A cross-sectional study of paratuberculosis in 1155 Danish dairy cows

In a cross-sectional study on milk samples from 1155 cows from 22 Danish da iry herds, selected risk factors for paratuberculosis were identified. The diagnostic procedure used was an indirect enzyme-linked immuno-sorbent assa y (ELISA) to detect antibodies against Mycobacterium avium subsp. paratuber culosis. A sample was considered test-positive if it had a corrected optica l density greater than or equal to 0.025 (test sensitivity 71.4% and test s pecificity 89.7%). Of the 1155 samples, 8.8% (102/1155) were rest-positive, and 19 out of the 22 dairy herds had greater than or equal to 1 test-posit ive cows. The significant risk factors in a multiple logistic regression an alysis were: Jersey versus large breeds, high parity versus low parity, the first month after calving versus other months of lactation, and a large he rd size compared to a small herd size. The highest probability (37-38%) of a positive test was observed among older cows (parity >4) and tested within the first month after calving (irrespective of breed). The lowest probabil ity (2%) of a positive test-result was observed among first parity, large-b reed cows tested before calving or later than one month after. (C) 2000 Els evier Science B.V. All rights reserved.