Genomic insight of avian reovirus circulating among desi-chickens in Tamil Nadu, South India.

Avian reovirus (ARV) is a major causative agent of viral arthritis (VA), tenosynovitis, and malabsorption syndrome (MAS) in chickens, with significant economic consequences due to growth retardation, reduced production performance, and immunosuppression. Despite routine vaccination of breeder chickens against ARV, cases of VA and MAS continue to be reported in commercial flocks in recent years. Moreover, there is a lack of recent data on the genetic characteristics of circulating field ARV strains in India. In light of these concerns, a study was conducted to investigate the involvement of ARV in chickens exhibiting clinical signs suggestive of VA or MAS. Samples were collected from 27 commercial broiler and desi-chicken flocks across the mid-western region of Tamil Nadu, South India. Molecular confirmation was performed using reverse transcription polymerase chain reaction (RT-PCR) targeting a partial region of the σC gene within the S1 segment. Of the 27 flocks sampled, only two samples - both from desi-chickens aged two and three weeks - tested positive for ARV. Sequence analysis of these positive samples, compared against available ARV sequences in GenBank (including vaccine strains) revealed that the identified strains clustered within ARV genogroup II. This represents the first report of cluster II ARV in India, indicating the circulation of genetically distinct ARV strains in Indian poultry populations. These findings underscore the need for routine molecular surveillance of ARV genotypes in India and highlight the potential mismatch between circulating field strains and current vaccine strains. Comprehensive genotype monitoring is essential to upgrade vaccine design and implement effective control strategies for ARV-associated diseases in Indian poultry production.