Molecular epidemiological investigation of PEDV and analysis of genetic variation of S gene in South China during 2011-2015

The study conducted a large scale molecular epidemiological investigation and five years monitoring of nine swine herds with the outbreak of diarrhea located in geographically separate regions of south China by RT-PCR. Porcine intestinal and fecal samples were collected from 18 swine farms in five provinces（ Guangdong province，Guangxi province，Fujian province，Sichuan province，Jiangsu province） in south China with the piglets younger than 7 days old that showed watery diarrhea and dehydration. 35 spike（ S） genes were determined to analyze the genetic diversity and epidemiological features during 2011-2015. The results showed that all PEDV strains could be divided into two groups，Group1 and Group 2. Group1 had a close relationship with the United States strains and Taiwan strains，and had four subgroups，G1-1，G1-2，G1-3 and G1-4. Group 2 felled into the same branch with the previous Chinese isolates from 2004 that had two subgroups，G2-1 and G2-2. The subgroup G1-2 and G1-3 comprised most of the strains isolated in south China while the subgroup G2-2 comprised the strain isolated in 2004（ JS-2004-2） and eight else isolated in south China in our study. It is remarkably that clinical morbidity caused by two types of PEDV strains were quite different，strains in G2-2 caused relatively minor mild clinical manifestations，presenting a smaller mortality and shorter onset period，while strains in G1-2 and G1-3 is caused an outbreak of acute infectious diseases，showing a larger mortality and longer period especially PEDV strains in G1-3.