Avian Bornavirus (PDD): symptoms and management

Proventricular Dilatation Disease (PDD), caused by Avian Bornavirus (ABV), is one of the most serious and heartbreaking diseases affecting pet parrots. It attacks the nervous system of the digestive tract, progressively preventing proper food digestion. Understanding it helps owners recognise it early and make informed decisions.

What it does to the bird

ABV infects the ganglia (nerve clusters) of the digestive system, particularly the proventriculus (the first stomach) and ventriculus (gizzard). These structures become inflamed and dilated, losing the ability to contract and move food through the gut. The result:
- Food passes through incompletely digested — undigested seeds visible in droppings
- Progressive weight loss despite normal or increased eating
- Regurgitation of whole seeds or food
- Crop impaction in some cases
- Neurological signs in some birds: ataxia (wobbling), seizures, weakness, unusual feather destruction

The nervous system symptoms occur because ABV also infects the brain and peripheral nerves.

Which birds are affected?

ABV has been found in over 80 species of parrots. African Greys, Macaws, Cockatoos, and Amazon parrots appear most frequently diagnosed, but this may partly reflect that these species are more commonly tested. It has also been found in finches and canaries.

Transmission

The exact transmission route is not fully established. Faeces and urine appear to be a primary route. Some infected birds are carriers without showing signs, which makes introduction of new birds into an established flock risky without quarantine and testing.

Diagnosis

- Blood test for ABV antibodies (indicates exposure, not necessarily active disease)
- PCR test on faeces or crop swabs (detects viral RNA)
- Crop biopsy under anaesthesia is the most definitive test but invasive
- Radiographs may show a dilated proventriculus

Management — there is no cure

PDD is currently incurable. Management focuses on quality of life:
- COX-2 inhibitors (meloxicam): strong evidence suggests NSAIDs reduce the inflammatory process and can significantly slow progression; some birds stabilise for years
- Highly digestible diet: cooked, ground, or easy-to-digest food reduces the work of a compromised digestive system; some birds do better on a wet/mash diet or cooked grains
- Nutritional support: ensure adequate nutrition when absorption is impaired
- Isolation from other birds: to prevent transmission