Submitted to: American Association of Veterinary Laboratory Diagnosticians
Publication Type: Abstract Only
Publication Acceptance Date: November 3, 2001
Publication Date: N/A
Technical Abstract: Tuberculosis due to Mycobacterium bovis infection is endemic in white-tailed deer in the northeastern portion of the lower Michigan peninsula. Various wild carnivores and omnivores, including raccoons, have also been found to be infected with M. bovis within the endemic area. To investigate the pathogenesis of tuberculosis in raccoons and the likelihood of M. bovis transmission from infected raccoons to other susceptible hosts, we experimentally inoculated raccoons with single oral dosages of M. bovis (ranging from 30 to 1.7 X 10**5 CFU), repeated (5 days) oral dosages of M. bovis (ranging from 10 to 1 X 10**5 CFU), or a single IV dose of 1 X 10**5 CFU of M. bovis. Granulomatous lesions consistent with tuberculosis, or tissue colonization with M. bovis, were seen in 1/5 raccoons in the single low oral dose group, 1/5 raccoons in the multiple low oral dose group, 2/5 raccoons in the multiple medium oral dose group, 5/5 raccoons in the multiple high oral dose group, and 5/5 raccoons in the IV inoculated group. In orally inoculated raccoons, lesions were most commonly seen in the tracheobronchial and mesenteric lymph nodes and lung. Excretion of M. bovis in saliva or nasal secretions was seen in 5/5 IV inoculated raccoons and 2/5 multiple low oral dose raccoons. Mycobacterium bovis was not isolated from urine or feces from any experimentally inoculated raccoons. The necessity of multiple large oral dosages to establish infection in raccoons, and the low number of orally inoculated raccoons that excrete M. bovis in nasal secretions or saliva, make it unlikely that raccoons serve as important reservoir hosts of M. bovis, or transmitters of M. bovis to other susceptible hosts.