Neoplasms in budgerigars (Melopsittacus undulatus): clinical, pathomorphological and serological findings with special consideration of kidney tumours.

According to findings of others and to our own investigations, kidney tumours represent a remarkably high proportion of all tumours in budgerigars. Therefore, 74 budgerigars, clinically suspicious for abdominal tumours, were analysed individually by monitoring clinical signs, gross lesions, histology, the expression of the group-specific (gs) antigen of avian leukosis virus (ALV), the expression of immunoglobulins M and G, and the distribution of age and tumour incidence. Lameness and abdominal enlargement were the predominant clinical signs giving indication for abdominal tumours. Among these, kidney tumours were most frequent, represented by 47 cases (63.5%), followed by gonad tumours in 22 cases and liver tumours in 17 cases. These neoplasms partially occurred associated with each other. Direct evidence for the presence of ALV was obtained in 35 sera (47.3%) of all budgerigars examined. The expression of ALV gs antigen, however, was not necessarily associated with the presence or absence of tumours in these birds. In a few cases, IgM or IgG levels appeared to be enhanced in tumorous birds. A peak of the overall tumour incidence was observed between the 3rd and 6th year of age. Kidney tumours were mainly found within the 5th year of age. These findings suggest a marked predisposition of budgerigars to kidney tumours. Compared with ALV-induced tumours in chickens, the increased frequency of tumours in budgerigars relatively late in life is unusual. Although a direct aetiological role of ALV is likely, experimental data on the epidemiology and especially the latent period of ALV-induced tumour development in budgerigars are needed.