Avian Bornavirus (ABV) and PDD in Pet Birds

What Is Avian Bornavirus? 

Avian Bornavirus (ABV) is a group of RNA viruses that can infect many bird species, especially parrots and other psittacines. ABV has been identified worldwide and is best known for its association with Proventricular Dilatation Disease (PDD)—also called neuropathic ganglioneuritis or avian ganglioneuritis. 

PDD is a chronic inflammatory disease that can affect the nerves controlling the digestive tract and nervous system. Birds with PDD have trouble digesting food properly and may eventually develop neurologic signs. 

Not all birds infected with ABV will get PDD—some may carry the virus lifelong without symptoms, while others develop serious disease. 

How Does Bornavirus Cause Disease? 

• ABV infects nervous tissue and can cause inflammation of the nerve ganglia that control digestion, movement, and balance.
• The disease course is variable: some birds show no signs for years, others develop progressive illness, and some may die without warning. 
• Proventricular dilatation (enlargement of the glandular stomach) and poor motility lead to undigested food in droppings, weight loss, and malnutrition when PDD develops.

What Are Common Clinical Signs? 

Signs vary with the affected organ systems and may include: 

Digestive Signs 

• Weight loss despite eating 
• Regurgitation or vomiting 
• Undigested food in droppings 
• Slow crop emptying 
• Diarrhea or scant feces 

Neurologic Signs 

• Uncoordinated movement (ataxia) 
• Weakness 
• Head tremors 
• Seizures 
• Blindness potential

Not all infected birds exhibit both digestive and neurologic signs; some may show only one category.

How Is Bornavirus Diagnosed? 

Diagnosis is challenging and usually involves a combination of tests: 

1. PCR Testing

Detects viral RNA in:

• Blood 
• Cloacal swabs 
• Choanal swabs 

Because shedding is intermittent, a negative PCR doesn’t rule out infection.

2. Antibody Testing (Serology) 

Shows exposure to ABV but doesn’t confirm active shedding or disease. Results may be more informative when combined with PCR. 

3. Crop or Tissue Biopsy 

In selected cases, a small surgical sample from the crop or digestive tract can be examined microscopically for inflammatory nerve changes typical of PDD. This can help support a diagnosis but may yield false negatives. 

4. Imaging 

Radiographs (X-rays) with or without contrast can show enlargement of the proventriculus or delayed passage of food.

A definitive diagnosis often depends on combining clinical signs with multiple diagnostic tests and veterinary assessment. 

What Does a Positive Test Mean? 

• A positive PCR or antibody test means the bird has been exposed to or is carrying ABV.
• Not all infected birds develop disease. Many ABV-positive birds remain clinically healthy their entire lives. 
• A positive result does not guarantee PDD will develop, nor does it always indicate current disease activity. 

Is There a Cure or Treatment? 

There is no cure or consistently effective antiviral treatment for ABV or PDD. 

Veterinary management focuses on: 

• Supportive care (nutritional support, hydration) 
• Treating secondary infections 
• Anti-inflammatory therapies (in select cases, at your vet’s discretion) 

Although some reports suggest anecdotal benefit from anti-inflammatory medications, these are not universally effective and should be used only under veterinary guidance.

How Is Bornavirus Spread? 

The exact natural route of transmission is still being studied, but ABV is thought to spread most commonly through: 

• Fecal–oral contact 
• Exposure to infected droppings or feather dust 
• Close contact between birds 

Because shedding is intermittent and behaviorally mediated, a virus-free environment is difficult to guarantee in multi-bird households. 

What About Other Birds in the Home? 

Introducing a New Bird 

If a current bird has tested positive for ABV or shows signs consistent with PDD, bringing another healthy bird into the same household is not recommended at this time.

Why: 

• ABV can be shed intermittently even when birds appear healthy. 
• Transmission can occur despite strict quarantine and hygiene. 
• There is no reliable way to guarantee a virus-free environment if birds share the same airspace, caretakers, or household surfaces. 

Separate housing may reduce risk, but it cannot eliminate it completely given the nature of ABV and bird interactions. 

Practical Takeaways for Owners 

Bornavirus is a complex and evolving topic. 

Here’s what is key for you to understand: 

• Many birds carry ABV without ever becoming sick. 
• A positive test alone does not mean your bird will develop PDD. 
• Diagnosing disease relies on a combination of tests and clinical signs. 
• There is no cure; treatment focuses on supportive care. 
• Introducing additional birds is high risk when ABV is present in the home. 

Your veterinarian can guide you through testing, interpretation, and long-term management strategies tailored to your bird’s situation. 

Need Support? 

If you are considering testing, worried about signs, or thinking about another bird, please consult your avian veterinarian. They can help you understand the risks and develop a plan that aligns with your birds’ health and your goal. Call us today or book an appointment online.