BCSE Exotic, Avian, and Zoo Animal Medicine — Questions and Answers
Question 1: A psittacine bird presents with regurgitation, crop stasis, and neurological signs including ataxia and head tremors. Necropsy reveals proventricular and ventricular dilatation. The most likely diagnosis is:
- Aspergillosis
- Proventricular Dilatation Disease (PDD) caused by Avian Bornavirus (Correct answer)
- Psittacosis (Chlamydia psittaci infection)
- Newcastle disease
Correct answer: Proventricular Dilatation Disease (PDD) caused by Avian Bornavirus
Proventricular Dilatation Disease (PDD) is caused by Avian Bornavirus (ABV). It is characterized by lymphoplasmacytic ganglioneuritis affecting the enteric nervous system, leading to proventricular/ventricular dilatation, GI dysmotility, and CNS signs. Fluoroscopy or contrast radiography demonstrating a dilated proventriculus and crop biopsy for lymphocytic infiltration support the diagnosis. It is common in macaws, cockatoos, and other psittacines.
Question 2: Rabbits are obligate nasal breathers and are prone to respiratory disease. The most common bacterial cause of upper respiratory tract disease ('snuffles') in rabbits is:
- Bordetella bronchiseptica
- Pasteurella multocida (Correct answer)
- Staphylococcus aureus
- Mycoplasma pulmonis
Correct answer: Pasteurella multocida
Pasteurella multocida is the primary pathogen responsible for 'snuffles' in domestic rabbits, causing mucopurulent nasal discharge, dacryocystitis, otitis media/interna, and pneumonia. It is endemic in many rabbit colonies. Bordetella can act as a secondary pathogen or potentiate Pasteurella infection, but is not the primary cause. Mycoplasma pulmonis is the major pathogen in rats and mice, not rabbits.
Question 3: Metabolic bone disease (nutritional secondary hyperparathyroidism) in captive reptiles is most commonly caused by:
- Excessive dietary phosphorus without calcium supplementation only
- Inadequate UVB light exposure and/or calcium:phosphorus imbalance leading to hypocalcemia (Correct answer)
- Vitamin A toxicity from excess supplementation
- Hypothyroidism causing reduced bone turnover
Correct answer: Inadequate UVB light exposure and/or calcium:phosphorus imbalance leading to hypocalcemia
Reptiles require UVB radiation (290–320 nm) to synthesize vitamin D3 (cholecalciferol) in the skin, which is essential for intestinal calcium absorption. Without adequate UVB or dietary vitamin D3, secondary hyperparathyroidism develops as PTH mobilizes calcium from bone, causing pathological fractures, soft bones, and deformities. A poor Ca:P ratio (low calcium, high phosphorus) exacerbates the condition. This is extremely common in herbivorous lizards like green iguanas.
Question 4: Which analgesic opioid is commonly used in avian patients and has demonstrated efficacy in pain control in parrots based on pharmacokinetic studies?
- Morphine
- Butorphanol (Correct answer)
- Fentanyl transdermal patches
- Buprenorphine
Correct answer: Butorphanol
Butorphanol is the most commonly used and best-studied opioid analgesic in psittacine birds. Parrots have a higher density of kappa-opioid receptors than mu-opioid receptors compared to mammals, making kappa agonists like butorphanol particularly effective. Buprenorphine has limited efficacy in birds. Morphine has poor efficacy and can cause excitation. Transdermal fentanyl patches are unreliable in birds due to differences in skin structure and absorption.
Question 5: A ferret presents with episodic weakness, hypersalivation, pawing at the mouth, and blood glucose of 45 mg/dL. The most likely diagnosis is:
- Adrenal gland disease
- Insulinoma (pancreatic beta-cell tumor) (Correct answer)
- Aleutian disease (parvoviral infection)
- Lymphoma
Correct answer: Insulinoma (pancreatic beta-cell tumor)
Insulinoma is the most common pancreatic neoplasm in ferrets, typically occurring in middle-aged to older animals. Excessive insulin secretion causes profound hypoglycemia, leading to weakness, salivation, pawing at the mouth (nausea), and seizures in severe cases. Diagnosis is supported by hypoglycemia with inappropriately elevated serum insulin. Adrenal disease is also common in ferrets but causes alopecia and sexual signs, not hypoglycemia.
Question 6: Chelonians (turtles and tortoises) differ from most other reptiles in that they:
- Thermoregulate endothermically like mammals
- Lack a urinary bladder and excrete only uric acid
- Cannot be intubated for general anesthesia due to a fused shell
- Have a three-chambered heart with incomplete ventricular septation allowing cardiac shunting (Correct answer)
Correct answer: Have a three-chambered heart with incomplete ventricular septation allowing cardiac shunting
Like most reptiles (except crocodilians), chelonians have a three-chambered heart with two atria and one ventricle that has an incomplete interventricular septum. This anatomy allows right-to-left or left-to-right cardiac shunting, which has anesthetic implications (inhalant agents may bypass the pulmonary circulation). Chelonians are ectothermic, do possess a urinary bladder (unlike snakes/lizards), and can be intubated for anesthesia.
BCSE Exotic, Avian, and Zoo Animal Medicine
A psittacine bird presents with regurgitation, crop stasis, and neurological signs including ataxia and head tremors.
Necropsy reveals proventricular and ventricular dilatation.
The most likely diagnosis is: