BOVINE TUBERCULOSIS IN FREE-RANGING WHITE-TAILED DEER FROM MICHIGAN

A 4.5 yr-old male white-tailed deer (Odocoileus virginianus) killed by a hunter during the 1994 firearm hunting season in northeastern Michi gan (USA) had lesions suggestive of tuberculosis and was positive on c ulture for Mycobacterium bovis the causative agent for bovine tubercul osis. Subsequently, a survey of 354 hunter-harvested white-tailed deer for tuberculosis was conducted in this area from 15 November 1995 thr ough 5 January 1996. Heads and/or lungs from deer were examined grossl y and microscopically for lesions suggestive of bovine tuberculosis. G ross lesions suggestive of tuberculosis were seen in 15 deer. Tissues from 16 deer had acid-fast bacilli on histological examination and in 12 cases mycobacterial isolates from lymph nodes and/or lungs were ide ntified as M. bovis. In addition, lymph nodes from 12 deer (II females and I male) without gross or microscopic lesions were pooled into 1 s ample from which M. bovis was cultured. Although more male (9) than fe male (3) deer had bovine tuberculosis infections, this difference was not statistically significant. Mycobacterium bovis culture positive de er ranged in age from 1.5 to 5.5 yr with a mean of 2.7 yr (median 2.5 yr) for males and 3.2 yr (median 3.5 yr) for females. This appears to be the first epidemic occurrence of M. bovis in free-ranging cervids i n North America. A combination of environmental (high deer density and poor quality habit) and management-related factors (extensive supplem ental feeding) may be responsible for this epizootic.