| Porcine epidemic diarrhea(PED),one of the major viral diseases of piglet diarrhea,is an intestinal infectious disease caused by porcine epidemic diarrhea virus(PEDV).PED has high infection and lethality on piglets,which has brought huge economic losses to China’s pig industry.Since the discovery of PED in China in 1984,the Gla subtype strain has been circulating,then controlled by the CV777 vaccine developed by Chinese scholars.In 2010,highly pathogenic G2b subtype mutant strains broke out in many provinces in China.G2b has a large antigenic difference from the Gla subtype vaccine strain,and there is currently no effective targeting of new variant strains.Therefore,there is an urgent need to carry out an epidemiological investigation of PEDV strains in the region and to formulate comprehensive control measures in accordance with the current epidemic situation.1.The Epidemiological Survey of PEDV during 2017 to 2019.A total of 5584 suspected PED-affected pig tissues and stool samples were collected from 2017 to 2019 in some pig farms in Jiangsu Province,detected by fluorescent quantitative PCR.A total of 1516 samples were tested positive,with a total positive rate of 27.15%.S gene sequencing and analysis performed on the positive samples has found 41 samples of the S gene sequence.G2b subtype mutants was confirmed by the genetic evolution analysis on this 41 samples2.Formulation of integrated PED control measures for intensive pig farms.The results of disinfectant on live virus were analyzed by using fluorescence quantitative PCR detection and cell infection test,and the threshold of environmental sample disinfection eligibility was determined,so as to evaluate the efficacy of environmental sample disinfection.The simulated disinfection test of live virus and several disinfectants commonly used in pig farm was carried out.It was found that 20%glutaraldehyde solution had the best disinfection effect in all test groups.The standards of 5 minutes shower and 12 hours isolation for the technicians of the pig farm,2 times of flushing and drying of the vehicles of the pig farm,and the testing and sampling of feed and feed transfer station were formulated.Through comparative tests,it is found that PEDV residues in the environment can be reduced to a certain extent after people and environment are controlled.Efficacy of PED inactivated vaccine was evaluated in pregnant sows of 26 pig farms according to different immunization procedures,and colostrum was taken for IgA antibody detection after production.The results showed that there was no significant difference in the efficacy of once and twice inactivated vaccines.However,the effects of primary inactivated immunization at different prenatal times(7 days,14 days and 21 days)were significantly different,prenatal 21-day inactivated immunization vaccine can obtain the optimal protection effect.In this study,a combined immunization program was developed for the return feeding of spare sows and inactivated vaccination of pregnant sows for 21 days before delivery,and the efficacy of the combined immunization program was evaluated in 26 pig farms.The results showed that the combined immunization regimen could significantly improve the positive rate of IgA antibody in the colostrum of sows and the level of neutralizing antibody in the serum of sows.Serum neutralizing antibody was detected with the serum of 20 days after delivery in 11 pig farms.The protection rate of serum neutralizing antibody in 10 pig farms was greater than 80%,and in 1 pig farm the protection rate only 40%. |
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