Epidemiological Investigation Of Porcine Epidemic Diarrhea(PED) In Shandong Province

Porcine epidemic diarrhea (PED), caused by porcine epidemic diarrhea virus, is a kind ofintestinal infectious disease, commonly in characteristic of severe enteritis, vomiting, waterydiarrhea, weight loss and high mortality rates. Since the winter of2010, PED had broken outin some districts of Shandong province in China and this outbreak mainly threatened suckingpiglets by severe vomiting and watery diarrhea. Several large scale pig farms were seriouslyimpacted and sick sucking piglets had died with a mortality rate close to100percent. Thisresearch included the following aspects:1. The prevalence investigation and pathogen detection were conducted in fifteen largescale pig farms in five districts, including Dezhou, Taian, Yantai, Jining and Jinan, inShandong province from January2012to April2012. The results showed that the positive rateof REDV was62.86%（44/70） and all the fifteen investigated farms were positive, whichindicated that PEDV was the causative agent in2012spring’s PED outbreak..2. The major structural protein M gene was sequenced and analyzed for the fifteen PEDVstrains isolated from Shandong province. The results showed that M gene of all the fifteenstrains was681nt and the different strains have closed genetic distance with each other.Compared with other Chinese isolates and foreign isolates, the15PEDV isolates had a closergenetic relationship with the Korea isolate BIF256and Thailand isolates KU04RB08,KU06RB08, KU07RB08and MNIAH10054208, but more distant genetic relationship withChinese isolates SJZ-2011and QY2isolated in2011as well as the vaccine strain CV777.Meanwhile, by gene sequencing and analysis of the major structural protein N gene of12wild-type viruses, the12PEDV isolates have closed genetic distance with99.0%to100%ofidentity to each other.3. By comparison of complete genome sequence, the Vero cell adapted strain SD-M(passage level4) showed the97.7%and99.9%in nucleotides identity with vaccine strainCV777and wild-type strain DR13-. The genetic structure of SD-M strain was 5’UTR-ORF1ab-S-ORF3-E-M-N-3’UTR, and292nt of5’UTR,20321nt of ORF1ab,4149ntof S gene,276nt of ORF3,231nt of E gene,681nt of M gene and1326nt of N gene wereplaced orderly. Compared with the complete genome sequence of PEDVs reported, there were49nt losing in ORF3of PEDV SD-M strain, which leaded to the reading frame shift from675nt to276nt.