The Investigation Of Molecular Epidemiology Of Porcine Epidemic Diarrhea Virus In Fujian Province In 2012-2014

Porcine epidemic diarrhea(PED)is a contagious disease,caused by porcine epidemic diarrhea virus(PEDV).All ages of swine are susceptible to the disease.Clinically,it is characterized by diarrhea,vomiting and dehydration with high mortality of sucking piglets.In recent years,it has been widespread in China,which caused severe economic loss in pig industry.133 swine farms suspected of PED were investigated and 285 intestinal samples selected from the piglets were tested by RT-PCR from 2012 to 2014 in Fujian province,China.The results showed that 92450 piglets were suffered and 57230 piglets were died with the infection.The total mortality of piglets in was 61.90%.But the mortality in different farms was various because of immunization strength.The mortality in large intensive farms,middle farms and small farms were 51.31%,66.64%and 67.80%,respectively.The positive rate of PEDV in 2012,2013 and 2014 was 58.82%(60/102),65.49%(112/117)and 58.33%(7/12),respectively.14 S genes,19 E genes,18 M genes,16 N genes and 17 OFR3 genes of PEDV were cloned and sequenced.The sequence result showed that 2 of 14 S genes were composed of 4149 nucleotides,12 of 14 S genes were composed of 4161 nucleotides.Compared with CV777 strain,homologies of nucleotides and amino acids of S genes were 92.4%?93.3%and 92.8%?93.7%,respectively,showing that there were amino acids mutations including 26-29 glycosylation sites,4-5 amino acids insertion,2 amino acids deletion,but difference of antigenic epitope was not significant.19 E genes were composed of 231 nucleotides,encoding 77 amino acids.Compared with strain CV777,the homologies of nucleotide sequence and amino acid of E genes were 96.2%?97.4%and 98.7%?100%,respectively.8 M genes were composed of 681 nucleotides,encoding 227 amino acids.Compared with strain CV777,the homologies of nucleotide sequence and amino acid of M genes were 96.5%?99.6%and 98.2%?99.6%,respectively.16 N genes were composed of 1326 nucleotides,encoding 442 amino acids.Compared with strain CV777,the homologies of nucleotide sequence and amino acid of N genes were 97.8%?99.6%and 96.5%?98.2%,respectively.17 ORF3 genes were composed of 675 nucleotides,encoding 225 amino acids.Compared with strain CV777,the homologies of nucleotide sequence and amino acid of ORF3 genes were 98.2%?99.6%and 95.1%?96.5%,respectively.Phylogenetic tree showed that 14 S genes,18 M genes and 17 ORF3 genes were close to the Thailand strain;19 E genes and 16 N genes were far apart from strain CV777.Obvious mutations were observed in 14 S genes and 17 ORF3 genes which were quite different from other strains and might be originated from Korea strains and Thailand strains.Conclusions:PEDV is dominant in the piglet diarrhea pathogen in Fujian province.In 2012 to 2014,the Fujian PEDV isolates S genes had big degree variation including amino acids mutations,4-5 amino acids insertion and 2 amino acids deletion.PEDV M genes,E genes and N genes are conservative except point mutations,which were agreed with other isolated strains.The Fujian PEDV isolates were field virus,which were far apart from vaccine strains.