Antibodies against Yersinia among farmers and slaughterhouse workers.

Antibodies to immunoglobulins (Ig) M, G, and A against Yersinia enterocolitica serotypes O:3, O:5, O:8, and O:9 and Yersinia pseudotuberculosis serotypes I and III were analyzed by enzyme immunoassay of the serum samples of 161 slaughterhouse workers, 147 pig farmers, and 114 grain or berry farmers. The crude risk ratios for elevated serum antibody concentrations were calculated with the use of the grain and berry farmers as the reference population. The risk for an elevated Y enterocolitica O:3 Ig G concentration was 3.0 (95% confidence interval (95% CI) 1.3-7.1) for the pig farmers and 1.8 (95% CI 0.7-4.4) for the slaughterhouse workers and the respective risks for elevated Y enterocolitica O:9 Ig G were 2.4 (95% CI 1.1-5.5) and 1.7 (95% CI 0.7-4.0). Since these two serotypes are commonly associated with swine, the increased number of subjects with elevated antibody levels could be causally related to occupational contact with this animal.