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 enzyme-linked immunosorbent assay (ELISA) for detection of antibody to Mycoplasma gallisepticum (MG) compared for use as confirmatory tests for the National Poultry Improvement Plan program. Samples from three different poultry populations with different prevalences of MG infection were studied: commercial broiler breeder birds (low prevalence of infection), fair and exhibition birds (moderate prevalence of infection), and experimentally infected birds (high prevalence of infection). Western immunoblots were used to confirm infection status in samples that had discrepancies between HI and ELISA results. The prevalence of infection in commercial broiler birds and in exhibition and fair birds in Florida was determined. Samples from culture-positive Mycoplasma synoviae (MS) flocks also were tested and compared for potential cross-reactions. The prevalence of MG infection was very low (< 1%) in the commercial population, with no significant difference between the HI and ELISA test results (P = 0.3157). The prevalence of MG infection in the fair and exhibition birds tested was approximately 40%, and ELISA was more accurate than HI for confirmation of MG infection in this population (P = 0.036). In birds experimentally infected with MG, there was no significant difference between HI and ELISA results (P = 0.6542). Of the 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 differences between ELISA and HI as confirmatory tests in populations with a low prevalence of MG infection. However, ELISA was superior to HI in a population with moderate levels of MG infection.