The protection of the commercially available vaccines was evaluated against two Egyptian variant IBV isolates that was found to be related to IS/885 variant II strain by 86% and 84% respectively in commercial broiler chickens. The protection assessment was detected by clinical signs, gross lesions, detection of viral shedding in tracheal and cloacal swabs, estimation of kidney function tests (Creatinine and Uric acid), detection of specific IBV antibody titer and histopathological examination. No significant protection could be provided against both challenging viruses using the classical live H120, Ma5 vaccines at day 1 and 14 of age respectively. Also no significant protection could be provided using 2 different inactivated vaccines at day 5 of age. The results indicated that the used vaccine strains and the challenging IBV field isolates are not the same protecteotype, therefore, change in the program of field vaccination is required to obtain a relative improvement of protection.
Bronchitis Virus, Broiler, Protection.