The pathology and transmission of Mycobacterium bovis in Michigan wildlife

Michigan currently has an endemic strain of Mycobacterium bovis tuberculosis in its free-ranging white-tailed deer (Odocoileus virginianus) herd. The disease has been identified in deer and a large number of small mammalian species throughout the Lower Peninsula of the state, has spread to domestic cattle herds, and has been identified in a captive cervid herd. Cases identified through surveillance programs in wildlife are primarily concentrated in the northeastern portion of the Lower Peninsula thus far, but new counties with positive cases are identified each year as the span of surveillance widens and the numbers of animals included in the program grow.; The objectives of this body of work all sought to better define this endemic strain of tuberculosis in Michigan wildlife. A primary objective was to evaluate several common species for their potential in the transmission of the disease, two native passerine bird species, the European starling ( Sturnus vulgaris) and the American crow (Corvus brachyrhynchos ), and the North American opossum (Didelphis virginianus ) were studied. Although they would certainly figure prominently in transmission if they were efficient hosts of the disease, none of these species had ever been challenged with the M. bovis organism experimentally, and no reports describing natural infection exist, so a large part of this thesis was to describe any pathology resultant from experimental inoculation of these animals. Birds were challenged intraperitoneally and orally with M. bovis, but infections were only established by the intraperitoneal exposure route. Opossums were challenged intramuscularly and orally with M. bovis. Infection was established via both exposure routes in opossums.; Major concerns with tuberculosis in all species include the zoonotic potential of the disease and the emerging threat of these microorganisms becoming increasingly resistant to drugs used in treatment. A fundamental question that had not been examined until the time of this work was whether or not the strain of M. bovis causing endemic tuberculosis in Michigan's wildlife had any evidence of drug resistance. The objective to determine the susceptibility of the strain to common antimycobacterials was achieved successfully, it was found that there is no evidence of resistance to date in this strain. Moreover, comparison of the strain to that of several human cases of M. bovis identified in Michigan showed differences in both susceptibility profiles and in genetic fingerprints when compared to the animal case strain.; The final objective of this dissertation was to evaluate a novel cytologic technique for its potential application in the detection of mycobacteria in clinical samples. Cells were obtained from the tracheal, nasal, and oral mucosae of white-tailed deer experimentally inoculated with M. bovis. These samples were examined for the presence of intracellular mycobacteria after being prepared using the new technique, the ThinPrep 2000 automated cytology device. Results were compared to mycobacterial cultures taken from the same sites in these deer. The technique showed some promise in the antemortem diagnosis of mycobacterial disease, but was less sensitive and specific than existing veterinary diagnostic tests.