First Isolation and Characterization of Three Strains of Porcine Sapelovirus in Yunnan Province, China

In order to investigate the causes of swine diarrhea in Yunnan Province, this study was conducted to detect and monitor diarrhea viruses through regular sampling and reverse transcription polymerase chain reaction (RT-PCR). In October 2023, porcine sapelovirus (PSV) was detected in fecal specimens collected from diarrheal pigs in Honghe City, and three strains of PSV were successfully isolated by inoculating them into PK-15 cells; electron microscopy revealed virus particles with diameters of ~32 nm. Next-generation sequencing (NGS) revealed that the PSV isolate genomes ranged from 7480 to 7515 nucleotides in length. Homology analyses indicated that ML-15 and ML-16 showed the highest nucleotide and amino acid identities with the Asian PSV strains, ML-19 showed the highest sequence identities with the Zambia PSV strains, and the VP1 to VP4 genes of the three PSV isolates were in the hypervariable region. Phylogenetic analyses showed that the three PSVs isolated in this study all clustered together with Chinese PSV strains; furthermore, recombination analyses indicated that PSV-ML-19 might be a recombined strain and may have emerged through genetic recombination between the major putative parent strain PSV-21-V and the minor putative parent GER L00798-K11 14-02. This was the first reported instance of the isolation and phylogenetic analyses of the PSV strains in Yunnan Province, which enriched the understanding of Chinese PSV strains and indicated the need to prevent and control PSV; the mutation of the VP1 and 3D genes may also provide an important reference for the development of PSV vaccines.