Clinical Evaluation Of Immune Effect Of Four PEDV Vaccines

Porcine viral diarrhea is mainly caused by Porcine Epidemic Diarrhea Virus,Transmissible Gastroenteritis of Pigs Virus,Porcine Rota Virus,Infectious diseases,the main clinical watery diarrhea,vomiting,dehydration and other characteristics,the speed of transmission,the age of pigs were shown susceptibility,high incidence of breast-feeding piglets mortality is low,and there are a variety of mixed diseases Infection,in the epidemic season may be an outbreak of epidemic,to the breeding industry caused serious economic losses.Effective prevention of viral viral diarrhea is mainly through vaccination of vaccines,it has been reported that the combination of attenuated vaccine and inactivated vaccine will produce good results.But a wide range of vaccines,the immune effect is not clear,there are still immune pig farms have a large area of diarrhea,failed to achieve the purpose of prevention.So the PEDV vaccine immune effect of further scientific evaluation becomes necessary.Therefore,the aim of this study is to design a different vaccine immunization program to determine the clinical efficacy of the combination of different vaccine types to determine the best immunization program for the prevention of swine viral diarrhea,and to provide a reference for the prevention and treatment of diarrheal diseases in pigs in accordance with.(1)Grouping and immunization of experimental animals.In this study,five immunization regimens were designed by using four diarrhea vaccines,mainly vaccine a(triple live vaccine),vaccine b(secondary inactivated vaccine),vaccine c(double live vaccine),vaccine d The experimental animals were divided into five groups according to the requirements of PEDV vaccine immunization program.Specific treatment: group A was vaccine a + vaccine b,group C was vaccine c +vaccine d,D group for the vaccine a + b and vaccine a + b,group E were two normal saline,the above two groups were immunized twice after the sea cave;group B for the vaccine a + vaccine b,the first for oral vaccination,The second time for the sea after the inoculation.The two immunizations in group A,B,C and E were prenatal 40 d and20 days before delivery.(2)Study on serum IgG antibody in sow.PEDV IgG antibody was detected in the sows before the first 5 days of immunization,20 d after the first of immunization,and 20 d after the second of the immunization.The changes of serum IgG antibody in each immunization stage were analyzed.The antibody distribution showed that the IgG antibody was in an ascending trend in the blood of a pregnant sow and thedifference of antibody level between group A and group C was significantly higher than that of pre-immune(P <0.01).The level of serum IgG in group B was significantly higher than that in pre-immunization group(P <0.05),and the level of antibody in group B was significantly higher than that before immunization The level of antibody was significantly higher than that of the control group(P <0.05).Indicating that after the vaccine immunization group C program can stimulate the production of high levels of IgG antibodies,followed by group A and group B.(3)Study of sow milk IgA antibody.PEDV IgA antibody was detected at 0d,3d,7d and 15 d after sowing.The changes of IgA antibody levels in milk were analyzed.The results of antibody showed that the average level of IgA antibody in milk was decreased at 0-3 d after delivery,and the difference of IgA antibody level between the two groups was significantly higher than that of group B and group C(P<0.01).The average level of IgA antibody in each group was higher than that in group A,B,D and E at 3 days after delivery,and the difference was significant(P <0.01)(P<0.05).The average level of antibody in group A,B,C and E was decreased after7-15 days after delivery,but only the antibody level of group D was on the ascending trend.Compared with postpartum the difference was significant(P <0.01).It was suggested that the swine group produced a high level of IgA antibody,followed by group C and group B,after immunization with group A.(4)Study on Diarrhea and Death in Piglets.The diarrhea rate and mortality of piglets were measured at 24 h and 48 h after challenge,and the intestinal PEDV was detected by RT-PCR.rate.The diarrhea rate was the lowest in the group A,and the diarrhea rate was the lowest in the A group at 48 h after challenge.The diarrhea rate was 50% in the group A and 100% in the other groups.The PEDV was 100% in the intestinal group and 80% in the other groups,indicating that the immunoprotective effect of group A was the highest.(5)Determination of small intestine villi,crypt and V/C values.The duodenum,jejunum and ileum were fixed by formalin solution,and the pathological changes were observed under the microscope.The height of the villi,the depth of the crypts and the calculation The V / C values were compared with those of healthy pigs at the same age using SPSS 13.0 data analysis.According to the results of observation and data,it was found that the peritonal atrophy was serious in each group,and the change of crypt was not obvious,the V / C value became smaller and the difference was significant(P < 0.01).The results showed that the intestinal injury was serious afterinfection with PEDV,but the damage was smaller in group A and B,followed by group C and group D.In this study,we designed the immunization program of different vaccine combinations and made the clinical evaluation of the immune effect.The immunization program of group A was the best,that is the immunization triple vaccine was prenatal 40 d,and pregnant before 20 days immunization inactivated vaccine.Thus providing a good technical basis for clinical scientific selection of PEDV vaccine immunization.