The first isolation, identification and pathogenicity of a goose-origin duck astrovirus type 3 strain

To investigate the molecular epidemiological characteristics and pathogenicity of waterfowl astroviruses, tissue samples were collected from geese exhibiting suspected Duck astrovirus type 3 (DAstV-3) infection on a goose farm in Shandong Province of China. These samples underwent real-time RT-PCR detection, followed by virus isolation, whole-genome sequencing, phylogenetic analysis, and pathogenicity challenge experiments. This study was the first to isolate a goose-origin DAstV-3 strain (DAstV-3/goose/shandong/2023/SD455), with a complete genome of 7,363 bp. Sequence analysis revealed that the strain was closest to domestically circulating DAstV-3 strains with 96.2-99.9% nucleotide identities. High variability in amino acid residues was predominantly observed in ORF1b (encoding RNA-dependent RNA polymerase) and ORF2 (encoding capsid protein) regions. Phylogenetic analysis clustered this strain within the DAstV-3 clade, forming a distinct sub-branch with the duck-origin reference strain Q3001 (bootstrap value = 92%). The pathogenicity tests conducted on 7-day-old goslings and ducklings demonstrated that the isolated strain caused similar clinical symptoms, followed by recovery. Histopathological examination revealed lesions in the lungs, liver, spleen, and kidneys, characterized by inflammation cell infiltration and parenchymal degeneration. The results of the epidemiological investigation showed that 88 DAstV-3 samples were detected from 13 provinces of the 15 provinces surveyed, and the positive rate of DAstV-3 was 6.51%. Among them, the positive rate of DAstV-3 in geese (5.15%) was slightly lower than that in ducks (7.14%). This study elucidated the cross-host transmission potential of goose-derived DAstV-3 among waterfowl and provided critical insights for viral surveillance and control strategies.