Molecular characterization of infectious bronchitis viruses isolated from broiler and layer chicken farms in Egypt...

One of the major problems of avian infectious bronchitis virus (IBV) is the frequent emergence of new variants. In the present study 205 tracheal swabs and organs were collected from broilers and layers chicken farms during January to August 2012 from 19 governorates all over Egypt. The chickens demonstrated respiratory signs and mortality. Out of the examined samples, 130 of which (about 64%) of suspected farms were positive for IBV with real time RT-PCR. 13 IBV-positive samples were selected for further isolation and characterization. Isolation in specific pathogen free (SPF) embryos was carried out after studies three blind successive passages and the hypervariable region of spike protein1 (SP1) was amplified by RT-PCR and sequenced to study the genetic diversity between the isolated viruses. Phylogenetic analysis of the obtained sequences of 13 isolates compared with other IBV strains from the Middle East and worldwide reveled that 11 out of the 13 isolates had close relationship the Israeli variants (IS/885 and IS/1494/06) with nucleotide homology reached up to 89.9% and 82.3%, respectively. Only two isolates had close relationship with CR/88121 and 4/91 viruses with identities of 95% and 96%, respectively. This study indicates existence of two variant groups of IBV circulating in Egypt during 2012. Group I was similar but distinguishable from Israeli variant IS/885 and group II was related to 4/91 and CR/88121 vaccine strains. There was no geographical link between the 2 groups as they were distributed all over the country. These findings necessitate the need to revise the vaccination programs and control measures for IBV.