Molecular Characterization and Phylogenetic Analysis of the S1 Gene of Infectious Bronchitis Virus (IBV) Isolates from Broiler Farms in Markazi Province, Iran

Ebrahimi, Saeideh; Vahidi, Vahide; Akbari, Neda; Jafari, Parvaneh

doi:10.22092/ari.2026.371023.3896

Molecular Characterization and Phylogenetic Analysis of the S1 Gene of Infectious Bronchitis Virus (IBV) Isolates from Broiler Farms in Markazi Province, Iran

Articles in Press

Document Type : Original Articles

Authors

¹ Central branch, Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Arak, Iran

² Department of Microbiology, Arak branch, Islamic Azad University, Arak, Iran

10.22092/ari.2026.371023.3896

Abstract

Infectious bronchitis (IB) is a contagious disease affecting chickens of any age and causes an extremely contagious disease that results in significant financial losses to the worldwide chicken industry. It affects both vaccinated and unvaccinated flocks globally. More information is needed about the recent IBV strains that have spread in Iran's Markazi province. Therefore, this study was designed to isolate IBV from broiler farms showing respiratory distress in Iran’s Markazi province and to analyze the evolutionary and molecular traits of the obtained isolates collected between 2017 and 2019. In this investigation, tracheal and lung tissues were obtained from 42 poultry farms where chickens showed respiratory distress. These samples were inoculated into 9–11-day-old embryonated eggs, resulting in virus isolation from 10 of the examined farms. Afterwards, RT-PCR was applied to amplify fragments of the S1 gene from the newly detected isolates, and the obtained amplicons were sequenced and phylogenetically compared with a reference dataset. As determined by phylogenetic analysis, in total, 10 of 42 (23.80%) samples were evaluated as positive for Bronchitis virus . All ten isolates were sent for sequencing but three of them were failed in sequencing (two time) and finally, seven isolates were sequenced correctly. six isolates were in the GI-23 genotype from seven sequenced samples, and one isolate was in the GI-1 genotype. Therefore, GI-23 is the dominant genotype of IBV circulating in chicken farms of Markazi province, which has a low degree of homology with the vaccines used in the country. Continuous monitoring of each region's circulating genotypes and compliance with health and biosecurity principles can be applied to reduce the complications of viral diseases involved in respiratory syndrome.

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