Vaccination is usually consideredthe most effective way to control infectious diseases and offer some protectionto an animal (Conlanet al. 2015).
The use of live attenuated vaccines (LAVs) has been used toprotect humans and animals from multiple infectious diseases (Pandeyet al. 2016). Immunity through the use of LAVs is the resultof weakening a pathogen so it is unable to cause the infection in the host(Pandeyet al. 2016).
The use of LAVs has proven to be successful in humans andanimals, including against bTB (Calmette1931; Waters and Palmer 2015; Pandey et al. 2016). Studies on vaccine efficacy and their immune response tohuman TB, have been applied in the development of cattle vaccines (Watersand Palmer 2015). Development of wide-range vaccination approaches to controlbTB in wildlife will have a positive effect on high bTB areas and understandingimmunity for wildlife and human control of bTB (Watersand Palmer 2015). Buddle et al(2016) studied three groupsof calves: vaccinated with no prior infection, unvaccinated, and vaccinatedwith high dose of BCG after infection.
There was asignificant reduction in lesions in lymph nodes and lungs of the calves whenvaccination prior to exposure to M. bovis,and no significant difference between lesions and pathology in non-vaccinatedand post-challenge BCG groups (Buddleet al. 2016). Ten weeks after M. bovischallenge, post-challenge BCG groups showed a significant increase in TST (23.
3mm increase in skin fold thickness) compared to average of 16.0 mm thicknessfor non-vaccinated groups (Buddleet al. 2016). Buddle et al (2016) concluded that administering high dosesof BCG vaccine post-challenge does not offer any protection to the animal.
Although, there are vaccines for cattle against bTB, it isnot a common government practice to immunize domestic cattle as it interfereswith the accuracy of the TST (Charleset al. 2013). The main challenge is there is no good vaccine to date thatcan fully prevent mycobacterial infection, they may only reduce the rate ofdevelopment or the burden of bTB (Waterset al. 2012; Tompkins et al.
2013). Without a reliable screening test that coulddistinguish between immunized and infected animals it will be difficult tointroduce routine immunization in cattle. Contributing to the difficulties ofvaccine development is the fact that M bovis is able to evade the immune system(Widdisonet al. 2009).