Proventricular Dilatation Disease With Neurologic Signs in African Grey Parrots

See your vet immediately if your African grey parrot has tremors, weakness, trouble perching, regurgitation, or rapid weight loss. Proventricular dilatation disease, usually called PDD, is a serious condition linked to avian bornavirus. It causes inflammation of nerves, especially the nerves that help move food through the digestive tract, but it can also affect the brain, spinal cord, heart, and other organs.

In many parrots, PDD first shows up as digestive trouble. Food may move too slowly, the proventriculus can become enlarged, and whole seeds or other undigested food may appear in the droppings. In birds with neurologic involvement, signs can include ataxia, tremors, weakness, blindness, seizures, or behavior changes. Some birds have both digestive and neurologic signs, while others show mainly one pattern.

African grey parrots are among the species commonly reported with PDD. The disease can be slowly progressive, but some birds worsen quickly. Not every bird carrying avian bornavirus becomes sick, which is one reason diagnosis can be frustrating and why your vet usually needs to combine history, exam findings, imaging, and lab testing before making decisions.

PDD is strongly linked to avian bornavirus, also called parrot bornavirus in psittacine birds. This virus is neurotropic, meaning it targets nervous tissue. In affected parrots, inflammation develops in the nerves that control the digestive tract and sometimes in the central nervous system. That is why one bird may show undigested food and weight loss, while another may show tremors, ataxia, or seizures.

The exact reason one exposed bird becomes ill and another remains a healthy carrier is still not fully understood. Current veterinary sources note that many parrots can test positive for bornavirus without developing clinical PDD. Stress, crowding, reproductive activity, and concurrent illness may play a role in whether signs appear, but they are not considered the sole cause.

Transmission is thought to occur mainly through exposure to infected droppings and body secretions, although shedding can be intermittent and the full transmission picture is still being studied. Because clinically normal birds may carry and shed the virus, flock management matters. If one bird in a home or aviary is suspected to have PDD, your vet may recommend testing and separation plans for other birds.

Diagnosis usually starts with a careful avian exam, body weight trend, diet history, and a review of droppings, appetite, and neurologic changes. Your vet will also consider other causes of weight loss, regurgitation, weakness, or tremors, because PDD is not the only condition that can cause these signs.

Common first-line tests include CBC and chemistry, along with whole-body radiographs. If PDD is suspected, your vet may recommend contrast imaging or fluoroscopy to look for delayed movement of food and enlargement of the proventriculus. These tests help support a presumptive diagnosis and can also identify complications such as severe stasis.

Testing for avian bornavirus often includes PCR on cloacal, fecal, choanal, or blood samples and sometimes serology. One important point for pet parents: a single negative PCR does not rule out infection, because viral shedding can be intermittent. Some experts recommend repeat testing over time when suspicion remains high.

A definitive diagnosis is most often made with histopathology, meaning microscopic evaluation of tissue showing the characteristic nerve inflammation. Crop biopsy may be discussed in select cases, but it can miss disease and is not always diagnostic. In many birds, final confirmation happens at necropsy if the parrot dies or is euthanized. Your vet can help you decide how far to pursue testing based on your bird's stability, goals of care, and budget.

Prevention focuses on biosecurity, quarantine, and reducing stress, not on a vaccine or guaranteed screening shortcut. New birds should be quarantined before introduction to resident parrots, and your vet may recommend bornavirus testing during that period. Because shedding can be intermittent and some infected birds appear healthy, testing lowers risk but does not eliminate it.

Good hygiene matters. Clean cages, bowls, and perches regularly, and avoid sharing equipment between birds unless it has been disinfected. Veterinary sources note that the virus is susceptible to heat, dryness, and many disinfectants, which makes routine sanitation worthwhile. Separate sick birds promptly, and wash hands between handling birds.

Supportive daily care may also help lower the chance that a carrier bird develops clinical disease. Feed a balanced diet, avoid overcrowding, keep the environment predictable, and work with your vet to reduce reproductive stress or chronic illness when possible. If one bird in your home is diagnosed or strongly suspected to have PDD, ask your vet for a household plan that covers testing, housing, cleaning, and monitoring for every bird.