Submitted to: Journal of Wildlife Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 15, 2003
Publication Date: July 1, 2003
Citation: Stabel, J.R., Palmer, M.V., Whitlock, R.H. 2003. Immune responses after oral inoculation of weanling bison or beef calves with a bison or cattle strain of mycobacterium paratuberculosis. Journal of Wildlife Diseases. 39:545-555. Interpretive Summary: Johne's disease is a chronic, debilitating intestinal disorder in ruminants characterized by diarrhea, reduced feed intake, weight loss, and death. Cattle usually become infected as young calves by ingesting feces containing the causative bacteria. However, symptoms of disease do not usually present themselves until the animals reach 3 to 5 years of age or even older. During this time the animal is infected and may be shedding the organism in its feces without showing any clinical signs of disease. In addition to reduced production by these animals through reduced milk production, they also present a potential infective threat to the rest of the herd and to other susceptible populations of animals. Little is known about the transmission of this disease between different species of animals. In this study, we experimentally infected young beef calves and bison calves with the causative bacterium and evaluated their immune responses to the infection. Results of this study suggest that there is a difference in the susceptibility of beef and bison calves to infection. In addition, the host immune responses were different between the two species of animals. This information is important to producers to promote awareness of potential transmission of infection between ruminant species in animals that may share pastures, water or feed.
Technical Abstract: Paratuberculosis is endemic in domestic and wild ruminants worldwide. We designed the following study to compare host immune responses and pathologic changes in beef calves and bison calves after challenge with either a cattle (bos taurus) or bison (bison bison) strain of M. paratuberculosis. In the first part of the study, 6 bison and 6 beef calves were orally inoculated over a 2-week period with a cattle isolate of M. paratuberculosis. In the second part, 6 bison and 6 beef calves were similarly inoculated with a bison strain of M. paratuberculosis. Throughout each of the studies, blood and fecal samples were taken monthly for a 6-month infection period. Tissue samples were obtained at necropsy for culture and histopathologic analyses. Results from this study demonstrated that bison calves were more susceptible to tissue colonization than beef calves, regardless of bacterial strain. Although lesions were minimal they were most apparent in the jejunum and distal ileum. Interferon-gamma responses were noted in some calves by one month post-inoculation and were sustained longer in beef calves after challenge with the bison isolate. Antibody was not detected in either beef or bison calves during the 6-month infection period. These results indicate that the host response to strains of M. paratuberculosis may differ between ruminant species.