Tuberculosis (TB), a chronic infectious illness caused by Mycobacterium tuberculosis, is still a major worldwide disease. According to the World Health Organization, TB is a considerable public health problem in Latin America, Asia and Africa. Over the last few years an increase in the incidence of TB has been observed, attributed to weak control programs, the AIDS pandemic which predisposes individuals to develop TB and to the appearance of M. tuberculosis strains resistant to first-line antibiotics. In addition, bovine tuberculosis (bTB) caused by Mycobacterium bovis has increased its incidence and is thought to be due, at least in part, to a wildlife reservoir.
M. bovis is also able to infect humans and on a worldwide basis it accounts for up to 10% of TB human cases. Thus, the increased incidence of bTB, besides being a major economic problem, poses an additional risk to human health. Indeed, in many countries the incidence of bTB continues to rise despite the use of the tuberculin test and slaughter control policy, highlighting the need for improved control strategies. Vaccination of cattle, in combination with more specific and sensitive diagnostic tests, is suggested as the most effective strategy for bTB control. The only vaccine currently available for human and bovine TB is the live attenuated Bacille Calmette Guerin (BCG). BCG is thought to confer protection through the induction of Th1 responses against mycobacteria.