Diagnosis And Control Practice Of PEDV And Mixed Infections In A Pig Farm In Sichuan Province

Porcine diarrhea is a major epidemic currently in the pig industry.The reasons lead to pig diarrhea are complex,porcine epidemic diarrhea?PED?is the most prominent disease.PED mainly causes diarrhea,vomiting,dehydration and death in piglets,which causes a large economic loss to the pig industry.It is meaningful to explore the true cause of the disease in the PED-affected piggery and develop a scientific and reasonable prevention and control plan for controlling diarrhea.In 2017 and 2018,total two cases of diarrhea in a pig farm in Sichuan were chosen to study,we performed clinical diagnosis,etiological diagnosis,antibody detection and gene variation analysis and explored the corresponding control programs to provide pig diarrhea,which will be reference for clinical control of pig diarrhea.1.Pathogenic diagnosis of diarrhea cases:we studied pigs with diarrhea during 2017 and 2018,and performed clinical diagnosis,necropsy,bacterial isolation,and detected porcine epidemic diarrhea virus?PEDV?,porcine potavirus?PoRV?,porcine transmissible gastroenteritis virus?TGEV?,classical swine fever virus?CSFV?,porcine pseudorabies virus?PRV?and porcine circovirus type 2?PCV2?.The results showed that the piggery was diagnosed as FEDV and PRV mixed infection form the 4 diseased piglets in 2017;and was diagnosed as PEDV and PCV2 mixed infection from the 6 diseased piglets in 2018.2.Detection of serum antibody in diarrhea cases:a total of 86 serums were collected and detected during 2017 and 2018.Antibodies of CSFV,PRV,PCV2,PRRSV and PEDV were detected by ELISA antibody kit.The results showed that the PRV,PCV2 and CSFV antibody levels were high?positive rate was 83.33%-100%?in the piggery in 2017 while the PRRS antibody?positive rate 5.53%?and PEDV antibody?positive rate 28.99%?were lower overall.The results of serum detection showed that the antibody positive rate of PRV,PCV2 and CSFV were all 100%,and the PRRSV antibody positive rate was 46.15%in 2018.3.PEDV S gene mutation analysis in the diarrhea cases:each S gene from three positive PEDV samples were amplified and sequenced.The CV777 PEDV S gene sequence was used as the reference genome to compare with that three S gene sequences,which isolated from the piggery in 2017?named:SCNJ₂017₁,SCNJ₂017₂?and in 2018?named:SCNJ₂018?.The CV777 PEDV S gene sequence compared with SCNJ₂017₁,SCNJ₂017₂,SCNJ₂018,the number of single base variation sites between them was 28,19,305,and the number of insertion sites was 5,2,3;the number of deletion sites was 3,3,and 4,respectively.The three PEDV S gene sequences obtained in this experiment were systematically analyzed with the homologous regions of 35 published PEDV sequences from domestic and foreign.All strains can be divided into two categories?Group I and Group II?,SCNJ₂017₁ and SCNJ₂017₂ were close to CV777,three of them belong to Group I;SCNJ₂018 is classified into Group II,indicating S gene mutation appear among the PEDV strains from the piggery in 2017 and 2018.4.Control measures of the diarrhea cases:we should strengthen biosafety and environmental control,implement disinfection works,and choose the suitable vaccine according to the detection results.In 2017,CV777 triple live vaccine was effective to PEDV and CV777 triple live vaccine was chosen by analyzing the genotype of PEDV S gene in this piggery.PED was broken out again in this piggery in 2018,we replaced the previous vaccine?CV777 triple live vaccine?with Wuhankeqianxiening bivalent live vaccine,which chosen by the same way as 2017,to control PEDV successfully.In this study,a comprehensive approach,including pathogen diagnosis,antibody monitoring,and gene mutation analysis,to study two typical cases of diarrhea in a piggery in Sichuan.Corresponding controlmeasures were adopted in time and good control effect was achieved.This study could provide some useful information for clinical prevention and control of piglet diarrhea.