Identification and characteristics analysis of the Porcine epidemic diarrhea virus (PEDV) Isolated In Shanghai

Porcine epidemic diarrhea virus (PEDV) belonging to the Group I coronavirus is the major cause of lethal diarrhea disease in piglets. In recent years, there are many case reports of PEDV infection in pigs in China and caused large economic losses. To better control this disease, it’s necessary to explore the epi demiological status and genomic characteristics of the new PEDV isolates.

Fifty five feces samples of piglets with diarrhea symptom in farms of Shanghai were collected and used for RTPCR detection. Then the postive samples were inoculated on Vero cells with trypsin for subculture. After detection of the cell cultures by RT - PCR and indirect immunofluorescence assay (IFA) with monoclonal antibody (MAb) against PEDV, genomic characteristics of the isolates were analyzed u sing Lasergene software.

For further confirmation of the pathogen, six one - day old piglets were divided randomly into three groups. Two groups were orally feed with 20ml concentrated virus 30 - 3 (10^5.4 TCID₅₀/0.1ml), W14 (10^3.4 TCID₅₀/0.1ml). The third group was used as control with DMEM inoculation. Clinical features especially the diarrhea sym ptom of the piglets were observed. Diarrhea feces and intestine contents of dead pigs were also collected and detected by RT-PCR.

Two of fifty - five samples were PEDV positive and were blindly passaged in Vero cells with different concentrations of trypsin. After several continuous passages, the t wo PEDV isolates in cell cultures were positive in RT - PCR and IFA with monoclonal antibody (MAb) against PEDV and were named 30 - 3and W14. Genomic comparison and phylogenetic analyses revealed that 30 -3 and W14 isolates share highly homology with the isolates of BJ -2012 - 1 and HLJ - 2012 respectively. There are 138 amino acids deletion in ORF3 of the isolates which were characterized of cell adapted strains. Both of the two piglets inoculated with 30 - 3 isolate appeared diarrhea at 24h after inoculation and died at 4 dpi. Piglets inoculated with W14 showed clinical symptom of diarrhea and one pig died at 6 dpi. With post mortem examination, the small intestines were full of bleeding and gas, which was the typical characteristic of PEDV infection. The faeces and intestinal contents of the pigs inoculated with 30 -3 and W14 were PEDV positive.

In conclusion, the two isolates of the PEDV were identified in vero cell successfully. And the phylogenetic analysis indicates the viruses were different form the classic CV777 and were similar with those isolated in China in recent years.

Disclosure of Interest: None Declared.