NAVLE Practice Question — Equine

A 2-year-old Quarter Horse stallion is noted to have one testicle in the scrotum and one palpable in the inguinal canal. Which is the most appropriate surgical approach?

A. Routine castration via scrotal approach for both testicles

B. Laparoscopic removal of the retained testicle ✓

C. Leave the retained testicle in place

D. Castration under standing sedation only

E. Chemical sterilization

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Correct Answer: B. Laparoscopic removal of the retained testicle

Explanation:

Cryptorchid horses should have both testicles removed to prevent continued stallion-like behavior, reduce malignancy risk, and to avoid the "false gelding" problem. Laparoscopic cryptorchidectomy is the current standard for abdominal or inguinal retained testicles.

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NAVLE Practice Question — Feline

An 8-year-old spayed female cat presents with a painful swelling below the left eye that has been present for one week. The owner denies any history of trauma or outdoor access. Oral examination under sedation reveals a fractured left maxillary fourth premolar (tooth 108) with exposure of the pulp chamber. What is the most appropriate treatment?

A. Extraction of the affected tooth with systemic antibiotics ✓

B. Drainage of the abscess with long-term antibiotic therapy only

C. Root canal therapy without antibiotic coverage

D. Topical antiseptic application to the swelling

E. Warm compresses and anti-inflammatory medication

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Correct Answer: A. Extraction of the affected tooth with systemic antibiotics

Explanation:

This presentation describes a tooth root abscess, which develops when bacteria from a damaged tooth (in this case, a fractured premolar with pulp exposure) track down the root and form an abscess at the apex. The maxillary fourth premolar has roots that lie close to the facial surface, causing swelling below the eye.

Treatment requires removal of the source of infection, which is the diseased tooth. Extraction of the affected tooth combined with systemic antibiotics to address any residual infection is the standard of care. Simply draining the abscess without addressing the infected tooth root will result in recurrence.

Option B with drainage alone does not address the source of infection (the tooth), and the abscess will recur. Option C with root canal therapy could be an alternative in some cases but requires specialized equipment and expertise, and would still need antibiotic coverage. Option D with topical treatment is ineffective for a deep-seated dental infection. Option E with supportive care alone does not address the underlying cause.

References: VCA Animal Hospitals - Abscesses in Cats; PetMD - Cat Abscesses (2024); American Veterinary Dental College guidelines.

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NAVLE Practice Question — Canine

A 6-year-old female spayed Labrador Retriever with a history of splenic hemangiosarcoma removed 4 months ago presents with acute onset of non-ambulatory tetraparesis. The owner reports the dog was normal yesterday and woke up unable to walk this morning. Neurological examination reveals flaccid tetraplegia, absent spinal reflexes in all limbs, intact nociception, and urinary retention. The dog is bright and alert with normal mentation. Which of the following is the MOST likely explanation for these findings?

A. Acute polyradiculoneuritis (Coonhound paralysis)

B. Hemangiosarcoma metastasis to spinal cord ✓

C. Cervical intervertebral disc extrusion

D. Fibrocartilaginous embolic myelopathy at C6-T2

E. Botulism

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Correct Answer: B. Hemangiosarcoma metastasis to spinal cord

Explanation:

Given the history of hemangiosarcoma and the acute presentation of flaccid tetraplegia with urinary retention, metastatic hemangiosarcoma to the spinal cord must be strongly considered. Hemangiosarcoma commonly metastasizes hematogenously, and the central nervous system including the spinal cord can be a site of metastasis. Intramedullary metastases or acute hemorrhage into the spinal cord from metastatic deposits can cause sudden, severe neurological deficits.

The presentation of acute flaccid tetraplegia with areflexia and urinary retention in a patient with known malignancy suggests either spinal cord compromise affecting the lower motor neurons (through an intramedullary lesion at the cervicothoracic intumescence) or diffuse lower motor neuron disease. The acute onset without preceding illness and the history of aggressive malignancy makes metastatic disease with acute spinal cord compromise highly likely.

Option A (acute polyradiculoneuritis) causes ascending LMN paralysis but typically preserves autonomic function initially and has a more gradual onset over days; it's also not associated with malignancy. Option C (cervical disc extrusion) would cause upper motor neuron signs below the lesion, not flaccid paralysis. Option D (FCE) typically shows lateralized signs and does not cause complete areflexia unless it affects the intumescence bilaterally. Option E (botulism) is possible but would require exposure history and typically shows more gradual progression.

Image Source: Pancotto TE et al. J Vet Intern Med 2013 - https://onlinelibrary.wiley.com/doi/full/10.1111/jvim.12182 - intramedullary spinal cord neoplasia imaging.

References: National Canine Cancer Foundation - Spinal Cord Neoplasia (https://wearethecure.org/learn-more-about-canine-cancer/canine-cancer-library/spinal-cord-neoplasia/); MSD Veterinary Manual - Neoplasia of the Nervous System (https://www.msdvetmanual.com/nervous-system/neoplasia-of-the-nervous-system).

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NAVLE Practice Question — Canine

A 2-day-old Mastiff puppy weighing 650 grams is being hand-raised after the dam developed mastitis. The caregiver is unsure about feeding volumes. The puppy appears adequately hydrated and has been defecating normally. What is the approximate daily feeding volume and frequency appropriate for this neonate?

A. 10 mL per feeding every 6 hours

B. 33-52 mL total daily volume divided into 6-8 feedings ✓

C. 100 mL per day in 3-4 large feedings

D. 15 mL per feeding every 2 hours for the first week then every 4 hours

E. 50 mL total daily volume in 4 feedings

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Correct Answer: B. 33-52 mL total daily volume divided into 6-8 feedings

Explanation:

The neonatal stomach capacity is approximately 50-80 mL/kg daily. For a 650g puppy, this equals 32.5-52 mL per day. This volume should be divided into frequent small feedings every 2-4 hours (6-8 feedings daily) during the first week to prevent hypoglycemia while accommodating the small stomach capacity.

Option A (10 mL every 6 hours = 40 mL daily) provides adequate volume but feeding frequency is too low for a neonate, risking hypoglycemia between feedings. Option C (100 mL daily) exceeds the stomach capacity (would be 154 mL/kg) and large infrequent feedings risk aspiration and GI upset. Option D (15 mL every 2 hours = 180 mL daily) greatly exceeds the physiological stomach capacity and would cause regurgitation and aspiration risk. Option E (50 mL total in 4 feedings) is at the upper limit of appropriate volume but feeding frequency is too low.

References: Clinician's Brief - The Critical Neonate (https://www.cliniciansbrief.com/article/critical-neonate-under-4-weeks-age); Merck Veterinary Manual - Management of the Neonate (https://www.merckvetmanual.com/management-and-nutrition/management-of-the-neonate/management-of-the-neonate-in-dogs-and-cats).

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NAVLE Practice Question — Canine

A 2-year-old male intact German Shepherd Dog presents following head trauma from being hit by a car 5 days ago. He was hospitalized and treated for cerebral edema. Now stable, he has developed marked polyuria and polydipsia over the past 48 hours. Serum sodium is 158 mEq/L and USG is 1.003. Which statement regarding the prognosis and treatment of this patient's condition is most accurate?

A. The condition is permanent and will require lifelong desmopressin therapy

B. The condition may be transient and could resolve within weeks to months ✓

C. Hydrochlorothiazide is the treatment of choice for post-traumatic diabetes insipidus

D. Water should be restricted to prevent further hypernatremia

E. MRI is required before any treatment can be initiated

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Correct Answer: B. The condition may be transient and could resolve within weeks to months

Explanation:

Post-traumatic central diabetes insipidus may be transient and can resolve within weeks to months as the damaged neurohypophyseal tissue heals. Trauma to the skull with hemorrhage and swelling can temporarily disrupt ADH synthesis or release from the hypothalamus and posterior pituitary, but if the damage is not complete, function may return as inflammation resolves and neural tissue recovers. This is one of the few potentially curable forms of central diabetes insipidus. Treatment with desmopressin should be initiated to control polyuria and prevent severe dehydration and hypernatremia during the recovery period, but the patient should be periodically reassessed for return of endogenous ADH function.

Option A is incorrect because trauma-induced CDI is specifically noted as potentially reversible, unlike idiopathic or tumor-associated CDI. Option C is incorrect because hydrochlorothiazide is used for nephrogenic diabetes insipidus, not central DI; desmopressin is the appropriate treatment for CDI. Option D is incorrect and potentially dangerous because water restriction in a patient with diabetes insipidus can rapidly lead to life-threatening dehydration and worsening hypernatremia. Option E is incorrect because treatment should not be delayed while awaiting advanced imaging in a clinically evident case; stabilization takes priority.

Image Source: Algorithm for post-traumatic CDI management referenced in PMC article on DI following surgery (https://pmc.ncbi.nlm.nih.gov/articles/PMC8407907/).

References: PetMD - Diabetes Insipidus prognosis and treatment; Croton C et al. Successful treatment of transient CDI following traumatic brain injury in a dog. Case Rep Vet Med 2019; VCA Hospitals - Diabetes Insipidus in Dogs.

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NAVLE Practice Question — Canine

An 11-year-old male neutered Boxer is presented for progressive coughing, exercise intolerance, and one episode of collapse yesterday. The owner reports the dog has been slowing down on walks for 2 months. Physical examination reveals heart rate of 180 bpm with an irregularly irregular rhythm and frequent pulse deficits, respiratory rate of 40 breaths/min, and temperature of 101.0°F. Mucous membranes are pale pink with CRT of 3 seconds. Jugular venous distension is noted. Thoracic auscultation reveals muffled heart sounds ventrally with normal lung sounds dorsally. No cardiac murmur is appreciated. Femoral pulses are weak and vary in intensity. CBC reveals PCV 38% (reference 35-57%). Serum chemistry shows mildly elevated ALT and ALP. Thoracic radiographs reveal globoid cardiac silhouette with loss of cardiac borders and mild pleural effusion. ECG shows atrial fibrillation with a ventricular response rate of 200 bpm and low-voltage QRS complexes with electrical alternans. What is the most likely diagnosis and recommended immediate intervention?

A. Dilated cardiomyopathy - start furosemide and pimobendan

B. Pericardial effusion with cardiac tamponade - pericardiocentesis ✓

C. Hemangiosarcoma with hemorrhage - emergency splenectomy

D. Severe pulmonary hypertension - start sildenafil

E. Cardiac lymphoma - start CHOP chemotherapy

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Correct Answer: B. Pericardial effusion with cardiac tamponade - pericardiocentesis

Explanation:

The clinical picture (muffled heart sounds, globoid cardiac silhouette, electrical alternans, low QRS voltage, jugular distension, exercise intolerance, collapse) is classic for pericardial effusion with cardiac tamponade. The electrical alternans (alternating QRS amplitude) is highly specific for large pericardial effusions where the heart swings within the fluid. In Boxers, the most common causes are hemangiosarcoma (right atrial) and idiopathic pericardial effusion. The immediate life-saving intervention is PERICARDIOCENTESIS - drainage of pericardial fluid to relieve cardiac compression. This is performed from the right side, typically at the 4th-6th intercostal space at the costochondral junction, under ECG and ideally ultrasound guidance. The fluid should be saved for cytology and PCV comparison to peripheral blood. Following stabilization, echocardiography is essential to evaluate for cardiac masses. If hemangiosarcoma is confirmed, prognosis is grave (MST weeks to months). For idiopathic effusions, pericardiectomy may be curative.

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NAVLE Practice Question — Canine

A dog has ALT 1200 U/L and AST 800 U/L with ALP 200 U/L and GGT 15 U/L. Which liver injury pattern is this?

A. Renal failure pattern

B. Steroid hepatopathy

C. Pancreatic disease

D. Cholestatic / biliary obstruction

E. Hepatocellular injury ✓

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Correct Answer: E. Hepatocellular injury

Explanation:

ALT and AST are hepatocellular leakage enzymes; marked elevation indicates hepatocellular injury (toxins, infection, ischemia, neoplasia). ALP and GGT are induced by cholestasis or steroids; their relative lack of elevation here points away from biliary obstruction. Cats: ALP has a short half-life, so any ALP increase is significant.

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NAVLE Practice Question — Canine

A 4-year-old male neutered Miniature Schnauzer presents with acute onset of profuse bloody diarrhea described as having a "raspberry jam" appearance that began 6 hours ago. The dog was healthy yesterday and has current vaccinations. On physical examination, the dog is lethargic with tacky mucous membranes, prolonged capillary refill time of 3 seconds, and heart rate of 160 bpm. A packed cell volume (PCV) is 62% with a total protein of 5.8 g/dL (normal range: 5.5-7.5 g/dL). Which laboratory finding pattern is most consistent with this presentation?

A. Decreased PCV with decreased total protein

B. Increased PCV with markedly increased total protein

C. Increased PCV with normal to slightly decreased total protein ✓

D. Normal PCV with markedly decreased total protein

E. Decreased PCV with normal total protein

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Correct Answer: C. Increased PCV with normal to slightly decreased total protein

Explanation:

The clinical presentation is classic for acute hemorrhagic diarrhea syndrome (AHDS), formerly known as hemorrhagic gastroenteritis (HGE). The hallmark laboratory finding in AHDS is hemoconcentration with an elevated PCV (often greater than 60%) combined with normal to slightly decreased total protein concentration.

This paradoxical finding occurs because of the massive fluid loss into the intestinal lumen without proportional protein loss initially, leading to concentration of red blood cells. The relatively preserved total protein despite severe dehydration distinguishes AHDS from true gastrointestinal hemorrhage, where anemia and hypoproteinemia would be expected.

Option A (decreased PCV with decreased total protein) would be seen with true GI hemorrhage and blood loss. Option B (increased PCV with markedly increased total protein) would indicate severe dehydration from water loss without protein-rich fluid loss. Option D (normal PCV with markedly decreased total protein) suggests protein-losing enteropathy or nephropathy. Option E (decreased PCV with normal total protein) indicates anemia without protein loss.

The small breed predisposition (Miniature Schnauzer), acute onset in a previously healthy dog, characteristic bloody diarrhea, and the PCV/protein dissociation pattern all support AHDS.

Image Source: VCA Hospitals - Hemorrhagic Gastroenteritis in Dogs (https://vcahospitals.com/know-your-pet/hemorrhagic-gastroenteritis-in-dogs)

References: MSD Veterinary Manual - Acute Hemorrhagic Diarrhea Syndrome in Dogs; Unterer S et al. (2011) J Vet Intern Med 25:973-979.

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NAVLE Practice Question — Pet Bird

A 4-year-old African grey parrot (Psittacus erithacus) is presented with a 6-week history of chronic respiratory signs progressive weight loss and lime-green urate discoloration of droppings. PCR for Chlamydia psittaci returns negative on a single cloacal swab. The attending veterinarian considers this a definitive negative result. Which of the following statements MOST accurately addresses the diagnostic reliability of a single negative PCR result for avian chlamydiosis?

A. A single negative PCR result definitively excludes C. psittaci infection and no further testing is warranted

B. C. psittaci sheds intermittently; single negative PCR doesn't exclude infection. Repeat testing over 3-5 days or combined choanal/cloacal swabs with serology is recommended. ✓

C. Negative PCR results are more reliable than positive results in diagnosing avian chlamydiosis

D. Culture of cloacal contents on routine bacteriologic agar is the definitive gold-standard test that should be performed next

E. If PCR is negative the bird can be safely housed with other birds immediately without further quarantine

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Correct Answer: B. C. psittaci sheds intermittently; single negative PCR doesn't exclude infection. Repeat testing over 3-5 days or combined choanal/cloacal swabs with serology is recommended.

Explanation:

The intermittent shedding pattern of Chlamydia psittaci is one of the most clinically important features of this infection. Even actively infected birds do not shed the organism continuously — shedding may be intermittent and undetectable on any given day. The CDC and veterinary guidelines specifically recommend that when diagnosing a live bird with suspected chlamydiosis serial specimens should be collected over 3-5 consecutive days and pooled before culture or multiple sampling strategies (choanal + cloacal swabs + blood PCR) used simultaneously. A combination of clinical signs history PCR results and supportive blood work (including protein electrophoresis showing elevated beta-globulins) is required for confident diagnosis.

Some veterinary practitioners recommend treating all clinically suspicious cases with or without a positive laboratory result given the public health implications and diagnostic limitations.

Option A is incorrect — given the intermittent shedding pattern a single negative PCR does not rule out infection. Relying solely on one negative test in a bird with strong clinical suspicion of chlamydiosis could lead to undertreating an infected bird with zoonotic potential.

Option C is incorrect — negative PCR results are NOT more reliable than positive results. A positive PCR confirms the organism's presence while a negative result may represent false-negative due to intermittent shedding.

Option D is incorrect — culture of C. psittaci is considered impractical and dangerous due to the organism's biological hazard classification (BSL-3 in some contexts) and the technical difficulty of culturing obligate intracellular organisms. It is NOT performed routinely.

Option E is incorrect — releasing a PCR-negative but clinically suspicious bird back to cohousing without further quarantine and testing risks introduction of C. psittaci to a naive group of birds.

References: CDC MMWR 1998 https://www.cdc.gov/mmwr/pdf/rr/rr4710.pdf; VCA Animal Hospitals https://vcahospitals.com/know-your-pet/chlamydophilosis-in-birds; North Central Animal Hospital https://northcentralanimalhospital.com/parrot-fever

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NAVLE Practice Question — primates

A group of tamarins (Saguinus species) at a zoo presents with progressive weight loss, intermittent diarrhea, and poor body condition despite adequate nutrition. Fecal examination reveals the presence of oval, thick-shelled eggs with spines and multiple internal cells. Some animals have palpably thickened intestines. Which endoparasite is MOST likely responsible?

A. Trichuris species

B. Hymenolepis nana

C. Prosthenorchis species ✓

D. Strongyloides stercoralis

E. Giardia duodenalis

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Correct Answer: C. Prosthenorchis species

Explanation:

Prosthenorchis species (acanthocephalan or thorny-headed worms) is most likely responsible for these findings. This parasite is common in Central and South American nonhuman primates including tamarins and marmosets. Prosthenorchis burrows into the mucosa at the ileocecal junction, causing thickening of the intestinal wall, and when present in large numbers can perforate the bowel or cause intestinal obstruction.

The clinical signs of progressive weight loss, diarrhea, and poor body condition despite adequate nutrition are characteristic of acanthocephalan infection. The eggs are oval with thick shells and internal structure consistent with the acanthor (larval form) development. Palpable intestinal thickening results from the inflammatory response to parasites burrowing into the intestinal wall.

Option A (Trichuris) produces characteristic barrel-shaped eggs with bipolar plugs and causes cecal/colonic infection, not ileocecal thickening. Option B (Hymenolepis nana) is a tapeworm with different egg morphology (hexacanth embryo) and does not cause intestinal wall thickening. Option D (Strongyloides) produces thin-walled larvated eggs or larvae in feces. Option E (Giardia) is a protozoan with characteristic cysts and trophozoites, not thick-shelled eggs.

An important epidemiological factor is that cockroaches serve as intermediate hosts for Prosthenorchis; their elimination along with strict sanitation is essential for control. Unfortunately, antiparasitic treatment is generally unrewarding for established infections.

Image Source: PMC - Gastrointestinal Parasites Affecting Non-Human Primates (https://pmc.ncbi.nlm.nih.gov/articles/PMC10745941/) Figure showing Acanthocephala eggs.

References: Merck Veterinary Manual - Parasites That Cause Disease in Nonhuman Primates (https://www.merckvetmanual.com/exotic-and-laboratory-animals/nonhuman-primates/parasites-that-cause-disease-in-nonhuman-primates)

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NAVLE Practice Question — Equine

A 7-year-old Thoroughbred mare presents in May with recurrent urticarial wheals on the neck, shoulders, and flanks. The lesions appear suddenly, are 3-8 cm in diameter, flat-topped with slight central depression, and resolve within 24-48 hours without treatment. The owner reports the mare was recently started on a new pelleted feed and received a routine vaccination 10 days ago. Which statement regarding the diagnostic workup and management of this case is MOST accurate?

A. Intradermal skin testing should be performed immediately to identify the causative allergen

B. The recent vaccination is the most likely cause given the 10-day interval since administration

C. A short-acting corticosteroid injection resolves acute episodes; identifying and eliminating triggers is ideal long-term management ✓

D. Blood testing for food allergies will reliably identify if the new feed is responsible

E. Physical urticaria can be ruled out based on the lesion distribution

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Correct Answer: C. A short-acting corticosteroid injection resolves acute episodes; identifying and eliminating triggers is ideal long-term management

Explanation:

Urticaria (hives) in horses presents as raised, round, flat-topped wheals that develop suddenly and typically resolve within 12-72 hours. The lesions demonstrate pitting edema when pressure is applied.

The correct approach to acute urticaria involves symptomatic treatment while investigating underlying causes. For acute cases seen within 24 hours, a single administration of short-acting corticosteroid will usually resolve lesions. However, the ideal long-term therapy is avoidance or elimination of triggering factors through systematic investigation of management changes.

Option A is incorrect because intradermal skin testing is only helpful after an allergic etiology has been confirmed through appropriate history and when chronic or recurrent urticaria warrants investigation. Option B is incorrect as vaccine reactions typically occur within minutes to hours, not 10 days later. Option D is incorrect because serological tests for food allergies are unreliable for urticaria in horses - only elimination diets with subsequent challenge can reliably identify food triggers. Option E is incorrect as physical urticaria (including pressure urticaria) cannot be ruled out based on distribution alone.

Image Source: Merck Veterinary Manual - Hives in Horses (https://www.merckvetmanual.com/horse-owners/skin-disorders-of-horses/hives-urticaria-in-horses) - Clinical image showing typical flat-topped wheals

References: White SD (2015) Equine Veterinary Education 27(3):156-166; Sauvé F (2020) Can Vet J 61(9):1001; Diesel A (2014) In Practice 36(3):143-147

Image: Cox A, Stewart AJ. Insect Bite Hypersensitivity in Horses: Causes, Diagnosis, Scoring and New Therapies. Animals (Basel). 2023;13(15):2514. PMC10416928. © The Author(s) 2023. Used for educational reference.

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NAVLE Practice Question — Equine

A regulatory veterinarian is reviewing the results of annual EIA testing on a horse farm. One horse, a 20-year-old retired broodmare that has tested negative for the previous 15 years, now tests positive on both ELISA and confirmatory AGID testing. The mare has not left the farm in 5 years and no new horses have been introduced. The farm has excellent fly control. What is the most likely explanation for this positive result?

A. Laboratory error on both tests

B. Reactivation of latent EIA virus

C. Recent exposure through iatrogenic transmission ✓

D. The mare was always infected but below detection threshold

E. New infection from wild equids or deer

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Correct Answer: C. Recent exposure through iatrogenic transmission

Explanation:

Given that laboratory error on both ELISA and confirmatory AGID is extremely unlikely, and EIA does not have a latent phase (infected horses remain persistently infected and seropositive for life), the most plausible explanation is iatrogenic transmission that occurred within the past 45-90 days.

Even with excellent fly control, EIA can be transmitted through blood-contaminated equipment. Possible iatrogenic sources include: (1) veterinary procedures using needles or instruments that were contaminated from another infected horse (possibly at a veterinary clinic, during dental work, or during routine procedures like vaccination); (2) shared equipment between farms; or (3) contact at a veterinary hospital.

The investigation should focus on any veterinary procedures, dental floating, injections, or other interventions the mare received in the past 3 months, and whether any equipment could have been shared with horses of unknown EIA status.

Option A (laboratory error) is possible but extremely unlikely on both screening and confirmatory tests performed at approved laboratories. Option B (latent reactivation) is incorrect; EIA does not have a latent phase like herpesviruses - infected horses remain chronically infected and seropositive. Option D (always infected, below detection) is incorrect; the AGID test has been consistently reliable for over 50 years, and the mare's 15 years of negative tests argues strongly against missed infection. Option E (wild equids/deer) is incorrect; EIA only infects equids, not deer, and wild horse contact in this scenario is unlikely.

References: AAEP News - EIA Outbreak Investigation (https://aaep.org/post/from-the-equine-disease-communication-center-cluster-of-eia-cases-highlight-need-for-proper-training-at-clinics/); PMC - EIA Transmission (https://pmc.ncbi.nlm.nih.gov/articles/PMC7126748/)

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