Case Scenario 03

Bringing vets and medics together to deal with bovine TB in the United Republic of Tanzania

Bovine tuberculosis in Tanzanian cattle was first confirmed in the early 1950s. Tuberculosis lesions are found from meat inspections – for example surveys undertaken in the districts at the centre of the southern highlands indicate the presence of tuberculosis lesions in 20% of cattle slaughtered. However, the lack of facilities to culture mycobacteria means that it has been difficult for the Veterinary Investigation Centres which are responsible for livestock disease surveillance to identify and report the disease.

Tuberculosis in humans due to M. bovis generally occurs as the extrapulmonary form. In Tanzania, the proportion of extra-pulmonary TB amongst all forms of tuberculosis stands at nearly 16%. The majority of these cases have been recorded in the Arusha region in the northern part of the country, where regional data indicate up to 30% of total TB cases are those of the extra-pulmonary form. Cases of extra-pulmonary tuberculosis are on a simultaneous increase with the total cases of tuberculosis reported each year (which increased from 7 000 to 63 000 between 1992 and 2004). In the regions with a high number of cattle kept per head of the human population an exceptionally high proportion of extra-pulmonary TB was found during surveys: Arusha, 30%, Mbeya, 28.1%, Iringa, 27.3%, Shinyanga, 19.8%, Mara, 19.7%, Dodoma, 19.4%, and Mwanza, 10.8%.

A phase of intensive research on bovine tuberculosis, its incidence and risk factors in people and livestock began in the early 1990s. The signing of the first Memorandum of Understanding between Sokoine University of Agriculture (SUA) and the National Medical Research Institute (NIMR) in 1996 formalized and facilitated the growing collaboration between veterinary and medical researchers which has now extended to work on other zoonoses, notably brucellosis and rabies. For the first time in tropical Africa, it was possible to demonstrate unequivocally that M. bovis does contribute to the human epidemic, with about 10% of extra-pulmonary human TB cases and 4% of pulmonary cases caused by M. bovis in the United Republic of Tanzania. A further key finding has been the identification of atypical mycobacteria species as a cause of 50% of cases of extrapulmonary TB. The standard medical treatment for human TB has been directed towards M. tuberculosis, but these research findings suggest that consideration needs to be given to non-M. tuberculosis forms of the disease and the zoonotic component of the tuberculosis epidemic. This collaboration and the research results have been instrumental in a number of policy changes. The perception regarding M. bovis infection in cases of extra-pulmonary human TB cases was changed. In the third edition of the Manual for National Tuberculosis and Leprosy Programme, a statement regarding the rarity of M. bovis infection in cases of extrapulmonary TB was deleted. A change has also been made by the national veterinary authorities as TB is now among the diseases being reported to the OIE. A section dealing with non-epizootic diseases and in particular zoonotic diseases, has been set up in the ministry responsible for livestock. Changes have also occurred at NIMR where the Muhimbili Research Station, which was the focal contact unit within NIMR, has been elevated to Centre status. It has been proposed that a department responsible for studies on zoonotic diseases is established within this Centre.