Submitted to: American Dairy Science Association Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 22, 1997
Publication Date: N/A
Technical Abstract: Paratuberculosis (Johne's disease) is a chronic, progressive enteric disease of ruminants caused by infection with Mycobacterium paratuberculosis. Cattle become infected with M. paratuberculosis as calves but often do not develop clinical signs until two to five years of age. Clinical disease is characterized by chronic or intermittent diarrhea, emaciation, and death. Although animals with clinical disease are often culled from the herd, animals with subclinical paratuberculosis may cause economic losses due to reduced milk production and poor reproductive performance. Although the economic impact of paratuberculosis on the national cattle industry has not been determined, it is estimated to exceed $1.5 billion per year. Diagnosis of subclinical paratuberculosis is difficult. Bacteriologic culture is the most definitive method of diagnosis but is time consuming and labor intensive. Serological assays are not very useful because animals do not develop an antibody response until the clinical stages of disease. Development of assays to measure cell-mediated immunity is critical to accurate detection of paratuberculosis in subclinically infected animals. Although not considered a zoonotic agent, M. paratuberculosis has been identified in intestinal biopsy tissue from patients with Crohn's disease, an inflammatory enteritis in humans. Currently, the potential human health risk is being addressed by research evaluating pasteurization of dairy products in the United States.