Avian mycobacteriosis in psittacines: a retrospective study of 123 cases

One hundred and twenty-three cases of mycobacterioses were diagnosed in psittacine birds from a total of 9,241 submissions for necropsy examination or histopathology made to the California Animal Health and Food Safety Laboratory System between 1990 and 2007. The species affected most commonly were Amazon parrots (Amazona spp.)(n = 32; 26%) and grey-cheeked parakeets Brotogeris pyrrophterus (n = 23; 18.7%). The main gross findings on necropsy examination were enlarged and mottled pale livers and spleens and thickening of the small intestinal wall with numerous pale miliary nodules on the mucosa. Microscopical examination revealed infiltration of foamy macrophages and giant cells containing acid-fast bacteria in various organs. The gene encoding mycobacterial 65 kDa heat shock protein (hsp65) was amplified by nested polymerase chain reaction (PCR) from DNA extracted from 22 cases. The species of Mycobacterium involved was determined by analysis of restriction endonuclease patterns of the PCR products. Mycobacterium genavense was detected in 19 cases and Mycobacterium avium in two cases. One parrotlet (Touit spp.) had a mixed infection of both species of mycobacteria. It is concluded that M. genavense is the primary cause of mycobacteriosis in psittacine birds and the potential for zoonotic disease should be considered, especially for immunocompromised owners.