EXPERIMENTAL INOCULATION OF NORTH AMERICAN OPOSSUMS (DIDELPHIS VIRGINIANA) WITH MYCOBACTERIUM BOVIS

Eight North American opossums (Didelphis virginiana) were inoculated with 1 × 10⁵ colony forming units of Mycobacterium bovis to investigate their potential as reservoir hosts for bovine tuberculosis in Michigan. Four animals received this dose orally and four were inoculated intramuscularly (IM). In each group, two animals were euthanized 1 mo postinoculation (PI) and two at 2 mo PI. Four control animals were housed separately and sacrificed in the same manner as those inoculated. One of four orally inoculated opossums and three of four IM-inoculated opossums were positive for M. bovis by culture of tissues obtained at necropsy. The oral recipient had positive cultures from intestine and pooled lymphoid samples. Pooled lymphoid samples were positive in three IM-inoculated animals and two of these also had positive liver and lung cultures. One animal with gross and histologic lesions compatible with tuberculosis had negative tissue cultures. The findings suggest that opossums are susceptible to M. bovis infection by multiple routes, although their relative susceptibility compared to true reservoir hosts appears to be low.