| Popis: |
Sera from 5325 chickens representing 71 commercial poultry flocks were tested for Mycoplasma synoviae (MS) using standard National Poultry Improvement Program (NPIP) testing guidelines. Based on the NPIP guidelines, only sera (N = 195) from flocks that test positive by specific plate agglutination (SPA) were submitted for additional confirmatory tests. Flocks from three multihouse farms were identified as seropositive for MS and confirmed by culture and polymerase chain reaction (PCR). Serum samples (N = 195) from these seropositive flocks were compared by SPA, enzyme-linked immunoassay (ELISA), and hemagglutination-inhibition (HI). Of the 195 sera tested for MS from these flocks, 145 (74%) sera were positive by SPA. Of the 145 SPA-positive sera, the HI test was positive for 127 samples (90.2%), whereas the ELISA was positive for 141 samples (98.6%). This difference between the two tests was significant (P = 0.0006). Significant differences (P = 0.0002) in titer were obtained from paired serum samples that were submitted to three different laboratories for HI analysis. Both the SPA and HI tests failed to detect early infection in newly introduced flocks following depopulation of MS-positive facilities. Both ELISA and PCR detected new infections on these farms. In the MS outbreak described in this study, SPA was not adequate as the sole screening test and HI was not adequate for confirmation of flock infection status. Continued reliance on the same or a similar type of testing could result in missed infections. Confirmation of infection by PCR was preferable to HI and also may be used in place of culture. The findings of this study suggest that ELISA should be considered as a serologic screen in lieu of SPA, screening with SPA may miss MS-infected flocks, and PCR should be considered as a confirmatory test. |
