TB caused by Other Members of the Mycobacterium tuberculosis Complex Angel Cataldi and Maria Isabel Romano in Tuberculosis 2007, Palomino, Rittacco and Leao (Eds)

ANGEL CATALDI; MARIA ISABEL ROMANO

Amedeo

Lugar: Berlin ; Año: 2007 p. 450

Chapter 3: EPIDEMIOLOGY 3.2. Human tuberculosis caused by other members of the Mycobacterium tuberculosis complex Angel Cataldi and Maria Isabel Romano   3.2.1. Mycobacterium bovis disease in humans Bovine TB is caused by Mycobacterium bovis, a mycobacterium highly similar to M. tuberculosis and belonging to the M. tuberculosis complex. The main host of M. bovis is cattle (Bos taurus) but it affects many other mammalians including man. In man, it is the most frequent cause of zoonotic TB, i.e. TB transmitted from animals to humans, which is clinically indistinguishable from TB caused by M. tuberculosis. Before milk pasteurization M. bovis was an important cause of human TB, especially intestinal TB in children. After the generalized adoption of pasteurization of milk and other dairy products zoonotic TB dropped sharply. Very few studies are published on zoonotic TB. In the last 50 years research on zoonotic TB was influenced by scientific trends, societal worries (AIDS, contaminated food) and by the availability of tools for the identificarion of the bovine bacillus. For example, the development of PCR and other molecular tools to identify M. bovis and differentiate this species from other members of the M. tuberculosis complex have allowed the discovery of more cases in retrospective studies and have suggested new forms of transmission. The medical literature on the incidence of zoonotic TB is marked by numerous clinical descriptions of cases, search for M. bovis at regional or nosocomial level, but there are very few systematic surveys of M. bovis diagnosis at national level (Barrera L, De Kantor 1987, Anon 2003, Cousins 1999, Pavlık 1998). There are three main explanations for the absence of an accurate and methodical estimation of the contribution of M. bovis to the global TB burden. First, at the clinical or radiological level there is no difference between TB caused by M. tuberculosis and M. bovis. Second, most laboratories use Löwenstein-Jensen culture medium with glycerol, which does not promote M. bovis growth. Furthermore, for many low-income countries cultivation is always an expensive option compared to the cheaper and faster acid-fast staining. Third, and perhaps most important, in most cases the treatment of TB caused by M. tuberculosis or M. bovis was the same; therefore, there was no clinical interest in differentiating the causative agent.