COMPARISON OF ENZYME-LINKED-IMMUNOSORBENT-ASSAY AND HEMAGGLUTINATION-INHIBITION FOR DETECTION OF ANTIBODY TO MYCOPLASMA-GALLISEPTICUM IN COMMERCIAL BROILER, FAIR AND EXHIBITION, AND EXPERIMENTALLY INFECTED BIRDS

Hemagglutination-inhibition (HI) assay and a new affinity-purified enz yme-linked immunosorbent assay (ELISA) for detection of antibody to My coplasma gallisepticum (MG) compared for use as confirmatory tests for the National Poultry Improvement Plan program. Samples from three dif ferent poultry populations with different prevalences of MG infection were studied: commercial broiler breeder birds (low prevalence of infe ction), fair and exhibition birds (moderate prevalence of infection), and experimentally infected birds (high prevalence of infection). West ern immunoblots were used to confirm infection status in samples that had discrepancies between HI and ELISA results. The prevalence of infe ction in commercial broiler birds and in exhibition and fair birds in Florida was determined. Samples from culture-positive Mycoplasma synov iae (MS) flocks also were tested and compared for potential cross-reac tions. The prevalence of MG infection was very low (<1%) in the commer cial population, with no significant difference between the HI and ELI SA test results (P = 0.3157). The prevalence of MG infection in the fa ir and exhibition birds rested was approximately 40%, and ELISA was mo re accurate than HI for confirmation of MG infection in this populatio n (P = 0.036). In birds experimentally infected with MG, there was no significant difference between HI and ELISA results (P = 0.6542). Of t he 195 sera collected from flocks confirmed positive for MS by culture , 15% cross-reacted with the MG serum plate agglutination (SPA) test. There were no cross-reactions observed with either the MG ELISA or HI. There was a positive correlation of HI titers to ELISA values (R = 0. 621, P < 0.01). Results from this study showed there were no differenc es between ELISA and HI as confirmatory tests in populations with a lo w prevalence of MG infection. However, ELISA was superior to HI in a p opulation with moderate levels of MG infection.