A European inter-laboratory trial to evaluate the reliability of serological diagnosis of bovine herpesvirus 1 infections.

The detection of cattle latently infected with bovine herpesvirus 1 (BHV1) is of importance in control programs and in international trade activities. Therefore, tests to detect specific antibodies in serum must be highly sensitive. To evaluate the reliability of serological diagnosis of BHV1 infections in Europe, seventeen laboratories in 15 European countries were asked to determine BHV1-specific antibodies in a panel of bovine serum samples using the serological tests available in their laboratory. Laboratory tests included virus neutralisation tests (1, 2 and 24 h), indirect immunofluorescence tests and ELISAs. The serum panel consisted of 12 duplicate lyophilised samples which were randomly coded from 1 to 24 and included negative, weak- and strong-positive samples as well as international reference sera. Virus neutralisation tests and ELISAs showed a high specificity. All participants using neutralisation tests (n = 13) scored the negative samples correctly. Twenty three of 25 ELISAs showed 100% specificity. A serum sample obtained at day 7 after infection was scored as negative by all tests except one home-made blocking ELISA. Samples obtained at day 9 and at day 11 after infection were scored as positive by approximately half and by all tests, respectively. To score the weak-positive European reference standard (EU2) correctly, 24 h neutralisation tests (positive by 8 of 9 laboratories) and home-made blocking ELISAs (positive by 5 of 6 laboratories) were the most reliable. The results indicate that standardisation is urgently needed to ensure that BHV1-infected animals with low antibody titres are recognised.