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

Question 1: 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?

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

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 2: 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)
Prolonging anesthesia until the horse is fully awake
Placing the horse in dorsal recumbency during recovery
Administering acepromazine immediately post-surgery

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

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

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

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

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

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

Question 5: 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?

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

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 6: 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?

These inclusions represent viral intranuclear inclusions displaced to the cytoplasm during erythrocyte maturation
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

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 7: CT of the abdomen in a 5-year-old intact male dog reveals a retroperitoneal mass cranial to the kidney with heterogeneous contrast enhancement and central necrosis. The ipsilateral kidney is displaced ventrally. No primary tumor is identified. The MOST likely diagnosis is:

Adrenocortical carcinoma
Retroperitoneal liposarcoma
Paraganglioma (extra-adrenal pheochromocytoma) (Correct answer)
Renal cell carcinoma

Correct answer: Paraganglioma (extra-adrenal pheochromocytoma)

Extra-adrenal paragangliomas (extra-adrenal pheochromocytomas) arise from chromaffin cells along the aorta and adjacent sympathetic ganglia, most commonly in the retroperitoneum cranial to or between the kidneys. On CT, they appear as large, heterogeneously enhancing masses with central necrosis that displace adjacent structures. Their location separate from the adrenal gland distinguishes them from adrenocortical carcinoma. Renal cell carcinoma would originate within the renal parenchyma. Retroperitoneal liposarcoma would contain macroscopic fat attenuation on CT. The intact male status and retroperitoneal location cranial to the kidney are classic for paraganglioma in dogs.

Question 8: A 5-year-old Thoroughbred racehorse undergoes nuclear scintigraphy for investigation of right forelimb lameness that has not localized with nerve blocks. The bone scan shows markedly increased radiopharmaceutical uptake (IRU) in the mid-diaphysis of the right third metacarpal bone on the lateral cortex. What is the most appropriate next diagnostic step to characterize this lesion before formulating a treatment plan?

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

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

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

Question 9: 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?

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

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

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

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

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

Correct answer: Intra-articular distal interphalangeal joint block

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

Question 12: 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?

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

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 13: 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 14: 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 15: A dog presents with polydipsia, polyuria, and a urine specific gravity of 1.006. A water deprivation test is performed; after 8 hours the USG remains 1.007. Following ADH administration, USG rises to 1.022. What is the diagnosis?

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

Correct answer: Central diabetes insipidus

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

Question 16: During fluoroscopic evaluation of a 9-month-old Labrador Retriever with regurgitation, barium swallow demonstrates a persistent filling defect in the dorsal esophagus at the level of the heart base that does not change shape with peristalsis. A 'reversed 3 sign' or 'E sign' is noted on the aortic knob region. What is the most likely diagnosis?

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

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

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

Question 17: 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?

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

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 18: A 9-year-old dog is presented for chronic, unilateral nasal discharge. To evaluate the extent of disease, including potential bone destruction of the nasal turbinates and integrity of the cribriform plate, which advanced imaging modality is superior?

Rhinoscopy with biopsy
Magnetic Resonance Imaging (MRI)
Computed Tomography (CT) (Correct answer)
Dental radiography

Correct answer: Computed Tomography (CT)

Computed Tomography (CT) is the imaging modality of choice for evaluating the nasal passages because of its excellent spatial resolution and superior ability to detail bone. It eliminates the superimposition of structures seen on radiographs and is better than MRI for assessing fine bony changes like turbinate destruction or lysis of the cribriform plate, which is critical for staging nasal tumors or fungal disease. While rhinoscopy is needed for biopsy, CT provides the best anatomical map for surgical or radiation planning.

Question 19: 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?

Third-degree (complete) AV block (Correct answer)
Atrial fibrillation
Sick sinus syndrome
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 20: A kitten born to a queen with Toxoplasma gondii primary infection during pregnancy is most at risk for which clinical outcome?

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

Correct answer: Fading kitten syndrome with hepatic necrosis

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

Question 21: Under the Food Safety Modernization Act (FSMA), which rule specifically addresses hazard analysis and preventive controls for human food facilities?

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

Correct answer: Preventive Controls for Human Food Rule

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

Question 22: A cat anesthetized with isoflurane develops bradycardia (HR 70 bpm). What is the MOST appropriate first step before administering any drug?

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

Correct answer: Lighten anesthetic depth and reassess all parameters

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

Question 23: 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?

Mycoplasma hyorhinis
Streptococcus suis serotype 2 (Correct answer)
Erysipelothrix rhusiopathiae
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 24: A 9-year-old cat with a 2-month history of small-bowel diarrhea and weight loss undergoes intestinal biopsy. Histopathology reveals mucosal architectural distortion, villous blunting, and a mixed population of lymphocytes and plasma cells. Immunohistochemistry shows a CD3+/CD20− predominant infiltrate. What is the most appropriate next diagnostic step to distinguish small cell lymphoma from inflammatory bowel disease?

PARR (PCR for antigen receptor rearrangement) to assess clonality of the lymphocyte population (Correct answer)
Serum cobalamin and folate measurement to confirm small intestinal involvement
Trial therapy with prednisolone — clinical response definitively differentiates IBD from lymphoma
Repeat biopsy using endoscopic forceps to obtain deeper tissue samples

Correct answer: PARR (PCR for antigen receptor rearrangement) to assess clonality of the lymphocyte population

Distinguishing feline small cell (low-grade) lymphoma from lymphoplasmacytic IBD is one of the most challenging problems in feline gastroenterology, as both share similar histologic appearances and CD3+ T-cell infiltrates. PARR (PCR for antigen receptor rearrangement) assesses whether the lymphocyte population is clonal (lymphoma) or polyclonal (reactive/IBD) and is the gold-standard adjunct test when histology is equivocal. Response to steroids is not definitive because both IBD and small cell lymphoma can respond to chlorambucil/prednisolone. Cobalamin/folate confirms small intestinal involvement but does not differentiate the two diseases. Deeper biopsies improve histologic yield but do not resolve the clonality question.

Question 25: 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
Ectopic ureter with secondary hydronephrosis and hydroureter
Prostatic abscess with paraprostatic cyst formation

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

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

Question 26: Which statement most accurately describes the use of bisphosphonates (e.g., tiludronate) in equine lameness management?

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

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

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

Question 27: 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:

Nodular hyperplasia
Splenic hemangiosarcoma
Splenic myelolipoma (Correct answer)
Extramedullary hematopoiesis

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

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

Correct answer: 10–30 mg/kg/day

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

Question 29: 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:

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

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

Hyperkalemia
Hypokalemia (Correct answer)
Hypercalcemia
Hypernatremia

Correct answer: Hypokalemia

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

Question 31: A 3-year-old intact male cat tests FIV-positive. What is the most reliable route of transmission for this virus?

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

Correct answer: Bite wounds

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

Question 32: Which drug is used to treat hyperthyroidism in cats by blocking thyroid hormone synthesis?

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

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 33: A 9-year-old DSH cat is diagnosed with oral squamous cell carcinoma and the oncologist considers platinum-based chemotherapy. A technician asks whether cisplatin can be dose-reduced for safer use in this cat. Which statement most accurately describes cisplatin use in cats?

Cisplatin is absolutely contraindicated in cats because it causes fatal pulmonary edema and pleural effusion regardless of dose (Correct answer)
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 toxicity in cats manifests primarily as nephrotoxicity and peripheral neuropathy, identical to other species

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

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

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

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

Question 35: 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?

Fructosamine is unreliable in cats with concurrent hemolytic anemia and should be repeated
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

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 36: A horse undergoes exploratory laparotomy for small intestinal volvulus. After 3 hours of surgery, the horse develops tachycardia, hypotension, and pale mucous membranes. Lactate is 12 mmol/L. What does this lactate value primarily indicate?

Normal response to surgical stress
Severe tissue hypoperfusion and anaerobic metabolism (Correct answer)
Hepatic failure from anesthetic agents
Excessive intraoperative fluids causing hemodilution

Correct answer: Severe tissue hypoperfusion and anaerobic metabolism

A lactate of 12 mmol/L indicates severe systemic hypoperfusion with anaerobic metabolism, which is a poor prognostic indicator in equine colic surgery.

Question 37: A ferret presents for adrenalectomy. Which induction agent combination is most commonly used in ferrets for short procedures?

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

Correct answer: Ketamine and midazolam IM

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

Question 38: A group of yearling beef cattle on pasture for the first time during late summer exhibit profuse watery diarrhea, poor growth, and submandibular edema ('bottle jaw'). Which of the following is the most likely diagnosis?

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

Correct answer: Type I Ostertagiasis

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

Question 39: An 8-year-old Arabian endurance horse undergoes elective arthroscopy of the left carpal joints. During closure, the surgeon notes excessive hemorrhage from the dorsal aspect of the antebrachiocarpal joint. Which vessel, if lacerated during carpal arthroscopy via the standard dorsolateral or dorsomedial portals, is the most common source of significant intraoperative hemorrhage and what is the recommended immediate management?

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

Correct answer: Dorsal carpal branch of the radial artery; controlled lavage with epinephrine-containing saline and direct cautery

The dorsal carpal branch of the radial artery crosses the dorsal aspect of the carpus and is at risk during portal placement or instrument manipulation in equine carpal arthroscopy. Significant hemorrhage from arterial origin can obscure visualization and complicate closure. Initial management includes copious joint lavage to clear the field, followed by direct electrocautery of the vessel if it can be visualized arthroscopically. Epinephrine in irrigation fluid is used as an adjunct to promote vasoconstriction. The cephalic and accessory cephalic veins are also at risk but produce lower-pressure venous bleeding more readily managed with pressure alone.

Question 40: Which of the following medications is a potent, broad-spectrum antiemetic that functions by antagonizing neurokinin-1 (NK-1) receptors in the central vomiting center?

Maropitant (Correct answer)
Metoclopramide
Ondansetron
Famotidine

Correct answer: Maropitant

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

Question 41: A shelter veterinarian is investigating a cluster of cats with a highly virulent calicivirus (VS-FCV) outbreak. Affected cats exhibit facial and limb edema, ulceration of the nasal planum, pinnae necrosis, jaundice, and a mortality rate approaching 60%. Which of the following distinguishes VS-FCV from classical FCV strains and has the MOST direct implication for infection control?

VS-FCV is antigenically identical to classical FCV strains, so current vaccines provide complete cross-protective immunity and vaccination immediately halts outbreak spread.
VS-FCV is significantly more resistant to commonly used disinfectants, including quaternary ammonium compounds, and requires 1:32 dilution household bleach with extended contact time; it also causes high mortality in vaccinated adult cats. (Correct answer)
VS-FCV only affects immunocompromised cats; fully vaccinated immunocompetent adults are not susceptible regardless of exposure dose.
VS-FCV is exclusively transmitted via aerosolized droplets and does not persist on fomites, making hand hygiene the sole critical control measure.

Correct answer: VS-FCV is significantly more resistant to commonly used disinfectants, including quaternary ammonium compounds, and requires 1:32 dilution household bleach with extended contact time; it also causes high mortality in vaccinated adult cats.

VS-FCV (virulent systemic FCV) is notable for causing severe systemic disease and death even in vaccinated adult cats, highlighting the limitations of current vaccines against divergent strains. Like classical FCV, it is non-enveloped and highly environmentally stable, resistant to many disinfectants; dilute bleach (1:32) with adequate contact time remains effective. Fomite transmission is a critical route, making environmental decontamination and isolation essential. Vaccines do not provide sterilizing immunity against VS-FCV. Immunocompetent vaccinated adults can and do die.

Question 42: A 2-year-old Thoroughbred colt has bilateral forelimb angular limb deformity (valgus) at the carpus identified at 4 months of age. Radiographs show the deformity originates at the distal radial physis. The foal is now presenting at 6 months without improvement. What surgical option should be considered?

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

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

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

Question 43: 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?

Pulmonary consolidation
Pleural effusion
Cardiomegaly (Correct answer)
Pneumothorax

Correct answer: Cardiomegaly

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

Question 44: 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?

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

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

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

Correct answer: Slobbers (dental malocclusion)

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

Question 46: During fluoroscopic esophagram in a 2-year-old German Shepherd, liquid barium rapidly opacifies the esophagus but you observe persistent, focal retention of barium in a fusiform dilation of the esophagus at the level of the heart base. The esophagus proximal and distal to this region is normal in caliber. Manometric data (if available) would MOST likely show which of the following?

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

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

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

Question 47: A 10-year-old Quarter Horse presents with recurrent episodes of forelimb lameness that worsen after exercise. Radiographs of the navicular region reveal radiolucent 'lollipop' lesions (synovial invaginations) in the distal border of the navicular bone with concurrent cortical thinning of the flexor cortex. Nuclear scintigraphy shows markedly increased radiopharmaceutical uptake in the palmar aspect of the foot. Which finding on MRI would MOST specifically confirm active navicular disease (podotracheritis) versus normal aging change?

T2 hyperintensity within the navicular bone marrow
Fluid signal within the navicular bursa on T2-weighted sequences
Thickening of the deep digital flexor tendon insertion
Ill-defined T1 hypointensity in the navicular bone correlating with the scintigraphic hot spot (Correct answer)

Correct answer: Ill-defined T1 hypointensity in the navicular bone correlating with the scintigraphic hot spot

Ill-defined T1 hypointensity (bone marrow edema pattern) within the navicular bone that correlates spatially with the scintigraphic hot spot is the MRI finding most specifically linked to active pathology (edema, vascular compromise, remodeling) rather than incidental aging change. T2 hyperintensity alone can represent fluid or edema but is less specific. Navicular bursal fluid (T2 fluid signal) can be physiologic. DDFT thickening is a complication but not specific for active navicular bone disease itself. The T1 hypointensity + scintigraphy correlation confirms the lesion is metabolically active.

Question 48: A 4-year-old Border Collie presents with episodic muscle tremors, hypersalivation, and mydriasis after being on a rural property. Organophosphate toxicosis is suspected. What is the mechanism and antidote?

GABA antagonism; diazepam
Nicotinic receptor blockade; atropine
Acetylcholinesterase inhibition; atropine and pralidoxime (Correct answer)
Sodium channel blockade; lipid emulsion therapy

Correct answer: Acetylcholinesterase inhibition; atropine and pralidoxime

Organophosphates irreversibly inhibit acetylcholinesterase causing acetylcholine accumulation; atropine blocks muscarinic effects while pralidoxime reactivates the enzyme if given early.

Question 49: A cow at 60 days postpartum has been anestrus. Body condition score is 2/5. Progesterone profiles confirm ovarian inactivity. The primary cause is most likely:

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

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

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

Question 50: 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?

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

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 51: A 5-year-old FeLV-positive cat presents with a rapidly growing sublumbar mass. Fine-needle aspirate reveals a monomorphic population of large lymphocytes with prominent nucleoli and scant cytoplasm. Immunophenotyping shows CD3-negative, CD20-positive cells. Which statement about this neoplasm's relationship to FeLV is MOST accurate?

Reverse transcriptase error during FeLV replication generates B-cell-tropic recombinant proviruses in somatic tissue
FeLV envelope glycoprotein gp70 directly transforms B-lymphocytes through binding to the thiamine transporter receptor
This B-cell lymphoma likely arose independently of FeLV; FeLV-associated lymphomas are almost exclusively T-cell in immunophenotype (Correct answer)
FeLV proviral integration near c-myc via insertional mutagenesis is the primary oncogenic mechanism for this B-cell phenotype

Correct answer: This B-cell lymphoma likely arose independently of FeLV; FeLV-associated lymphomas are almost exclusively T-cell in immunophenotype

FeLV-associated lymphomas are overwhelmingly T-cell in origin (>90%), typically thymic/mediastinal lymphoma in young cats. B-cell lymphomas, such as this sublumbar presentation, are generally NOT FeLV-associated and likely arose through FeLV-independent mechanisms (e.g., chronic antigenic stimulation, Helicobacter-associated alimentary lymphoma). The co-occurrence with FeLV positivity is incidental in this case. Understanding immunophenotype-retrovirus associations is critical for prognosis and etiology — FeLV-positive T-cell lymphomas carry a particularly poor prognosis. The FeLV receptor is the thiamine transporter (THTR1), but this does not directly transform B-cells.

Question 52: A 4-year-old Greyhound is prescribed phenobarbital for epilepsy. Compared to a Labrador Retriever of the same weight, which pharmacokinetic difference most significantly affects dosing in Greyhounds?

Greyhounds have reduced hepatic CYP450 enzyme activity, leading to slower phenobarbital clearance
Greyhounds have a lower volume of distribution for lipophilic drugs due to minimal body fat, resulting in higher plasma concentrations (Correct answer)
Greyhounds exhibit increased P-glycoprotein expression at the blood-brain barrier, reducing CNS penetration
Greyhounds have accelerated renal tubular secretion of phenobarbital, requiring higher doses to maintain therapeutic levels

Correct answer: Greyhounds have a lower volume of distribution for lipophilic drugs due to minimal body fat, resulting in higher plasma concentrations

Greyhounds have exceptionally low body fat (1–3% vs. 15–25% in mixed breeds). Phenobarbital is a lipophilic drug that distributes into adipose tissue. With minimal fat stores, the volume of distribution is reduced, leading to higher peak plasma concentrations at standard mg/kg doses. This means Greyhounds are at greater risk for toxicity and often require lower initial doses. Hepatic clearance differences exist for some drugs (e.g., propofol, thiopental) but are not the primary concern with phenobarbital dosing.

Question 53: A cat with confirmed hypertrophic cardiomyopathy (HCM) and left atrial enlargement (LA:Ao ratio 1.7) is asymptomatic and has no pleural effusion. Which of the following treatment decisions is BEST supported by current evidence-based feline cardiology guidelines?

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

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

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

Question 54: 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?

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

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 55: 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
Long-term systemic antifungal therapy
Transarterial coil embolization of the affected artery (Correct answer)
Surgical removal of the fungal plaque

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 56: 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?

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

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

Ketoconazole
Amphotericin B
Voriconazole (Correct answer)
Griseofulvin

Correct answer: Voriconazole

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

Question 58: A 450 kg dairy cow at 10 days postpartum develops acute septic metritis with a fetid red-brown uterine discharge, fever of 40.8°C, and milk drop. Culture yields a pure growth of Trueperella pyogenes. Her BCS at dry-off was 4.0/5.0, and she had a twins delivery. You elect to treat with intrauterine cephapirin. Which additional systemic treatment is MOST pharmacologically justified given the likely concurrent metabolic status of this cow?

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

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

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

Question 59: 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 C1-C5 spinal cord segment
Right cerebral hemisphere (forebrain)
Right vestibular apparatus (peripheral)
Right side of the cerebellum (Correct answer)

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 60: Following a bilateral thyroidectomy, a 11-year-old female domestic shorthair cat is released from the hospital. The patient is reevaluated two days later due to panting, agitation, and a recent seizure. Which postoperative complication is most likely to account for these clinical symptoms?

Hypoparathyroidism (Correct answer)
Hypocalcemia
Renal disease
Horner's syndrome

Correct answer: Hypoparathyroidism

Bilateral thyroidectomy in cats often involves inadvertent removal or damage to the parathyroid glands, which are closely associated with the thyroid. The parathyroid glands regulate calcium levels via PTH. Postoperative hypoparathyroidism leads to hypocalcemia, causing increased neuromuscular excitability that manifests as panting, agitation, and seizures, making it the most likely complication.

Question 61: A cow in early lactation is treated with systemic flunixin meglumine (2.2 mg/kg IV) for acute coliform mastitis. Which mechanism best explains why this NSAID may paradoxically worsen endotoxemia outcomes despite reducing fever?

COX inhibition shifts arachidonic acid metabolism toward the 5-lipoxygenase pathway, increasing leukotriene-mediated vascular permeability
Flunixin competitively inhibits TNF-α receptors, impairing the cytokine cascade needed for bacterial clearance
Flunixin upregulates thromboxane A2 production by sparing COX-2 activity in platelets, promoting microthrombi formation
Blockade of prostacyclin (PGI2) synthesis removes a protective vasodilatory signal in splanchnic vasculature, worsening gut ischemia (Correct answer)

Correct answer: Blockade of prostacyclin (PGI2) synthesis removes a protective vasodilatory signal in splanchnic vasculature, worsening gut ischemia

In endotoxemia, prostacyclin (PGI2) serves a protective role in maintaining splanchnic blood flow through vasodilation. Flunixin inhibits both COX-1 and COX-2, blocking PGI2 synthesis. Loss of this protective vasodilation in the gut vasculature worsens mucosal ischemia and intestinal barrier failure, potentially allowing greater endotoxin translocation. While fever reduction is clinically desirable, the trade-off in severe endotoxemia is impaired splanchnic perfusion. This explains why outcome data on NSAID use in severe bovine endotoxemia is mixed and dose timing matters.

Question 62: A 12-year-old cat with known hyperthyroidism controlled on methimazole develops acute azotemia (creatinine 3.8 mg/dL, BUN 58 mg/dL) after 3 weeks of therapy. Pre-treatment creatinine was 1.1 mg/dL. Which pathophysiologic explanation is most accurate?

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

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

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

Question 63: 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?

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

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

Bladder calculi
Hepatic lipidosis
Gastrointestinal obstruction
Pneumonia (Correct answer)

Correct answer: Pneumonia

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

Question 65: A beef cow herd experiences a cluster of late-term abortions (7–9 months gestation) over 3 weeks. Fetuses show autolysis with placentitis. Serologic titers for Neospora caninum are elevated in affected cows but not in non-aborted herdmates. Which epidemiologic pattern best supports transient epidemic neosporosis rather than endemic neosporosis in this herd?

Abortions are concentrated in first-calf heifers and 2-year-olds with a rapid onset and high attack rate, while older cows are largely spared (Correct answer)
Abortions occur in cows of all ages with no clustering by age cohort and seroprevalence is uniformly distributed across the herd
Affected cows have daughters with high seropositivity, suggesting vertical transmission is the dominant route of introduction
Abortion rate is 2–3% annually and steadily increases each year as new heifers enter the breeding herd

Correct answer: Abortions are concentrated in first-calf heifers and 2-year-olds with a rapid onset and high attack rate, while older cows are largely spared

Epidemic (point-source) neosporosis typically results from a sudden environmental exposure—such as contamination of feed or water with dog feces containing Neospora oocysts. This produces a high attack rate concentrated in a short time window and often disproportionately affects naive younger animals that lack any prior immunity. Endemic neosporosis, by contrast, is maintained by vertical (transplacental) transmission and tends to show a steady low-level abortion rate (1–3%) distributed across all age groups with seropositive dams producing seropositive offspring over successive years.

Question 66: A 12-year-old Warmblood sport horse presents with subtle, intermittent right forelimb lameness that worsens on soft footing and improves on firm ground. Flexion tests are negative. Diagnostic analgesia of the distal limb fails to improve the lameness. MRI reveals focal cartilage erosion on the palmar aspect of the lateral trochlear ridge of the distal radius. Which condition does this BEST describe?

Subchondral bone cyst of the proximal third carpal bone
Osteochondritis dissecans of the distal radial carpal bone
Palmar osteochondral disease (POD) of the radiocarpal joint (Correct answer)
Distal interphalangeal joint synovitis

Correct answer: Palmar osteochondral disease (POD) of the radiocarpal joint

Palmar osteochondral disease (POD), also called 'sport horse carpus,' involves cartilage erosion and subchondral bone pathology on the palmar aspects of the radiocarpal and intercarpal joints. It is characteristically worse on soft footing because greater fetlock extension loads the palmar carpal structures. Distal limb analgesia does not block this region, explaining the negative response. MRI is often required for definitive diagnosis as radiographs may be unremarkable early in the disease.

Question 67: A 7-year-old spayed female cat is presented for progressive weight loss, hyperglobulinemia (total protein 10.8 g/dL, globulins 7.2 g/dL), and a serum albumin:globulin ratio of 0.4. Serum protein electrophoresis reveals a polyclonal gammopathy. Abdominal ultrasound shows mesenteric lymphadenopathy and a focal hyperechoic jejunal mass. Fine needle aspirate of the mass reveals macrophages with intracytoplasmic coronavirus antigen confirmed by immunofluorescence. Which statement regarding antigen testing in this context is MOST accurate?

Positive immunostaining for coronavirus antigen within macrophages in a granulomatous lesion is highly specific for FIP and distinguishes virulent from avirulent FCoV strains (Correct answer)
Polyclonal gammopathy effectively rules out FIP because FIP characteristically produces a monoclonal spike
Immunofluorescent detection of coronavirus in macrophages has low specificity because enteric FCoV can also infect macrophages in healthy cats
A positive result confirms systemic FeLV co-infection, which is required for macrophage tropism of feline coronavirus

Correct answer: Positive immunostaining for coronavirus antigen within macrophages in a granulomatous lesion is highly specific for FIP and distinguishes virulent from avirulent FCoV strains

Immunohistochemistry (IHC) or immunofluorescence detecting coronavirus antigen within macrophages in pyogranulomatous tissue is considered highly specific for FIP — it reflects the macrophage-tropic phenotype of the mutant virulent FCoV. This distinguishes FIP from enteric (avirulent) FCoV infection, in which the virus remains confined to intestinal epithelium and does not productively infect monocytes/macrophages. Polyclonal (not monoclonal) gammopathy is the classic finding in FIP. FeLV co-infection is not required for macrophage tropism. While no test is 100% sensitive/specific, antigen-positive macrophages in a granuloma represent the closest thing to a definitive antemortem FIP diagnosis.

Question 68: A 4 kg cat requires ketamine for induction. Which statement about ketamine in cats is most accurate?

It is hepatically metabolized to active metabolites that extend sedation
It significantly depresses cardiovascular function
It provides excellent visceral analgesia alone
It must be combined with a benzodiazepine or alpha-2 agonist to prevent seizure-like muscle rigidity (Correct answer)

Correct answer: It must be combined with a benzodiazepine or alpha-2 agonist to prevent seizure-like muscle rigidity

Ketamine alone causes muscle hypertonicity and vocalization; co-administration of diazepam or medetomidine produces smooth induction.

Question 69: A 6-year-old Doberman Pinscher is being treated for dilated cardiomyopathy with digoxin. The dog develops acute renal failure secondary to a urinary obstruction. Which pharmacokinetic change requires the MOST urgent dose adjustment?

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

Correct answer: Reduced renal clearance causing digoxin accumulation and toxicity

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

Question 70: 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?

Pheochromocytoma
Hyperaldosteronism (Conn's syndrome) (Correct answer)
Addison's disease
Hypothyroidism

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 71: A 6-year-old Rottweiler presents with acute vomiting and melena. Gastroscopy reveals a deep ulcer in the antrum. Which drug class is most effective at preventing NSAID-induced gastrointestinal ulcers in dogs?

H2-receptor antagonists
Proton pump inhibitors (Correct answer)
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 72: A 3-year-old Quarter Horse gelding presents for acute onset of right forelimb lameness (grade 4/5) after a barrel racing event. Hoof testers elicit a strong positive reaction over the lateral heel. Perineural anesthesia of the lateral palmar digital nerve abolishes the lameness. Radiographs reveal a thin, radiolucent line through the lateral palmar process of the distal phalanx (P3). Which pathophysiologic mechanism best explains why this specific fracture configuration carries a guarded prognosis for return to competition?

Chronic repetitive tension from the deep digital flexor tendon preventing fracture healing
Involvement of the distal interphalangeal joint articular surface increasing the risk of degenerative joint disease (Correct answer)
Avascular necrosis of the distal phalanx due to disruption of the terminal arch
High risk of septic osteitis due to proximity to the white line

Correct answer: Involvement of the distal interphalangeal joint articular surface increasing the risk of degenerative joint disease

Palmar process (wing) fractures of P3 are classified by Sanders & Stashak. Non-articular fractures carry a good prognosis, but when the fracture line extends into the distal interphalangeal (coffin) joint, articular surface damage predisposes to post-traumatic osteoarthritis, significantly worsening the prognosis for return to high-performance competition. Avascular necrosis is not a primary mechanism in wing fractures. Septic osteitis is a complication of solar penetration wounds, not this fracture type specifically. DDFT tension is more relevant to the middle third fractures.

Question 73: A 6-month-old intact female Border Collie is presented with a 2-week history of progressive hindlimb ataxia, hypermetria, and intention tremors. The puppy was purchased from a farm where the dam was fed a selenium-deficient diet during gestation. Cerebrospinal fluid analysis is unremarkable. Which diagnosis is most consistent with these findings?

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

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

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

Question 74: Which inhalant anesthetic is associated with the GREATEST cardiovascular depression and sensitization of the myocardium to catecholamine-induced arrhythmias?

Isoflurane
Desflurane
Sevoflurane
Halothane (Correct answer)

Correct answer: Halothane

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

Question 75: 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 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
Use Test B alone annually, because its higher specificity minimizes false-positive culls at this prevalence

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 76: A 4-year-old indoor cat develops acute epistaxis and retinal hemorrhages. Blood pressure is 225/160 mmHg. Which primary disease is most commonly responsible for severe hypertension in cats under 7 years of age?

Pheochromocytoma
Hyperthyroidism
Chronic kidney disease
Primary hyperaldosteronism (Correct answer)

Correct answer: Primary hyperaldosteronism

Primary hyperaldosteronism is an important cause of severe hypertension in younger cats and should be investigated when CKD and hyperthyroidism are absent.

Question 77: A 4-year-old spayed female Doberman Pinscher is presented for a pre-breeding cardiac clearance (owner is unaware she is spayed). Auscultation reveals a soft, grade II/VI left apical systolic murmur. Echo shows mild left ventricular dilation with an ejection fraction of 48%. Which statement most accurately describes the appropriate management and genetic counseling?

Begin pimobendan therapy immediately; the dog should not be bred regardless of spay status due to DLVM genetic risk
Begin enalapril therapy; the murmur is most likely due to mitral valve degeneration at this age
Recheck echocardiogram in 6 months; this likely represents physiologic athlete's heart in an active breed
No treatment indicated; repeat echo in 6 months, and inform the owner the dog is spayed before discussing breeding (Correct answer)

Correct answer: No treatment indicated; repeat echo in 6 months, and inform the owner the dog is spayed before discussing breeding

The dog has pre-clinical dilated cardiomyopathy (DCM), which is common in Doberman Pinschers. Current evidence (PROTECT study) supports pimobendan initiation when occult DCM is confirmed by echo criteria (LVIDd >46mm or LVIDs >38mm in females, or EF <50%). However, the immediate priority in the clinical scenario is to address the factual error — the dog is spayed and cannot be bred. Pimobendan would be appropriate once DCM criteria are confirmed, but answering the counseling question requires first correcting the owner's misunderstanding. Enalapril alone is not first-line for pre-clinical DCM in Dobermans.

Question 78: A 7-year-old cat presents with icterus, anemia, and splenomegaly. Blood smear shows intraerythrocytic organisms. Which organism is most likely responsible?

Bartonella henselae
Mycoplasma haemofelis (Correct answer)
Babesia felis
Cytauxzoon felis

Correct answer: Mycoplasma haemofelis

Mycoplasma haemofelis (formerly Haemobartonella felis) is the most common cause of feline infectious anemia, attaching to the surface of red blood cells.

Question 79: During a toxicology consult, you receive a call about a cat that ingested permethrin-containing dog spot-on approximately 1 hour ago. The cat is currently showing mild whole-body tremors and hypersalivation. The owner asks about inducing emesis at home with hydrogen peroxide. What is the most accurate and complete response?

Do not induce emesis; the neurological signs indicate the window for decontamination benefit has passed and emesis risks aspiration
Hydrogen peroxide is unreliable for emesis induction in cats and is contraindicated — instruct the owner to bring the cat in immediately for methocarbamol therapy and professional decontamination (Correct answer)
Hydrogen peroxide can be used at 1 mL/kg PO; the owner should administer it once and transport immediately
Instruct the owner to administer xylazine orally as a safer emetic, then transport the cat

Correct answer: Hydrogen peroxide is unreliable for emesis induction in cats and is contraindicated — instruct the owner to bring the cat in immediately for methocarbamol therapy and professional decontamination

Hydrogen peroxide is a dangerous and ineffective emetic in cats. Unlike dogs, cats do not reliably vomit in response to hydrogen peroxide, and it causes severe hemorrhagic gastroenteritis in this species. The appropriate feline emetics are dexmedetomidine (IM) or xylazine (IM/IV) administered by a veterinarian — never orally at home. Furthermore, although neurological signs are mild, the presence of tremors signals CNS involvement and increases aspiration risk with any emetic. The owner should immediately transport the cat for professional decontamination (bathing with dish soap to remove dermal permethrin), methocarbamol (muscle relaxant of choice for pyrethroid-induced tremors in cats), IV fluid support, and thermoregulation. Pyrethroids are not absorbed through the GI mucosa as efficiently as through skin, so dermal decontamination is the priority.

Question 80: Among commonly used local anesthetics in veterinary medicine, which agent provides the LONGEST duration of nerve block?

Lidocaine
Procaine
Bupivacaine (Correct answer)
Mepivacaine

Correct answer: Bupivacaine

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

Question 81: A veterinarian suspects a case of highly pathogenic avian influenza (HPAI) in a commercial flock. The first regulatory notification must be made to:

CDC influenza division
State veterinarian or USDA APHIS (Correct answer)
FDA Center for Veterinary Medicine
Local law enforcement

Correct answer: State veterinarian or USDA APHIS

HPAI is a federally reportable disease; the state veterinarian and USDA APHIS must be notified immediately upon suspicion.

Question 82: 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
Cranial mediastinal lymphoma
Thymoma
Branchial cyst (Correct answer)

Correct answer: Branchial cyst

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

Question 83: A 12-year-old Miniature Schnauzer presents with hypercalcemia (Ca 14.2 mg/dL), weight loss, and peripheral lymphadenopathy. Which test is most useful to differentiate hypercalcemia of malignancy from primary hyperparathyroidism?

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

Correct answer: PTH and PTHrP assay

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

Question 84: Which MRI finding is characteristic of syringomyelia (syrinx) in a Cavalier King Charles Spaniel with Chiari-like malformation?

T2 hyperintense fluid-filled cavity within the spinal cord (Correct answer)
T2 hypointense lesion in the dorsal columns
T1 hyperintense intramedullary lesion
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 85: A new pen-side antigen test for Bovine Respiratory Syncytial Virus (BRSV) is evaluated in a group of 300 calves. The results are as follows: 85 calves that are truly positive for BRSV test positive. 190 calves that are truly negative for BRSV test negative. 15 truly positive calves test negative. 10 truly negative calves test positive. What is the specificity of this new test?

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

Correct answer: 95.0%

Specificity measures a test's ability to correctly identify disease-free individuals. The formula is: Specificity = [True Negatives / (True Negatives + False Positives)] * 100. In this scenario, the True Negatives are 190 and the False Positives are 10. Therefore, Specificity = [190 / (190 + 10)] * 100 = [190 / 200] * 100 = 95.0%.

Question 86: A 9-year-old cat presents with acute collapse, jugular distension, muffled heart sounds, and pulsus paradoxus. Echocardiography confirms pericardial effusion with right atrial collapse. Which etiology is most common for pericardial effusion causing tamponade in cats, and how does it differ from dogs?

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

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

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

Question 87: What is the primary concern when using ketamine as the sole anesthetic in a dog?

Severe respiratory depression
Profound hypotension
Inadequate muscle relaxation and increased muscle tone (Correct answer)
Prolonged recovery

Correct answer: Inadequate muscle relaxation and increased muscle tone

Ketamine alone causes increased muscle tone and catalepsy rather than muscle relaxation, so it is typically combined with a benzodiazepine or alpha-2 agonist for adequate relaxation.

Question 88: During inhalant anesthesia maintenance in a dog, the end-tidal CO2 (EtCO2) rises to 65 mmHg despite manual ventilation at 15 breaths/min with a tidal volume of 15 mL/kg. Arterial blood gas confirms PaCO2 of 70 mmHg. Which condition is the MOST likely cause of this disproportionately elevated PaCO2 relative to minute ventilation?

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

Correct answer: Increased dead space ventilation from pulmonary thromboembolism

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

Question 89: 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:

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

Correct answer: Fetlock synovitis

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

Question 90: 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?

CHOP-based protocol (cyclophosphamide, doxorubicin, vincristine, prednisolone) (Correct answer)
Single-agent lomustine (CCNU)
Toceranib phosphate targeting c-Kit mutation
Chlorambucil and prednisolone (COP equivalent)

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

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

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

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

Correct answer: At least 4 weeks

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

Question 93: An 8-year-old Dachshund presents with acute onset of severe back pain and inability to ambulate. MRI confirms acute thoracolumbar IVDD at T12-13. Deep pain perception is absent. Within what time frame should surgical decompression ideally occur to maximize neurological recovery?

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

Correct answer: Within 48 hours

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

Question 94: A 10-year-old DSH cat presents with polyuria, polydipsia, and a serum potassium of 2.8 mEq/L. Blood pressure is 195 mmHg. Aldosterone-to-renin ratio is markedly elevated. CT reveals a 1.2 cm unilateral adrenal mass. Which of the following is the MOST appropriate next step in management?

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

Correct answer: Adrenalectomy after preoperative potassium and blood pressure stabilization

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

Question 95: A food inspector observes condensation dripping from overhead pipes onto exposed ready-to-eat food contact surfaces. This represents a violation of which food safety principle?

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

Correct answer: Sanitation and hygienic design (environmental sanitation)

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

Question 96: 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 97: A positive response to a distal limb flexion test in a horse is most useful for localizing pain to which general anatomical area?

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

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 98: 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?

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

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 99: 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?

Azathioprine
Cisplatin (Correct answer)
Prednisone
Vincristine

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 100: 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
Facial pruritus and excoriation (Correct answer)
Bone marrow aplasia

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

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

Correct answer: Furosemide + pimobendan + enalapril

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

Question 102: When evaluating a horse for subtle hindlimb lameness, which surface is MOST useful for accentuating the gait abnormality?

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

Correct answer: Soft, deep sand arena

A soft, deep surface increases concussion and proprioceptive demands on the hindlimb, accentuating subtle lameness signs that may not be visible on a firmer surface.

Question 103: Which antibiotic classes are contraindicated in rabbits due to the risk of fatal clostridial enterotoxemia?

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

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

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

Question 104: 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
Praziquantel
Selamectin
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 105: A 12-year-old Quarter Horse presents with a chronic, progressive, bilateral forelimb lameness and a short, choppy gait. The owner notes the horse frequently points one foot forward while at rest. Hoof testers elicit pain over the central third of the frog. Which of the following is the most likely diagnosis?

High ringbone (pastern arthritis)
Navicular syndrome (Correct answer)
Suspensory ligament branch desmitis
Acute laminitis

Correct answer: Navicular syndrome

This clinical presentation is classic for navicular syndrome (podotrochleosis), which involves pathology of the navicular bone and associated soft tissues. Key signs include chronic bilateral forelimb lameness, pointing a foot to relieve heel pressure, and pain over the frog/heel region with hoof testers. Ringbone affects the pastern, laminitis often has a more acute onset with different hoof tester responses, and suspensory issues are typically located more proximally.

Question 106: A veterinarian treats a group of feeder calves for bovine respiratory disease (BRD) with enrofloxacin. What is the primary reason for the strict prohibition of extra-label use of this drug in food-producing animals?

It promotes the development of antimicrobial resistance in human pathogens. (Correct answer)
It causes severe and irreversible nephrotoxicity in cattle.
There is a high risk of fatal anaphylactic reactions in human consumers.
It causes permanent discoloration of meat products.

Correct answer: It promotes the development of antimicrobial resistance in human pathogens.

The FDA prohibits the extra-label use of fluoroquinolones like enrofloxacin in food animals primarily to mitigate the risk of promoting antimicrobial resistance. Bacteria such as Salmonella and Campylobacter can develop resistance, which may then be transferred to human populations through the food chain, compromising the efficacy of this critically important class of antibiotics in human medicine.

Question 107: A horse with endotoxemia requires treatment with flunixin meglumine. What is the primary reason flunixin is preferred over other NSAIDs in this scenario?

It effectively inhibits COX-mediated thromboxane production at low doses, reducing endotoxin-induced vascular effects (Correct answer)
It has the longest duration of action of any equine NSAID
It crosses the blood-brain barrier more effectively than other NSAIDs
It is the most potent analgesic available for horses

Correct answer: It effectively inhibits COX-mediated thromboxane production at low doses, reducing endotoxin-induced vascular effects

Flunixin meglumine at low doses inhibits thromboxane synthesis and attenuates some hemodynamic effects of endotoxin, making it particularly beneficial in horses with endotoxemia.

Question 108: Which vaccine-preventable feline disease is caused by a parvovirus and requires only biannual boosters in adult cats after the initial series?

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

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

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

Correct answer: Navicular bone or navicular bursa

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

Question 110: Gabapentin is increasingly used in cats for anxiety and pain. Which pharmacokinetic property is clinically important in feline dosing?

It is renally excreted unchanged and dose must be reduced with renal insufficiency (Correct answer)
It undergoes extensive first-pass hepatic metabolism
It is highly protein-bound and interacts with NSAIDs
It requires CYP2D6 for activation to its active form

Correct answer: It is renally excreted unchanged and dose must be reduced with renal insufficiency

Gabapentin is eliminated renally with minimal hepatic metabolism, so dose intervals must be extended in cats with chronic kidney disease.

Question 111: A beef cow herd experiences an outbreak of abortion storms affecting 30% of pregnant cows. PCR testing confirms Neospora caninum. What is the primary route of transmission in cattle?

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

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

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

Question 112: On a lateral thoracic radiograph of a dog, you note the cardiac silhouette contacts the sternum across more than 2.5 intercostal spaces. The trachea is elevated and the caudal vena cava is not visible. Which condition BEST explains this constellation of findings?

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

Correct answer: Peritoneopericardial diaphragmatic hernia (PPDH)

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

Question 113: An outbreak of West Nile Virus neurological disease is detected in horses in a county. What is the primary public health concern for veterinarians to communicate?

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

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

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

Question 114: A 3-year-old Quarter Horse presents with right forelimb lameness localized to the foot by perineural anesthesia. MRI (low-field standing unit) shows a hyperintense T2 signal lesion within the lateral lobe of the deep digital flexor tendon (DDFT) at the level of the navicular bone, with a corresponding hypointense T1 signal. The navicular bone shows focal subchondral signal loss on T1 at the flexor cortex. Which combination of lesions is present?

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

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

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

Question 115: Which opioid is most appropriate for epidural administration in dogs to provide extended postoperative analgesia with minimal motor blockade?

Morphine (Correct answer)
Meperidine
Fentanyl
Butorphanol

Correct answer: Morphine

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

Question 116: 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?

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)
Peristaltic waves are increased to 6-7 contractions per minute throughout the small intestine.
The intestinal wall is diffusely thickened with preserved layering.
Hyperechoic mesenteric fat is noted surrounding the entire small bowel.

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

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

Question 117: 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?

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

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

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

Question 118: A 5-year-old dog presents with acute vomiting and abdominal pain. Abdominal radiographs reveal a segment of small intestine that is severely dilated with gas, proximal to a segment of normal-caliber, empty-appearing small intestine. What is this radiographic finding, often referred to as 'two populations of bowel,' most indicative of?

Functional ileus
Mechanical obstruction (Correct answer)
Pancreatitis
Gastroenteritis

Correct answer: Mechanical obstruction

The presence of two distinct populations of bowel (one severely dilated and one normal or empty) is a classic radiographic sign of a complete or high-grade mechanical obstruction. The intestine proximal to the blockage becomes distended with gas and fluid, while the intestine distal to the obstruction remains empty. Functional ileus and gastroenteritis typically cause a more generalized, mild to moderate dilation of the intestines without a clear transition point.

Question 119: Which fungal organism causes 'yellow fungus disease' (invasive necrotizing mycosis) in bearded dragons?

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

Correct answer: Nannizziopsis guarroi

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

Question 120: Among the currently used inhalant anesthetics, which has the LOWEST blood:gas partition coefficient, resulting in the fastest induction and recovery?

Halothane
Sevoflurane
Isoflurane
Desflurane (Correct answer)

Correct answer: Desflurane

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

Question 121: Which of the following is the preferred site for intravenous catheter placement in a rabbit?

Cephalic vein
Lateral saphenous vein
Marginal ear vein (Correct answer)
Jugular vein

Correct answer: Marginal ear vein

The marginal ear vein is the most accessible and commonly used IV catheter site in rabbits due to its visibility and ease of access.

Question 122: Equine degenerative joint disease of the proximal interphalangeal joint (high ringbone) is BEST confirmed with:

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

Correct answer: Lateromedial and dorsopalmar radiographs of the pastern

High ringbone (periarticular or articular osteoarthritis of the PIP joint) is diagnosed radiographically, with lateromedial and dorsopalmar views demonstrating periarticular osteophytes and joint space narrowing.

Question 123: When performing musculoskeletal ultrasound in a dog, a tendon appears hyperechoic with a fibrillar pattern when the beam is perpendicular, but becomes hypoechoic when the transducer is angled. This phenomenon is called:

Enhancement
Refraction
Anisotropy (Correct answer)
Shadowing artifact

Correct answer: Anisotropy

Anisotropy is the property of tendons and ligaments whereby echogenicity changes dramatically with beam angle relative to fiber orientation.

Question 124: 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 125: Propylene glycol is present in some semi-moist cat foods and medications. Why is it contraindicated in cats?

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

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 126: A public health veterinarian is investigating a Q fever outbreak among abattoir workers processing pregnant ewes. Serology confirms acute Coxiella burnetii infection in 14 of 22 workers. Which of the following control measures has the STRONGEST evidence base for reducing occupational exposure in this specific setting, and which worker subpopulation requires the most rigorous exclusion from the work area?

Universal use of N95 respirators alone is sufficient; elderly workers over 65 are the highest-risk group due to cardiac complications
Negative-pressure isolation of lambing/kidding and parturition areas combined with high-efficiency particulate air (HEPA) filtration; pregnant women and immunocompromised workers require exclusion due to risk of chronic Q fever and adverse pregnancy outcomes (Correct answer)
Antibiotic prophylaxis with doxycycline for all exposed workers; workers with valvular heart disease require exclusion due to endocarditis risk
Pre-exposure vaccination of all workers with Phase I killed whole-cell vaccine; workers with prior Coxiella seropositivity are the primary exclusion group due to hypersensitivity reactions

Correct answer: Negative-pressure isolation of lambing/kidding and parturition areas combined with high-efficiency particulate air (HEPA) filtration; pregnant women and immunocompromised workers require exclusion due to risk of chronic Q fever and adverse pregnancy outcomes

C. burnetii is shed in massive quantities in placental tissues, birth fluids, and feces of parturient ruminants. Engineering controls (negative pressure, HEPA filtration) combined with PPE provide the strongest occupational protection. Pregnant women face risk of placentitis, spontaneous abortion, and premature birth; immunocompromised individuals risk chronic Q fever (endocarditis, hepatitis). While Australian Q-VAX exists, pre-exposure skin testing is mandatory due to severe hypersensitivity in previously sensitized individuals — making 'universal vaccination without testing' incorrect. Doxycycline prophylaxis is not standard practice for all exposed workers. Workers with valvular disease are high-risk for chronic infection but are not the primary exclusion group in the parturition work context.

Question 127: A 6-year-old Bernese Mountain Dog presents with progressive exercise intolerance and a 3-week history of ascites. Physical exam reveals jugular venous distension, muffled heart sounds, and hepatomegaly. Echocardiography demonstrates a large pericardial effusion. Pericardiocentesis is performed, yielding 600 mL of serosanguineous fluid. Cytology of the fluid is non-diagnostic. Which of the following is the most common underlying etiology in this breed and age group, and what is the most appropriate long-term management?

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

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

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

Question 128: A 450-cow dairy herd has a rolling herd average of 28,000 lbs milk/cow/year but a 21-day pregnancy rate of only 12%. The reproductive technician reports a first-service conception rate of 38%. Which metric most accurately identifies the PRIMARY bottleneck limiting reproductive efficiency in this herd?

The conception rate of 38% is too low and is the primary driver of poor pregnancy rate
21-day submission rate is likely below 60%, reducing the pregnancy rate independent of conception rate (Correct answer)
The interval from calving to first service is too long, causing dilution of the 21-day pregnancy rate
High milk production is causing negative energy balance sufficient to suppress ovarian activity in most cows

Correct answer: 21-day submission rate is likely below 60%, reducing the pregnancy rate independent of conception rate

The 21-day pregnancy rate (PR) = submission rate × conception rate. With a 38% conception rate, achieving a 21-day PR of 18–22% (industry target) requires a submission rate of ~47–58%. A 12% PR with 38% CR implies a submission rate of only ~32%, meaning fewer than one-third of eligible cows are being detected in estrus or enrolled in a timed-AI protocol every 21 days. The conception rate itself is acceptable; the failure to get cows submitted is the primary bottleneck. Addressing detection of estrus or expanding synchronization protocols would have the greatest impact.

Question 129: A veterinarian recommends a Selective Dry Cow Therapy (SDCT) program instead of blanket dry cow therapy. What is the PRIMARY advantage of SDCT?

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

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

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

Question 130: A herd of stocker cattle develops red-water disease (bacillary hemoglobinuria). Which organism and predisposing factor is responsible?

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

Correct answer: Clostridium haemolyticum, liver fluke migration

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

Question 131: 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?

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

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

Low fat (<10% DM) (Correct answer)
Moderate fat (15-20% DM)
Fat-free diet
High fat (>25% 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 133: A 5-year-old Thoroughbred racehorse presents with acute-onset bilateral forelimb lameness, a classic sawhorse stance, and refusal to move. The trainer reports the horse received a phenylbutazone injection yesterday for a minor muscle strain. Careful examination reveals bilateral forelimb digital pulses of 4/4 and marked heat in all four feet. Which diagnostic finding would most strongly support laminitis secondary to phenylbutazone toxicosis rather than sepsis-induced laminitis in this horse?

Protein-losing enteropathy with hypoalbuminemia on chemistry panel (Correct answer)
Serum amyloid A concentration >1000 µg/mL
Elevated fecal alpha-1 protease inhibitor indicating GI inflammation
Symmetric rotation on radiographs with ventral lamellar wedge formation

Correct answer: Protein-losing enteropathy with hypoalbuminemia on chemistry panel

NSAID toxicosis (right dorsal colitis or gastric ulceration) causes protein-losing enteropathy through mucosal damage, resulting in hypoalbuminemia. This decreased oncotic pressure promotes digital lamellar edema and precipitates laminitis via a distinct vascular mechanism separate from inflammatory cytokine cascades. Hypoalbuminemia on a chemistry panel, combined with the recent NSAID exposure and absence of a septic focus, strongly implicates phenylbutazone-induced colitis as the trigger. Elevated SAA suggests systemic inflammation but is nonspecific. Radiographic rotation is a consequence of laminitis, not a cause-differentiator. Fecal alpha-1 PI elevation confirms enteropathy but is more useful for chronic protein loss confirmation.

Question 134: A 9-year-old Golden Retriever is diagnosed with protein-losing nephropathy. UPC ratio is 4.8. Which antihypertensive class is considered first-line therapy to reduce proteinuria?

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

Correct answer: ACE inhibitors

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

Question 135: In a spayed female ferret presenting with vulvar swelling, which disease is the most likely diagnosis?

Diabetes mellitus
Ovarian remnant syndrome
Adrenal gland disease (Correct answer)
Insulinoma

Correct answer: Adrenal gland disease

Adrenal gland disease in ferrets causes excess sex hormone secretion from adrenocortical tissue, leading to vulvar swelling even in spayed females.

Question 136: Kinematic gait analysis of a Warmblood dressage horse reveals a decreased protraction arc of the right forelimb with a shortened cranial phase of the stride but a normal caudal phase. Flexion tests are equivocal. Diagnostic analgesia of the coffin and pastern joints is negative. Which anatomical structure's pathology BEST explains decreased protraction with preserved caudal phase?

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

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

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

Question 137: Which radiographic view is MOST useful for evaluating the flexor cortex of the navicular bone for lollipop lesions in a horse?

Lateromedial view
Dorsopalmar view
Flexor tangential (skyline) view (Correct answer)
Oblique view

Correct answer: Flexor tangential (skyline) view

The flexor tangential (skyline) view projects the flexor cortex of the navicular bone en face, allowing visualization of corticomedullary defects and lollipop lesions.

Question 138: A 5-year-old event horse has hindlimb lameness localized to the sacroiliac region by positive pressure on the tuber sacrale and a positive response to gluteal muscle palpation. The BEST imaging modality for confirming sacroiliac pathology is:

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

Correct answer: Nuclear scintigraphy or ultrasound of the sacroiliac joint

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

Question 139: On CT of the nasal cavity in a dog with nasal discharge, which finding most strongly suggests fungal rhinitis (Aspergillus) rather than nasal neoplasia?

Periosteal reaction along the frontal bones
Fluid-filled nasal cavity with intact turbinates
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 140: 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?

CT myelography showing nerve root compression at the lumbosacral junction
Nuclear scintigraphy showing bilaterally increased IRU at the sacroiliac joints; subchondral uptake pattern
Radiography demonstrating subchondral sclerosis and periarticular osteophyte formation
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 141: 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 metabolize propylene glycol via alcohol dehydrogenase to methylglyoxal, which preferentially binds feline hemoglobin at the Bohr effect site
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

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 142: Which of the following causes of exophthalmos in cattle occurs most frequently?

Retrobulbar lymphosarcoma (Correct answer)
Sinusitis
Orbital arteriovenous fistula
Extracranial meningioma

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

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

Correct answer: Immune-mediated thrombocytopenia (IMT)

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

Question 144: What is the most reliable and practical method for assessing failure of passive transfer (FPT) in a 2-day-old calf on-farm?

Zinc sulfate turbidity test
Radial immunodiffusion (RID) assay
Visual assessment of calf vigor and suckle reflex
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 145: Which radiographic sign is MOST characteristic of a diaphragmatic hernia in a dog?

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

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

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

Question 146: A 5-year-old intact female German Shepherd Dog presents with a 3-week history of protein-losing enteropathy confirmed by a serum albumin of 1.1 g/dL and alpha-1 protease inhibitor fecal test positivity. Endoscopic biopsies reveal lymphangiectasia with marked villous blunting and diffuse mucosal infiltration with CD3+ lymphocytes and plasma cells. Despite 6 weeks of dietary hydrolyzed protein with ultra-low fat and prednisolone (2 mg/kg/day), albumin remains at 1.2 g/dL. What is the MOST appropriate next therapeutic escalation?

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

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

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

Question 147: A cat is presented for evaluation of recurrent upper respiratory signs and oral ulcerations. FHV-1 PCR is positive on conjunctival swab. Which of the following statements about feline herpesvirus-1 pathophysiology is MOST accurate?

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

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 148: 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?

Cast application for 8 weeks
Surgical debridement and sequestrum removal (Correct answer)
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 149: A goat kid presents at 2 days of age with failure to nurse, profuse watery diarrhea, and rapid dehydration. Feces are negative for Cryptosporidium and E. coli. Rotavirus ELISA is positive. Treatment priorities include:

Anthelmintic deworming
Corticosteroids to reduce intestinal inflammation
Sulfonamide antibiotics and probiotics
Oral electrolyte fluid therapy and supportive care (Correct answer)

Correct answer: Oral electrolyte fluid therapy and supportive care

Rotavirus diarrhea in neonatal ruminants is managed supportively with oral electrolyte replacement because the disease is viral and antibiotics are ineffective; correction of dehydration is paramount.

Question 150: A 7-year-old FIV-positive cat is being treated for Cryptococcus neoformans meningoencephalitis with fluconazole. After 8 weeks, the cat shows neurological deterioration despite antigen titers decreasing. What is the MOST likely explanation for this paradoxical worsening?

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

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

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

Question 151: A 4-year-old cat requires post-operative analgesia following a routine ovariohysterectomy. Considering feline-specific metabolism and safety profiles, which of the following NSAIDs is licensed and generally considered a safer short-term option for this patient?

Carprofen
Phenylbutazone
Robenacoxib (Correct answer)
Acetaminophen

Correct answer: Robenacoxib

Robenacoxib is a COX-2 selective NSAID that is specifically licensed for short-term post-operative pain management in cats. Cats have a deficiency in glucuronyl transferase, an enzyme crucial for metabolizing many NSAIDs, making them highly susceptible to toxicity from drugs like acetaminophen (which is extremely toxic) and phenylbutazone. While carprofen is used in dogs, its use in cats is extra-label and more controversial. Robenacoxib's feline-specific approval and COX-2 selectivity provide a better safety margin.

Question 152: A 12-year-old hyperthyroid cat is treated with methimazole and achieves euthyroidism. Six weeks later, serum creatinine rises from 1.4 to 3.8 mg/dL and BUN from 22 to 68 mg/dL. Urine specific gravity is 1.018. What is the most accurate explanation for this finding?

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

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

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

Question 153: 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?

Diaphragmatic hernia; the preserved diaphragmatic line rules out rupture but the aortic effacement confirms herniated content
Pleural effusion in the caudodorsal costophrenic recess; the indistinct dorsal border reflects fluid-air interface
Middle mediastinal mass; loss of cardiac silhouette confirms mediastinal origin
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)

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 154: 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
Hypokalemia-induced ventricular tachycardia following dietary indiscretion
Arrhythmogenic right ventricular cardiomyopathy (ARVC) (Correct answer)

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

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

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

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

Question 156: A 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?

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

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

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

Question 157: Which flea and tick preventive acts as a selective antagonist of insect GABA-gated chloride channels?

Imidacloprid
Spinosad
Fipronil (Correct answer)
Selamectin

Correct answer: Fipronil

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

Question 158: In equine radiography, 'rotation' of the distal phalanx relative to the hoof wall is measured by which imaging technique?

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

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

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

Question 159: 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?

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

Correct answer: Blackleg (Clostridium chauvoei)

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

Question 160: 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 161: A veterinarian is assessing a feedlot for bovine respiratory disease (BRD). Which scoring system is most widely used to objectively evaluate respiratory signs in individual cattle at the pen level?

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

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

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

Question 162: 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?

Feline sublingual vasculature bypasses hepatic first-pass metabolism via direct lymphatic drainage into the thoracic duct
Cats have a significantly higher density of mu-opioid receptors in the buccal mucosa, enabling receptor-mediated transcytosis of buprenorphine
Cats express lower levels of P-glycoprotein efflux pumps in oral epithelium, reducing active buprenorphine efflux back into the oral cavity
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)

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 163: A veterinarian administers a drug that causes dose-dependent sinus bradycardia in a horse. Atropine is given but produces no improvement. Which drug class most likely caused this atropine-resistant bradycardia?

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

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

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

Question 164: Pinkeye (infectious bovine keratoconjunctivitis) caused by Moraxella bovis is most prevalent in summer months. Which management practice MOST effectively reduces its spread in a beef herd?

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

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

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

Question 165: When using buprenorphine in cats, which route of administration achieves good bioavailability due to the cat's naturally alkaline oral pH?

Intravenous
Intramuscular
Transmucosal (sublingual/buccal) (Correct answer)
Subcutaneous

Correct answer: Transmucosal (sublingual/buccal)

The alkaline oral pH of cats promotes ionization of buprenorphine at mucosal surfaces, giving transmucosal administration ~100% bioavailability.

Question 166: 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?

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

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

True
False (Correct answer)

Correct answer: False

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

Question 168: 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 169: A 9-year-old spayed female Border Collie is evaluated for a 3-month history of polydipsia, polyuria, and bilateral symmetric alopecia of the flanks. Serum cortisol post-LDDS test is 3.2 µg/dL at 8 hours (non-suppressed). An HDDS test shows 85% suppression. Abdominal ultrasound reveals bilateral adrenal enlargement. Which diagnosis BEST fits this presentation?

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

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

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

Question 170: A community outbreak of E. coli O157:H7 is traced to a petting zoo. The primary mode of transmission in this setting is:

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

Correct answer: Fecal-oral transmission through direct animal contact

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

Question 171: A producer is implementing a control program for Bovine Viral Diarrhea Virus (BVDV). What is the most critical step to eliminate the primary reservoir of the virus within the herd?

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

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

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

Question 172: 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?

Pass for cooking only.
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.

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 173: A 10-year-old Quarter Horse with chronic, bilateral forelimb lameness undergoes a radiographic examination of the feet. Which of the following radiographic findings is most indicative of navicular disease (podotrochleosis)?

Smooth, well-defined new bone formation on the extensor process of the distal phalanx.
Enlarged, flask-shaped synovial invaginations ('lollipops') on the distal border of the navicular bone. (Correct answer)
Rotation and sinking of the distal phalanx (P3) within the hoof capsule.
Narrowing of the distal interphalangeal joint space with extensive periarticular osteophytes.

Correct answer: Enlarged, flask-shaped synovial invaginations ('lollipops') on the distal border of the navicular bone.

While many radiographic changes can be seen with navicular disease, the presence of more than 6-7 enlarged, flask-shaped or branching synovial invaginations (vascular channels) on the distal border is a classic and significant finding. Other key signs include flexor cortex erosions and medullary sclerosis.

Question 174: 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:

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

Correct answer: Hepatocellular carcinoma

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

Question 175: 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:

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

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 176: 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)
Multilobular tumor of bone (MLO); MRI for soft-tissue extension into the masticatory muscles
Osteosarcoma of the mandible; nuclear scintigraphy to detect skip metastases
Dentigerous cyst; dental radiographs only are sufficient for definitive characterization

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

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

Correct answer: Mediastinal cyst (branchial or thymic)

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

Question 178: A 7-year-old spayed female cat presents with polyuria, polydipsia, and a palpable ventral neck mass. T4 is markedly elevated. Which treatment option is considered curative?

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

Correct answer: Radioactive iodine (I-131) therapy

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

Question 179: A cow with a right-displaced abomasum (RDA) complicated by abomasal volvulus is most likely to present with which set of electrolyte and acid-base abnormalities?

Hyponatremia, metabolic acidosis, normal chloride
Hypokalemia, hypochloremia, metabolic alkalosis (Correct answer)
Normal electrolytes with respiratory acidosis
Hyperkalemia, hyperchloremia, metabolic acidosis

Correct answer: Hypokalemia, hypochloremia, metabolic alkalosis

Abomasal outflow obstruction causes sequestration of HCl, leading to hypochloremia, hypokalemia, and a paradoxical metabolic alkalosis with paradoxical aciduria.

Question 180: A dairy producer wants to monitor transition cow health. Which single blood test best predicts subclinical ketosis in fresh cows?

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

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 181: A 3-year-old Quarter Horse mare is presented with a history of recurrent episodes of mild colic, weight loss despite a good appetite, and loose feces. Fecal egg count is 0 EPG. Serum chemistry reveals hypoalbuminemia (2.1 g/dL) and elevated beta-globulins. Rectal palpation reveals thickened large colon walls. Which condition is highest on the differential list?

Cyathostominosis (larval cyathostomiasis) with mucosal larval emergence (Correct answer)
Granulomatous enteritis (multisystemic eosinophilic epitheliotropic disease)
Equine proliferative enteropathy due to Lawsonia intracellularis
Right dorsal colitis secondary to NSAID toxicity

Correct answer: Cyathostominosis (larval cyathostomiasis) with mucosal larval emergence

Larval cyathostomiasis (Type II cyathostominosis) occurs when large numbers of encysted early third-stage (EL3) cyathostomin larvae simultaneously emerge from the intestinal mucosa, causing protein-losing enteropathy, diarrhea, weight loss, and colic. Critically, adult egg-shedding larvae are absent during this phase, so fecal egg counts are zero or very low — this is a key distinguishing feature. Hypoalbuminemia and elevated beta-globulins reflect the protein loss and acute-phase response. Thickened colon walls on rectal palpation support mucosal infiltration. Equine proliferative enteropathy (Lawsonia) is seen primarily in weanlings and yearlings. Right dorsal colitis would have a history of NSAID use. MEED is rare and typically involves multiple organ systems.

Question 182: 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:

Bacterial culture of feather follicle
PCR for Psittacine Beak and Feather Disease virus (Correct answer)
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 183: A 6-year-old Standardbred pacer develops progressive bilateral hindlimb ataxia and weakness that worsens going downhill. Cervical radiographs show vertebral canal stenosis at C4-C5. What is the most likely diagnosis?

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

Correct answer: Cervical vertebral stenotic myelopathy (Wobbler syndrome)

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

Question 184: A 6-year-old Standardbred pacer presents with an acute onset Grade 4/5 right forelimb lameness after a race. On examination there is moderate fetlock effusion, periarticular swelling, and pain on deep palpation of the lateral proximal sesamoid bone. Radiographs reveal a mid-body, sagittal fracture of the lateral proximal sesamoid bone without articular involvement. The horse is otherwise systemically healthy. Which treatment offers the BEST prognosis for return to racing performance in this specific fracture configuration?

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

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

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

Question 185: A cat with pleural effusion undergoes thoracocentesis. Analysis reveals chylous effusion (triglycerides > serum). What is the most common underlying cause in cats?

Diaphragmatic hernia
Idiopathic chylothorax (Correct answer)
Congestive heart failure
Thoracic duct lymphoma

Correct answer: Idiopathic chylothorax

Idiopathic chylothorax is the most common cause in cats when lymphoma and cardiac disease have been excluded, though thoracic duct abnormalities are suspected.

Question 186: A 7-year-old intact male German Shepherd presents for progressive pelvic limb ataxia. Myelography reveals an extradural compressive lesion at L7-S1 with a 'golf tee' sign on the lateral view. CT confirms a lateralized, calcified mass with a 'popcorn' mineralization pattern within the intervertebral foramen. Which diagnosis is most consistent with this imaging constellation?

Hansen Type I intervertebral disc extrusion with foraminal migration (Correct answer)
Synovial cyst arising from the articular facet joint
Degenerative lumbosacral stenosis with foraminal osteophytosis
Nerve sheath tumor of the L7 nerve root

Correct answer: Hansen Type I intervertebral disc extrusion with foraminal migration

Hansen Type I disc extrusion can migrate laterally into the intervertebral foramen, producing the classic 'golf tee' extradural sign on myelography. Calcified disc material from Type I (chondroid metaplasia) produces the 'popcorn' mineralization pattern on CT. Nerve sheath tumors are typically non-mineralized and cause foraminal widening/erosion. Synovial cysts are periarticular soft-tissue densities without calcification in this pattern. Degenerative lumbosacral stenosis shows diffuse stenosis rather than a discrete foraminal mass.

Question 187: A beef producer wants to improve weaning weights and post-weaning growth. Which management practice during the preconditioning period (45-60 days post-weaning) has the GREATEST impact on feedlot health outcomes?

Keeping calves on the cow for 9 months before weaning
Completing vaccination series, weaning, castration, and dehorning at least 45 days before sale (Correct answer)
Providing ad libitum grain access from birth
Administering growth implants immediately at weaning

Correct answer: Completing vaccination series, weaning, castration, and dehorning at least 45 days before sale

Preconditioning programs that complete the BRD vaccination series, castration, and dehorning at least 45 days before sale reduce feedlot morbidity and mortality by allowing stress recovery and vaccine immune response maturation.

Question 188: A 10-year-old Miniature Schnauzer with a history of hyperlipidemia presents with acute onset of vomiting, anorexia, and cranial abdominal pain. Physical examination reveals a 'praying posture.' Laboratory findings include neutrophilia, elevated amylase, and markedly elevated lipase. Which of the following is the most appropriate initial treatment?

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

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 189: 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 ≈ 1.1; above threshold — epidemic continues
Rₑ ≈ 0.9; below threshold — epidemic controlled
Rₑ ≈ 1.5; above threshold — epidemic continues
Rₑ ≈ 2.2; above threshold — epidemic continues (Correct answer)

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

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

Correct answer: Feline herpesvirus-1

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

Question 191: A 2-year-old intact male DSH cat from a multi-cat household presents with progressive weight loss, anorexia, and a palpable abdominal mass. Abdominal effusion is present, and fluid analysis reveals a protein concentration of 5.8 g/dL, a Rivalta test that is positive, and a cell count of 4,200 cells/μL (predominantly non-degenerate neutrophils and macrophages). An immunofluorescence assay on the effusion detects coronavirus antigen within macrophages. Which statement BEST describes the pathogenesis underlying this cat's condition?

FIP develops exclusively in cats with concurrent FeLV or FIV co-infection, which suppresses regulatory T-cell responses and permits macrophage invasion.
A biotype shift from enteric coronavirus to FIP virus occurs via two key mutations in the spike protein receptor-binding domain and the 3c accessory gene, enabling macrophage tropism and systemic spread. (Correct answer)
Antibody-dependent enhancement allows serum anti-coronavirus IgG to facilitate viral entry into macrophages via Fc receptors, and this is the sole mechanism of monocyte/macrophage infection.
The cat was infected with a highly virulent serotype II feline coronavirus strain acquired horizontally from a shedding cat, bypassing the need for any mutational events.

Correct answer: A biotype shift from enteric coronavirus to FIP virus occurs via two key mutations in the spike protein receptor-binding domain and the 3c accessory gene, enabling macrophage tropism and systemic spread.

FIP arises from in-host mutation of feline enteric coronavirus (FECV), most critically in the spike protein (affecting cell tropism) and the 3c gene (disrupting immune evasion), converting FECV into FIP virus (FIPV) with macrophage-tropic capability. This internal mutation model—not horizontal transmission of a FIPV strain—is the current consensus. Co-infection with FeLV/FIV is a risk factor but not a prerequisite. Antibody-dependent enhancement may play a contributory role but is not the sole or primary mechanism.

Question 192: Which imaging modality is BEST for evaluating the extent of soft tissue masses adjacent to bone in a dog?

Plain radiography
Nuclear scintigraphy
Fluoroscopy
MRI (Correct answer)

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 193: Which drug is the first-line treatment for feline arterial thromboembolism (ATE) prevention?

Heparin
Aspirin
Warfarin
Clopidogrel (Correct answer)

Correct answer: Clopidogrel

Clopidogrel (Plavix) is superior to aspirin for secondary prevention of ATE in cats with cardiomyopathy, as demonstrated in the FAT CAT study.

Question 194: A dog receives an overdose of acepromazine. Which statement about acepromazine reversal is correct?

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

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

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

Question 195: 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
Ovariohysterectomy (Correct answer)
Broad-spectrum antibiotics for 4 weeks
Progesterone receptor antagonist therapy

Correct answer: Ovariohysterectomy

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

Question 196: Which internal parasite of cattle causes 'bottle jaw' (submandibular edema) due to hypoproteinemia?

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

Correct answer: Haemonchus placei

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

Question 197: 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?

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

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 198: A 6-year-old cat is presented for evaluation of a suspected portosystemic shunt. Fasting ammonia is 210 µmol/L (ref <60). On abdominal ultrasound, multiple tortuous vessels are identified in the splenic and left gastric regions but no single large shunting vessel. Which statement about this cat's condition is most accurate?

This represents portal vein hypoplasia (microvascular dysplasia) with compensatory collateral formation
Multiple shunts in this distribution are typical of right divisional intrahepatic shunts with collateral reconstitution
Multiple acquired portosystemic shunts indicate portal hypertension, most likely from hepatic fibrosis or cirrhosis (Correct answer)
This pattern is consistent with a congenital extrahepatic portosystemic shunt requiring surgical attenuation

Correct answer: Multiple acquired portosystemic shunts indicate portal hypertension, most likely from hepatic fibrosis or cirrhosis

Multiple acquired portosystemic shunts (APSS) develop as a consequence of portal hypertension, typically from hepatic parenchymal disease causing increased sinusoidal resistance — most commonly hepatic fibrosis, cirrhosis, or non-cirrhotic portal hypertension in cats. Unlike congenital shunts (which are typically single large vessels), acquired shunts are multiple small vessels that open as portosystemic pressure gradients increase. In cats, hepatic lipidosis, cholangitis, and inflammatory bowel disease can drive fibrosis. Surgery is contraindicated in APSS; treating underlying hepatic disease is the goal.

Question 199: Tritrichomonas foetus causes large-bowel diarrhea in cats. Which drug is currently recommended for treatment despite limited efficacy data?

Metronidazole
Ronidazole (Correct answer)
Sulfadimethoxine
Fenbendazole

Correct answer: Ronidazole

Ronidazole is the only drug shown to eliminate Tritrichomonas foetus in cats, though resistance and neurotoxicity at high doses are concerns.

Question 200: A 4-year-old Soft Coated Wheaten Terrier is presented for chronic small bowel diarrhea, significant weight loss, and peripheral edema. Bloodwork reveals severe panhypoproteinemia (both albumin and globulin are low). Which of the following conditions is the most likely underlying cause?

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

Correct answer: Protein-losing enteropathy (PLE)

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

Question 201: On thoracic radiographs of a 9-year-old DSH cat, you identify a soft tissue opacity in the cranial mediastinum that causes tracheal elevation and rightward deviation. Echocardiography confirms the heart is normal. The mass does not move independently from the cardiac silhouette on fluoroscopy. Which of the following is the LEAST likely differential diagnosis?

Aortic body chemodectoma (Correct answer)
Mediastinal lymphoma
Cranial mediastinal cyst (branchial or thymic)
Thymoma

Correct answer: Aortic body chemodectoma

Aortic body chemodectomas (heart base tumors) are rare in cats and arise at the heart base, not the cranial mediastinum; they typically cause a mass effect at the level of the great vessels rather than causing cranial mediastinal widening with tracheal elevation. Thymoma and mediastinal lymphoma are the two most common cranial mediastinal masses in cats, and cranial mediastinal cysts are an uncommon but recognized entity. The lack of independent cardiac movement on fluoroscopy helps exclude a cardiac origin but does not distinguish between the other differentials.

Question 202: During a reproductive program audit on a 550-cow dairy, you find that 22% of cows diagnosed pregnant at 30 days post-AI by transrectal ultrasonography are subsequently found non-pregnant at the 60-day confirmation exam. Progesterone supplementation (CIDR insert days 14–25 post-AI) was trialed with no improvement in pregnancy loss rate. Necropsy of three aborted fetuses at 45–55 days gestation reveals placentitis with intranuclear inclusion bodies on histopathology. Which pathogen is MOST consistent with this pattern of reproductive loss?

Leptospira borgpetersenii serovar Hardjo causing mid-gestation abortion storms
Neospora caninum causing recurrent abortion clustering in multiparous cows
Bovine viral diarrhea virus (BVDV) causing early embryonic death in PI-exposed heifers
Bovine herpesvirus 4 (BoHV-4) causing placentitis in the second trimester (Correct answer)

Correct answer: Bovine herpesvirus 4 (BoHV-4) causing placentitis in the second trimester

Bovine herpesvirus 4 (BoHV-4) causes sporadic to endemic placentitis in dairy cattle, typically presenting as pregnancy losses between 30 and 120 days of gestation. The hallmark histopathological finding is intranuclear inclusion bodies (Cowdry type A) in trophoblast and endometrial cells — a feature of herpesvirus replication. This distinguishes it from Neospora (which causes protozoal placentitis without inclusion bodies), Leptospira (which causes interstitial nephritis in the fetus and a characteristic 'abortion storm' pattern), and BVDV (which causes embryonic death before recognizable placentitis at 30+ days). The failure of progesterone supplementation rules out luteal insufficiency. BoHV-4 is underdiagnosed and often overlooked in differential lists for early-to-mid gestation loss with histologic lesions.

Question 203: Cytology of a fine-needle aspirate from a splenic mass in a 9-year-old Golden Retriever shows large cells with abundant cytoplasm containing hemosiderin, erythrophagocytosis, and rare mitotic figures with no distinct cell clusters. The most appropriate interpretation is:

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

Correct answer: Histiocytic sarcoma — aggressive malignancy requiring staging

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

Question 204: A 7-year-old Quarter Horse cutting horse has a 2/5 right hindlimb lameness. Intra-articular analgesia of the tarsometatarsal and distal intertarsal joints produces 50% improvement. A subsequent high plantar nerve block produces complete resolution. MRI is unavailable. Which additional diagnostic step is MOST likely to differentiate proximal suspensory desmitis from a cunean tendon lesion as the remaining pain source?

Computed tomography of the distal tarsus under general anesthesia
Radiographic oblique views of the hock at 45° and 60°
Nuclear scintigraphy with focal uptake mapping of the mid-cannon bone
Ultrasound of the proximal third metatarsal region in both transverse and sagittal planes (Correct answer)

Correct answer: Ultrasound of the proximal third metatarsal region in both transverse and sagittal planes

After confirming the pain source is proximal to the plantar nerve block level (consistent with the high plantar block resolving lameness) and ruling out a tarsal joint contribution, ultrasound of the proximal suspensory ligament (PSL) in both transverse and sagittal planes is the most practical next step. PSL desmitis in hindlimbs frequently occurs without obvious fiber disruption and requires systematic probe placement on the palmaroproximal metatarsus. The cunean tendon runs superficially and can be distinguished from the PSL by its more medial course and distinct echogenic envelope. CT and scintigraphy provide complementary data but are less accessible and not the first-line differentiation tool.

Question 205: 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 lack µ-opioid receptors, making premedication protocols less effective
Rabbits have obligate nasal breathing and a relatively small thoracic cavity with diaphragm-dependent ventilation (Correct answer)
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 206: 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?

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

Correct answer: Small intestinal bacterial overgrowth

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

Question 207: A dog is presented with acute onset of severe muscle tremors, hypersalivation, and miosis after potential exposure to a pesticide. Organophosphate toxicity is suspected. Which combination of drugs is the most appropriate treatment to counteract both the muscarinic and nicotinic effects?

Naloxone and Epinephrine
Diazepam and Fomepizole
Atropine and Pralidoxime (2-PAM) (Correct answer)
Vitamin K1 and Methocarbamol

Correct answer: Atropine and Pralidoxime (2-PAM)

The standard treatment for organophosphate toxicity involves a combination of Atropine and Pralidoxime (2-PAM). Atropine is a muscarinic antagonist that controls signs like salivation, urination, and bronchoconstriction. Pralidoxime is a cholinesterase reactivator that works to reverse the nicotinic effects, such as muscle tremors and paralysis, by breaking the bond between the organophosphate and the acetylcholinesterase enzyme.

Question 208: 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)
Torsemide
Hydrochlorothiazide
Spironolactone

Correct answer: Furosemide

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

Question 209: A cat presents with acute-onset ptyalism, vomiting, ataxia, and mydriasis after being seen chewing on a lily bouquet. Bloodwork 36 hours later reveals a BUN of 98 mg/dL and creatinine of 7.2 mg/dL. Which statement BEST describes the mechanism of lily nephrotoxicity in cats?

Lily stamen pollen contains calcium oxalate crystals that deposit in renal tubules and cause obstructive nephropathy
Lycorine alkaloids found in Lilium species competitively inhibit renal organic anion transporters, causing tubular toxin accumulation
The toxic glycoside tuliposide A is activated in the renal cortex and alkylates mitochondrial DNA of tubular cells
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 210: Feline infectious peritonitis dry (non-effusive) form most commonly causes granulomatous lesions in which anatomical sites?

Eyes, CNS, and abdominal organs (Correct answer)
Skin and ear canal
Lungs and pleural cavity
Joints and synovium

Correct answer: Eyes, CNS, and abdominal organs

Dry FIP granulomas typically affect the eyes (uveitis), CNS (ataxia, seizures), and abdominal organs (kidney, mesenteric lymph nodes).

Question 211: Which vaccination protocol is most effective for preventing Bovine Virus Diarrhea (BVD) in a cow-calf operation?

Modified live BVD vaccine given before breeding (Correct answer)
Killed BVD vaccine given at weaning only
Killed BVD vaccine given in the third trimester
Modified live BVD vaccine given at parturition

Correct answer: Modified live BVD vaccine given before breeding

MLV BVD vaccines given pre-breeding provide superior mucosal immunity and prevent fetal infection that leads to persistently infected (PI) calves.

Question 212: 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 corneal opacity indicates active FHV-1 viral replication in keratocytes, requiring intensified antiviral monotherapy with oral famciclovir alone and avoidance of all immunosuppressive agents.
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 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)

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

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

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 214: 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 215: Which radiographic view is most useful for evaluating the dens (odontoid process) of the axis (C2) in a dog for atlantoaxial instability?

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

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 216: A poultry flock develops acute respiratory distress, cyanosis of the comb and wattles, and hemorrhagic tracheitis with 40% mortality over 5 days. Which disease is most consistent with these findings?

Newcastle disease (velogenic form)
Avian influenza (HPAI)
Infectious bronchitis
Infectious laryngotracheitis (ILT) (Correct answer)

Correct answer: Infectious laryngotracheitis (ILT)

Infectious laryngotracheitis, caused by Gallid alphaherpesvirus 1, presents with severe hemorrhagic tracheitis, bloody mucus, gasping, and high mortality in affected flocks.

Question 217: 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?

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

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

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

Question 218: Which of the following correctly describes 'first-pass metabolism'?

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

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

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

Question 219: 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)
Strangles (Streptococcus equi subsp. equi) abscessation
Squamous cell carcinoma of the inguinal lymph node
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 220: Which zoonotic pathogen is primarily transmitted to humans through contact with infected animal urine, particularly in flooded environments?

Coxiella burnetii
Brucella abortus
Leptospira interrogans (Correct answer)
Francisella tularensis

Correct answer: Leptospira interrogans

Leptospira interrogans is shed in animal urine and transmitted via water or soil contact, with flooding increasing exposure risk.

Question 221: 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 permanent substitute for footbathing in herds where compliance with bath maintenance is consistently poor
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 twice-weekly injection program in feedlot pens exhibiting greater than 2% monthly footrot incidence
As a once-monthly mass medication of the entire herd regardless of environmental conditions to maintain subclinical suppression of Fusobacterium

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 222: 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?

Pulmonic Stenosis
Patent Ductus Arteriosus (Correct answer)
Mitral Valve Dysplasia
Ventricular Septal Defect

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 223: 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?

High-dose dexamethasone suppression test (HDDST) to confirm PDH vs. ADH
Endogenous ACTH concentration measurement
No further testing is needed; the 8-hour suppression pattern is diagnostic for pituitary-dependent hyperadrenocorticism (PDH) (Correct answer)
Adrenal ultrasonography to rule out adrenal-dependent hyperadrenocorticism

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 224: A 12-year-old Warmblood sport horse presents with insidious-onset bilateral forelimb lameness that is worse on hard surfaces and improves after 20 minutes of work. Flexion tests are mildly positive bilaterally. Nerve blocks are unremarkable through the pastern. Radiographs reveal bilateral palmar osteochondral fragments at the proximal interphalangeal joint. Which finding on MRI would most strongly implicate the distal interphalangeal joint collateral ligaments as the primary pain source in this presentation?

Diffuse synovial thickening of the distal interphalangeal joint with moderate joint effusion
Increased T1 signal in the navicular bone medullary cavity
Cartilage thinning on the lateral condyle of the middle phalanx
T2 hyperintensity within the collateral ligament substance with associated focal subchondral bone edema at the ligament enthesis (Correct answer)

Correct answer: T2 hyperintensity within the collateral ligament substance with associated focal subchondral bone edema at the ligament enthesis

T2 hyperintensity within the collateral ligament substance paired with focal subchondral bone edema at the enthesis indicates active ligamentous injury with an enthesopathy response — the hallmark MRI signature of collateral ligament desmitis at the DIP joint. Joint effusion and synovial thickening are nonspecific secondary findings, cartilage thinning points to osteoarthritis rather than ligamentous origin, and increased T1 navicular signal suggests fatty change or sclerosis, not collateral ligament pathology.

Question 225: Which opioid analgesic is commonly used in cats but must be used cautiously due to their limited glucuronidation capacity?

Morphine
Fentanyl
Hydromorphone
Buprenorphine (Correct answer)

Correct answer: Buprenorphine

Buprenorphine is preferred in cats because its partial agonist activity and high mu-receptor affinity make it effective at lower doses, reducing the risk of adverse effects from impaired glucuronidation.

Question 226: 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?

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
The combination of >11.5-degree rotation AND <6 mm sole depth defines a negative prognosis threshold; this case is borderline and surgical options such as deep digital flexor tenotomy should be considered (Correct answer)
Coffin bone rotation beyond 10 degrees is an absolute indication for euthanasia regardless of sole depth

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

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

Question 227: 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
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
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)

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 228: 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 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)
IV bretylium tosylate 5 mg/kg as an alternative antiarrhythmic
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 229: A pig farm reports sudden death in 3-week-old piglets with gross necropsy findings of fibrinous polyserositis, arthritis, and meningitis. The most likely causative agent is:

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

Correct answer: Haemophilus parasuis (Glässer's disease)

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

Question 230: A lesion causing ipsilateral hemiparesis, ipsilateral facial paralysis (CN VII), and ipsilateral loss of the menace response with intact vision best localizes to which neuroanatomical site?

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

Correct answer: Ipsilateral brainstem (pons/medulla)

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

Question 231: A dairy herd has an elevated somatic cell count (SCC) averaging 450,000 cells/mL despite a rigorous post-dip protocol and dry cow therapy. Bulk tank cultures repeatedly grow Streptococcus agalactiae. Which intervention is MOST likely to eliminate this pathogen from the herd?

Switch post-dip solution from iodine to chlorhexidine and increase milking frequency to three times daily
Segregate and cull all chronically infected cows, treat all culture-positive cows with intramammary penicillin, and implement herd-level blanket dry cow therapy (Correct answer)
Administer a Streptococcus agalactiae bacterin vaccine to all lactating cows to reduce new infection rate
Implement selective dry cow therapy based on individual cow SCC thresholds above 200,000 cells/mL

Correct answer: Segregate and cull all chronically infected cows, treat all culture-positive cows with intramammary penicillin, and implement herd-level blanket dry cow therapy

Streptococcus agalactiae is a contagious mastitis pathogen that is obligately associated with the bovine mammary gland. It is exquisitely sensitive to penicillin and can be eradicated from a herd through a combination of treating all infected cows (culture-positive), applying blanket dry cow therapy, segregating or culling chronic cases, and strict milking hygiene. Switching teat dip chemistry (B) addresses teat-end exposure but does not treat existing infections. There is no licensed S. agalactiae bacterin shown to eliminate an active herd infection (C). Selective dry cow therapy (D) would leave infected cows untreated at dry-off, perpetuating the reservoir.

Question 232: 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?

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)
Direct cytopathic destruction of enteric neurons in the myenteric and submucosal plexuses
ABV-encoded protease directly cleaving neurofilament proteins in vagal efferent fibers

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

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

Question 233: A rabbit (Oryctolagus cuniculus) is presented for acute anorexia and abdominal distension. On physical exam, there is tympany in the cecal region, hypothermia (98.4°F), and the cecum is palpably enlarged and doughy. Radiographs confirm massive cecal dilation with a gas cap. The rabbit has been on a high-pellet, low-hay diet. Which statement MOST accurately describes the pathophysiology of cecal dysbiosis in this patient?

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

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

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

Question 234: A dairy herd is experiencing an elevated somatic cell count (SCC) averaging 400,000 cells/mL. Which organism is most commonly associated with contagious mastitis causing elevated bulk tank SCC?

Streptococcus uberis
Klebsiella pneumoniae
Staphylococcus aureus (Correct answer)
Escherichia coli

Correct answer: Staphylococcus aureus

Staphylococcus aureus is the classic contagious mastitis pathogen spread cow-to-cow during milking, and is the leading cause of elevated bulk tank SCC in dairy herds.

Question 235: A 6-year-old domestic shorthair cat with vocal discomfort is examined for acute bilateral hind limb paralysis. A grade 3/6 left-sided systolic murmur is audible during a physical examination. The patient's footpads are chilly and pallid, and there are no femoral pulses. Additionally, the gastrocnemius and quadriceps muscles have painful contracture. Which of the following ailments has the highest likelihood of being diagnosed?

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

Correct answer: Arterial thromboembolism

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

Question 236: On orthogonal radiographs of a long bone, periosteal new bone with a 'sunburst' pattern is MOST characteristic of:

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

Correct answer: Primary bone tumor (osteosarcoma)

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

Question 237: A cat anesthetized with ketamine/diazepam develops prolonged apnea after induction. Which characteristic of ketamine best explains this risk?

Ketamine causes dose-dependent respiratory depression at high doses (Correct answer)
Ketamine increases upper airway secretions causing obstruction
Ketamine stimulates mu-opioid receptors
Ketamine inhibits NMDA receptors in the brainstem

Correct answer: Ketamine causes dose-dependent respiratory depression at high doses

While ketamine is generally considered a respiratory-sparing agent, high or rapidly administered doses can cause dose-dependent apnea in cats.

Question 238: A rancher reports abortions in 8% of his beef cows in the last trimester. Brucella abortus is confirmed. Which test is used for the official US brucellosis eradication program to test individual cattle?

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

Correct answer: Card test (Rose Bengal plate test)

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

Question 239: A ball python is presented for anorexia and regurgitation. Endoscopy reveals thickened gastric mucosa with abundant mucus. The most likely causative organism is:

Nidovirus
Salmonella spp.
Cryptosporidium serpentis (Correct answer)
Ophidiomyces ophiodiicola

Correct answer: Cryptosporidium serpentis

Cryptosporidium serpentis causes hypertrophic gastritis in snakes, presenting with chronic regurgitation and thickened gastric mucosa on endoscopy.

Question 240: A 5-year-old Labrador Retriever presents with acute onset hemolytic anemia (PCV 14%, spherocytes on smear, positive Coombs test). Which treatment combination is most appropriate as initial therapy?

Cyclosporine alone
Prednisone alone
Prednisone + azathioprine or mycophenolate (Correct answer)
Dexamethasone + vincristine

Correct answer: Prednisone + azathioprine or mycophenolate

Combination immunosuppression with a corticosteroid plus a steroid-sparing agent (azathioprine or mycophenolate) is recommended for IMHA to reduce relapse rates.

Question 241: A 7-year-old Thoroughbred racehorse undergoes nuclear scintigraphy after a 4-week history of right hindlimb lameness. The scan shows intense increased radiopharmaceutical uptake (IRU) at the right tuber sacrale. Standing rectal palpation reveals mild asymmetry. Radiographs are normal. Which diagnosis BEST explains these findings, and what is the primary mechanism of injury?

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

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

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

Question 242: Weakness, despair, lethargy, ptyalism, and posterior paresis are symptoms that a 5-year-old ferret exhibits. The patient's owner reports that these symptoms frequently appear every morning before feeding and typically subside after the meal. The symptoms have recently gotten worse and lasted longer. Which of the subsequent diagnoses is most likely?

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

Navicular suspensory ligament desmotomy via a palmar approach
Palmar digital neurectomy at the level of the proximal sesamoid bones
Inferior check ligament desmotomy (accessory ligament of the DDFT) (Correct answer)
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 244: A cat presents with a 'ground-glass' opacity on thoracic radiographs. Which condition is MOST associated with this finding?

Pneumothorax
Rib fracture
Pulmonary edema (Correct answer)
Pleural effusion

Correct answer: Pulmonary edema

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

Question 245: Which principle of disease prevention is represented by routine vaccination of dogs against rabies in the US?

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

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 246: A 7-year-old Thoroughbred presents with acute-onset, severe left forelimb lameness following a race. Radiographs reveal a complete, non-displaced sagittal fracture of the proximal phalanx. Intraoperative lag screw fixation is planned. Which cortex should the lag screw thread engage to achieve interfragmentary compression?

Both cortices with equal thread engagement to distribute load
The far cortex with a washer placed under the screw head at the near cortex
The near cortex only, leaving the far cortex unthreaded
The far cortex only, with the near cortex overdrilled to gliding hole diameter (Correct answer)

Correct answer: The far cortex only, with the near cortex overdrilled to gliding hole diameter

Lag screw technique requires overdrilling the near (glide) cortex to the outer thread diameter so it does not engage, while the thread bites only the far cortex. As the screw head seats against the near cortex, it pulls the far fragment toward the head, generating interfragmentary compression. Engaging both cortices or the near cortex alone negates the compression mechanism.

Question 247: A bearded dragon is presented with a black beard, lethargy, and yellow-white caseous plugs in the intestine on necropsy. The causative agent is:

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

Correct answer: Entamoeba invadens

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

Question 248: Which of the following is the gold standard post-exposure prophylaxis regimen for unvaccinated humans exposed to rabies?

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

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

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

Question 249: 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?

Left-sided rumen atony with no ping detected
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
Bilateral pings with fluid splashing sounds in the lower abdomen

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 250: 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
Cardiac-origin transudative pleural effusion
Chylothorax (Correct answer)
Pyothorax secondary to migrating foreign body

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

Mirror artifact
Reverberation (Correct answer)
Enhancement
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 252: 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?

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

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

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

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

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

Question 254: 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 255: 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 infects porcine alveolar macrophages and spreads hematogenously to the fetoplacental unit during the last trimester (Correct answer)
PRRSV crosses the placenta during early gestation and integrates into fetal DNA

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

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

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

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

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

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

Correct answer: Single-layer simple interrupted appositional pattern

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

Question 259: A 4-year-old spayed female cat tests positive on an ELISA for FeLV p27 antigen. She is clinically healthy. A proviral PCR on peripheral blood leukocytes is also positive, but a repeat ELISA 12 weeks later is negative, and a subsequent proviral PCR on bone marrow is negative. What is the MOST accurate classification of this cat's infection status, and what is the recommended management?

The cat has a focal/compartmentalized infection limited to the mammary gland and salivary glands; she remains infectious via grooming despite the negative bone marrow PCR.
Discordant ELISA results indicate a defective ELISA assay; a Western blot for gp70 envelope protein is needed to confirm progressive infection before any management decisions.
The cat experienced a regressive (previously called 'abortive' or 'latent') FeLV infection; proviral DNA is absent from bone marrow, indicating viral clearance; she is likely not infectious and can be managed as a healthy cat with periodic monitoring. (Correct answer)
The cat has a progressive infection with bone marrow sequestration of virus; the negative bone marrow PCR is a false negative due to low viral load, and she should be treated with antiviral therapy immediately.

Correct answer: The cat experienced a regressive (previously called 'abortive' or 'latent') FeLV infection; proviral DNA is absent from bone marrow, indicating viral clearance; she is likely not infectious and can be managed as a healthy cat with periodic monitoring.

FeLV infection outcomes include progressive infection (persistent antigenemia, high viral load, immunosuppression) and regressive infection (transient antigenemia that resolves, with proviral DNA integrated but not actively replicating—detectable in blood but not bone marrow). A cat with an initial positive ELISA that reverts to negative, combined with negative bone marrow proviral PCR, has most likely achieved regressive infection with viral clearance. These cats are generally not infectious, have a near-normal life expectancy, and do not require antiviral treatment—only periodic wellness monitoring. Focal/compartmentalized infection is a separate category involving persistent antigen in specific tissues despite negative blood tests.

Question 260: 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 261: A dog receives acepromazine premedication followed by isoflurane anesthesia. It develops refractory hypotension unresponsive to fluids. Which vasopressor is most appropriate?

Phenylephrine bolus
Ephedrine IV bolus (Correct answer)
Norepinephrine CRI
Dopamine at 2 mcg/kg/min

Correct answer: Ephedrine IV bolus

Ephedrine has both alpha and beta agonist activity and is effective for treating hypotension caused by vasodilation from acepromazine plus inhalant anesthesia.

Question 262: You are treating a 450 kg horse with a severe gram-negative septicemia. You choose gentamicin and wish to use pharmacokinetic/pharmacodynamic (PK/PD) optimization. Which dosing strategy best exploits gentamicin's concentration-dependent killing and post-antibiotic effect (PAE)?

Continuous rate infusion at 0.5 mg/kg/hour to maintain a stable drug concentration above the MIC
2.2 mg/kg IV every 8 hours to achieve a steady-state trough below nephrotoxic thresholds
6.6 mg/kg IV every 24 hours (once-daily dosing) to maximize Cmax:MIC ratio while allowing renal recovery (Correct answer)
6.6 mg/kg IV every 8 hours to maintain levels above the MIC for >50% of the dosing interval

Correct answer: 6.6 mg/kg IV every 24 hours (once-daily dosing) to maximize Cmax:MIC ratio while allowing renal recovery

Aminoglycosides like gentamicin exhibit concentration-dependent killing — efficacy correlates with peak (Cmax) to MIC ratio (target Cmax:MIC ≥8-10:1) rather than time above MIC. They also have a prolonged post-antibiotic effect (PAE), meaning bacterial suppression continues even after serum concentrations fall below MIC. Once-daily dosing (6.6 mg/kg q24h in horses) maximizes the Cmax:MIC ratio, exploits the PAE, and critically allows trough concentrations to fall near zero, reducing tubular aminoglycoside accumulation and nephrotoxicity risk. Continuous infusion or time-dependent dosing strategies are appropriate for beta-lactams, not aminoglycosides.

Question 263: Which of the following is considered the most effective method for long-term monitoring of glycemic control in a diabetic dog, reflecting average blood glucose over the preceding 2-3 months?

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

Correct answer: Glycosylated hemoglobin (HbA1c) concentration

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

Question 264: A slaughter plant veterinarian observes a pig with depression, erythematous skin lesions, and sudden death in the pen. The most important zoonotic differential diagnosis to consider is:

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

Correct answer: Erysipelothrix rhusiopathiae infection

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

Question 265: A 4-year-old intact female Doberman Pinscher presents with acute collapse. Echocardiography reveals a large hypoechoic space surrounding the heart with compression of the right atrium during diastole. The most appropriate NEXT imaging step to identify the underlying etiology is:

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

Correct answer: CT angiography of the thorax with IV contrast after stabilization via pericardiocentesis

In a Doberman with cardiac tamponade, after life-saving pericardiocentesis, CT angiography with IV contrast is the superior next step for identifying the etiology. Hemangiosarcoma of the right auricle and heart base tumors (chemodectoma) are the most common causes. CT provides superior soft tissue characterization, detects small auricular masses invisible on echocardiography (especially post-pericardiocentesis when fluid is removed), and evaluates for concurrent thoracic or abdominal metastatic disease. CEUS can visualize auricular masses but has more limited anatomic coverage. Repeat echo alone after 48 hours is inferior — CT is now the standard of care for neoplastic pericardial effusion workup.

Question 266: A 4-year-old domestic shorthair cat presents with a 3-week history of progressive neurological signs including head tremors, cerebellar ataxia, and vertical nystagmus. The owner recently moved from the Ohio River Valley. CSF analysis shows eosinophilic pleocytosis. Serum Cryptococcus antigen is negative. Which organism is the most likely causative agent?

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

Correct answer: Blastomyces dermatitidis

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

Question 267: 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?

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

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

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

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

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

Question 269: 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 arthroscopic debridement under general anesthesia immediately without lavage
Initiate systemic corticosteroids
Repeat radiographs in 2 weeks
Perform through-and-through joint lavage and systemic antimicrobials (Correct answer)

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

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

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

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

Question 271: 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?

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

Correct answer: Balloon valvuloplasty via cardiac catheterization

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

Question 272: Foot rot (Fusobacterium necrophorum infection) is common in beef feedlots. Which environmental management change has the greatest impact on reducing foot rot incidence?

Routine zinc supplementation in the diet
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

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 273: 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?

Prednisolone (oral)
Cyproheptadine (oral)
Terbutaline (subcutaneous) (Correct answer)
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 274: Toxoplasma gondii infection in pregnant women is most commonly acquired in the US through:

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

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

Dorsoventral with horizontal beam
Standing lateral with horizontal beam (Correct answer)
Lateral recumbency with affected side down
Ventrodorsal 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 276: 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?

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

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

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

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

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

Question 278: On a lateral skull radiograph of a rabbit, you observe bilateral tympanic bullae with significantly increased opacity and thickened walls. The petrous temporal bones appear sclerotic. This pattern is MOST consistent with:

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

Correct answer: Otitis media/interna with secondary bulla osteitis

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

Question 279: A 4-year-old Labrador Retriever is presented for episodic weakness and collapse after exercise. The owner reports the dog recovers within 10–20 minutes of rest. On examination, the dog is normal between episodes. Serum chemistry and CBC are unremarkable. An ECG during an induced episode shows a wide complex tachycardia at 280 bpm. Which breed-specific genetic mutation is most directly responsible for this presentation?

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

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

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

Question 280: A Quarter Horse presents with acute, severe forelimb lameness and a draining tract near the coronary band. Radiographs show gas lucency within the third phalanx. What condition do these findings most strongly suggest?

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

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

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

Question 281: A dairy herd has a high prevalence of digital dermatitis (Mortellaro's disease). Which treatment is most effective for active, painful lesions?

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

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

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

Question 282: A feedlot veterinarian is investigating a cluster of sudden deaths in newly arrived stocker cattle (500–700 lb) that had been on feed for 8–14 days. Gross necropsy findings include: marked rumen distension with frothy ingesta, marked pulmonary edema and emphysema, hepatic lipidosis, and no evidence of blackleg or other clostridial lesions. Histopathology shows acute tubular necrosis in the kidneys. Which diagnosis BEST unifies these pathologic findings, and what is the most likely predisposing management factor?

Polioencephalomalacia secondary to high-sulfur water; the renal lesions reflect concurrent dehydration-associated prerenal azotemia
Acute interstitial pneumonia (fog fever / atypical interstitial pneumonia) caused by L-tryptophan→3-methylindole conversion; predisposed by abrupt lush pasture access after a period of nutritional restriction
Grain overload (ruminal acidosis) with secondary mycotoxin-related hepatonephropathy; predisposed by rapid ration step-up exceeding rumen adaptation capacity (Correct answer)
Urea toxicosis from excessive non-protein nitrogen (NPN) supplementation; frothy rumen contents reflect ammonia-driven disruption of rumen microflora and gas production

Correct answer: Grain overload (ruminal acidosis) with secondary mycotoxin-related hepatonephropathy; predisposed by rapid ration step-up exceeding rumen adaptation capacity

The combination of frothy rumen distension, pulmonary edema/emphysema, hepatic lipidosis, and acute tubular necrosis in feedlot cattle 8–14 days post-arrival that died suddenly is the classic picture of grain overload (acute rumen acidosis) with systemic sequelae. Rapid fermentation of excessive starch produces lactic acid, driving pH below 5.5, which causes rumenitis, systemic acidemia, endotoxemia, hepatic lipid accumulation (from mobilization during the metabolic crisis), and renal tubular injury from circulating toxins and hemodynamic compromise. The frothy rumen content is distinct from frothy bloat—here it reflects disrupted motility and gas trapping from acidic pH. Predisposing factor: an aggressive ration step-up that exceeds rumen papillae adaptation. Fog fever occurs in pastured cattle moved to lush grass, not feedlot receiving. Polioencephalomalacia would show cerebrocortical necrosis histologically. Urea toxicosis causes tetany, cerebral edema, and bloat but not the hepatorenal pattern seen here.

Question 283: A 6-year-old Miniature Poodle has chronic small bowel diarrhea. Serum TLI is 2.0 µg/L (normal >2.5 µg/L). What is the most likely diagnosis?

Exocrine pancreatic insufficiency (Correct answer)
Inflammatory bowel disease
Lymphangiectasia
Intestinal lymphoma

Correct answer: Exocrine pancreatic insufficiency

A serum TLI below 2.5 µg/L is diagnostic for exocrine pancreatic insufficiency, reflecting markedly reduced pancreatic enzyme secretion.

Question 284: A 6-year-old male intact Beagle presents with a 4-month history of recurrent urinary tract infections and intermittent hematuria. Ultrasound reveals a 2.8 cm hyperechoic mass in the prostatic urethra. Biopsy confirms transitional cell carcinoma (TCC). Thoracic radiographs are clear. Which statement regarding treatment and prognosis is MOST accurate?

COX-2 inhibitor therapy is indicated regardless of other treatment modality due to documented partial response rates (Correct answer)
Surgical resection via total prostatectomy is curative in >50% of cases if margins are clean
Urethral stenting is contraindicated because it promotes tumor seeding along the stent tract
Piroxicam alone provides equivalent survival to piroxicam plus mitoxantrone combination therapy

Correct answer: COX-2 inhibitor therapy is indicated regardless of other treatment modality due to documented partial response rates

Canine TCC (now termed urothelial carcinoma) overexpresses COX-2, and piroxicam (a non-selective COX inhibitor) has documented partial response rates (~17%) and stable disease rates (~57%), making it a cornerstone of TCC management regardless of whether chemotherapy is added. Piroxicam plus mitoxantrone has shown improved response rates over piroxicam alone in studies (not equivalent). Surgical resection is rarely curative due to urethral/trigone involvement and high local recurrence. Urethral stenting is actually used palliatively for urethral obstruction in TCC dogs, with tumor seeding along stent tracts not a documented clinical contraindication.

Question 285: A cat presents with bilateral anterior uveitis. FIP testing is negative. Which other infectious agent should be high on the differential list?

Feline panleukopenia virus
Feline calicivirus
Toxoplasma gondii (Correct answer)
Feline parvovirus

Correct answer: Toxoplasma gondii

Toxoplasma gondii is a leading cause of feline uveitis and should be tested via serology when FIP is ruled out.

Question 286: A cattle producer wants to treat a cow with bacterial pneumonia. Which beta-lactam antibiotic has an approved long-acting formulation for cattle?

Ceftiofur (Correct answer)
Penicillin G procaine
Ampicillin
Amoxicillin

Correct answer: Ceftiofur

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

Question 287: A cat is accidentally administered a dose of acetaminophen (paracetamol). Which clinical sign is most characteristic of this specific toxicity in felines due to their metabolic differences?

Acute fulminant hepatic necrosis
Profound coagulopathy
Severe gastrointestinal ulceration
Methemoglobinemia and facial edema (Correct answer)

Correct answer: Methemoglobinemia and facial edema

Cats have a deficiency in the glucuronidation pathway, a major route for acetaminophen metabolism in other species. This shunts metabolism down alternative pathways, leading to the production of toxic metabolites that cause oxidative damage to red blood cells. This results in the formation of methemoglobin, which cannot carry oxygen, leading to cyanosis (often described as 'muddy' or brown mucous membranes), dyspnea, and often concurrent facial or paw edema. While liver damage can occur, methemoglobinemia is the more prominent and life-threatening feature in cats.

Question 288: Which of the following reproductive strategies describes the boa constrictor?

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

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

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

Question 289: 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?

Bacterial overgrowth consuming cobalamin before ileal absorption can occur
Hepatic failure impairing cobalamin storage and enterohepatic recirculation
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 290: A cat is diagnosed with feline infectious anemia caused by Mycoplasma haemofelis. Which treatment is most appropriate?

Enrofloxacin monotherapy
Amoxicillin-clavulanate
Metronidazole and ivermectin
Doxycycline with supportive care including blood transfusion if needed (Correct answer)

Correct answer: Doxycycline with supportive care including blood transfusion if needed

Doxycycline is the first-line antibiotic for Mycoplasma haemofelis, with blood transfusion reserved for severely anemic cats.

Question 291: During a routine health exam on a 3-year-old Burmese python, you palpate a mid-body mass. Ultrasound reveals a well-defined, echogenic structure with posterior acoustic shadowing adjacent to the left kidney. The snake has been fed a rodent diet exclusively and appears otherwise healthy. What is the most likely diagnosis and the most important next diagnostic step?

Paramyxovirus-associated hepatocellular carcinoma — submit serology for Ferlavirus antibodies
Hepatic lipidosis — obtain a liver biopsy via endoscopy to confirm lipid vacuolation
Nutritional secondary hyperparathyroidism — measure ionized calcium and PTH levels
Renal calculus — measure uric acid and perform contrast radiography to assess urinary outflow (Correct answer)

Correct answer: Renal calculus — measure uric acid and perform contrast radiography to assess urinary outflow

In snakes, a well-defined echogenic structure with posterior acoustic shadowing adjacent to the kidney is characteristic of a nephrolith (renal calculus). Snakes are uricotelic, and uric acid nephropathy with urolithiasis is the most common renal pathology in captive pythons, often secondary to dehydration, excess protein, or renal disease. The critical next step is measuring uric acid (hyperuricemia suggests active renal impairment) and using contrast radiography or CT to determine if urinary outflow is obstructed. Hepatic lipidosis and hepatocellular carcinoma are not consistent with acoustic shadowing adjacent to the kidney.

Question 292: 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?

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
Feline bronchopneumonia (bacterial); transtracheal wash for cytology and culture
Cardiogenic pulmonary edema; echocardiography to detect occult hypertrophic cardiomyopathy with normal cardiac size (Correct answer)

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 293: Which grading scale is the standard used in the United States to assess equine lameness severity?

Obel grading system
AAEP lameness scale 0-5 (Correct answer)
British Equine Veterinary Association (BEVA) 1-10 scale
FEI grading 0-4

Correct answer: AAEP lameness scale 0-5

The American Association of Equine Practitioners (AAEP) 0-5 lameness scale is the standard used in the US, with 0 being sound and 5 being non-weight-bearing.

Question 294: 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 integrates its proviral DNA preferentially adjacent to the c-myc locus, causing insertional mutagenesis analogous to FeLV, making it a directly transforming retrovirus.
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-associated lymphoma is always of T-cell origin and occurs exclusively in cats with CD4:CD8 ratios below 0.5, making immunophenotyping unnecessary for prognostication.
FIV encodes an oncoprotein (Tax) that directly transactivates proto-oncogenes in T lymphocytes, causing T-cell lymphoma as the predominant malignancy in FIV-infected cats.

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

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

Correct answer: NPH insulin

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

Question 296: In equine foot radiography, which landmark is used to assess the position of the navicular bone relative to the distal 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)
Dorsal cortex width of the middle phalanx

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 297: 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; 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
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)

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

Atipamezole (Correct answer)
Neostigmine
Flumazenil
Naloxone

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

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

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

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

Question 300: A 9-year-old Cairn Terrier has chronic hepatitis with copper accumulation on liver biopsy (>2000 µg/g dry weight). Which chelation agent is most commonly used in dogs to reduce hepatic copper?

Deferoxamine
EDTA
D-penicillamine (Correct answer)
Deferasirox

Correct answer: D-penicillamine

D-penicillamine is the most widely used copper chelator in dogs with copper-associated hepatopathy, mobilizing hepatic copper for urinary excretion.

Question 301: A beef producer asks about strategies to reduce the use of medically important antimicrobials in the feedlot. Which intervention is the best alternative for reducing bovine respiratory disease (BRD) morbidity?

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

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

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

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

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

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

Histoplasmosis
Blastomycosis
Cryptococcosis (Correct answer)
Sporotrichosis

Correct answer: Cryptococcosis

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

Question 305: A 4-year-old male Shar-Pei presents with recurrent fever episodes lasting 1–3 days, swollen hocks, and intermittent vomiting. Between episodes the dog appears normal. CBC and chemistry during a febrile episode show neutrophilia with a left shift and mildly elevated BUN. Urinalysis shows 3+ proteinuria. Which underlying pathophysiologic mechanism is most directly responsible for the proteinuria in this dog?

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

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

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

Question 306: Amlodipine is the first-line treatment for systemic hypertension in cats. What is its primary mechanism of action?

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

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

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

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

Question 308: The Hazard Analysis Critical Control Point (HACCP) system was originally developed to ensure food safety for which population?

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

Correct answer: NASA astronauts

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

Question 309: During a routine equine breeding soundness evaluation (BSE) in a 4-year-old Thoroughbred stallion, semen evaluation reveals: total motility 65%, progressive motility 45%, morphology 55% normal sperm. Per AAEP guidelines, how should this stallion be classified?

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

Correct answer: Questionable potential breeder

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

Question 310: Which of the following findings on an ACTH stimulation test is most consistent with a diagnosis of typical hypoadrenocorticism (Addison's disease) in a dog?

Normal baseline cortisol with an exaggerated response post-ACTH
Low baseline cortisol with an exaggerated response post-ACTH
Low baseline cortisol with a minimal to no response post-ACTH (Correct answer)
High baseline cortisol with a minimal response post-ACTH

Correct answer: Low baseline cortisol with a minimal to no response post-ACTH

The definitive diagnosis of hypoadrenocorticism is made with an ACTH stimulation test. Dogs with Addison's disease have adrenal glands that cannot produce cortisol, so both the baseline (pre-ACTH) cortisol level and the post-ACTH cortisol level will be low, showing a minimal or flat-line response to stimulation.

Question 311: 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?

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

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

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

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

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

Question 313: On thoracic radiographs of a dog, which cardiac silhouette finding is most consistent with left atrial enlargement?

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

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

Robenacoxib (Correct answer)
Ketoprofen
Meloxicam
Grapiprant

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

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

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

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

Question 316: Which preanesthetic agent is CONTRAINDICATED in patients with suspected splenic masses because it causes splenic engorgement and sequestration of red blood cells?

Dexmedetomidine
Butorphanol
Acepromazine (Correct answer)
Midazolam

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 317: A 3-year-old Soft-Coated Wheaten Terrier presents with hypoalbuminemia (1.4 g/dL), ascites, and normal liver enzymes. Protein-losing enteropathy is suspected. Which finding on intestinal biopsy would be most consistent with lymphangiectasia?

Dilated lacteals and lipid-laden macrophages (Correct answer)
Plasma cell and lymphocyte infiltration of the lamina propria
Eosinophilic infiltration of the mucosa
Crypt abscesses and villous blunting

Correct answer: Dilated lacteals and lipid-laden macrophages

Dilated lacteals with lipid-laden macrophages (lipogranulomas) are the hallmark histopathologic findings of intestinal lymphangiectasia.

Question 318: Which critical temperature range is considered the 'danger zone' for bacterial growth in potentially hazardous foods?

60°F to 180°F (16°C to 82°C)
32°F to 40°F (0°C to 4°C)
50°F to 165°F (10°C to 74°C)
40°F to 140°F (4°C to 60°C) (Correct answer)

Correct answer: 40°F to 140°F (4°C to 60°C)

The USDA defines the temperature danger zone as 40°F to 140°F (4°C to 60°C), where most foodborne pathogens multiply rapidly.

Question 319: In avian anatomy, the proventriculus is best described as which of the following?

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

Correct answer: The glandular stomach that secretes HCl and pepsin

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

Question 320: A 10-year-old female Labrador Retriever presents with a history of panting, pot-bellied appearance, bilateral symmetrical alopecia, and PU/PD. Urine cortisol:creatinine ratio is elevated. Which test best differentiates pituitary-dependent from adrenal-dependent hyperadrenocorticism?

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

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

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

Question 321: A 2-year-old Miniature Schnauzer is presented to the emergency clinic with acute onset of vomiting and profuse hemorrhagic diarrhea, described as 'raspberry jam' in appearance. The dog is tachycardic, has weak pulses, and a PCV of 62% with normal total solids. What is the most critical initial treatment for this patient?

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

Correct answer: Aggressive intravenous fluid therapy

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

Question 322: A dog under isoflurane anesthesia has an end-tidal CO2 (ETCO2) reading of 62 mmHg. What does this finding indicate?

Adequate ventilation
Hypoventilation with CO2 retention (Correct answer)
Hyperventilation with CO2 washout
Adequate tissue oxygenation

Correct answer: Hypoventilation with CO2 retention

Normal ETCO2 in anesthetized patients is 35–45 mmHg; a value of 62 mmHg indicates hypoventilation, meaning the patient is not eliminating CO2 adequately and intervention (e.g., manual or mechanical ventilation) is needed.

Question 323: A herd of 30 beef cow-calf pairs is experiencing an outbreak of bloody diarrhea in calves 5–21 days of age. Mortality has reached 30% despite oral electrolyte therapy. Post-mortem findings include hemorrhagic enteritis of the jejunum and ileum with villous necrosis and blunting. Gram-positive, spore-forming rods are visualized on intestinal smear. PCR of intestinal contents is positive for NetB toxin gene. Which pathogen and the toxin most responsible for villous destruction are correctly identified?

Clostridium difficile; toxin B
Clostridium perfringens Type A; alpha toxin
Clostridium perfringens Type C; beta toxin (Correct answer)
Clostridium perfringens Type D; epsilon toxin

Correct answer: Clostridium perfringens Type C; beta toxin

NetB toxin is produced by Clostridium perfringens Type C and is a pore-forming toxin. However, the primary virulence factor in Type C hemorrhagic enteritis of neonatal calves is beta toxin (cpb gene), which causes severe necrotizing enteritis by disrupting intestinal epithelium. Beta toxin is protease-sensitive, which is why it preferentially affects neonates lacking tryptic activity. Type A causes mild diarrhea via alpha toxin; Type D causes pulpy kidney/edema disease via epsilon toxin; C. difficile produces toxins A and B in a different syndrome. The NetB gene in the PCR confirms Type C.

Question 324: A 900-cow Holstein dairy herd participates in a reproductive program using GnRH-based synchronization (Ovsynch). Despite high estrus synchronization compliance, 21-day pregnancy rates have plateaued at 18%. Detailed records show: AI submission rate 92%, conception rate (CR) 21%, pregnancy loss 12% (day 28–56). The reproductive specialist suspects subclinical endometritis. Which diagnostic criterion BEST defines subclinical endometritis in lactating dairy cows, and what is the recommended threshold for treatment intervention in this herd?

Rectal palpation detecting a uterus >10 cm diameter at 28 days postpartum; treat with PGF2α to induce luteolysis
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)
Vaginoscopy revealing mucopurulent discharge (Metricheck score ≥2) at any point in the first 60 days in milk; treat with systemic ceftiofur at 35 DIM

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

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

Question 325: During a pre-purchase examination, a 5-year-old Dutch Warmblood mare shows a 2/5 lameness on the lunge that is eliminated by an abaxial sesamoid nerve block but NOT by a palmar digital nerve block. High-field MRI of the pastern and foot is normal. Which structure, when anesthetized by the abaxial block but not the palmar digital block, MOST likely harbors the pathology?

The collateral ligaments of the proximal interphalangeal (PIP) joint (Correct answer)
The deep digital flexor tendon at the level of the navicular bursa
The impar ligament of the distal sesamoid bone
The digital annular ligaments of the fetlock

Correct answer: The collateral ligaments of the proximal interphalangeal (PIP) joint

The palmar digital nerve block desensitizes the caudal third of the foot including the navicular region, the DIP joint, and solar corium. The abaxial sesamoid block additionally desensitizes the PIP joint, fetlock, and proximal pastern structures. When the abaxial block is positive but the palmar digital block is negative, the pathology must lie in the region uniquely anesthetized by the more proximal block — most commonly the collateral ligaments or the PIP joint itself. MRI being normal of the distal foot further narrows the source to the pastern/PIP region.

Question 326: During lameness examination on the lunge, a horse with LEFT forelimb lameness will characteristically:

Nod the head UP when the left forelimb strikes (Correct answer)
Show a hip hike when the left forelimb strikes
Lower the croup when lunging to the right
Nod the head DOWN when the right 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 327: A 3-year-old intact male cat presents with acute onset of pelvic limb paralysis, cold limbs below the stifle, absent femoral pulses bilaterally, and cyanotic nail beds. The most likely diagnosis is:

Traumatic spinal cord injury with T3-L3 myelopathy
Fibrocartilaginous embolism (FCE) of the thoracolumbar spinal cord
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 328: A cat is presented for suspected oleander (Nerium oleander) ingestion. What is the primary mechanism of toxicity?

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

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

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

Question 329: 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?

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
Dehydration secondary to decreased water intake now that polydipsia has resolved

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 330: 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?

Oral sotalol loading dose
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)
IV diltiazem at 0.25 mg/kg over 2 minutes

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

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

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

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

Question 332: 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 inhibits glycolysis in chondrocytes by alkylating sulfhydryl groups of glyceraldehyde-3-phosphate dehydrogenase, causing chondrocyte death and cartilage destruction (Correct answer)
It chelates calcium ions within the synovial fluid, precipitating calcium monoiodoacetate crystals that mechanically abrade cartilage
It directly stimulates osteoblastic activity at subchondral bone, promoting bridging osteophyte formation across the joint space
It activates the complement cascade within the joint, inducing a sterile neutrophilic arthritis that ablates the synovial membrane

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 333: 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
Fine needle aspirate is diagnostic in the majority of splenic masses
Splenectomy is contraindicated until coagulopathy is corrected

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

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

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

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

Question 335: A 10-year-old dog is diagnosed with stage 3 chronic kidney disease (IRIS). Which dietary modification is most appropriate?

Phosphorus restriction with moderate protein reduction (Correct answer)
High protein diet to offset catabolism
Sodium restriction only
Increased calcium supplementation

Correct answer: Phosphorus restriction with moderate protein reduction

Phosphorus restriction slows CKD progression by reducing renal secondary hyperparathyroidism, and moderate protein reduction decreases uremic toxin accumulation without worsening malnutrition.

Question 336: Ketamine is commonly used as an induction agent, particularly in cats. What is its PRIMARY mechanism of anesthetic action?

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

Correct answer: NMDA receptor antagonism

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

Question 337: What is the recommended colostrum management '1-2-3 rule' for newborn dairy calves?

2 liters within 1 hour, IgG ≥22 g/L confirmed by colostrometer
3 feedings within the first day, 1 liter each time
1 pint within 3 hours, tested by refractometer at ≥30% Brix
1 gallon within 2 hours of birth, immunoglobulin concentration ≥50 g/L (Brix ≥22%) (Correct answer)

Correct answer: 1 gallon within 2 hours of birth, immunoglobulin concentration ≥50 g/L (Brix ≥22%)

The 1-2-3 rule recommends 1 gallon (≈4 L) of high-quality colostrum (≥50 g/L IgG) fed within the first 2 hours after birth, with a Brix refractometer reading ≥22% confirming adequate quality.

Question 338: Necropsy of an 8-year-old dog reveals a 4 cm hepatic mass with a tan cut surface, no central necrosis, and a pushing border compressing but not invading adjacent parenchyma. Histology shows well-differentiated hepatocytes in a solid pattern. The most appropriate classification is:

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

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

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

Question 339: A cattery owner presents with a problem of recurrent feline calicivirus (FCV) outbreaks despite strict vaccination protocols using modified-live calicivirus vaccines. PCR confirms FCV in affected cats. Affected cats display high fever (>106°F), facial and limb edema, skin ulceration, and 40% case fatality rate — a pattern different from classic FCV upper respiratory disease. Which statement BEST characterizes the virological basis of this outbreak and the limitation of current vaccines?

VS-FCV outbreaks are caused by FCV recombination with feline coronavirus, creating a chimeric virus not covered by monovalent vaccines
Virulent systemic FCV (VS-FCV) strains have undergone antigenic drift sufficient to escape neutralizing antibodies induced by vaccine strains, as FCV has an ssRNA genome with high mutation rates (Correct answer)
VS-FCV is a prion-mediated conformational variant of classic FCV that is resistant to inactivation by standard disinfectants used in cattery settings
Current vaccines fail because VS-FCV exclusively targets macrophages via a different receptor (junctional adhesion molecule-1 rather than feline junctional adhesion molecule)

Correct answer: Virulent systemic FCV (VS-FCV) strains have undergone antigenic drift sufficient to escape neutralizing antibodies induced by vaccine strains, as FCV has an ssRNA genome with high mutation rates

Virulent systemic FCV (VS-FCV or hemorrhagic fever-like FCV) represents highly pathogenic FCV strains capable of causing systemic disease with high mortality. FCV is a positive-sense single-stranded RNA virus (Caliciviridae) with a high mutation rate, allowing continuous antigenic drift. Studies have demonstrated that VS-FCV strains show reduced cross-neutralization by antibodies raised against vaccine strains — a key reason why fully vaccinated cats in outbreaks can still become severely ill. FCV does not recombine with coronavirus. Feline junctional adhesion molecule (fJAM-A) is the receptor for both classic and VS-FCV strains. VS-FCV is not prion-mediated. FCV is susceptible to bleach (1:32 dilution) but survives many quaternary ammonium compounds.

Question 340: Organophosphate toxicity in animals is treated with which combination of drugs?

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

Correct answer: Atropine and pralidoxime (2-PAM)

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

Question 341: What is the primary mechanism by which ivermectin kills parasites?

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

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 342: In a One Health investigation of a novel influenza A virus detected in a Great Lakes commercial mink farm, whole-genome sequencing reveals a reassortant virus with PB2 from a North American H5N1 clade 2.3.4.4b wild bird isolate, PA and PB1 from a human seasonal H3N2 virus, and HA/NA from swine IAV-S. Which of the following statements BEST characterizes the public health threat assessment for farm workers?

The swine-origin HA/NA is the primary risk factor because swine influenza has established pandemic potential through direct zoonotic transmission, and avian and human gene segments in internal proteins are epidemiologically irrelevant
The PB2 gene segment origin from a highly pathogenic avian influenza (HPAI) strain warrants heightened concern because avian-origin PB2 (particularly the E627K or D701N mutation) is a key mammalian adaptation marker, and the presence of human seasonal gene segments suggests prior human-to-animal transmission that could facilitate further human adaptation (Correct answer)
The primary concern is avian influenza spread back to wild bird populations via mink feces, not direct human infection, because influenza A viruses require receptor binding site mutations in HA to infect humans regardless of internal gene composition
The virus poses minimal risk because mink-to-human transmission has never been documented in peer-reviewed literature, and reassortant viruses are inherently less fit than parental strains

Correct answer: The PB2 gene segment origin from a highly pathogenic avian influenza (HPAI) strain warrants heightened concern because avian-origin PB2 (particularly the E627K or D701N mutation) is a key mammalian adaptation marker, and the presence of human seasonal gene segments suggests prior human-to-animal transmission that could facilitate further human adaptation

The PB2 gene segment is critical in influenza A host adaptation. Avian-origin PB2 with mutations at position 627 (E627K) or 701 (D701N) dramatically increases replication efficiency at mammalian lower respiratory tract temperatures (33°C vs. 41°C in birds). Detection of human seasonal H3N2 internal gene segments in a mink-farm virus indicates prior reverse zoonosis (human→mink), meaning the virus has already had exposure to a mammalian host capable of selecting for human-adaptive mutations. Mink are also relevant historically — a 2021 Danish mink SARS-CoV-2 cluster demonstrated efficient mink-human transmission. Reassortant viruses are not inherently less fit; pandemic influenza strains (2009 H1N1) were reassortants. The HA receptor binding site is important, but internal gene constellations profoundly affect mammalian pathogenicity independent of HA binding.

Question 343: A hyperthyroid cat on methimazole develops a platelet count of 40,000/µL on a CBC. What is the most appropriate next step?

Add prednisone to counteract methimazole-induced immune suppression
Discontinue methimazole immediately and consider radioactive iodine or surgical thyroidectomy (Correct answer)
Reduce the methimazole dose by 50%
Continue methimazole and recheck CBC in 2 weeks

Correct answer: Discontinue methimazole immediately and consider radioactive iodine or surgical thyroidectomy

Severe thrombocytopenia is a serious hematologic adverse effect of methimazole requiring immediate discontinuation; alternative definitive therapies should be pursued.

Question 344: Which anesthetic protocol is most commonly associated with post-anesthetic myopathy in horses undergoing prolonged recumbency?

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

Correct answer: Inhalant anesthesia with hypotension and poor padding

Post-anesthetic myopathy in horses is most strongly associated with inhalant anesthesia combined with hypotension and inadequate padding, leading to compartment syndrome of dependent muscles.

Question 345: 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?

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

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

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

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 347: 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 348: Which radiographic finding is MOST consistent with pyloric outflow obstruction in a dog?

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

Correct answer: Markedly distended stomach with delayed gastric emptying

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

Question 349: A 9-year-old Miniature Schnauzer presents with vomiting, cranial abdominal pain, and a 'praying' posture. Abdominal radiographs are taken to rule out other causes. Which of the following radiographic signs would be most consistent with acute pancreatitis?

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

Correct answer: Focal loss of serosal detail and increased soft tissue opacity in the right cranial abdomen.

The radiographic signs of pancreatitis are often subtle and non-specific, but they reflect the focal inflammation and peritonitis in the area of the pancreas. The most common findings are a focal loss of serosal detail (a 'ground glass' appearance) and a soft tissue mass effect in the right cranial abdomen, which may cause widening of the pyloro-duodenal angle.

Question 350: A dog is prescribed phenobarbital for seizure control. Which of the following is the most important monitoring parameter for long-term therapy?

Serum electrolytes
Urinalysis
Complete blood count
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 351: 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)
Alfaxalone (3 mg/kg IV bolus)
Propofol (4 mg/kg IV, titrated slowly) (Correct answer)
Ketamine (5 mg/kg IV)

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 352: A horse undergoing a 3-hour exploratory celiotomy under general anesthesia (dorsal recumbency) develops post-anesthetic myopathy (PAM) in the triceps muscle group. Which of the following intraoperative factors contributes MOST directly to compartment syndrome-type PAM in the dependent muscles of an anesthetized horse?

Hyperthermia elevating muscle metabolic demand
Excessive inhalant concentration causing direct myotoxicity
Hypotension reducing perfusion pressure below compartment pressure (Correct answer)
Hypokalemia impairing neuromuscular junction recovery

Correct answer: Hypotension reducing perfusion pressure below compartment pressure

Post-anesthetic myopathy in horses is primarily caused by ischemia of dependent muscles due to the weight of the horse compressing muscle compartments. In dorsal recumbency, the triceps bears significant compressive pressure. When mean arterial pressure drops below the compartment pressure (commonly due to anesthetic-induced hypotension), perfusion pressure to the muscle is insufficient, causing ischemia, rhabdomyolysis, and potential compartment syndrome. Maintaining MAP ≥70 mmHg is a key intraoperative goal in equine anesthesia to prevent PAM.

Question 353: A 9-year-old spayed female Miniature Schnauzer presents with a 3-week history of anorexia, vomiting, and icterus. Serum chemistry reveals: ALT 820 U/L, ALP 2400 U/L, total bilirubin 8.2 mg/dL, cholesterol 620 mg/dL, and triglycerides 1850 mg/dL. Urinalysis shows bilirubinuria and ammonium biurate crystals. Abdominal ultrasound reveals a markedly hyperechoic liver with diffuse loss of portal vein contrast. What is the MOST specific mechanism linking the hyperlipidemia to the liver disease in this patient?

Pancreatitis-induced fat malabsorption with subsequent chylomicronemia
Decreased synthesis of bile acids impairing micellar solubilization and causing retrograde lipid accumulation
Primary familial hypertriglyceridemia common in Miniature Schnauzers exacerbating hepatic lipidosis
Reduced hepatic lipoprotein lipase activity and impaired VLDL clearance due to cholestasis (Correct answer)

Correct answer: Reduced hepatic lipoprotein lipase activity and impaired VLDL clearance due to cholestasis

Cholestasis impairs the normal biliary excretion of cholesterol and disrupts the enterohepatic circulation of bile acids. This leads to reduced hepatic lipoprotein lipase activity and impaired clearance of VLDL and chylomicrons, resulting in secondary hyperlipidemia. In this dog, the marked ALP elevation, hypercholesterolemia, and hypertriglyceridemia with icterus are consistent with severe cholestatic liver disease—most likely vacuolar hepatopathy or hepatic lipidosis compounded by the breed's lipid metabolism tendencies. While Miniature Schnauzers have a breed predisposition to primary hypertriglyceridemia, the degree of icterus and transaminase elevation indicates cholestasis is the primary driver of the current lipid abnormalities. The ammonium biurate crystals indicate concurrent portosystemic shunting or severe hepatic failure.

Question 354: Which drug is used to treat urinary incontinence in spayed female dogs by increasing urethral sphincter tone?

Propranolol
Prazosin
Phenylpropanolamine (PPA) (Correct answer)
Bethanechol

Correct answer: Phenylpropanolamine (PPA)

Phenylpropanolamine is an alpha-adrenergic agonist that increases urethral sphincter muscle tone and is the drug of choice for hormone-responsive incontinence in spayed dogs.

Question 355: A high-producing dairy cow, 3 days post-calving, presents with a head turned into her flank, muscle fasciculations, a dry muzzle, and a heart rate of 100 bpm with weak pulse quality. She is afebrile and unable to stand. What is the most likely diagnosis?

Hypocalcemia (Milk Fever) (Correct answer)
Ketosis
Metritis
Displaced abomasum

Correct answer: Hypocalcemia (Milk Fever)

The clinical signs described—flaccid paralysis (inability to stand), S-shaped neck curve, tachycardia, and GI stasis (dry muzzle), occurring shortly after calving—are classic for Parturient Paresis, or Hypocalcemia (Milk Fever). Ketosis typically presents with neurologic signs or anorexia but not flaccid paralysis. A displaced abomasum would present with a 'ping' on auscultation and percussion. Metritis would typically present with fever and a foul-smelling uterine discharge.

Question 356: 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:

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

Correct answer: Controlled rest with hand-walking rehabilitation program

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

Question 357: A 3-year-old Thoroughbred presents with acute-onset severe lameness. Radiographs of the fetlock region are initially unremarkable. Nuclear scintigraphy (bone phase) shows a focal, intensely increased radiopharmaceutical uptake (IRU) at the palmar/plantar aspect of the proximal sesamoid bones. MRI performed 48 hours later shows a T2-hypointense linear signal defect traversing the body of the medial proximal sesamoid bone. What is the MOST likely diagnosis and its implication?

Abaxial fracture of the proximal sesamoid — surgical arthroscopy is curative
Basilar fracture of the proximal sesamoid — low catastrophic failure risk if managed conservatively
Sesamoiditis (chronic degenerative change) — requires 4-6 weeks of stall rest
Body fracture of the proximal sesamoid — high risk for catastrophic failure and suspensory apparatus breakdown (Correct answer)

Correct answer: Body fracture of the proximal sesamoid — high risk for catastrophic failure and suspensory apparatus breakdown

A T2-hypointense linear defect traversing the body of the proximal sesamoid bone represents a body fracture — the most serious type of sesamoid fracture in racehorses. Unlike apical (tip) or abaxial (side) fractures, body fractures involve the entire cross-section of the bone and risk complete disruption of the suspensory apparatus, which can cause catastrophic breakdown. The scintigraphic hot spot on the palmar/plantar aspect with subsequent MRI correlation is the advanced imaging sequence used when plain radiographs are unremarkable early in the injury. Sesamoiditis causes diffuse rather than focal linear T2 hypointensity. Basilar fractures involve the base and have a better prognosis than body fractures.

Question 358: 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?

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

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

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

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

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

Question 360: 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?

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

Correct answer: Central diabetes insipidus

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

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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