COMPARISON BETWEEN VIRUS NEUTRALISATION TESTS AND AN INDIRECT ENZYME-LINKED IMMUNOSORBENT ASSAY FOR DETECTING ANTIBODIES TO RINDERPEST VIRUS IN CATTLE SERA

摘要

Sera from 1916 cattle were screened for antibodies to rinderpest virus using the microtitre virus neutralisation test (MVNT) and an indirect enzyme-linked immunosorbent assay (ELISA). Eleven sera (0.6%) could not be assayed in the MVNT due to contamination or non-specific cytotoxicity and another 177 (9%) required retesting in the MVNT due to difficulties in reading the initial screening results. Comparison of the 1905 fully testable sera showed agreement for 1414 (74,2%) and disagreement for 491 (25.8%) of the sera. One hundred and fourteen of the 491 sera with discrepant results were then assayed by the tube neutralisation test (VNT) and the results extrapolated to reinterpret the results of the original screen. Overall the MVNT was more sensitivebut less specific than the indirect ELISA for detecting antibodies to rinderpest virus. This study also showed that the MVNT was more sensitive but less specific than the ELISA when compared to the tu be neutralisation test. In contrast, pre-vaccinationsera from 44 cattle were free of rinderpest virus neutralising antibodies in seven of these sera. Three weeks after vaccination of 31 of these cattle the MVNT and VNT detected antibodies in all of the vaccinated cattle but the ELISA detected antibodiesin the sera of only 27. Following virulent challenge all of the 31 vaccinates survived while the 13 unvaccinated cattle died from clinical rinderpest. The indirect ELISA offers a practical alternative tothe MVNT for mass sero-monitoring of cattle populations with expected high antibody prevalences. However, neutralisation tests are more reliable when assaying small numbers of sera especially for detecting antibody negative animals.