Investigation On Immune Effect Of Diarrhea Vaccines And Phylogenetic Analysis Of PEDV S Gene In Some Pig Farms In Anhui Province

Porcine epidemic diarrhea(PED)is an acute intestinal infectious disease caused by porcine epidemic diarrhea virus(PEDV).The clinical manifestations of affected pigs were water-like diarrhea,severe dehydration,and vomiting,which caused severe economic losses in the pig breeding industry.At present,there is still no specific treatment drug for this disease.In general,it often depends on vaccination to prevent the occurrence of diarrheal diseases.There is a large area of diarrhea after vaccination in the pig farms.Therefore,it is urgent to investigate the prevention and control effect of PED vaccine in large scale pig farms.Therefore,this study intends to investigate the effect of PED prevention and control on 152 large-scale pig farms in some areas of Anhui Province,the emergency immunization effect of diarrhea pig farms,and the evolution of the S gene of PEDV epidemic strains in order to determine the clinical immunization efficacy and The phylogenetic relationship of PEDV epidemic strains,providing an important reference for scientifically and rationally selecting vaccines for diarrhea.(1)Evaluating the immunization against the immune-preventive effect of PED vaccine in some large-scale pig farms in Anhui Province.This study investigated the effects of PED vaccine immunization on 152 large-scale farms,and the incidence and mortality of labored litters in primary and secondary sows.The results showed that the total number of infected farms was 55 and the incidence rate was 36%.Scheme 1: there were 22 pig farms without immunized diarrhea vaccine,the incidence of diarrhea was 77.3%;scheme 2: immune diarrhea triad and two inactivated vaccine were 89,the incidence of diarrhea was 19.1%;scheme 3: vaccinated and dead seedlings were 41,and the incidence of diarrhoea was 56.1%.In addition,there were 31 pig farms adopting the general immunization + fetal immunization scheme 2 and the incidence of diarrhea was 3.2%;33 pig farms were used for the immunization scheme 2 of the general immunization method,and the incidence of diarrhea was 30.3%;There are 25 pig farms in 2,and the incidence of diarrhea is 24.0%.A total of 780 litters were found in 152 littermates at birth.The number of diarrhea-occupied litters was 49.9%.The number of littermates was 65.8%;the total number of litters per litter was 408 litters;The ratio was 34%,and the number of sick-bowls was 40.3%.The results suggest that the immunization program of universal immunization + heel heel method 2 has the best effect on the prevention and control of PED in piggery,and the incidence and fatality rate of the piglets produced by the production sows are lower.It provides an important reference for the prevention and control of PED for the scientific selection of the diarrhea vaccine in the pig farm.(2)Evaluating the effect of emergency immunization on diarrhea farms.In this study,16 emergency vaccinations were conducted on selected pig farms where diarrhea epidemics occurred after immunization with diarrhea vaccines.Statistics were collected on the incidence and mortality of piglets in each field before and after emergency immunization,and the recovery of pigs after emergency immunization.The results showed that there were a total of 197 litters at 16 sites.The prevalence of diarrhea before emergency immunization was 52.8%,and the number of diseased litters was 72.1%;the incidence of diarrhea after emergency immunization was 28.84%,and the number of diseased litters was 30%.The emergency immune recovery status of pigs showed that 25% of farms returned to normal 5 days after immunization;50% of farms returned to normal 7 days after immunization;18.8% of farms returned to normal 9 days after immunization;6.2% of farms returned to normal 13 days after immunization.In summary,the results suggest that the incidence and mortality of diarrhea in pigs after the implementation of emergency immunization program 2 were reduced,and most of the farms returned to normal 9 days after the emergency immunization,which provided reference value for the pig farms to actively respond to the prevention and control of the diarrhea epidemic.(3)To study the PEDV PCR identification and phylogenetic analysis of S gene in some pig farms in Anhui Province.Thirty samples from the diarrhea farms were detected by RT-PCR,and S gene sequencing analysis was performed on PEDV-positive samples.The results showed that the positive rate of PEDV was 70%;the 7-segment S gene sequence was successfully amplified,and the homology of the nucleotide sequence between the S genes of the PEDV isolates in the 7 Anhui strains was 97%-100%;7 strains of PEDV isolates belong to the G1 group,and the phylogenetic relationship with the PEDV variants is more than 97%,while the phylogenetic relationship with the classic CV777 strains is only 94%.To lay a theoretical foundation for the study of molecular epidemiology of PEDV in Anhui Province.In summary,this study investigated the effect of diarrhea vaccine prevention and control of different scale pig farms and the evolution of PEDV S gene.The use of puerperal + fetal diarrhea attenuated vaccine and inactivated vaccine can significantly reduce the incidence of PED and mortality,and the pig farm can return to normal 9 days after the emergency immunization;In addition,the PEDV epidemic strains in some parts of Anhui Province had more than 97% genetic relationship with the variant strains,compared with 94% of the classic CV777 strains.Provides a good technical basis for diarrhea vaccine immunization and epidemiological survey of PEDV in Anhui.