Tuberculosis in free-ranging wildlife: detection, diagnosis and management

Mycobacterium bovis is emerging as an important pathogen of free-ranging wildlife in which it is a potential source of infection for domestic animals and a threat to valuable wildlife species. This review examines the procedures for the detection, diagnosis and management of M. bovis in wildlife populations. The ante-mortem detection of M. bovis infection in wildlife is difficult, due to the common occurrence of subclinical infections and the deficiencies of the currently available diagnostic tests. Serological tests are insensitive, while tests measuring cell-mediated immune responses show promise, but have not been sufficiently developed for routine use in most species. The diagnosis of M. bovis in free-ranging wildlife relies on post-mortem examination supported by histopathology and microbiology. A feature of M. bovis infections is the variation in the appearance and distribution of lesions in the different host species. Bacterial culture remains the gold standard for diagnosis of tuberculosis, while histopathology is limited by the frequent inability to distinguish lesions caused by M. bovis from those produced by other mycobacterial species. Deoxyribonucleic acid (DNA) fingerprinting and advanced typing techniques are increasingly being used to unravel the epidemiology of mycobacterial infections, including tuberculosis in free-ranging wildlife. An understanding of the epidemiology is essential if procedures are to be developed for the management of tuberculosis in wildlife. Few management options are currently available, especially for protected wildlife. Vaccination is the subject of much research, but further developments are required before it can be used to control tuberculosis in any animals, let alone in free-ranging wildlife.