Avian bornavirus (ABV) is the primary cause of proventricular dilatation disease (PDD), a chronic and often fatal illness of parrots that produces neurological signs and a dilated proventriculus (the avian glandular stomach) that cannot move food forward. Macaws, conures, and African greys are over-represented. There is no cure; supportive care with COX-2 selective NSAIDs, easily digested diets, and isolation can extend comfortable life. The 2019 AAV Basic Care for Companion Birds, 2019 supports careful diagnostic work-up in any chronically thin parrot.
Last reviewed: June 2026
What PDD Actually Is
Bornavirus infects nerve tissue of the GI tract, leading to lymphoplasmacytic ganglioneuritis. The proventriculus loses its ability to contract, food sits and stretches the organ, and digestion fails. The same viral process affects the brain and spinal cord in some birds, producing seizures, ataxia, and abnormal behavior. The viral relationship to disease was confirmed in 2008 and characterized in later studies.
Signs
Weight loss despite a strong appetite is the classic GI sign. Whole or undigested seeds in the droppings are highly suggestive — the proventriculus is not breaking food down. Regurgitation, intermittent diarrhea, and a noticeably enlarged crop or abdomen develop over weeks to months. Neurological signs include unsteadiness, leg weakness, head tremors, seizures, abnormal vocalizations, and self-injurious behavior. Some birds present primarily with neurological signs and no GI changes.
Diagnosis
Definitive antemortem diagnosis is challenging. PCR and serology for avian bornavirus are available; positive results support but do not confirm PDD because asymptomatic carriers exist. Radiographs and contrast studies show a dilated proventriculus. Crop biopsy with histopathology looking for lymphoplasmacytic ganglioneuritis is one of the few biopsy techniques available antemortem and supports the diagnosis. Differential diagnoses include heavy metal toxicity, foreign body, fungal infection, and other neurological disease.
Treatment
There is no cure. COX-2 selective NSAIDs (meloxicam, celecoxib) given long-term can reduce inflammation and extend comfortable survival, with reported improvements in appetite and weight in a subset of birds. Easily digested formulated diets, frequent small meals, and pellet softening with warm water help compensate for poor GI motility. Quiet stress-free housing reduces flares. Pain control and quality-of-life monitoring follow Carpenter's Exotic Animal Formulary.
Isolation and Flock Management
Bornavirus is shed in droppings, saliva, and feathers and can spread between birds in close contact. Confirmed positive birds should be isolated from negative flock members, and new birds should be quarantined and tested before introduction. The 2019 AAV Basic Care for Companion Birds, 2019 supports rigorous quarantine in multi-bird households.
When to See a Vet
Call your vet today if:
- Unexplained weight loss with a strong appetite
- Whole or undigested seeds in droppings
- Frequent regurgitation
- Subtle leg weakness, head tremors, or balance problems
- Abnormal vocalizations or behavior changes
Go to the ER immediately if:
- Seizures or sudden collapse
- Inability to perch or stand
- Severe regurgitation with refusal to eat
- Significant weakness or unresponsiveness
- Sudden labored breathing
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Frequently Asked Questions
Is bornavirus the same as PDD?
Not exactly. Avian bornavirus is the virus; PDD is the disease. Most PDD cases test positive for bornavirus, but some bornavirus-positive birds remain asymptomatic for years. The presence of clinical signs together with positive testing supports the diagnosis.
How much does PDD workup cost?
Avian vet exam typically runs $80 to $200. Bornavirus PCR is $100 to $300 per sample, radiographs and contrast study add $300 to $700, and crop biopsy at a referral center is $800 to $2,000. Hospitalization for severe cases runs $500 to $2,500. Long-term medications and special diets add $50 to $200 per month.
Can a PDD bird live a normal lifespan?
No, but lifespan varies widely. Some birds decline within months of onset; others live 2 to 5 years with good supportive care. Birds that respond to COX-2 NSAID therapy tend to do better. Honest quality-of-life conversations with the avian vet are essential.
Can bornavirus spread to people or other species?
There is no convincing evidence of human disease from avian bornavirus, but precautions (handwashing, separating clothing in busy multi-bird settings) are reasonable. The virus is primarily a concern for other birds in the household.
Should I test new birds before introducing them to my flock?
Yes. A 60- to 90-day quarantine with bornavirus PCR testing is recommended before introducing any new bird to a healthy flock. Testing imperfectly identifies all carriers but reduces risk substantially when combined with separation.
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