Mycobacterium bovis mastitis in an alpaca and its implications.

doi: 10.1136/vr.d5287 Histopathology of the lung, lymph node, kidney, liver and mammary gland identified multifocal coagulative necrosis surrounded by large numbers of degenerate leucocytes, small numbers of activated macrophages and fibroblasts. Ziehl-Neelsen staining identified moderate to large numbers of acid-fast bacilli in all tissues. These findings are consistent with disseminated M bovis infection including mastitis. TB in the mammary gland of cattle has been recognised for many years, and before pasteurisation was carried out routinely, it was the source of infection for many human cases (Gowland Hopkins Committee 1934). In the majority of cases of TB in alpacas, the source of infection is thought to be spillover of infection from other animals such as cattle and wildlife. Suspected alpacato-alpaca transmission has been reported (Twomey and others 2009). It is assumed that the offspring of dams with mycobacterial infections will be exposed to M bovis as a result of close contact, predominantly through the oronasal route. The considerable number of acid-fast bacilli in the mammary gland in this case strongly suggested that milk from this animal would have contained sufficient numbers of the organism to result in the infection of offspring. This demonstrates the potential for direct exposure to M bovis via milk and possible spread to other herds via movement of crias before the development of clinical signs. This alpaca was not lactating on submission; however, its cria born in 2010 had died at a young age and its death was not investigated. The owners and attending veterinary surgeon involved in this case had regularly flushed the discharging lesion, possibly creating bacterial aerosols. We would urge colleagues to be aware of the potential of TB in udder lesions of alpacas, and to consider the associated risk involved in the treatment of such lesions.