Avian Bornavirus and Proventricular Dilatation Disease in Cockatiels

Avian bornavirus is a contagious virus found in many parrots and parrot relatives, including cockatiels. In some birds, infection stays silent for a long time or never causes obvious illness. In others, it is associated with proventricular dilatation disease (PDD), an inflammatory nerve disease that can disrupt how the crop, stomach, intestines, and sometimes the brain and spinal cord work.

The word proventricular refers to the bird's glandular stomach. When the nerves that control the digestive tract become inflamed, food may move too slowly, the proventriculus can enlarge, and the bird may stop absorbing nutrients well. That is why some cockatiels keep eating but still lose weight, pass undigested food, or regurgitate.

PDD is not only a stomach problem. Some cockatiels also develop neurologic signs such as weakness, tremors, poor coordination, or behavior changes. Because signs can be vague at first, pet parents may notice only subtle weight loss or messy droppings before the condition becomes more obvious.

Not every ABV-positive cockatiel will develop PDD, and not every bird with weight loss or regurgitation has this disease. Your vet usually needs a combination of history, exam findings, imaging, and lab testing to decide how likely PDD is in your bird.

PDD is strongly linked to avian bornavirus, often called ABV or parrot bornavirus. The virus is contagious, but the exact way it spreads is still not fully settled. Viral shedding has been detected in feces and urine, and other sources note intermittent shedding in saliva and nasal secretions as well. In practical terms, shared airspace, contaminated surfaces, droppings, and close contact with infected birds are all reasonable concerns in homes, rescues, and aviaries.

One important detail is that infection does not always equal disease. Some birds test positive and stay clinically normal for long periods, while others go on to develop digestive or neurologic illness. Researchers believe the bird's immune response, stress level, species differences, and other health factors may influence whether PDD develops.

In cockatiels, stress may play a role in triggering clinical signs in a bird that was previously coping. Overcrowding, breeding stress, poor nutrition, and concurrent illness can all make management harder. Secondary bacterial or fungal infections may also develop when the digestive tract is not moving normally.

Because the virus can be shed intermittently, a bird may appear healthy and still expose others. That is why quarantine, repeat testing, and careful hygiene matter so much in multi-bird homes.

Diagnosis usually starts with a detailed avian exam. Your vet will look at body weight, body condition, hydration, droppings, crop function, and any neurologic changes. Baseline bloodwork and whole-body radiographs are often used to look for other causes of weight loss or regurgitation and to check whether the proventriculus appears enlarged.

If PDD is suspected, your vet may recommend ABV PCR testing from cloacal, choanal, fecal, or blood samples, sometimes along with serology. A key limitation is that birds can shed the virus intermittently, so one negative PCR does not rule out infection. Repeat testing over time may be needed, especially in exposed birds or multi-bird households.

Some birds also need a contrast study, such as a barium series, to evaluate how food moves through the digestive tract. In selected cases, your vet may discuss crop or proventricular biopsy for histopathology, although false negatives can still happen if affected tissue is missed. If a bird dies, necropsy with tissue submission to an avian pathologist is often the best way to confirm the diagnosis.

Because several diseases can mimic PDD, diagnosis is often about building a strong case rather than relying on one test alone. Your vet may also screen for secondary infections, heavy metal exposure, or other gastrointestinal and neurologic conditions before deciding on a treatment plan.

Prevention focuses on biosecurity and early detection, because there is currently no vaccine for avian bornavirus. Any new cockatiel or other bird should be quarantined in a separate airspace if possible before joining the household flock. During that period, your vet may recommend ABV testing, and in some situations repeat PCR and serology because shedding can be intermittent.

Good hygiene matters. Clean cages, bowls, and perches regularly, remove droppings promptly, and avoid sharing supplies between quarantined and resident birds without disinfection. ABV is not thought to survive for long in the environment, and it is susceptible to heat, dryness, and many disinfectants, so routine sanitation can help reduce spread.

Stress reduction is also part of prevention. Avoid overcrowding, support good nutrition, and work with your vet to manage breeding or hormonal stress if that is relevant in your home or aviary. A bird that is eating well, maintaining weight, and living in a lower-stress environment may be better able to cope, even though prevention is not perfect.

If one bird in the home tests positive or develops suspected PDD, separate that bird from others and talk with your vet about testing the rest of the flock. A positive test in a healthy bird does not automatically mean that bird will become sick, so decisions should be individualized rather than one-size-fits-all.