Proventricular Dilatation Disease

Proventricular dilatation disease is an inflammatory disease affecting the gastrointestinal and neurological systems in a variety of bird species. PDD is incurable, but manageable. Consequences of PDD range from gastrointestinal problems causing an increase in the size of the bird’s stomach to neurological symptoms. The disease is caused by avian bornavirus, which targets the bird’s nervous system. The damaged nervous system does not allow nutrients to be digested or absorbed. The virus does not always cause the disease, so a bird can have bornavirus and never develop PDD. Research on the virus and disease is still ongoing with much to be discovered.

Who gets it?

  • Age: any age
  • Sex: both male and female
  • Species:
    • Commonly Affected Species
      •   Macaws
      •   Amazon parrots
      •   African Grey parrots
      •   Cockatoos
      •   Electus Parrots
      •   Conures

These are only some of the affected species, but more than 50 different parrot species can be affected.


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Dilated proventriculus in a parrot with PDD, radiograph.
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  • Fecal-oral transmission, eating things contaminated with infected bird feces
  • Direct contact with infected bird, such as sharing a cage or housing
  • By air, although that is only suspected, not proven

How is it diagnosed?


The symptoms of PDD are not specific and there are a variety of potential causes explaining the bird’s illness such as lead toxicity, fungal or bacterial infection, or parasites. Therefore, other potential causes must be ruled out first before a diagnosis of PDD can be made. A physical examination by your veterinarian is first so a professional can see the clinical signs. Tests may include bloodwork, such as complete blood count or serology, radiographs to look for an enlarged stomach, a stomach biopsy to detect infected tissue and nerves, and other laboratory tests, such as PCR.

How is it treated?

There is no cure for PDD, so treatment reduces inflammation and the other symptoms.

  • Anti-inflammatories to decrease inflammation of GI tract and nerves
  • Steroids (used as a rescue drug in severe cases)
  • Broad spectrum antimicrobials
  • Broad spectrum antifungals
  • Good nutrition
  • Supplements
  • Warm and dry cage

How do you prevent it?

Infected birds should be isolated for life to prevent the virus spreading to other pet birds. New birds should be isolated and tested for the virus before they are introduced to the flock. Unfortunately, there is no vaccine to protect birds from PDD.

Proventricular Dilatation Disease in cockatiels (Nymphicus hollandicus) inoculated with brain homogenates.

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Macroscopic pathological findings in an ABV4-inoculated cockatiel. Bar size = 1 cm; F = peritoneal fat; H = heart; L = right liver lobe; V = ventriculus; A) Markedly reduced pectoral muscle mass and subcutaneous fat stores are clearly seen in an ABV4-inoculated cockatiel (cockatiel 3). B) Normal pectoral muscle mass and subcutaneous fat stores in a control bird (cockatiel 5). C) The peritoneal cavity of cockatiel 3, showing a severely distended and thin-walled proventriculus (arrows) that is visible well beyond the left liver lobe. The ventriculus is mildly distended and the peritoneal fat is dramatically reduced. D) In cockatiel 5, the proventriculus is of normal size, and; therefore, completely hidden behind the left liver lobe. Note the abundant peritoneal fat stores. E) The proventriculus and intestine of cockatiel 3. The thin wall has been cut, exposing a large amount of undigested seeds. Whole seeds are also visible through the intestinal wall.