NAVLE Avian and Exotic Animal Medicine 6

Question 1

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?

Accepted Answer

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

Answer

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 2

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?

Accepted Answer

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

Answer

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 3

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

Accepted Answer

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

Answer

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

Question 4

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

Accepted Answer

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

Answer

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

Question 5

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

Accepted Answer

Suboptimal thermal environment reducing enzymatic activity of immune effector cells

Answer

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

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE Avian and Exotic Animal Medicine 6