Abstract
Avian infectious bronchitis virus (IBV) is an evolving and dynamic virus that causes major economic losses for the poultry industry worldwide. Continuous evolution and emergence of new variants of this virus are the major challenges for controlling the disease with routine vaccination. Successful vaccination usually requires the use of a homologous vaccine, which in turn necessitates continuous investigation of the circulating strains. Herein, we performed a reverse transcriptase-polymerase chain reaction- (RT-PCR-) based investigation in broiler chicken flocks of the Eastern Region of Saudi Arabia. IBV was detected in 36.5% of the tested flocks (42 out of 115) from January 2012 to March 2014. Direct sequencing of hypervariable region-3 (HVR-3) of the Spike (S)-1 gene was performed, followed by phylogenetic analysis to determine the circulating IBV genotypes. Four lineages appear to coexist in this region, including the GI-13 or 4/91 IBV (31%), GI-16 or CK/CH/LDL/97I IBV (28.6%), GI-1 or Mass IBV (19%), and GI-23 or Middle East IBV (21.4%). The latter lineage include two subgroups: IS/720/99 IBV (16.7%) and IS/Variant2/98 IBV (4.7%). Some of the detections made in the 4/91 and Mass lineages are expected to belong to the vaccine strains. Lineages without a homologous vaccine in use (CK/CH/LDL/97I and Middle East) represent 50% of the isolates recovered in this study. Based on identity with the vaccine sequences, field observations, and frequent detection, these two lineages appear to be out of coverage of the IBV vaccines used in Saudi Arabia. This is the first time to identify Middle East lineage (IS/720/99 IBV and IS/Variant2/98 IBV) in the Eastern Region of Saudi Arabia.