Abstract: Porcine epidemic diarrhea (PED) is an acute contact intestinal infectious disease in pigs caused by the porcine epidemic diarrhea virus (PEDV). In this study, a PEDV strain was isolated and named PEDV-20200946. S protein gene was sequenced and analyzed, and the phylogenetic tree showed that the isolated strain belonged to G2 genotype. The virus titer of this strain was 106.1TCID50/mL determined by Reed-Muench method. Subsequently, the pathogenicity of the isolated strains on piglets was further explored through animal challenge. A total of twelve 20-day-old piglets were divided into three groups on average, and they were named oral group, oral and intramuscular injection group, and control group, respectively. After the viral infection, clinical symptoms were observed, and the feces of each group and the intestines of the affected pigs were collected 72 h later for RT-PCR detection and immunohistochemical analysis. The results showed that piglets in the oral and intramuscular injection group showed the fastest diarrhea occurrence, followed by the oral group, and the control did not have any clinical symptoms. Autopsy examination showed that the intestinal walls of diseased piglets got thinned, their intestines were swollen, and contained a large amount of yellow liquid. Immunohistochemical tests showed that a large number of PEDV positive signals could be detected in the small intestine of piglets in the challenge groups, while the control group showed normal. The piglet challenge model of PEDV-20200946 strain was established, which laid a foundation for in-depth study of the molecular characteristics of PEDV epidemic strains and the development of attenuated vaccines.

Key words: porcine epidemic diarrhea virus, epidemic strain, isolation and identification, challenge model, phylogenetic tree