Wildlife Tuberculosis Study Group

Several tests can be used to determine the TB status of animals. Not all tests are validated for use in all species; therefore culture of the Mycobacterium bovis organism remains the Gold Standard for confirmation of infection with bovine tuberculosis. The following tests and procedures are all used in South Africa to determine the disease status in both domestic and wild animals.

Bovine tuberculosis (BTB) is caused by the organism Mycobacterium bovis, which is part of the Mycobacterium tuberculosis complex. There are about 50 species within the Mycobacterium genus, of which most are environmental saprophytes thus only causing opportunistic diseases or no disease at all. However, members of the Mycobacterium tuberculosis genus are obligatory parasites and therefore transmitted by infected mammalian hosts.

The Mycobacteria are intracellular pathogens that have the ability to survive in both aerobic as well as anaerobic circumstances, considered to be Gram-positive, non-motile, non-spore forming, straight or slightly curved rods of about 1,5 – 4µm long and 0.3 – 0.5µm wide. Due to the high lipid contents of their cell walls, Mycobateria are resistant to acids, dessication and most disinfectants.

Transmission of the live M bovis organism is believed to occur mainly via aerosolized droplets from a coughing or sneezing animal with open pulmonary tuberculosis. The period of infectiousness may be extremely long and the carrier may transmit disease for several months or even years. The feeding of infected carcasses to animals may also lead to transmission of disease.

Although originally believed to be a disease of domestic cattle in Europe, the disease was spread to other continents when domestic cattle were exported all over the world during the colonial era. The success of disease’s spread and survival of the pathogen can be ascribed to the fact that most species worldwide are susceptible to Mycobacterium bovis.

The most important factors determining the spread of disease are the number of infected individuals and the number of young animals exposed to infected individuals. Possible routes of infection with Mycobacterium bovis include respiratory, alimentary, congenital, cutaneous, venereal and via the teat canal.

Since several wildlife species have been diagnosed with BTB and clinical signs differ between these species, only clinical signs for those more likely to be observed are listed below.