Does Mycobacterium bovis contribute to the case load of human tuberculosis in Namibia.

Abstract

Namibia has one of the highest infection rates of human tuberculosis (TB) in the world. The causative agent is generally asserted to be Mycobacterium tuberculosis. Renewed concerns have been raised globally in the last decades regarding the emergence of Mycobacterium bovis as a contributor to human TB. The pathogen is harbored by a number of mammalian animal species and, hence has a high zoonotic potential. Numerous investigations in recent years show evidence of the spread of M. bovis from the wildlifelivestock interface to humans in southern African countries. Rural communities in these regions are most at risk since livestock can easily be infected. Namibia is considered to be free of bovine TB in cattle because no cases have been reported since 1995. However the disease may be under-diagnosed in single cases especially in remote areas because of the slow and chronic course. Weakened animals might be slaughtered privately, with contaminated meat and raw milk from infected cows or goats being consumed. The aim of this review is to discuss the complex issues of diagnosis and epidemiology, and to highlight the importance of the differentiation of mycobacteria species in the medical laboratory for the outcome of patient treatment. M. bovis is clinically indistinguishable from human TB, possesses intrinsic resistance to at least one of the four first-line anti TB drugs, and shows a tendency to develop multidrug resistance. It poses a high risk predominantly for immuno-compromised individuals, as HIV-patients for example. Since Namibia has both - a high case load of HIV and TB - the occurrence and risk of zoonotic M. bovis in southern Africa should be discussed.