Objective: To evaluate the usefulness of testing bulk milk samples using 3 commercially available ELISA kits for rapid detection of paratuberculosis in dairy cattle herds.

Experimental design: Duplicate samples of bulk milk from 70 herds with paratuberculosis and 15 herds considered as free of infection were tested using 3 commercially available ELISA kits supplied by Prionics, Institut Pourquier and Svanova .

Results: The 3 ELISA kits showed limited ability to discriminate between herds with paratuberculosis and herds considered as free of the disease. Of the 70 herds with paratuberculosis, 9 (13%) tested positive by the Porquier ELISA and 12 (17%) tested positive by the Prionics ELISA when results were interpreted using a cut-off value that theoretically offers 95% specificity (2 SD + mean). However, at this cut-off value the Porquier ELISA gave a positive reaction in one of the 15 herds considered as free of paratuberculosis. Consequently, the results were also interpreted using a cut-off value of 3 SD + mean, which offers a test of approximately 99% specificity. Both the Porquier ELISA and the Prionics ELISA at the 3 SD cut-off detected 6 of the 70 (8.6%) herds with paratuberculosis. The Svanova ELISA consistently produced a high non-specific reaction in one sample of milk from the 15 herds considered to be free of paratuberculosis and was subsequently excluded from further analysis.

Conclusions: ELISA technology applied to bulk milk samples is not a sensitive method for the identification of dairy herds affected by paratuberculosis. With further evaluation and refinement the technology may be suitable for the identification of herds with a high prevalence of infected cows.