Proventricular dilatation disease (PDD) is a serious neurological and gastrointestinal condition caused by avian bornavirus. It affects parrots of all species and causes the bird to be unable to properly digest food — passing whole seeds in droppings despite eating normally.
Last reviewed: June 2026
What Is Proventricular Dilatation Disease in Parrots?
Proventricular dilatation disease (PDD), also called macaw wasting syndrome or avian ganglioneuritis, is caused by avian bornavirus (ABV). The virus infects the nervous system of the gastrointestinal tract, causing progressive inflammation and destruction of the nerve plexuses that control the proventriculus (the first stomach) and rest of the GI tract.
The result is a proventriculus that dilates massively — visible on radiographs — and loses the ability to properly process food. Birds with PDD may eat ravenously but still starve, because food cannot be adequately digested and absorbed. As described in Carpenter's Exotic Animal Formulary, PDD affects virtually all psittacine species (parrots, macaws, cockatoos, African Greys, amazons, conures, cockatiels, budgerigars) and is one of the most diagnostically challenging avian diseases.
The AAV Basic Care for Companion Birds, 2019 notes that ABV is shed in feces and urine of infected birds, and transmission between birds occurs through direct contact or contaminated environments.
Signs of PDD in Parrots
- Passing whole seeds or undigested food in droppings — the hallmark sign; seeds should be completely ground by normal digestion
- Regurgitation or vomiting — often of poorly digested material
- Progressive weight loss despite eating — the bird eats normally but still loses body condition
- Crop dilation — the crop (upper GI pouch) may feel enlarged and doughy
- General weakness and lethargy as malnutrition progresses
Neurological signs (when the virus also affects the central nervous system):
- Ataxia — wobbling, loss of balance, falling from perches
- Seizures
- Vision changes — head tilt, abnormal eye movements (nystagmus)
- Behavioral changes — depression, aggression, unusual vocalizations
The neurological form can appear without GI signs, making diagnosis challenging. Both forms can occur in the same bird sequentially or simultaneously.
Diagnosis
PDD diagnosis has historically been difficult and required crop biopsy (looking for lymphoplasmacytic inflammation of the nerves in the crop wall — the "gold standard"). Current diagnostic approach:
- Avian bornavirus serology (ABV antibody test or RT-PCR on blood/feces) — available through specialized avian labs; positive test supports PDD diagnosis but not all seropositive birds develop clinical disease
- Radiographs — proventricular dilation is visible as a dramatically enlarged proventriculus on abdominal X-ray; barium contrast study enhances visualization
- Crop biopsy — histopathology showing ganglioneuritis is highly diagnostic
- Blood work — assess nutritional status, rule out other disease
Treatment
There is currently no cure for PDD. Management focuses on supportive care and reducing GI inflammation:
- Celecoxib (COX-2 inhibitor) — a non-steroidal anti-inflammatory that reduces neurological inflammation; the most evidence-supported treatment for PDD. Dose: approximately 10 mg/kg twice daily in pellet form or compound.
- Dietary modification: easily digestible foods (cooked grains, soft pellets, cooked legumes) that require less gastric processing. Avoid whole seeds.
- Nutritional support: tube feeding or hand-feeding may be required to maintain body weight in advanced cases
- Antiviral therapy: mycophenolate mofetil has been used in some cases; research is ongoing
With appropriate management, some birds maintain acceptable quality of life for months to years. Others deteriorate rapidly. Neurological PDD cases generally carry a worse prognosis.
Cost: avian vet visit with radiographs, biopsy, and labs typically costs $300–800. Ongoing celecoxib medication compounded to appropriate dose: $50–150/month. Nutritional support and frequent rechecks add to ongoing cost.
When to See a Vet
Call your vet today if:
- You see whole seeds in your parrot's droppings
- Your bird is regurgitating food or material from the crop
- Unexplained weight loss is occurring despite the bird appearing to eat normally
- Any balance problems, head tilt, or sudden behavioral change in a parrot
Go to the ER immediately if:
- Your parrot has a seizure or collapses
- The bird cannot perch or stand and is on the cage bottom
- Regurgitation is severe, continuous, or the bird appears in acute distress
What's going on with your pet?
Describe symptoms or snap a photo. Voyage tells you urgency, home care, and whether you need a vet.
First, tell us about your pet
Breed and age make a real difference in how Voyage interprets symptoms.
Describe the symptoms
Love it? See everything Voyage can do
Frequently Asked Questions
Can PDD spread between birds? Yes — avian bornavirus (ABV) is shed in feces and urine and can spread between birds sharing an environment or through contaminated food and water sources. New birds should be quarantined for a minimum of 30–90 days and screened for ABV before introduction to an existing flock. Not all ABV-infected birds develop PDD.
Is PDD contagious to humans? Current evidence suggests ABV is not infectious to humans. No documented human cases of ABV infection from parrots exist, though standard hygiene practices (handwashing after bird contact) are always recommended.
How much does PDD management cost? Initial diagnostics (avian exam, radiographs, blood work, crop biopsy) typically cost $300–800. Compounded celecoxib for ongoing treatment runs $50–150/month. Nutritional support and bimonthly rechecks add $100–300/month. Owners managing PDD-affected parrots typically spend $1,500–4,000/year.
Can a bird with PDD live a normal lifespan? Some birds with mild PDD managed early with celecoxib and dietary modification maintain good quality of life for years. Advanced PDD with severe proventricular dilation and concurrent neurological disease carries a much shorter prognosis. The disease is progressive; management slows but does not stop progression.
What species are most affected by PDD? PDD has been documented in over 50 psittacine species. Macaws, African Greys, cockatoos, amazons, eclectus parrots, and conures are commonly affected larger species. Cockatiels and budgies are also susceptible. Non-psittacine birds (canaries, toucans, some raptors) have also been reported with ABV infection.
Still Not Sure if Your Parrot Needs a Vet?
When you're not sure if this is wait-and-see or call-tonight, Voyage AI Vet triages in under 2 minutes. Describe what you're seeing in chat, share photos of your bird's droppings or body condition, or hop on a live video call if you want a second pair of eyes. Every answer comes with citations to the actual veterinary literature it's pulling from — so you see exactly where the guidance comes from, not just a chatbot's word.