Molecular characterization of infectious bronchitis viruses isolated from broiler flocks in Bushehr province, Iran: 2014 - 2015

The aim of this study was to provide information on the molecular characteristic and the phylogenic relationship of infectious bronchitis viruses (IBV) strains in Bushehr province in comparison to other strains reported in the Middle East. Samples were collected from broiler flocks in Bushehr province during 2014 - 2015. These flocks had respiratory problems such as gasping, sneezing and bronchial rales. A number of 135 tracheal swabs were taken from fifteen flocks (nine swabs per flock). Each three swabs collected from each flock were pooled in one tube (finally, we had three tubes for each flock). The samples were subjected to reverse transcription polymerase chain reaction (RT-PCR). The PCR products of positive samples were analyzed by sequencing of a (392 bp) segment of the spike gene and the related results were compared with the other IBV sequences in GenBank database. Samples from twelve farms (80.0%) were found to be positive. The viruses from seven farms (46.6%) were identified as field viruses closely related to variant 2. The viruses from three farms (20.0%) were characterized as Mass type and were related to vaccine strains. Two different IB viruses (variant 2 and Mass) were detected in samples from two farms (13.3%). The variant 2 genotype detected in Bushehr had high similarity to variant 2 reported from the Middle East. These variants displayed homologies ranging from 72.9% to 76.5%, and 78.8% to 80.0% with H120 and 4/91, respectively. It is necessary to design vaccination program of poultry farms using IBV strains circulating in the region.