A recently recognized infectious agent is killing companion, aviary, and free-ranging birds throughout the world. At present, no birds or aviaries are known to be protected. Pacific, South American and Afro-Asian species have been described with characteristic lesions. Other non-psittacine birds also may prove to be susceptible to this disease as improved tests are developed to accurately diagnose affected individuals.
Clinical reports suggest that adults are more commonly affected than neonates.
Proventricular Dilatation Disease has been recognized since the late 1970's. Initially, the disease seemed to be limited to macaws. This fact, in conjunction with an unknown cause, gave rise to the terms macaw wasting or fading syndrome, wasting macaw syndrome, and gastric distension of macaws. As it became apparent that the disease occurred in psittacines other than macaws, a more general terminology was used to describe the disease, including psittacine wasting syndrome, proventricular hypertrophy, or proventricular dilatation syndrome. Various terminology also has been used to describe the pathological features of this disease, including neuropathic gastric dilatation, myenteric ganglioneuritis, proventricular and ventricular myositis, psittacine encephalomyelitis and infiltrative splanchnic neuropathy.