A generalized inclusion body disease in the budgerigar (Melopsittacus undulatus) caused by a papovavirus-like agent.

High mortality rates have been reported in budgerigars between one and 15 days of age in 19 aviaries in the Province of Quebec. The most consistent signs of disease were abdominal distention, lack of down feathers on the back and abdomen, lack of filoplumes on the head and neck, and retarded growth of the tail and contour feathers in birds that either survived or died later. Internal gross lesions were hydropericardium, enlarged heart and liver with multiple pinpoint white spots or large, yellow foci, pale or congested kidneys, congested lungs, and ascites. Histologic examination revealed large, slightly basophilic inclusion bodies in the enlarged nuclei of many different cells. These inclusion bodies were composed of viral particles. Multiple foci of coagulation necrosis were scattered in the myocardium and liver parenchyma, and granulovacuolar degeneration was common in renal tubular epithelial cells. Ballooning degeneration was multifocal in the epidermis and very extensive in the epithelial cells of developing feather follicles, and this led to their partial or complete destruction. Viral particles 50 to 55 nm in diameter were observed in negatively stained preparations from different organs of affected birds. These particles had the size and morphology of a papovavirus. In experimentally infected 25-day-old budgerigars, histologic examinations revealed the presence of intranuclear inclusions in hepatocytes, epithelial cells of the kidney tubules, and reticular cells of the spleen, despite the absence of clinical signs. We feel that this disease is caused by a papovavirus-like agent that can replicate in many tissues of the body, causing widespread lesions responsible for the high mortality rate of very young budgerigars and for the absence and/or incomplete development of feathers.