Prevalence of antibodies against Mycobacterium avium subsp paratuberculosis among beef cow-calf herds.

Objective: To estimate the prevalence of Mycobacterium avium subsp paratuberculosis infection among cows on beef operations in the United States.
Design: Cross-sectional seroprevalence study. Sample Population-A convenience sample of 380 herds in 21 states.
Procedures: Serum samples were obtained from 10,371 cows and tested for antibodies to M avium subsp paratuberculosis with a commercial ELISA. Producers were interviewed to collect data on herd management practices.
Results: 30 (7.9%) herds had 1 or more animals for which results of the ELISA were positive; 40 (0.4%) of the individual cow samples yielded positive results. None of the herd management practices studied were found to be associated with whether any animals in the herd would be positive for antibodies to M avium subsp paratuberculosis.
Conclusions and Clinical Relevance: Results suggest that the prevalence of antibodies to M avium subsp paratuberculosis among beef cows in the United States is low. Herds with seropositive animals were widely distributed geographically.