Submitted to: Journal Dairy Science Supplement
Publication Type: Review Article
Publication Acceptance Date: September 30, 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 (paratb). Cattle become infected with M. paratb as calves but often do not develop clinical signs until 2 to 5 years of age. Clinical disease is characterized by chronic or intermittent diarrhea, emaciation, and death. Although animals with clinical disease are often culled from th herd, animals with subclinical paratb may cause economic losses due to reduced milk production and poor reproductive performance. The economic impact of paratb on the national cattle industry has not been determined, however, it is estimated to exceed $1.5 billion per year. Diagnosis of subclinical paratb 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 paratb in subclinically infected animals. Although not considered a zoonotic agent, M. paratb 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.