Abstract
Proventricular Dilatation Disease - PDD-is killing captive and free-ranging birds on a global scale and poses a serious threat to aviculture, and even to the management of threatened species in the wild. The Loro Parque Fundacion has taken up the challenge to combat this serious threat through collaborative funding of the Psittacine Disease Research Group (PDRG) at the University of Georgia, USA. In union with The International Avian Research Fund, lnc., the Fundacion will provide 33 percent of the six-figure dollar sum to conduct the essential research required in 1996.
Recognized since the late 1970's, the first appearance of PDD in macaws led to the term macaw wasting disease. Its progressive appearance in other psittacines, and more recent reports of its occurrence in various non-psittacine birds have generated several other synonyms. Jn this context, the disease has now been recognized as infectious and no birds with confirmed POD have survived. In the order Psittaciformes alone, PDD has been reported in more than 50 species, including such disparate .groups as cockatoos, lovebirds, conures, Amazons, macaws and parakeets.
Although infectious, the causative agent of PDD remains elusive and further research by the PDRG is essential to profile what seems to he a virus and for us to arrive at effective control measures. The research effort may he assisted by the fact that not all birds exposed to PDD subsequently develop the disease. These birds perhaps develop a protective immune response, may have innate resistance, may develop a carrier state, could have characteristics preventing development of POD or even lack factors required to induce the disease.
POD seems to have suhacute, acute and chronic stages. Most diseased birds die within several months to a year after developing clinical signs, the most common of which include depression, weight loss and occasional or constant regurgitation, sometimes separate or combined with the occurrence of undigested food in the feces indicating a digestive disorder. Other signs reported include lethargy, weakness, hypotension, scant feces, diarrhea, polyuria, muscle atrophy, abdominal and proventricular enlargement. Lack of coordination, abnormal head movements or seizures indicate the involvement of the nervous system.
Part of the need for continuing research is that POD cannot he diagnosed hy clinical abnormalities or gross necropsy findings. At present a definitive diagnosis first requires microscopic examination of the ventriculus, proventriculus. crop or brain, with resulting demonstration of characteristic lymphoplasmacytic infiltrates within the nervous system. Previous presumptive diagnosis will he based on historical information, especially medical records, clinical signs and radiographic evidence of proventricu-
lar dilatation or dysfunction. Because biopsy or other potentially dangerous invasive techniques make confirmation of POD in living birds difficult, definitive diagnosis is frequently made postmortem. Changes in the living bird of the kind already described could also have a number of other causes, including parasitism, microbial infections, neoplasms, trauma, gastrointestinal ohstructions, malnutrition, malassirnilation, toxic ingestion, and therefore care needs to he taken in arriving at a diagnosis.
Thus it is clear that the avicultural community in particular is facing a very threatening situation which requires a concerted effort to combat, The major financial support of the Laro Parque Fundaci6n to the PDRG of the University of Georgia is a tremendous first step in the right direction. The PORG has deservedly acquired an excellent reputation for its research into psittacine diseases. Due to its previous work, Psittacine Beak and Feather Disease (PBFD) can now he prevented by use of a diagnostic test and polyornavirus, a major cause of death in young parrots, can he prevented with an effective and safe vaccine.
In regard to researching POD, the PDRG will first need to confirm the causative organism and then develop a management technique involving an accurate testing procedure, and possihly even a vaccine. Thus, the Loro Parque Fundaci6n makes this major investment with the conviction that it will help in the conservation of parrots and in all sectors of aviculture. +