridine with concurrent systemic interferon-omega will resolve both the opacity and underlying viral load permanently.
The opacity is a permanent corneal scar from the initial ulcer with no inflammatory component; no further treatment is needed beyond lubricating eye drops.
The corneal opacity indicates active FHV-1 viral replication in keratocytes, requiring intensified antiviral monotherapy with oral famciclovir alone and avoidance of all immunosuppressive agents.

Correct answer: The stromal opacity represents immune-mediated keratitis (eosinophilic or stromal keratitis) driven by viral antigen persistence or recurrent subclinical reactivation; treatment should include topical corticosteroids (used cautiously) combined with antiviral prophylaxis such as topical cidofovir.

After resolution of the acute dendritic ulcer phase of FHV-1 keratitis, some cats develop stromal keratitis—a non-ulcerative immune-mediated inflammation triggered by persistent viral antigen or low-level viral reactivation in the stroma. It presents with stromal vascularization and haze without active epithelial defects (negative fluorescein stain). This phase has an immune-mediated component and paradoxically benefits from judicious topical corticosteroids combined with antiviral cover (e.g., topical cidofovir BID or oral famciclovir) to prevent viral flare during immunosuppression. Using antivirals alone is insufficient. The lesion is not simply a scar—active vascularization indicates ongoing inflammation. Antiviral resistance developing to idoxuridine within 3 weeks is not a primary concern here.

Question 304: 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?

Adrenal ultrasonography to rule out adrenal-dependent hyperadrenocorticism
No further testing is needed; the 8-hour suppression pattern is diagnostic for pituitary-dependent hyperadrenocorticism (PDH) (Correct answer)
High-dose dexamethasone suppression test (HDDST) to confirm PDH vs. ADH
Endogenous ACTH concentration measurement

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 305: A cat with feline asthma is presented in respiratory distress with expiratory wheezes. After initial stabilization with oxygen, which drug is preferred for acute bronchodilation?

Terbutaline (subcutaneous) (Correct answer)
Prednisolone (oral)
Cyproheptadine (oral)
Theophylline (oral)

Correct answer: Terbutaline (subcutaneous)

Terbutaline given subcutaneously or IM is the drug of choice for acute bronchospasm in cats because of its rapid onset as a beta-2 agonist.

Question 306: Which imaging modality is BEST for evaluating the extent of soft tissue masses adjacent to bone in a dog?

MRI (Correct answer)
Nuclear scintigraphy
Fluoroscopy
Plain radiography

Correct answer: MRI

MRI provides superior soft tissue contrast resolution compared to CT, radiography, and scintigraphy, making it the modality of choice for soft tissue mass characterization.

Question 307: On ultrasound, a hypoechoic halo surrounding a hepatic mass in a dog is called:

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

Correct answer: Target lesion

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

Question 308: In a feedlot, the recommended withdrawal time before slaughter must be observed when using which antibiotic for treatment of bovine respiratory disease?

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

Correct answer: Tulathromycin

Tulathromycin (Draxxin) has a meat withdrawal time of 18 days in the US, and compliance is required to ensure drug residue-free beef at slaughter.

Question 309: A 10-year-old Miniature Schnauzer with a history of hyperlipidemia presents with acute onset of vomiting, anorexia, and cranial abdominal pain. Physical examination reveals a 'praying posture.' Laboratory findings include neutrophilia, elevated amylase, and markedly elevated lipase. Which of the following is the most appropriate initial treatment?

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

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

Ketoprofen
Robenacoxib (Correct answer)
Grapiprant
Meloxicam

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 311: You are consulting on a biosecurity plan for a seedstock beef operation importing 15 breeding bulls from three different sources. Johne's disease (paratuberculosis) is a primary concern. Which combination of testing and quarantine procedures reflects current AAVLD/USAHA Voluntary Johne's Disease Herd Status Program (VJDHSP) Tier 3 recommendations for incoming animals?

Two negative fecal PCR tests 30 days apart during a 60-day quarantine before introduction (Correct answer)
Two consecutive negative fecal PCR tests at entry and exit of a 14-day quarantine period
Negative fecal culture on a single pooled sample from all 15 bulls after a 30-day quarantine
One negative serum ELISA on arrival plus one negative fecal culture at 30 days during quarantine

Correct answer: Two negative fecal PCR tests 30 days apart during a 60-day quarantine before introduction

Under the VJDHSP framework, bulls entering a Tier 3 or higher herd should ideally have two negative high-sensitivity fecal tests (PCR or culture) performed at least 30 days apart during a quarantine period of at least 60 days. Fecal PCR has largely supplanted fecal culture as the preferred diagnostic due to faster turnaround and comparable sensitivity in intermittent shedders. A single serum ELISA has poor sensitivity in subclinical animals (50–60%) and is insufficient alone. Pooled samples reduce sensitivity further and are inappropriate for individual animal clearance. A 14-day quarantine is insufficient to detect intermittent shedders and does not meet Tier 3 biosecurity standards.

Question 312: A 6-year-old male neutered Domestic Shorthair cat is evaluated for a 6-month history of weight loss despite polyphagia, intermittent vomiting, and hyperactivity. T4 is 7.8 µg/dL (reference: 0.8–4.0). You initiate methimazole therapy. Four weeks later, the owner reports the cat is less active and has developed facial pruritus and excoriations. Repeat T4 is now 1.2 µg/dL. Creatinine has risen from 1.2 to 3.8 mg/dL. Which pathophysiological explanation BEST accounts for the creatinine increase?

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

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

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

Question 313: A 7-year-old Warmblood gelding presents with acute onset right forelimb lameness and a positive flexion test of the distal limb. Nerve blocks reveal pain originating from the palmar digital nerves. Radiographs show pedal osteitis. Which treatment is most appropriate for long-term management?

Deep digital flexor tenotomy
Coffin joint corticosteroid injection
Navicular bursa lavage
Palmar digital neurectomy (Correct answer)

Correct answer: Palmar digital neurectomy

Palmar digital neurectomy is indicated for horses with chronic foot pain (including pedal osteitis) that have failed conservative management, providing long-term desensitization of the heel and sole.

Question 314: Which statement correctly describes the feline estrous cycle?

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

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

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

Question 315: Under the National Incident Management System (NIMS), which position within the Incident Command System (ICS) coordinates animal care activities during a disaster response?

Safety Officer
Animal/Technical Specialist or Veterinary Medical Officer (Correct answer)
Logistics Section Chief
Public Information Officer

Correct answer: Animal/Technical Specialist or Veterinary Medical Officer

Veterinary Medical Officers or Animal Technical Specialists serve within ICS to coordinate animal care, biosecurity, and zoonotic disease control during disasters.

Question 316: A ferret with insulinoma is being treated medically. Which drug is used to increase blood glucose by inhibiting insulin secretion?

Phenobarbital
Prednisolone
Diazoxide (Correct answer)
Methimazole

Correct answer: Diazoxide

Diazoxide inhibits pancreatic insulin secretion and promotes glycogenolysis, making it useful for managing hypoglycemia in ferrets with insulinoma.

Question 317: 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?

USDA Brucellosis Eradication Program using ELISA
Federal-State TB Eradication Program using the caudal fold tuberculin test (CFT) (Correct answer)
National Animal Health Monitoring System using PCR of nasal swabs
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 318: 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
Retinal toxicity risk is substantially increased at doses exceeding 5 mg/kg/day; lesions typically occur within days and are irreversible (Correct answer)
Enrofloxacin causes retinal degeneration in a dose-independent fashion; even a single dose at any concentration poses equal risk
Enrofloxacin-induced retinopathy in cats is fully reversible if the drug is discontinued within 48 hours of the first visual deficit

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 319: A 7-year-old spayed female cat is diagnosed with intermediate-grade small cell lymphoma of the GI tract confirmed via full-thickness biopsy showing transmural infiltration with loss of normal architecture. Which chemotherapy protocol is MOST appropriate compared to the standard low-grade (small cell) lymphoma protocol?

Chlorambucil and prednisolone (COP equivalent)
Toceranib phosphate targeting c-Kit mutation
CHOP-based protocol (cyclophosphamide, doxorubicin, vincristine, prednisolone) (Correct answer)
Single-agent lomustine (CCNU)

Correct answer: CHOP-based protocol (cyclophosphamide, doxorubicin, vincristine, prednisolone)

Intermediate- to high-grade feline GI lymphoma (large cell lymphoma) carries a significantly worse prognosis than the indolent small cell (low-grade) form and requires a more aggressive CHOP-based multi-agent protocol. The chlorambucil/prednisolone protocol used for small cell lymphoma is insufficient for large or intermediate cell disease. Single-agent lomustine has activity in some lymphomas but is not the standard of care here. Toceranib targets receptor tyrosine kinases and is not the treatment of choice for GI lymphoma.

Question 320: 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?

Enteric bacteria (E. coli, Enterococcus); fluoroquinolone or amoxicillin-clavulanate (Correct answer)
Mycobacterium spp.; rifampicin
Toxoplasma gondii; clindamycin
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 321: A backyard chicken flock presents with sudden death, cyanosis of the comb and wattles, and neurological signs. Which disease should be the primary differential?

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

Correct answer: Newcastle disease (velogenic strain)

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

Question 322: A 6-year-old male Dachshund presents acutely with inability to walk in the hind limbs and deep pain perception is absent bilaterally. MRI confirms a thoracolumbar Hansen type I disc extrusion at T13-L1. What is the most critical prognostic indicator?

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

Correct answer: Presence or absence of deep pain perception

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

Question 323: 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:

Severity of disc extrusion on MRI (Grasso scale grade)
Age of the patient at time of surgery
Presence or absence of deep pain perception in the pelvic limbs (Correct answer)
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 324: A 10-week-old female Maltese puppy is presented for her first physical examination. On auscultation, you detect a continuous, 'machinery-like' murmur, heard best over the left heart base. The puppy is otherwise bright and alert. Which of the following is the most likely diagnosis?

Ventricular Septal Defect
Mitral Valve Dysplasia
Patent Ductus Arteriosus (Correct answer)
Pulmonic Stenosis

Correct answer: Patent Ductus Arteriosus

A continuous, machinery-like murmur heard best at the left heart base in a young dog is pathognomonic for a left-to-right shunting Patent Ductus Arteriosus (PDA). This occurs because the ductus arteriosus, a vessel that bypasses the lungs in the fetus, fails to close after birth, causing a constant flow of blood from the high-pressure aorta to the lower-pressure pulmonary artery.

Question 325: A 9-year-old spayed female Boxer is presented with episodic weakness, syncope, and a heart rate of 40 bpm. ECG reveals a P wave with no associated QRS complex occurring at irregular intervals. What is the diagnosis?

Sick sinus syndrome
Third-degree (complete) AV block (Correct answer)
Atrial fibrillation
Ventricular tachycardia

Correct answer: Third-degree (complete) AV block

Third-degree AV block is characterized by complete dissociation of P waves and QRS complexes with a slow escape rhythm, causing bradycardia and syncope.

Question 326: 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?

Iatrogenic hyperadrenocorticism; detailed medication history and cessation of exogenous glucocorticoids
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

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

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

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

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

Question 328: A horse is prescribed rifampin as part of a combination regimen for Rhodococcus equi pneumonia. The foal is also receiving erythromycin. Three weeks into therapy, serum erythromycin levels are subtherapeutic despite appropriate dosing. What is the most likely mechanism?

Erythromycin inhibits its own absorption through downregulation of OATP transporters
Rifampin induces hepatic CYP3A4 and P-glycoprotein, markedly increasing erythromycin metabolism and efflux (Correct answer)
Rifampin chelates erythromycin in the GI tract, reducing oral bioavailability
Erythromycin undergoes accelerated renal clearance due to rifampin-induced alkalinization of urine

Correct answer: Rifampin induces hepatic CYP3A4 and P-glycoprotein, markedly increasing erythromycin metabolism and efflux

Rifampin is a potent inducer of cytochrome P450 enzymes (particularly CYP3A4) and P-glycoprotein. Erythromycin is a CYP3A4 substrate and P-glycoprotein substrate. Rifampin induction increases both first-pass hepatic metabolism and intestinal P-gp-mediated efflux of erythromycin, dramatically reducing its systemic bioavailability and plasma concentrations. This interaction is clinically significant in R. equi treatment and may compromise efficacy; azithromycin is often preferred as an alternative macrolide in this context.

Question 329: Acoustic shadowing on ultrasound is caused by:

Amplification of returning echoes beyond the gain setting
Complete absorption or reflection of the sound beam by a highly attenuating structure (Correct answer)
Bending of the ultrasound beam at curved interfaces
Refraction of sound through soft tissue-fluid interfaces

Correct answer: Complete absorption or reflection of the sound beam by a highly attenuating structure

Dense structures such as calculi or bone absorb or reflect nearly all the ultrasound energy, preventing transmission and creating a shadow distal to the structure.

Question 330: 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?

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

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 331: In avian medicine, which drug is contraindicated in pigeons and doves due to severe toxicity?

Doxycycline
Enrofloxacin
Metronidazole
Fenbendazole at high doses (Correct answer)

Correct answer: Fenbendazole at high doses

Fenbendazole at high doses or prolonged use causes fatal bone marrow suppression in pigeons and doves; caution with dosing is essential.

Question 332: A cat with hyperthyroidism is started on methimazole. Two weeks later, the owner reports the cat is scratching its face intensely and has developed facial excoriations. Which mechanism best explains this idiosyncratic reaction, and what is the appropriate next step?

Compensatory increase in thyroid hormone causing pruritus; increase the methimazole dose
Methimazole accumulation causing direct neurotoxicity to facial nerve endings; reduce dose by 50%
Type IV delayed hypersensitivity reaction; discontinue methimazole and consider radioiodine or surgical thyroidectomy (Correct answer)
Methimazole-induced mast cell degranulation; administer diphenhydramine and continue methimazole at a lower dose

Correct answer: Type IV delayed hypersensitivity reaction; discontinue methimazole and consider radioiodine or surgical thyroidectomy

Facial pruritus and excoriation is a well-documented idiosyncratic adverse effect of methimazole in cats, occurring in approximately 2-3% of treated cats. It represents a Type IV (cell-mediated) delayed hypersensitivity reaction typically appearing within the first month of therapy. This reaction necessitates discontinuation of methimazole; dose reduction is not appropriate as re-exposure will trigger recurrence. Alternative management includes carbimazole (prodrug of methimazole, so cross-reactivity is possible), radioactive iodine (I-131), or surgical thyroidectomy.

Question 333: Which drug class is contraindicated in cats due to their deficiency in UDP-glucuronosyltransferase?

Fluoroquinolones
NSAIDs metabolized via glucuronidation (Correct answer)
Macrolide antibiotics
Aminoglycosides

Correct answer: NSAIDs metabolized via glucuronidation

Cats lack sufficient UDP-glucuronosyltransferase activity, making drugs like acetaminophen and certain NSAIDs dependent on glucuronidation highly toxic.

Question 334: A dog's abdominal ultrasound reveals a splenic mass with a 'target' or 'bull's-eye' lesion appearance (hypoechoic halo around a hyperechoic center). This pattern is most associated with:

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

Correct answer: Metastatic neoplasia

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

Question 335: 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?

McMaster flotation to identify the species causing disease
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

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 336: Which antifungal drug works by inhibiting the enzyme lanosterol 14-alpha-demethylase, disrupting ergosterol synthesis?

Griseofulvin
Fluconazole (Correct answer)
Amphotericin B
Nystatin

Correct answer: Fluconazole

Fluconazole (and other azole antifungals) inhibit lanosterol 14-alpha-demethylase, blocking ergosterol synthesis and disrupting fungal cell membrane integrity.

Question 337: A veterinarian observes a horse trotting on a hard, flat surface and notes a consistent head nod. The lameness is not apparent at a walk but is easily seen at the trot. According to the American Association of Equine Practitioners (AAEP) Lameness Scale, what is the most appropriate grade?

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

Correct answer: Grade 3

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

Question 338: Which fluoroquinolone antibiotic is most associated with acute retinal degeneration and blindness in cats when used at high doses?

Enrofloxacin (Correct answer)
Marbofloxacin
Orbifloxacin
Pradofloxacin

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

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

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 340: Ultrasonography of a 9-year-old Labrador Retriever with suspected splenic disease reveals a large, heterogeneous splenic mass with multiple hyperechoic foci casting acoustic shadows, admixed with anechoic cavitations. The most likely diagnosis is:

Extramedullary hematopoiesis
Nodular hyperplasia
Splenic myelolipoma (Correct answer)
Splenic hemangiosarcoma

Correct answer: Splenic myelolipoma

Splenic myelolipomas are rare benign tumors composed of mature adipose and hematopoietic tissue. On ultrasound, they appear as heterogeneous masses with hyperechoic foci (fat) causing acoustic shadowing and may contain cystic areas. This mixed echogenicity with shadowing foci is characteristic. Hemangiosarcoma is typically a large, heterogeneous cavitated mass but does not contain shadowing foci from calcification or fat. Nodular hyperplasia and extramedullary hematopoiesis are diffuse or multiple small nodular changes without the discrete mass architecture and shadowing foci described.

Question 341: Which finding on echocardiography best differentiates hypertrophic cardiomyopathy (HCM) from physiologic cardiac hypertrophy secondary to hyperthyroidism in a cat?

Mild left atrial enlargement
Increased fractional shortening >45%
Left ventricular free wall thickness >6 mm
Systolic anterior motion (SAM) of the mitral valve (Correct answer)

Correct answer: Systolic anterior motion (SAM) of the mitral valve

SAM of the mitral valve causing dynamic left ventricular outflow tract obstruction is characteristic of primary HCM and is not a feature of hyperthyroid-induced hypertrophy.

Question 342: On ultrasound of the urinary bladder, a non-shadowing, gravity-dependent echogenic material that shifts with patient repositioning is MOST consistent with:

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

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 343: A 9-year-old cat presents with hypercalcemia (total Ca 14.2 mg/dL), weight loss, and peripheral lymphadenopathy. Which condition is most likely?

Hypervitaminosis D
Primary hyperparathyroidism
Idiopathic hypercalcemia
Lymphoma (Correct answer)

Correct answer: Lymphoma

Lymphoma is the most common cause of hypercalcemia of malignancy in cats, mediated by PTHrP secretion.

Question 344: A commercial sow farm reports a sudden increase in late-term abortions, stillbirths, and weak-born piglets across multiple farrowing rooms. Serology confirms Porcine Reproductive and Respiratory Syndrome Virus (PRRSV). Which viral characteristic best explains the reproductive failure observed?

PRRSV preferentially infects uterine endometrial cells, causing direct placental necrosis
PRRSV causes reproductive failure exclusively through induction of hyperprogesteronemia
PRRSV crosses the placenta during early gestation and integrates into fetal DNA
PRRSV infects porcine alveolar macrophages and spreads hematogenously to the fetoplacental unit during the last trimester (Correct answer)

Correct answer: PRRSV infects porcine alveolar macrophages and spreads hematogenously to the fetoplacental unit during the last trimester

PRRSV targets porcine alveolar macrophages (PAMs) and monocyte-derived cells. During viremia — which is most consequential in the last trimester — virus crosses into the fetoplacental unit, causing fetal infection, death, and mummification. Early gestation infection rarely causes fetal loss; late gestation is the vulnerable window.

Question 345: A cat is found to have hypokalemia (K+ 2.8 mEq/L) and symmetric cervical ventroflexion. Which underlying disease is most commonly associated with this presentation in cats?

Addison's disease
Hypothyroidism
Pheochromocytoma
Hyperaldosteronism (Conn's syndrome) (Correct answer)

Correct answer: Hyperaldosteronism (Conn's syndrome)

Primary hyperaldosteronism (Conn's syndrome) causes chronic hypokalemia in cats, leading to hypokalemic polymyopathy characterized by ventroflexion of the neck.

Question 346: Insulinoma in ferrets is a tumor of which cell type, and what is its primary clinical consequence?

Hepatic cells, causing hyperbilirubinemia
Pancreatic beta cells, causing hypoglycemia (Correct answer)
Pancreatic alpha cells, causing hyperglycemia
Adrenal cortex cells, causing hyperadrenocorticism

Correct answer: Pancreatic beta cells, causing hypoglycemia

Insulinoma is a pancreatic beta cell tumor that secretes excess insulin, causing episodic hypoglycemia, weakness, and seizures in ferrets.

Question 347: A 6-year-old Rottweiler presents with acute vomiting and melena. Gastroscopy reveals a deep ulcer in the antrum. Which drug class is most effective at preventing NSAID-induced gastrointestinal ulcers in dogs?

Proton pump inhibitors (Correct answer)
H2-receptor antagonists
Sucralfate
Bismuth subsalicylate

Correct answer: Proton pump inhibitors

Proton pump inhibitors (e.g., omeprazole) provide the most potent and sustained acid suppression and are superior to H2 blockers for preventing and treating GI ulcers.

Question 348: 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?

Glycopyrrolate IV to treat bradycardia without reversing opioid (Correct answer)
Atipamezole IV
Flumazenil IV
Naloxone full dose 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 349: During lameness examination on the lunge, a horse with LEFT forelimb lameness will characteristically:

Nod the head DOWN when the right forelimb strikes
Lower the croup when lunging to the right
Nod the head UP when the left forelimb strikes (Correct answer)
Show a hip hike when the left forelimb strikes

Correct answer: Nod the head UP when the left forelimb strikes

With a painful forelimb, the horse lifts (nods up) the head when the painful limb contacts the ground to reduce load, and nods down on the sound limb.

Question 350: On a lateral thoracic radiograph, 'sternal contact' of the heart is increased in which cardiac condition?

Right ventricular enlargement (Correct answer)
Pulmonary hypertension
Pericardial effusion
Left atrial enlargement

Correct answer: Right ventricular enlargement

Right ventricular enlargement causes the heart to shift cranioventrally, increasing its contact with the sternum on the lateral view.

Question 351: A ventrodorsal thoracic radiograph of a 4-year-old Maine Coon cat shows a 'reverse D' or 'D-shaped' cardiac silhouette with straightening of the right heart border, tracheal deviation to the left, and post-stenotic dilation of the main pulmonary artery. Echocardiography confirms pulmonic stenosis. Which radiographic measurement, if applied, would MOST accurately quantify cardiac enlargement in this cat?

Cardiothoracic ratio on the VD view
Vertebral Heart Score (VHS) using lateral projection (Correct answer)
Vertebral Left Atrial Score (VLAS) on lateral projection
Right heart-to-thoracic 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 352: 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?

Presence of concurrent cartilage fibrillation extending beyond the lesion (Correct answer)
Patient age at time of surgery
Size of the original osteochondral fragment
Duration of lameness prior to 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 353: A shelter cat is diagnosed with feline panleukopenia. What is the minimum isolation period recommended after clinical recovery to prevent spread to susceptible cats?

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

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 354: On a lateral skull radiograph, which structure appears as a radiolucent line running through the calvarium and should not be mistaken for a fracture?

Foramen magnum
Sagittal suture (Correct answer)
Cribriform plate
Petrous temporal bone

Correct answer: Sagittal suture

The sagittal suture appears as a radiolucent line in the dorsal calvarium and is a normal anatomic finding.

Question 355: 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?

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

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 356: A cow-calf producer in a selenium-deficient region is using injectable sodium selenite (0.5 mg Se/lb BW) in neonatal calves to prevent white muscle disease. He now wants to supplement pregnant cows pre-calving to improve passive transfer of selenium via colostrum. He asks about adding selenium to the mineral mix at 120 ppm. Which response is most accurate?

This is inappropriate; the legal maximum for selenium in cattle mineral supplements is 120 ppm, but actual intake must not exceed 3 mg Se/head/day, which requires calculating expected mineral consumption to avoid toxicosis (Correct answer)
This is inappropriate; selenium cannot be supplemented via mineral mixes in cattle and must only be given via injectable or slow-release bolus forms
This is appropriate if the mineral is fed free-choice, because cattle self-regulate selenium intake
This is appropriate because dry matter intake of minerals is low enough that 120 ppm selenium is safe and will effectively raise colostral selenium

Correct answer: This is inappropriate; the legal maximum for selenium in cattle mineral supplements is 120 ppm, but actual intake must not exceed 3 mg Se/head/day, which requires calculating expected mineral consumption to avoid toxicosis

The FDA-mandated maximum for selenium in mineral supplements is 90 ppm in complete feeds and up to 700 ppm in salt-based mineral mixes (with a label restriction to 0.3 mg/kg of total diet DM), but the critical practical constraint is that total selenium intake must not exceed 3 mg/head/day to avoid selenium toxicosis. At 120 ppm Se in a mineral mix, if cows consume even 50 g of mineral/day they intake 6 mg Se — double the safe limit. Cattle do NOT self-regulate selenium intake (option C is false). Selenium CAN be supplemented via minerals (option D is false). The key is that the producer must calculate actual mineral consumption and adjust selenium concentration accordingly to stay ≤3 mg/head/day — the concentration alone does not guarantee safety.

Question 357: A 6-month-old calf dies acutely. Necropsy reveals a 'paint-brush' hemorrhage pattern on the epicardium, fibrinonecrotic plaques in the abomasum, and hemorrhagic lymph nodes. Which pathologic process most likely caused these lesions?

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

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

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

Question 358: On a thoracic radiograph of a 10-year-old DSH cat, you identify a soft-tissue opacity in the caudodorsal lung field that effaces the descending aorta but preserves the diaphragmatic silhouette. The lesion has a sharp ventral border and an indistinct dorsal border. Which anatomic compartment and silhouette sign interpretation is correct?

Pleural effusion in the caudodorsal costophrenic recess; the indistinct dorsal border reflects fluid-air interface
Caudodorsal pulmonary mass in the caudal lung lobe; positive silhouette sign with the aorta indicates the lesion is in contact with the aorta or the periaortic space (Correct answer)
Middle mediastinal mass; loss of cardiac silhouette confirms mediastinal origin
Diaphragmatic hernia; the preserved diaphragmatic line rules out rupture but the aortic effacement confirms herniated content

Correct answer: Caudodorsal pulmonary mass in the caudal lung lobe; positive silhouette sign with the aorta indicates the lesion is in contact with the aorta or the periaortic space

A positive silhouette sign occurs when two structures of the same opacity (soft tissue) are in contact, causing their borders to be indistinguishable. Loss of the aortic silhouette indicates the caudodorsal lung lesion is in anatomic contact with the aorta or periaortic mediastinum — this localizes the mass to the caudal lobe or posterior mediastinum. The preserved diaphragmatic line rules out diaphragmatic hernia. Pleural effusion would cause a diffuse gravity-dependent opacity, not a discrete mass with a sharp ventral border. This pattern is classic for a primary lung tumor (e.g., adenocarcinoma) in the caudal lung lobe abutting the mediastinum.

Question 359: Which of the following causes of exophthalmos in cattle occurs most frequently?

Sinusitis
Extracranial meningioma
Orbital arteriovenous fistula
Retrobulbar lymphosarcoma (Correct answer)

Correct answer: Retrobulbar lymphosarcoma

Retrobulbar lymphosarcoma is the most common cause of exophthalmos in cattle, especially in adult animals affected by Bovine Leukosis Virus (BLV). This neoplastic infiltration behind the globe creates a space-occupying lesion, pushing the eyeball forward. While other conditions can cause exophthalmos, lymphosarcoma is statistically the most frequent etiology in cattle.

Question 360: A producer wants to implement a PRRSV (Porcine Reproductive and Respiratory Syndrome Virus) control program. Wait—this is a bovine herd. Which respiratory virus causes 'shipping fever' complex and is commonly controlled with modified-live virus vaccines in beef cattle?

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

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

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

NAVLE (North American Veterinary Licensing Exam)

The NAVLE (North American Veterinary Licensing Exam) exam validates essential knowledge and skills required for certification or licensure in this field.

360

Questions

420 min

Time Limit

65%

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