Proventricular Dilatation Disease (PDD)

In recent years, the incidence of Proventricular Dilatation Disease has been increasing at an alarming rate. Originally termed Macaw Wasting Disease, PDD has been identified in many species of psittacine birds, most commonly in African Greys, Cockatoos, Eclectus, and Macaws. PDD is three times more likely to affect adults than juveniles and is responsible for symptoms such as:

decreased or increased appetite; weight loss; lethargy; regurgitation; the passage of undigested seeds or voluminous stools if on a pelleted ration; lameness; weakness; ataxia (loss of balance); tremors; and other neurologic symptoms.

There is strong evidence that PDD is caused by a virus and; therefore, may be transmitted to other birds creating a hazardous situation in a group of birds. A diagnosis of PDD can only be definitively made by the identification of a lymphoplasmacytic ganglioneuritis in biopsy specimens of the crop (up to a 75% sensitivity), and/or the proventriculus (stomach) or ventriculus (gizzard). Symptoms of this disease occur specifically due to the ganglionueritis affecting the automatic motility of the digestive tract and other parts of the nervous system .

Infected birds may show no symptoms for more than 2 years, but can be a source of the virus for long periods of time. PDD is eventually fatal in all cases regardless of whether symptoms of regurgitation, malabsorption, or nervous system involvement occur. The virus is very unstable and quickly dies outside of the bird so infected birds should be isolated in an outdoor aviary. When PDD is identified within a group of birds, proper hygiene, isolation, and quarantine procedures must be adhered to since only time will tell if other birds are affected. Thanks to the work of veterinarians in research programs, better control measures including vaccination may become available.

It is important to note that there are many diseases which mimic PDD and each of these must be carefully considered when symptoms suggestive of PDD occur. These include:
# gastric nematode infections capable of causing weight loss, anemia, and signs of gastric impaction (anorexia, regurgitation, scant feces);
# protozoa infections including trichomoniasis and cryptosporidiosis;
# bacterial infections;
# fungal infections;
# candidiasis;
# mycobacterial infections;
# viral infections such as Avian Viral Serositis, Adenovirus, and Paramyxovirus III
# ingestion of foreign material (metal objects, feeding tubes, plastics, grit, feathers, substrate bedding) that can cause signs of gastric (proventriculus and/or ventriculus) obstruction, impaction, and may be complicated by perforation, abscessation, or peritonitis;
# heavy metal toxicity (esp. lead) which can be accompanied by sings of esophageal or proventricular dilatation, intestinal ileus (paralysis), impaction, abnormal droppings, and neurologic signs;
# hypervitaminosis D and the accompanying mineralization of digestive organs;
# impaction or signs of maldigestion due to disorders of the lining of the ventriculus (known as the koilin layer) that can be caused by zinc and copper toxicity, fungal infection, candidiasis, parasitic infection, internal papillomatosis, and vitamin D toxicosis;
# ulceration and perforation of the ventriculus (gizzard) due to koilin disorders;
# vitamin e/selenium deficiency;
# gastric tumors or other masses causing obstruction or the digestive tract;
# pancreatitis;
# and any systemic illness.

Dr Paul Skellenger