The Study Of PED Epidemiological Investigation And Immunoprotection Experiment Of PED Vaccines

Porcine epidemic diarrhea (PED) is an acute intestinal infectious disease which is caused by the porcine epidemic diarrhea virus (PEDV),a member of the coronavirus.PED is widespread in our country’s pig industry and has become one of the most serious infectious diarrheal diseases. The longterm cold,humid weather of Guangxi Province and insufficient warm keeping measures make the piglets more susceptible to PED.In this study, epidemiological investigation was made around Nanning’s swine herd,PED vaccine’s immunoprotection experiment and emergence measures were carried out after the outbreak of PED.This will lie the basis for proper vaccine choice,immune procedure’s establishment,preventing and controling PED.Experiment1:444suspected diarrhea samples were collected from7scale piggeries around Nanning city,during January2011to April2013, multiple RT-PCR method was used to detect the pathogen.The results showed that79of the444samples were PEDV positive,rating17.1%of the total samples. All the7piggeries that were detected showed PED positive,this demonstrated that PED is wide spread around Nanning.The positive rate of the samples collected from intestinal tissues was much higher than from fecal samples.No positive samples were detected from sows’milk,this support the point that fecal-oral is the major transmission route of PED.Besides,the positive samples’ number and its rate during November to the next year’s march is the biggest,so we could conclude that the cold season is the main PED epidemic season.Further more,the positive rate of PEDV is increasing year by year over the past3years, indicating that PED is bringing more damage to the pig industry.Experiment2,a follow-up survey was conducted in a scale piggery after the out-breaks of PED.The morbidity and mortality rate of the piggery was100%and13.9%,respectively.After timely pathogeny identification combined with a series of emergency immunization,sterilization and treatment measures,the disease was well controled.By comparing the histological sections from the infected pig,pathological changes were identified in every parts of the gastro intestinal tract,the small intestinal was damaged vastly,and mainly manifested by dropping and shortenning of the intestinal villus.Moreover,after a follow-up survey of piglets and sows, we found that the infected herd could still carry and expel virus after recovery for10weeks.Experiment3,40piglets of6weeks old were randomly selected from a state-owned large-scale pig farm.7kinds of PED vaccines were used to immunize the piglets and the piglets were challenged21day after immunization. The result showed that all of the7vaccines’ immune efficacy was not ideal,the protective effect of the freeze-dried combined PED-TGE-PR vaccine is relatively better than others.