Submitted to: UJNR Food & Agricultural Panel Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/26/2005
Publication Date: 10/26/2005
Citation: Stabel, J.R., Bannantine, J.P., Paustian, M., Robbe Austerman, S. 2005. A Multi-facted Approach to Mycobacterium avium subsp. paratuberculosis Research in the Agricultural Research Service. UJNR Food & Agricultural Panel Proceedings. p. 120-123.
Interpretive Summary: Johne's disease is a chronic, debilitating intestinal disorder in cattle 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 milk production by these animals, they also present a potential infective threat to the rest of the herd. Johne's disease is difficult to diagnose and therefore to control. Development of accurate and sensitive diagnostic tests is dependent upon understanding the immune responses of the host animal during infection. This paper describes work that is currently being conducted on paratuberculosis by scientists within ARS. It is a multi-factorial approach to research with focus on understanding the immunology and pathogenesis of the disease in order to develop. It is possible that this information will lead to new preventative and therapeutic regimes.
Technical Abstract: Paratuberculosis (Johne's disease) is a chronic, progressive enteric disease of ruminants caused by infection with Mycobacterium avium subsp. paratuberculosis (MAP). Economic losses are estimated to be $200/infected cow/year and are the result of animal culling, reduced milk production, poor reproductive performance, and reduced carcass value. Johne's disease has become a high priority disease in the cattle industry. Herd prevalence of Johne's disease is estimated to be 22-40% as determined by a recent National Animal Health Monitoring Survey of dairy cattle. There are no adequate estimates of herd prevalence in beef cattle in the U.S. The economic impact of this disease on the dairy industry was estimated to be over $200 million per year in 1996 and is growing each year with the continued spread of this disease. In addition, MAP has been implicated as a causative factor in Crohn's disease, a chronic inflammatory bowel disease of human beings, which has served as a further impetus to control this disease in our national cattle industry. Research on MAP within ARS in the US has involved a multi-pronged approach to reducing the incidence of disease. One major objective in research is to improve diagnostic tests for detection of this disease thereby providing tools for reducing contamination of the environment with MAP and the spread of infection within herds. Research on the pathogenesis and immunology of MAP infections of cattle is conducted to allow design of more rational diagnostic and control procedures. Sequence and annotation of the MAP genome has lead to identification of specific antigens for MAP. Further characterization of these antigens will result in better diagnostic tests to allow early detection of subclinically infected animals and reduce the incidence of disease in herds.