Genetic and structural factors contributing to the dominance and persistence of goose astrovirus type 2

Goose astrovirus (GoAstV) has emerged as a significant pathogen affecting the goose industry in China, with GoAstV-2 becoming the dominant genotype since 2017. This study explored the genetic and structural factors underlying the prevalence of GoAstV-2, focusing on codon usage bias, spike protein variability, and structural stability. Phylogenetic and effective population size analyses revealed that GoAstV-2 underwent rapid expansion between 2017 and 2018, followed by population stabilization. Codon usage analysis indicated that GoAstV-2 exhibited a weaker codon usage bias compared to GoAstV-1, suggesting greater flexibility in synonymous codon usage and potentially enhanced adaptability across host environments. Additionally, the lower codon adaptation index values of GoAstV-2 point to a divergence from the host’s optimal codon usage, which may reduce competition with host tRNA pools and facilitate viral replication. The spike protein of GoAstV-2 demonstrated significantly lower variability than GoAstV-1, as shown by Shannon entropy analysis, indicating greater structural stability. This stability may reduce the need for frequent mutations, allowing GoAstV-2 to persist in host populations without undergoing constant evolution. The lower antigenic variability likely decreases immune-driven selective pressure, contributing to the sustained viral transmission and long-term persistence. These findings provide new insights into the evolutionary advantages of GoAstV-2 and its epidemiological success, which could inform future control strategies aimed at mitigating its impact on poultry populations. Goose astrovirus type 2 (GoAstV-2) became the dominant strain in China post-2017.GoAstV-2 exhibits weaker codon usage bias, enhancing adaptability across hosts.The stability of GoAstV-2 spike protein reduces mutation needs and selective pressure.GoAstV-2 low spike protein variability supports long-term persistence in host populations. Goose astrovirus type 2 (GoAstV-2) became the dominant strain in China post-2017. GoAstV-2 exhibits weaker codon usage bias, enhancing adaptability across hosts. The stability of GoAstV-2 spike protein reduces mutation needs and selective pressure. GoAstV-2 low spike protein variability supports long-term persistence in host populations.