The role of indirect transmission in the epidemiology of bovine tuberculosis in cattle and white-tailed deer in Michigan

Understanding the epidemiology of Mycobacterium bovis transmission in Michigan is an essential component of nationwide efforts to control and eradicate bovine tuberculosis (TB). Determining the role of indirect transmission in bovine TB dynamics is a key to the application of epidemiologically effective methods of disease control in both livestock and wildlife populations. The objective of this dissertation was to characterize the persistence of M. bovis in the environment and its potential role in the indirect transmission of disease among and between cattle (Bos taurus) and white-tailed deer (Odocoileus virginianus) in Michigan.; Optimized techniques for isolating M. bovis from environmental substrates were developed and applied to the testing of samples collected from cattle farms with a known history of M. bovis infection. Samples were also collected from locations within areas with a high prevalence of M. bovis infection in white-tailed deer. Though mycobacterial isolation was successful, none of the isolates were identified as M. bovis.; To address the question of M. bovis persistence, environmental substrates were inoculated with M. bovis and exposed to natural weather conditions over a 12-month long period. Persistence of M. bovis was recorded for an average of 30 days in the cooler months of the year (November--May), and an average of 7 days in the warmer months (May--August). These data supplement those produced through experimental M. bovis disease transmission studies that have proven the feasibility of indirect transmission of M. bovis among and between cattle and white-tailed deer as well as analyses of observational data that indicate the importance of indirect transmission in the interspecies transmission of M. bovis in Michigan.; Local, State and Federal bovine TB control and eradication policy needs to consider indirect transmission of M. bovis through contaminated environmental substrates in the creation and implementation of appropriate disease management plans. In the bovine TB endemic region of Michigan, interspecies transmission of bovine TB should be considered by both wildlife and livestock health agencies. If this component of the epidemiology of M. bovis transmission in the region is ignored, efforts to control and eventually eradicate the disease will fail.