Pathogenicity, infective dose and altered gut microbiota in piglets infected with porcine deltacoronavirus

Porcine deltacoronavirus (PDCoV) is an emerging swine enteropathogenic coronavirus that cause severe diarrhea, resulting in high mortality in neonatal piglets. Little is known regarding the pathogenicity of PDCoV in different infective dose and the dynamic changes in the composition of the gut microbiota in PDCoV-induced diarrhea piglets. In this study, 5-day-old piglets were experimentally infected with different dose of PDCoV. The challenged piglets developed typical symptoms, characterized by acute and severe watery diarrhea from 1 to 8 days post-inoculation (DPI), and viral shedding was detected in rectal swab until 11 DPI. Tissues of small intestines displayed significant macroscopic and microscopic lesions with clear viral antigen expression. However, no significant differences among groups were found in challenged piglets. Then alteration in gut microbiota in the jejunum and colon of PDCoV infected-piglets were analyzed using 16S rRNA sequencing. PDCoV infection reduced bacterial diversity and richness, and significantly altered the structure and abundance of the microbiota from the phylum to genus. Fusobacterium, and Proteobacteria was significantly increased (P < 0.05), while the abundance of Bacteroidota was markedly decreased in the infected-piglets. Furthermore, microbial function prediction indicated that the changes in intestinal bacterial also affected the immune system, excretory system, circulatory system, neurodegenerative disease, cardiovascular disease, xenobiotics biodegradation and metabolism, etc. These findings suggest that regulating gut microbiota community may be an effective approach for preventing PDCoV infection.