Accuracy of testing strategies using antibody-ELISA tests on repeated bulk tank milk samples and/or sera of individual animals for predicting herd status for Salmonella dublin in dairy cattle

Abstract

There is currently no perfect test for determining herd-level status for Salmonella Dublin in dairy cattle herds. Our objectives were to evaluate the accuracy, predictive ability, and misclassification cost term of different testing scenarios using repeated measurements for establishing the S. Dublin herd status. Diagnostic strategies investigated used repeated bulk tank milk antibody-ELISA tests, repeated rounds of blood antibody-ELISA tests on non-lactating animals or a combination of both approaches. When used for screening a population with an expected low prevalence of disease, for instance for screening herds with no clinical signs and no previous S. Dublin history, a diagnostic strategy consisting of two visits at 6 months interval, and with herd considered positive if bulk milk and/or ≥1/10 animals are positive on one or both visits could be used to confidently rule-out S. Dublin infection. With this approach, however, positive results should later be confirmed with more specific tests to confirm whether S. Dublin is truly present.