Comparison of RT-PCR assay and virus isolation in cell cultures for the detection of bovine viral diarrhoea virus (BVDV) in field samples.

The virus isolation-immunoperoxidase test (IPX) on cell cultures and the reverse transcription-polymerase chain reaction (RT-PCR) assay were compared for the detection of bovine viral diarrhoea virus (BVDV) directly in serum samples. Material for this study consisted of 403 sera originating from cattle in 41 BVDV-infected Finnish dairy herds and one suckler cow herd. The presence of virus was demonstrated in 48 samples by both assays. In addition, two more samples were found to be positive by the RT-PCR assay. Both methods proved to be extremely sensitive, detecting pestiviruses even in high serum dilutions, and thus to be suitable for demonstrating the occurrence of persistently infected (PI) cattle. In conclusion, the RT-PCR method used had the advantage of ascertaining BVDV nucleic acid sequences in samples in which the virus had been inactivated, eg during transport or due to the presence of neutralising antibodies.