Surveillance of Mycoplasma synoviae Infection in Mixed Thai Native Chickens in the Area of Nakornpathom Province

This study was to conduct a surveillance of Mycoplasma synoviae (MS) infection in mixed Thai native chickens. Samples were submitted from 30 mixed Thai native chicken flocks, 15 birds per flock, aged between 1-4.5 months in the area of Nakornpathom province in the September 2005-October 2006 period. Each bird was bled for MS serology by serum plate agglutination (SPA) and enzyme linked immunosorbent assay (ELISA) test kits and swabbed for MS antigen detection by polymerase chain reaction (PCR) technique. Results revealed that the positive reactors detected by the SPA test, ELISA and PCR procedure were 12, 9 and 8 flocks, respectively. There were 4 flocks that were detected to have positive reactors in all tests. The percentage of positive results depending on age: 1 month, 1-2 months, 2-3 months and 3-4.5 months tested by SPA, ELISA and PCR was 0-60%, 0-60% and 0-50%, respectively. This study found that the older the flock the higher the number of positive reactors found. MS DNA was determined in birds older than 2 months. Even so, clinical signs were not observed in the MS infected flocks in practical field.