| Porcine Epidemic Diarrhea(PED)is caused by Porcine Epidemic Diarrhea Virus(PEDV),An acute,highly contagious intestinal disease of pigs characterized by vomiting,diarrhea,dehydration,and death.In order to prevent and control the epidemic in a large-scale pig farm in Aksu area,the TGE-PED combined attenuated vaccine and inactivated vaccine were used to immunize sows at 85 and 105 days of gestation,respectively.However,in January 2021,diarrhea occurred in this farm,and the incidence of diarrhea in piglets at 7 days of age was as high as 100%,and the mortality rate was as high as 90%.Feces and anal swab samples of infected piglets were detected by colloidal gold test paper card,and the positive rate of PEDV detection was100%.In order to find a solution,this study was carried out.In this study,the M gene of porcine epidemic diarrhea virus in piglet diarrhea disease feed was cloned to identify the virus strain causing the epidemic of porcine epidemic diarrhea in this farm,and the epidemic situation of PEDV in this farm from January to December 2021 was monitored.At the same time,Ig G antibody and Ig A antibody of pregnant sows after immunization vaccine were tracked and monitored by indirect ELISA antibody detection kit,and the immune effect of PED vaccine was evaluated,which laid a foundation for selecting correct diarrhea vaccine for prevention and control of epidemic disease in this pig farm.Laboratory diagnosis: The clinical symptoms of the infected piglets were collected,and the pathological changes were in line with the disease material of porcine epidemic diarrhea.After RT-PCR amplification,cloning,identification and sequencing,and genetic evolution analysis,the homology of this strain was more than 96.7% with the main M gene strains isolated at home and abroad after 2011 published in Gene Bank.The closest genetic relationship with this strain was Hubei strain C3-HB2017,and the homology reached 99.5%.The PED vaccine strain used in this strain had a slightly distant genetic relationship with the isolated strain,and there were 13 base loci mutations in the M gene fragment.Tracking and monitoring: A total of 6567 samples of piglets suspected of diarrhea were collected from January to December 2021,and PEDV was detected by fluorescent quantitative PCR kit for porcine epidemic diarrhea.The results showed that the detection rates of PEDV in November,December,January and February were 35.46%,13.14%,27.71% and 7.34%,respectively.In other months,the detection rate was low in March,April,May,June,July,August,September and October,and the proportion was 2.12%,0.00%,0.00%,0.00%,0.00%,0.75%,0.00% and 0.00%.The prevalence of PED in this field still showed obvious seasonal change.Immune effect monitoring: the TGE-PED combined attenuated vaccine and inactivated vaccine were used to immunize sows on day 85 and day 105 of gestation,respectively.Blood samples were collected on day 15 and day 1 before delivery,serum was separated,colostrum was collected on the day of delivery,and 11 batches of pregnant sows were tracked and monitored with indirect ELISA kit for Ig G and Ig A antibodies.The results showed that the positive rate of Ig G and Ig A antibodies of all batches of pregnant sows reached 100% and the dispersion was less than 40% at 15 days before and on the day of delivery,indicating a good immune effect.One day before delivery,the positive rate of Ig G antibody of each batch still reached 100%,but the positive rate of Ig A antibody decreased to varying degrees,and the dispersion increased to varying degrees.The analysis suggested that sows might be detoxing at this stage.Although higher antibody levels were detected after immunization with the attenuated and inactivated TGE-PED vaccine,the disease was still not completely blocked.The site also needs to further improve the immunization procedures for diarrhea vaccines,find a better match for the epidemic strain for immunization,and do biosafety work to prevent the spread of the virus in the site. |
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