Characterisation of natural co-infection with Goose astrovirus genotypes I and II in gout affected goslings

In recent years, goose astrovirus (GoAstV) has emerged as the primary pathogen responsible for gout in goslings aged 1–20 days. This study presents a case of natural co-infection with GoAstV genotypes I and II in goslings afflicted with gout at 12 days of age. A post-mortem examination revealed the presence of urate deposits in the internal organs and within the coxofemoral joints. Histopathological analysis revealed congestion, haemorrhage, parenchymal cell necrosis, lymphocytic infiltration in the liver and kidney, and urate tophi in the kidneys, liver, spleen, and lungs. Reverse transcription polymerase chain reaction (RT-PCR) and sequencing were performed to identify GoAstV-I and II open reading frame (ORF) 2 genes in the liver and kidney tissues, respectively. Immunofluorescence staining confirmed the co-expression of GoAstV-I and II antigens in the kidney. A homogenate from pooled liver and kidney tissues was inoculated with Leghorn male hepatoma cells and passaged five times. The RT-PCR and immunofluorescence assay verified the successful isolation of GoAstV-II, whereas GoAstV-I could not be isolated. Sequence analysis demonstrated that both GoAstV-I (7255 nt) and GoAstV-II (7116 nt) exhibited typical structural arrangements and a series of conserved regions in astroviruses. Phylogenetic analysis revealed that the amino acid sequence of the full-length ORF2 between GoAstV-I and GoAstV-II had 42.5% homology, indicating that these genes should be classified as different GoAstV genotypes. These findings contribute to our understanding of GoAstV characterisation and provide a basis for the development of strategies to control these viruses.