Abstract
The paradigm that M. paratuberculosis (Mptb) infection is primarily a predicament for ruminants was broken when the organism was isolated from lagomorph, canid, mustelid, corvid, and murid species captured on Johne’s disease-positive dairy farms in Scotland.1 Whether any or all of these non-ruminant species represent reservoirs of the infection vs. dead end hosts is not yet known.
To better elucidate the epidemiology of Mptb infection under domestic agricultural husbandry protocols typical of two regions in the United States, we caught close to 100 individual wild animals on Johne’s disease test-positive farms (7) and test-negative farms (2) in Wisconsin and Georgia. Approximately 50 different wild species (of which 20% were birds) typical of dairy or beef farming habitats were captured. One fecal sample and three gastrointestinal tissue samples from each animal were processed for radiometric culture within 24 hours of collection. The mycobacterial isolates were identified by mycobactin dependency, HPLC and genetic insertion sequence patterns. Analysis of multiple polymorphic genetic markers will be completed to characterize the phylogenetic similarity of Mptb strains isolated from wildlife and cattle on each premise. Histopathology will be completed for Mptb culture-positive tissues.
Samples are still incubating. To date, Mptb has been isolated from 28 animals representing diverse species such as domestic cats, raccoons, starlings plus an armadillo, skunk, shrew, sparrow and a Norway rat. A number of these animals were shedding the environmentally hardy organism raising two possibilities: (1) once established, a cycle of infection may be maintained within a variety of wildlife species independent of further exposure to infected domestic livestock and (2) infected wildlife may represent a risk factor for susceptible livestock (<6 months) through contamination of feed or forage.
Literature Cited
1. Beard PM, Daniels MJ, Henderson D, Pirie A, Rudge K, Buxton D, et al. 2001. Paratuberculosis infection of nonruminant wildlife in Scotland. J Clin Microbiol 39(4):1517–1521.