Mitchell V. Palmer, Tyler C. Thacker, W. Ray Waters, Suelee Robbe-Austerman and Beth N. Harris
Mycobacterium bovis is the causative agent of tuberculosis in animals and can cause tuberculosis in humans clinically indistinguishable from that caused by Mycobacterium tuberculosis. Efforts to eradicate bovine tuberculosis have significantly decreased prevalence in developed countries. However, some countries have found it impossible to eradicate bovine tuberculosis due to the presence of a wildlife reservoir of M. bovis. In Michigan, USA there exists a reservoir of M. bovis in free-ranging white-tailed deer. Vaccination with M. bovis BCG is one approach to controlling tuberculosis in wildlife. Nevertheless, use of a live vaccine generates concerns about exposure risk to non-target species, including domestic livestock. Unintentional exposure of cattle to BCG may result in increased numbers of false positive tuberculin skin test reactions. Twenty-nine white-tailed deer received 1 SC dose of 107 colony-forming units of M. bovis BCG Danish 1331 (n=19) or no vaccination (n=10). Vaccinated and non-vaccinated deer were comingled with opportunity for direct and indirect contact. Twelve unvaccinated Holstein calves were housed in a separate paddock with no means of direct contact with deer; however, indirect contact through the sharing of feed and water was permitted. After 180 days, 11 out of 15 vaccinated deer and 4 out of 8 non-vaccinated deer were classified as reactors using the tuberculin skin test. All 12 calves were categorized as non-reactors, by both the tuberculin skin test and BOVIGAM™ assay. Vaccination of free-ranging white-tailed deer with BCG Danish is unlikely to have a deleterious effect on tuberculosis surveillance measures in cattle.