Chapter 9 : Experimental Infection Models of Tuberculosis in Domestic Livestock

Abstract:

Tuberculosis (TB) affecting domestic livestock, including cattle, goats, and deer, is predominantly caused by Mycobacterium bovis. The disease in cattle, defined as bovine TB, is a major economic animal health problem worldwide, costing U.S. $3 billion annually, with >50 million cattle infected ( 1 ). Costs from this disease are related to a reduction in productivity in severely affected animals, testing, culling of affected animals, movement controls, and restriction on trade. Goats and farmed deer are also readily affected by TB, causing economic losses due to trade limitations, culling of affected animals, and depopulation of herds ( 2 , 3 ). In addition, M. bovis affects feral deer, where it may establish a wildlife reservoir, for example, in white-tailed deer in the United States, often resulting in a source of infection to contiguous cattle herds ( 4 ). M. bovis has a wide host range affecting both domestic and wild animals, but infection of other livestock such as domestic pigs and sheep is relatively rare. M. bovis is also infectious to humans, and prior to mandatory pasteurization in many countries, M. bovis accounted for about one fourth of TB cases in children ( 5 ). Transmission of M. bovis to humans has been markedly reduced with the pasteurization of milk and the implementation of bovine TB control programs coupled with abattoir surveillance, although risks remain with the consumption of unpasteurized milk and cohabitation of infected animals with humans.