Isolation and characterization of goose astrovirus genotype 1 causing enteritis in goslings from Sichuan Province, China

Since 2017, goose astrovirus (GoAstV) has been widely prevalent in various provinces of China, causing economic losses in the goose industry, with outbreak mortality rates ranging from 10 to 60%. Notably, a goose farm in Sichuan Province has faced an outbreak of infectious disease in 1-3 weeks old goslings, with a mortality rate of approximately 30%. Viral metagenomic analysis of fecal samples identified Goose astrovirus genotype 1 (GoAstV-1), and PCR analysis confirmed the presence of GoAstV-1. Furthermore, we successfully isolated a GoAstV-C1 strain using goose embryos named AAstV/Goose/CHN/2023/C1 (GenBank No. PP108251), and its viral titer was calculated as 10^4.834 ELD₅₀/0.5 mL using the Reed-Muench method. The genome size of GoAstV-C1 was about 7,261 nucleotides through amplifying with Sanger sequencing and assembling with SeqMan software. Phylogenetic analysis revealed that GoAstV-1 strains are classified into three major subtypes: A, B, and C, with the GoAstV-C1 strain identified as a unique variant within subtype B, characterized by distinct genetic divergence features. Experimental inoculation of one-day-old goslings with the virus resulted in a mortality rate of 5 out of 15 (p-value = 0.0421) and a significant reduction in weight gain compared to controls (p-value = 0.005). Pathological examination revealed that GoAstV-C1 infection caused severe damage to the liver, spleen, and kidneys. Interestingly, unlike most GoAstV, which leads to characteristic gout symptoms, our isolates GoAstV-C1 caused obvious intestinal damage characterized by necrosis, inflammatory infiltration, and crypt architectural disruption. We indicated that GoAstV-C1 displays a unique intestinal tropism rather than characteristic gout symptoms and elucidated genomic features and evolutionary relationships of GoAstV strains. These findings help advance our knowledge of the epidemiology and pathogenicity of GoAstV-1, and the predicted structure of capsid protein could serve as a potential target for designing novel antiviral drugs or vaccines against GoAstV-1.