Proventricular Dilatation in Birds
First recognized in the early 1970's, proventricular dilatation disease (PDD) was originally called "Macaw Wasting Disease", as the disease caused a gradual wasting away of macaws. Since that time, the disease has been found to affect more than 50 different species of pet birds. It is found most commonly in Macaws, African Grey parrots, Amazon parrots, cockatoos and conures. There are some estimates that 20-35% of all birds are affected.
What is proventricular dilatation syndrome?
Proventricular dilatation disease is a condition affecting the nerves supplying the gastrointestinal tract of birds, mainly the proventriculus or true stomach. Nerves supplying other organs may also be affected, and in some cases, encephalitis (inflammation of the brain) may occur.
What causes the condition?
PDD has been linked to the Avian Bornavirus (ABV). Microscopically, the affected nerves are inflamed with an infiltration of certain types of white blood cells. This virus appears to be an unstable virus and is susceptible to heat, dryness and many disinfectants.
What are the signs of birds affected with PDD?
"No one sign is definitive for the condition."
PDD primarily targets the digestive system and the nervous system. The old name, "Macaw Wasting Disease", aptly describes affected birds. Birds have a lack of appetite, regurgitate, may pass undigested seeds in their feces, and exhibit progressive weight loss. Neurologic signs such as depression, weakness, ataxia (the loss of full control of bodily movements) head tremors and rarely, seizures, may occur. No one sign is definitive for the condition; however, proventricular dilatation disease should be suspected in birds with chronic unexplained regurgitation, weight loss, and any time undigested foods are seen in the droppings.
How is the condition diagnosed?
Clinical signs may suggest PDD. A complete physical examination with blood tests (CBC + Chemistry panels) is a logical start to rule out other problems that may be present. Radiographs (X-rays), including a contrast study or barium series may also strongly suggest the condition as it may demonstrate a dilation of the proventriculus, which is similar to the stomach (hense the name PDD). There is now a specific PCR test for ABV that requires a small sample of blood and a swab of the choana and cloaca (mouth and vent). It is possible to have false negative and rarely false positive results. A tissue biopsy and histology of the proventriculus or a biopsy of the crop,( which is easier to perform), is accurate most of the time in demonstrating ABV in the tissues. Biopsy is a minor surgery requiring a general anesthetic and may yield false negatives some of the time.
How do birds acquire the condition?
ABV is shed intermittently is the feces, saliva and nasal secretions. Therefore it is directly from fecal oral contamination and in the air as an aerosol. Not all birds that are exposed to an infected bird will develop the condition, although the condition can spread throughout a flock of birds. To be safe, birds diagnosed with PDD should be isolated from healthy birds.
Can the disease be treated?
There is unfortunately no definitive treatment for affected birds. Supportive care, including the use of certain anti-inflammatory drugs, treatment of any secondary diseases, and assisted feeding, can be given as needed, but the condition is ultimately fatal. Positive birds must be separated from healthy birds.
Speak to a veterinarian familiar with birds for more imformation.