Evaluation of an indirect enzyme-linked immunosorbent assay to study the specific humoral immune response of Muscovy ducks (Cairina moschata) and domestic geese (Anser anser var. domestica) after vaccination against Newcastle disease virus.

In this study, an indirect Newcastle disease virus enzyme-linked immunosorbent assay (ELISA) for waterfowl was evaluated concerning its efficiency and its suitability to monitor the antibody response in Muscovy ducks (Cairina moschata) and domestic geese (Anser anser var. domestica) following vaccination with a commercial inactivated NDV vaccine for chickens. Three weeks after vaccination seroconversion was already evident in the ELISA. Comparison of the ELISA results with those of the haemagglutination inhibition (HI) test provided a positive linear correlation between both tests (Pearson's product-moment correlation; r=0.652; P<0.001). However, a discrepancy of test results was evident in weeks 7 and 10, with 10 sera of vaccinated birds evaluated negative by HI test but positive by ELISA. Eight of these sera were confirmed to yield avian paramyxovirus specific reactivity by western blot analysis. Relative diagnostic sensitivity and specificity were determined to be 100.0% and 91.7% for the ELISA, compared with 91.1% and 97.2% for the HI test. Thus, the established ELISA represents a suitable alternative to the HI test in the monitoring of the immune response of waterfowl after vaccination, particularly for the analysis of high sample numbers. Further on, the results emphasize the immunogenicity of the inactivated Newcastle disease virus vaccine in domestic geese and Muscovy ducks.