Historical Perspectives
Bovine TB is a worldwide animal health problem, and the infection was most likely disseminated with the movement of people as they migrated, taking their livestock with them, and settled on the various continents and islands across the globe (Smith 2012).
In the 1800s and early1900s, BTB caused considerable losses in the cattle industry (Martin 1994), and with the development of an intensive livestock industry in Europe and America in the early part of the twentieth century, the disease was recognized as a significant problem when intensive cattle farming was practiced. At that time, BTB was considered characteristically to be a disease of housed animals, and it was virtually unknown in extensive, rural farming systems in which the opportunity for droplet transmission was remote.Because BTB, associated with intensified cattle production in the post-industrial revolution era, was a threat to animal and human health, several countries (led by the USA) attempted its eradication by:
1. Implementing BTB control programs for cattle
2. Improving milk hygiene and implementing pasteurization of milk for human consumption
3. Increasing public awareness of the zoonotic and economic significance of an M. bovis infection in cattle
The campaign in the USA drastically reduced the number of cattle with BTB in the national herd from 5% in 1917 to less than 0.03% by 1985 (Martin 1994). Several countries in Europe had similar successes, but a few are still experiencing difficulties to keep the disease under control primarily because of the presence of wildlife reservoirs that act as sustainable sources of reinfection for livestock and make eradication of the disease almost impossible (Miller and Sweeney 2013). Although BTB internationally receives special attention in livestock because of its economic impact, it is mainly because of the zoonotic risk that it poses to humans that there is an international drive for its control and eradication.
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