Epidemiology, molecular identification, and phylogenetic analysis of infectious bronchitis virus in free-range village chickens in Adana province

Avian infectious bronchitis (IB) is a highly contagious disease caused by the infectious bronchitis virus (IBV), leading to significant economic losses in the poultry industry. This study investigated the circulation of IBV among village chicken flocks in the Adana province of Türkiye. A total of 390 tracheal and cecal swab samples were collected from twelve districts of Adana and pooled into 65 sample groups, which were subsequently tested using RT-PCR. Overall, 15 samples (23.07%) were found to be positive for IBV. The highest prevalence was detected in the districts of Yumurtalık, Karataş, and Pozantı, while some districts tested entirely negative. Fifteen positive field isolates were sequenced and deposited in the GenBank database (accession numbers PP970560.1–PP970574.1). Phylogenetic and BLAST analyses of the partial S1 gene region revealed the coexistence of strains showing high nucleotide similarity (>95%) within distinct clusters, including lineages with low similarity to the Israel-like strain IS/1494/06 but high BLAST scores with other isolates. These results confirm the simultaneous presence of multiple IBV genotypes among free-ranging chicken flocks in Adana. The findings emphasize the importance and necessity of regular molecular surveillance and characterization studies to monitor the emergence of novel or vaccine-escape IBV variants circulating in the field. Keywords: Avian Infectious bronchitis virus, IBV, Molecular epidemiology, RT-PCR, Sanger sequencing, BLAST analysis, Phylogenetic analysis