Emergence of Canine Parvovirus Type 2a and Canine Enteric Coronavirus in Diarrheal Outbreaks Among Farmed Raccoon Dogs in China

Abstract

Canine parvovirus (CPV) and canine enteric coronavirus (CCoV) are primary viral pathogens responsible for causing diarrhea in carnivores. CCoV infection generally induces mild enteritis, whereas infections solely by CPV or coinfections involving both CPV and CCoV frequently result in severe diarrhea and can lead to fatal outcomes in affected animals. This study investigated CPV and CCoV infections in raccoon dogs farmed in China between 2018 and 2023. Among the 133 small intestine tissue samples from raccoon dogs with severe diarrhea, 107 of 133 (80.5%) were CPV nucleic acid positive, involving CPV-2 and CPV-2a subtypes. The CPV-2 amplicons maintained I418T, S927A, and T27S. Moreover, the CPV-2a subtype amplicons possessed G300S, N562V, and Y573F mutations compared to dog-ori CPV-2a. Moreover, 30 of the 133 (22.6%) samples were positive for CCoV, containing the CCoV-IIa and CCoV-IIb subtypes. Of these, 25 of 30 (83.3%) samples were coinfected with CPV and CCoV. In CCoV infection alone, mild inflammatory infiltration was observed in the lamina propria of the small intestine. Immunohistochemical staining revealed that CCoV antigens were mainly detected in the crypts of the small intestine. Furthermore, coronavirus-like particles were observed in small intestine samples. Next, we analyzed the detailed binding model for raccoon dog-origin (RD-ori) CCoV-IIa with host aminopeptidase N (APN). The receptor-binding domain (RBD) of RD-ori CCoV-IIa showed robust binding to raccoon dog APN but not to human APN. Our results demonstrated that CPV-2a and CCoV are emerging in farmed raccoon dogs in northern China. Further investigations should be performed to monitor the potential evolution and recombination events of RD-ori CPV and CCoVs.