Aichivirus C isolate is a diarrhoea-causing pathogen in goats

Aichivirus C is an emerging virus in goats, but its biological significance remains unknown. In this study, 18 diarrheic and 16 non-diarrheic faecal samples of kids were collected from a farm with an on-going diarrheic outbreak in Sichuan Province, China in May 2021. Of these samples, 77.8% (14/18) of diarrheic samples were detected as Aichivirus C positive by RT-PCR, which was significantly higher than that of non-diarrheic faces (0%, p < .001); meanwhile, other common diarrhoea-causing pathogens in goats were not detected in diarrheic samples, except for two samples that were detected as caprine enterovirus positive, suggesting that Aichivirus C was associated with goat diarrhoea. Furthermore, five Aichivirus C strains were successfully isolated from positive samples using Vero cell lines and two isolates were further plaque-purified, named SWUN/F5/2021(10^-6.7 TCID₅₀ /0.1 mL) and SWUN/F6/2021(10^-7 TCID₅₀ /0.1 mL). Interestingly, Aichivirus C strain could cause systemic infection in experimental kids via oral administration, with the main clinical manifestation being severe watery diarrhoea. Histopathological changes observed in the duodenum and jejunum were characteristic, with shedding of mucosal epithelial cells. In addition, the virus was detected in tissues of diarrhoea kids naturally infected with Aichivirus C, exhibiting pathological changes similar to those of experimental infections. Overall, this study first isolated Aichivirus C and confirmed its pathogenicity in kids, with further study needed to better understand the virus pathogenicity. As Aichivirus C has been detected in South Korea, Italy and the USA and widely prevalent in southwest China, the results obtained here have significant implications for the diagnosis and control of diarrhoea in goats.