Molecular Studies on Infectious Bronchitis Virus Isolated from Broiler Chickens in Damietta Governorate, Egypt

Fifty-two samples of tracheal swabs and organs were collected from broiler chickens at different districts from Damietta Governorate during December 2012 to August 2014. The samples were collected from chicken farms suffered from respiratory signs, diarrhea and high mortality. Thirty-six samples tested positive for IBV infection when screened by real time quantitative polymerase chain reaction (RT-qPCR). Seven of them were subjected for further isolation and characterization of the virus. The seven selected IBV isolates were propagated in embryonated chicken eggs (ECE) and were confirmed using PCR amplification of the partial sequence of the S1 spike gene. The amplified products were sequenced and the phylogenetic analysis was performed. The seven IBV viruses were closely related to each other with 94-100% nucleotide identity and clustered within the same group with IBV/Eg/CLEVB-2/IBV/012 and Eg/12120s/2012 strains (variant 2-like strain), while their identity with the vaccinal strains used in Egypt was ranged from 67-91%, particularly D274 (89%-91%). These results indicated the complexity of IBV control in relation to the current vaccination programs in Damietta.