Proventricular Dilatation Disease
is a disease affecting psittacines
). It was first recognized and described in 1978 by Dr. Hannis L. Stoddard. Since the first reported cases were involving species of Macaw
, the condition was termed Macaw Wasting Syndrome
The symptoms of the illness are varied but invariably include a problem in food digestion, tiredness, sleepiness and rapid loss of weight, followed by death. The food is passed undigested, so the bird's body relies on its reserves of fat, and since they are quite small in most birds, the bird dies within a few weeks.
In autopsies it has been found that the nerve supply to the digestive tract is being disabled, impairing its function and slowing down the passage of food through the digestive tract. The proventriculus (or crop) has been dilated as the bird keeps eating, but the food is not being processed fast enough in the ventriculus and the intestine.
For decades, there has been speculation that PDD has a viral cause, but the identity of the virus was unknown. In July 2008, a team of researchers at the University of California, San Francisco
was able to identify the virus, which they have named Avian Bornavirus (ABV). A member of the bornavirus
family, Avian Bornavirus was isolated in 71 percent of samples from infected birds, but in none of the healthy birds. The researchers were able to clone a full-length genome
of the virus from avian tissue, and analysis of that tissue revealed that there are at least 5 distinct varieties of the avian virus.