Abstract:
To evaluate of efficacy of vaccination program of Infectious Bronchitis (IB) virus in broilers against THA80151 and THA90151 isolated in Thailand. The experimental groups were divided into 6 groups. Group 1 was administered by Poulvac IB QX like at 1 day old. Group 2 was administered by Poulvac IB QX like at 1 and 14 days old. Group 3 was administered by Nobilis IB H120 and Poulvac IB QX like at 1 and 14 days, respectively. Group 4 was administered by Nobilis IB H120 and Nobilis IB 4-91 at 1 and 14 days, respectively. Group 5 served as a positive control group. Group 6 served as a negative control group. First experiment (5 groups), all groups were challenged by IBV THA80151 at a concentration 105.62 ELD50/0.1 ml. at 28 day-old. Second experiment (6 groups), groups 1-5 were challenged by IBV THA90151 at a concentration 105.78 ELD50/0.1 ml. at 28 day-old. Group 6 served as a negative control group. The tracheal rales, mortality rate, body weight, ciliostasis, histopathological lesions, immunological responses and virus isolations were monitored. All groups demonstrated the protection to damage after challenged with live IB QX-like virus. The vaccines could decrease the tracheal rales, ciliarry activity and histological lesion scores in the vaccinated groups compared to the positive control group. Anyhow, the vaccination programs could not prevent the infection because IB QX like virus was still be re-isolated from some infected organs. The booster vaccine with the heterologous strain could increase the cross protection of IBV THA80151 and THA90151.