INFECTIOUS DISEASE Avian Mycobacteriosis in Psittacines: A Retrospective Study of 123 Cases C. Palmieri * , P. Roy † ,1 , A. S. Dhillon † and H. L. Shivaprasad ‡ *School of Veterinary Science, University of Queensland, Gatton Campus, Queensland 4343, Australia, † Avian Health and Food Safety Laboratory - WADDL, Washington State University, 2607 West Pioneer, Puyallup, WA 98327 and ‡ California Animal Health and Food Safety Laboratory System - Tulare Branch, University of California, Davis, 18830 Road 112, Tulare, CA 93274, USA Summary 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 ¼ 32; 26%) and grey-cheeked parakeets Brotogeris pyrrophterus (n ¼ 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 re- vealed 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. Ó 2012 Elsevier Ltd. All rights reserved. Keywords: heat shock protein 65; Mycobacterium genavense; pathology; psittacines Introduction Mycobacteriosis is a common contagious disease re- ported worldwide in pet and exotic birds, domestic poultry and free-living and captive wild birds (Hoop et al., 1996; Tell et al., 2001). With the excep- tion of backyard domestic fowl, the disease is sporadic and rarely reported in commercial poultry (Tell et al., 2001), while the incidence ranges from 14 to 27% in birds from zoological collections (Keymer et al., 1982; Portaels et al., 1996). The disease in birds is gen- erally caused by Mycobacterium avium subsp. avium (Tell et al., 2001), although the involvement of other species of mycobacteria, for example Mycobacterium genavense, has also been reported (Hoop et al., 1993, 1996; Portaels et al., 1996; Miranda et al., 2009). M. avium belongs to the M. avium/Mycobacterium intracellu- lare complex (MAIC) (Gerlach, 1994) and infection occurs mainly by ingestion, occasionally by inhala- tion of aerosols of contaminated faeces (Van der Heyden, 1986) or by arthropod transmission (Kovalev, 1983). Mycobacteria can survive in soil and water for a long time, being a potential source of infection to other susceptible birds (Van der Heyden, 1986). Fol- lowing oral ingestion, M. avium infects the intestine and then spreads to liver, spleen, bone marrow, lungs, air sacs, gonads and, rarely, kidney and pancreas (Van der Heyden, 1986; Lennox, 2007). Classical chronic lesions are non-caseated, non-mineralized nodules in different organs of most birds (Van der Correspondence to: H. L. Shivaprasad (e-mail: hlshivaprasad@ucdavis. edu). 1 Present address: Central University Laboratory, Tamil Nadu Veterinary and Animal Sciences University, Chennai 600051, India. 0021-9975/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jcpa.2012.06.005 J. Comp. Path. 2013, Vol. 148, 126e138 Available online at www.sciencedirect.com www.elsevier.com/locate/jcpa