Epidemiological Investigation Of Major Swine Diarrhea Virus And Isolation And Identification Of PEDV In Yunnan Province

In order to clarify the epidemiology of the main pig diarrhea virus disease in Yunnan province,analyze the genetic evolution characteristics of Spike Protein(S protein)of swine epidemic diarrhea virus(PEDV)in Yunnan in recent years,and provide theoretical reference for the prevention and control of PED and the screening of candidate vaccine strains.By establishing the common RT-PCR detection method for PEDV,TGEV,triple RT-PV of Po RV and other diarrhea viruses Po Sa V,Pa St V and PDCo V,a total of 1851 pig diarrhea samples collected from Honghe,Dali,Kunming,Yuxi,Qujing,Wenshan,Lincang,Chuxiong,Baoshan,Zhaotong,Lijiang,11 cities from 2013 to 2022,6 kinds of pig diarrhea virus nucleic acid detection,and amplified PEDV strains for S gene sequence analysis,Meanwhile,the PEDV epidemic strains were isolated and identified,and the PEDV SYBR Green I RT-q PCR method will be established to determine the dynamic proliferation curve of PEDV isolates.Isolates S and N whole genes were amplified for genetic evolution analysis.The experimental resμLts are presented as follows:The total positive rate of the main diarrhea virus of six pigs was 52.95%(980/1851),among which the detection rate of single virus infection was 46.46%(857/1851),and the detection rate of mixed infection was 6.65%(123/1851).The mixed infection was mainly double and triple infection,and more than four infections were not found.All 28 Yunnan circμLating strains were in the same evolutionary branch and belonged to group G,which were all mutant strains.Amino acid identity between 91.4% and 98.4%;between domestic and foreign strains,between 99.6% and 99.3%;with classical weak vaccine strain CV777,between 86.2% and 89.8%,and between 90.1% and 96.2%.By amino acid site analysis,all 28 Yunnan epidemic strains were CV777;11 amino acid mutations compared with variant vaccine strain AJ1102.In the genetic recombination,one potential recombinant strain was found to be YN-LC-1803,while the remaining 27 strains showed no recombination phenomenon.PEDV epidemic strain was isolated and cμLtured blind to the sixth generation.The cell monolayer showed swelling and rounding,vacuoles and syncytium,which was named CH/YNQJ/2022 strain.the established SYBR Green I RT-q PCR method was characterized by high specificity,strong sensitivity and repetition.The proliferation of this strain on Vero cells occurred at 8h and reached the peak at 32 h.CH/YNQJ/2022 is a Ga subgroup and a variant strain.In conclusion,from 2013 to 2022,6 main swine diarrhea viruses were detected,with simple infection and mixed infection.The highest infection rate was PEDV,followed by Po RV and Po Sa V,indicating the general trend of swine diarrhea disease infection in Yunnan Province.The S genes of 28 PEDV Yunnan circμLating strains were all variant strains,which were very different from the traditional classical vaccine strain CV777,which improved a new idea for the screening of novel PEDV vaccine candidates.A PEDV strain,named CH/YNQJ/2022,was analyzed as a variant strain by genetic evolution.