Molecular epidemiology and genetic diversity of infectious bronchitis virus in Iranian poultry: A systematic review

Infectious bronchitis virus (IBV) is a highly contagious avian coronavirus that causes substantial economic losses in poultry production due to respiratory disease, reduced performance, and impaired egg production. In Iran, IBV has been repeatedly reported over the past two decades; however, evidence on diagnostic approaches and circulating lineages remains fragmented. This systematic review aimed to summarize the available Iranian literature on the molecular epidemiology and genetic diversity of IBV in poultry. We conducted a comprehensive search for relevant papers that reported the identification or molecular characterization of infectious bronchitis virus in Iranian poultry using key scientific databases and associated resources. We included 32 studies published between 2003 and 2022. Most investigations were conducted in broiler flocks, and most studies used molecular diagnostic methods, with RT-PCR being the most frequently reported approach, followed by real-time RT-PCR and nested RT-PCR; ELISA was used in a limited number of studies. Diverse circulating lineages were reported; GI-1 (Massachusetts-type), GI-13 (793/B-type), GI-19 (QX-like), and GI-23 (Variant-2/IS-1494/06-like) strains were often documented, suggesting co-circulation of many lineages in Iranian poultry populations. Genotype reporting was inconsistent across studies, and several investigations lacked complete molecular characterization. Additionally, quantitative synthesis of prevalence estimates could not be performed because the extracted dataset did not consistently report denominators (sample size) and numbers of positive samples. Overall, the evidence suggests sustained circulation of genetically diverse IBV lineages in Iran, supporting the need for continuous molecular surveillance, harmonized reporting, and vaccination strategies aligned with locally circulating strains to improve control of infectious bronchitis in Iranian poultry.