Isolation, identification and phylogenetic analysis of a novel goose astrovirus 2 strain.

An outbreak of acute nephritis and growth retardation occurred on a goose farm in Jiangsu Province, China, in 2025. Affected goslings exhibited typical symptoms of gout, and RT-PCR confirmed infection with goose astrovirus 2 (GAstV-2) alone. A novel strain, designated JSYC2503, was isolated from liver tissue using Leghorn male hepatoma (LMH) cells. This strain induced clear cytopathic effects within 72 h and remained stable after 20 serial blind passages. The complete genome of JSYC2503 consisted of 7,180 nucleotides and displayed the typical astrovirus genome organization, including a conserved ribosomal frameshift signal and a stem-loop II-like motif (s2m) in the 3'-UTR. Phylogenetic analysis placed JSYC2503 within the GAstV-2 clade, showing the highest sequence identity to the Chinese GAstV-2 strain JXNC1 (99.6% at the whole-genome level) but much lower identity (29.9%-47.1%) to other avian astroviruses. In an experimental infection study, 3-day-old goslings inoculated intraperitoneally with JSYC2503 developed clinical signs, showed 50% mortality by day 6, and exhibited pathological changes including splenomegaly, bursal atrophy, and urate deposition in the kidneys. Viral shedding was continuously detected in cloacal swabs. These results indicate that JSYC2503 is a highly pathogenic GAstV-2 strain that may pose a substantial threat to goose health, and its genomic characterization provides insight into the evolution and pathogenesis of goose astroviruses.