Genetic diversity and pathogenicity of goose astrovirus genotype 2 in geese, ducks and chickens

Goose astrovirus genotype 2 (GAstV-2), a member of the Avastrovirus (AAstV) genus, is an important emerging pathogen closely associated with gosling gout that has caused enormous economic losses to the goose industry since it was first reported in 2015 in China. However, public GAstV-2 sequencing data remain scarce (with only 278 records to date), and its genetic evolution, pathogenic features, and cross-species transmission potential have not been fully elucidated. To address this gap, we isolated 12 GAstV-2 strains from clinical samples of gout-affected goslings in Shandong and Guangdong Provinces (2021-2024) and successfully sequenced their complete genomes. Bayesian time-resolved phylogenetic analyses revealed that GAstV-2 has evolved into two distinct lineages, with our 12 isolates distributed in both lineages (nine viruses clustered in Lineage 1 and three viruses clustered in Lineage 2). Animal infection experiments demonstrated that all the strains replicated efficiently in goslings, causing renal hyperemia and swelling and mild urate deposition in the ureter, with two strains causing 20% mortality. Significantly, histopathological lesions and viral antigens were detected in the heart, liver, and kidney of the inoculated geese. Notably, GAstV-2 could infect and replicate in both ducks and chickens without prior adaptation, resulting in histopathological lesions to the heart, liver and kidney of the birds. These findings enrich our understanding of the GAstV-2 prevalence, clarify the evolutionary dynamics of this virus, and highlight its role as cross-species infection potential, providing a critical basis for targeted surveillance and control strategies.