Isolation, Identification and Genetic Evolution Analysis of Porcine Epidemic Diarrhea Virus SNJ-P Strain in Sichuan Province

PurposeTo investigate the epidemic variation of porcine epidemic diarrhea virus (PEDV) strains in Sichuan Province, and to analyze the causes of poor vaccination effect.

MethodsPiglet intestinal samples were collected from a pig farm in Sichuan Province for PCR detection, virus purification, determination of virus titer and virus infection experiments. Whole genome sequencing of isolated strains was determined. The S gene sequence of the isolated strain was compared with the strains from other regions and vaccine strains, and the phylogenetic tree was established. The amino acid site variation of S protein between the isolated strain and the classical vaccine strain CV777 was compared.

ResultsA PEDV strain was successfully isolated and named as PEDV SNJ-P. The determination of virus titer was 1×10^7.5/100 μL. Animal infection experiments showed that the isolated strain could cause diarrhea, dehydration and other symptoms and lead to death in piglets. Genome sequencing and phylogenetic tree analysis showed that the whole gene of PEDV SNJ-P strain was 28003 bp, and the genotype of the strain was S non-INDEL type. The strains were closely related to the strains of PEDV-WS, CH/JLDH/2016 and CH/HNLH/2015 isolated from China, and were relatively distant with the same type vaccine strain, and were far from the classical vaccine strain. Compared with the classical vaccine strain CV777, the S protein of SNJ-P strain had multiple amino acid mutations, deletions and insertions.

ConclusionDue to the continuous variation of strains, SNJ-P strain is far from the vaccine strain, and the current vaccines cannot provide effective protection. The results of this study are expected to provide reference for the study of PEDV strains and vaccine development in China.