Experimental Aerosol Inoculation and Investigation of Potential Lateral Transmission of Mycobacterium bovis in Virginia Opossum (Didelphis virginiana)

An endemic focus of Mycobacterium bovis (M. bovis) infection in the state of Michigan has contributed to a regional persistence in the animal population. The objective of this study was to determine if Virginia opossums (Didelphis virginiana) contribute to disease persistence by experimentally assessing intraspecies lateral transmission. One wild caught pregnant female opossum bearing 11 joeys (young opossum) and one age-matched joey were obtained for the study. Four joeys were aerosol inoculated with M. bovis (inoculated), four joeys were noninoculated (exposed), and four joeys plus the dam were controls. Four replicate groups of one inoculated and one exposed joey were housed together for 45 days commencing 7 days after experimental inoculation. At day 84 opossums were sacrificed. All four inoculated opossums had a positive test band via rapid test, culture positive, and gross/histologic lesions consistent with caseogranulomatous pneumonia. The exposed and control groups were unremarkable on gross, histology, rapid test, and culture. In conclusion, M. bovis infection within the inoculated opossums was confirmed by gross pathology, histopathology, bacterial culture, and antibody tests. However, M. bovis was not detected in the control and exposed opossums. There was no appreciable lateral transmission of M. bovis after aerosol inoculation and 45 days of cohabitation between infected and uninfected opossums

ECOLOGY OF MENINGEAL WORM, PARELAPHOSTRONGLYUS TENIUS (NEMATODA) IN WHITE-TAILED DEER AND TERRESTRIAL GASTROPODS OF MICHIGAN'S UPPER PENINSULA WITH IMPLICAITONS FOR MOOSE

Moose (Alces alces) were reintroduced to Michigan's Upper Peninsula in the mid-1980's. Because of some of the subsequent mortalities were attributed to meningeal worm, Parelaphostrongylus tenuis, a study was done in 1995 - 1996 to determine potential exposure of moose to this parasite. Objectives were to determine parasite population size in white-tailed deer (Odocoileus virginianus) of the region as well as the abundance and distribution of gastropod intermediate hosts with emphasis on their role in the transmission of P. tenuis. Prevalence and intensity of adult worms were lower in fawns (28%, all with 1 worm) than in older deer (51%, x̄ = 1.7). Numbers of first-stage larvae were more numerous in deer feces collected in winter and spring than in feces collected in summer and autumn. Gastropods, collected June - October 1995 and June - August 1996, were most abundant in lowland areas (predominantly mixed conifer - deciduous habitat). Canonical correspondence analysis showed that % canopy cover, soil type, and soil depth best explained the distribution of snails among 35 collection sites. Eight of 23 species of gastropods collected were infected with P. tenuis larvae; 2 members of the genus Discus spp. were considered to be the most important intermediate hosts. Deer concentrated in areas called 'yards' in winter. One such type of yard where deer were fed artificially tended to have more infected gastropods than other areas, but their role in transmission of P. tenuis to moose is probably limited for several reasons including that these sites were spatially separated from primary moose range. Another type of yard that involves logging activity poses some threat to moose because numbers of gastropods in it are relatively high and, unlike artificial feeding sites, it is more accessible to moose because of seasonal decreases in human activity

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 Michigan (USA) had lesions suggestive of tuberculosis and was positive on culture for Mycobacterium bovis the causative agent for bovine tuberculosis. Subsequently, a survey of 354 hunter-harvested white-tailed deer for tuberculosis was conducted in this area from 15 November 1995 through 5 January 1996. Heads and/or lungs from deer were examined grossly and microscopically for lesions suggestive of bovine tuberculosis. Gross 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 identified as M. bovis. In addition, lymph nodes from 12 deer (11 females and 1 male) without gross or microscopic lesions were pooled into 1 sample from which M. bovis was cultured. Although more male (9) than female (3) deer had bovine tuberculosis infections, this difference was not statistically significant. Mycobacterium bovis culture positive deer 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 in North America. A combination of environmental (high deer density and poor quality habit) and management-related factors (extensive supplemental feeding) may be responsible for this epizootic