Dr. Darge Lulu and Dr. Mohammed Hussen
Bovine tuberculosis is a disease caused by Mycobacterium bovis that affects cattle and other species, including humans. Mycobacterium bovis resides mainly in macrophages, so bacilli survival within macrophages is related to virulence. The role of bacterial genetic variability in the infection’s outcome remains uncertain. Until the early 1990s, when DNA fingerprints were introduced, it was believed that the M. tuberculosis complex was a group of highly genetically conserved bacteria, with limited phenotypic differences that influenced pathogenesis. However, epidemiological data suggest that differences in transmissibility and virulence between strains are related to their genotypes. Bovine tuberculosis is a chronic, debilitating infection that infects a wide range of hosts including domesticated and wild animals. Unlike M. tuberculosis, M. bovis has an unusually extensive host range including humans as recognized by the World Health Organization4 with a greater zoonotic potential in developing countries. M. bovis is also the progenitor of the Bacillus Calmette–Guérin (BCG), the only licensed tuberculosis vaccine and the gold standard for protection against childhood disseminated tuberculosis. Isolation and strain identification are important for disease control. However, little is known about virulence factors of the circulating strains in cattle populations. Therefore, the aim of this paper is to review the genetics and virulence factors of intracellular Mycobacterium bovis strains in pathogenicity and pathogenesis of the disease.
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