Dave J. Rupiper DVM, Dipl. ABVP East Petaluma Animal Hospital 1420-B South McDowell Blvd., Petaluma, CA 94954 Phone: (707) 765-9098 Fax: (707) 765-2984 Web: EPAH.net Proventricular Dilatation Disease History Proventricular Dilatation Disease (PDD, PDS, Macaw Wasting Disease, MWD) is a disease not only of macaws but of many psittacine species. Cockatoos, conures, eclectus parrots and many African and Asian species have been infected. A causative agent has recently been identified and appears to be a virus which is currently being further characterized. Signs PDD affects the nerves of the GI tract and results in dilation of the stomach and lack of normal muscular contractions. The birds then regurgitate, pass undigested seed in the feces and lose weight. Weanlings fail to wean or revert back to handfeeding and will have slow crop emptying times. Some birds may have neurologic signs such as weakness, incoordination and head tremors, in addition to the gastrointestinal problems. The onset of these signs can be very slow and the symptoms often mimic those of other diseases. Mortality often approaches 100%. Diagnosis Classic signs of weight loss, regurgitation, juvenile behavior and passing undigested seed in a susceptible species is suggestive of infection. PDD-suspect birds can be radiographed (X-rayed) to identify a dilated stomach. Oftentimes, laboratory values will reveal elevated muscle enzymes due to the weight loss and damaged stomach muscles. The most diagnostic test is stomach biopsy, as evidence of nerve damage may be recognizable upon microscopic examination of the stomach tissue. This may be obtained by surgery or by performing a necropsy (autopsy). An alternative crop biopsy has been used in juveniles demostrating clinical signs but is generally a poor test for an adult bird. The technique, however, has fewer risks. Transmission The transmission of PDD appears to be by the fecal route but other modes may exist. Treatment Isolation or euthanasia of affected birds is necessary in order to control an outbreak. Treatment with antiviral medications has been attempted, but their effectiveness has not demonstrated any improvement. Preliminary trials of immuno-modulating drugs and feeding a liquid diet show some promise at improving an infected pet bird's quality of life. Currently, isolation is the only way to prevent transmission of the disease to other birds in the household or aviary. Disinfection with bleach, nolvalsan, wavicide and virkon-s is recommended and may help reduce the possibility of transmission.