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Clinical and Vaccine Immunology, October 2006, p. 1125-1130, Vol. 13, No. 10
1071-412X/06/$08.00+0 doi:10.1128/CVI.00236-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota 55108,1 School of Veterinary Medicine, University of Wisconsin, 2015 Linden Drive, Madison, Wisconsin 53706-1102,2 University of Minnesota Veterinary Diagnostic Laboratory, 1333 Gortner Ave., St. Paul, Minnesota 55108,3 Minnesota Board of Animal Health, St. Paul, Minnesota,4 University of Pennsylvania, Kennett Square, Pennsylvania5
Received 23 June 2006/ Returned for modification 4 August 2006/ Accepted 18 August 2006
A high-throughput TaqMan PCR assay for detection of bovine paratuberculosis was evaluated by using fecal samples from 1,808 dairy cattle in seven naturally infected herds and 347 dairy cattle in seven herds considered free of paratuberculosis. Fecal, blood, and milk samples were submitted to laboratories where the PCR-based assay, three different fecal culture procedures for Mycobacterium avium subsp. paratuberculosis (centrifugation, sedimentation, and the BACTEC filter concentration method), two serologic enzyme-linked immunosorbent assays (ELISAs), and one milk ELISA were performed. Results from testing of dairy cattle in herds free of M. avium subsp. paratuberculosis showed that the PCR assay's specificity was 99.7%. Twenty-three percent of the dairy cows that were fecal culture positive by at least one of the three methods were positive by the PCR assay. By Bayesian non-"gold standard" analysis methods, the TaqMan PCR assay had a higher specificity than the serum ELISAs (99.3%; 95% confidence interval [CI] = 98.6 to 99.7%) and a test sensitivity similar to that of the serum ELISAs (29%; 95% CI = 24 to 35%). By classical methods, the estimated relative sensitivity of the fecal PCR assay was 4% for light and moderate fecal shedders (compared to 12 to 13% for the ELISAs) and 76% for heavy fecal shedders (compared to 67% for the milk ELISA). The PCR assay has higher sensitivity for detection of heavy fecal shedders than the evaluated milk ELISA but lower sensitivity than a serum or milk ELISA for detection of light and moderate fecal shedders. This assay can be used as a quick test for detection of cattle with heavy fecal shedding, those cattle with the highest risk of transmitting infection to susceptible cattle.
Published ahead of print on 23 August 2006.
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