Molecular characterization and recombination analysis of <i>Gyrovirus homsa2</i> in chickens

<i>Gyrovirus homsa2</i> (GyVh2), originally identified in Tunisian children with diarrhoea, was previously known as Gyrovirus 6. In this study, chickens from 36 poultry farms across four major poultry-producing provinces in China (Henan, Hubei, Anhui, and Jiangsu) were screened for GyVh2 using polymerase chain reaction (PCR) from 2022-2024. As a result, 12 farms positive for GyVh2 were detected and subsequently subjected to whole-genome sequencing for GyVh2. The genomes of the 12 GyVh2 from positive farms were all 2282 nucleotides (nt) in length. Sequence similarity analysis showed high similarity (94.87%-99.65%) among the obtained and reference GyVh2 strains with no significant determining effect of years or geographic distribution, but low similarity (48.99%-57.60%) with other Gyrovirus species (<i>Gyrovirus chickenanemia</i>, <i>Gyrovirus galga1</i>, <i>Gyrovirus galga2</i> and <i>Gyrovirus homsa1</i>). Phylogenetic analysis of the whole genome sequences of all 12 GyVh2-positive farms revealed that they formed a unique branch, clearly separated from other Gyrovirus species. Recombination analysis suggested that HN220604 (accession no.: PQ519595.1) and HN221228 (accession no.: PQ519596.1) may have originated from recombination with the human-derived GyVh2 strain (accession no.: NC_022789.1). A hypervariable region (located at sites 140-152) and highly mutated sites at positions 149, 254 and 380 were identified in the capsid protein through amino acid mutation analysis. The observed association between GyVh2 cross-species transmission and complex mutations and recombination offers a basis for future studies on its molecular epidemiology and evolution.