Protection Against Middle East Variant Infectious Bronchitis Viruses: Use Of Heterologous Live Vaccines In Commercial Broiler Chicks
F. Awad, R. Chhabra, A. Forrester, M. Baylis, S. Lemiere, Capua, H. Hussein and K. Ganapathy
lnfectious bronchitis (IBV) virus is an important and common cause of respiratory, renal and reproductive diseases in chicken. ln recent years, there has been increased detection of variant IBVs in the Middle East causing marked !osses mainly due to respiratory, reproductive and renal lesions. Important and frequently identified variant IBVs are those closely related to IS/494/06 and IS/885/00. This paper reports on the efficacy of current vaccination strategies against these variant IBVs. Commercial day-old chicks were sourced from a local hatchery. Chicks were divided into three groups. Group 1 maintained as unvaccinated control. The other two groups were vaccinated according to the following programmes, i) Group 2, given H 120 at day-old and CR88 at 14 days-old, ii) Group 3, given H 120 and CR88 at day-old and CR88 at 14 days-old. Chicks were observed for clinical signs thought out the experimental duration. At 21 days post vaccination, 10 chicks from each group were challenged with virulent strains of IS/885/00-Iike or IS/1494/06- Iike. No clinical signs were seen in the unvaccinated contrais but bath vaccinated groups showed mild respiratory signs following each vaccination. After the challenge, based on the ciliary scores at five days post challenge, the unvaccinated group were not protected. ln Group 2, the protection conferred were 60 % and 80 % against IS/885/00-Iike and IS/1494/06-Iike respectively. For the Group 3, the protection provided were 83% and 94% respectively against the virulent IBVs. Vaccination with H120 and CR88 at day-old and CR88 at day-14 provided the best protection against the virulent Middle East IBVs.
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