Epidemiological evaluation of a monoclonal ELISA detecting bovine viral diarrhoea pestivirus antigens in field blood samples of persistently infected cattle.

An enzyme-linked immunosorbent assay (ELISA), using monoclonal antibodies for capture and detection, was developed for detecting bovine viral diarrhoea virus (BVDV) antigens in blood samples. The test was evaluated using 761 field samples of known status (viraemic or not). When an appropriate cut-off value was chosen, the sensitivity, specificity, and predictive values of the assay were 100%, higher than the values obtained by classical virus isolation. Correlation with the latter technique exceeded 90%. The ELISA is a good candidate for replacing virus isolation as a reference method for BVDV antigen detection in persistently infected carriers. A method based on the mean of the standard deviation ratio can be used to choose the cut-off value in order to optimise reproducibility.