Epidemiological Investigation Of PRRS In Liaoning Area And Study The Effect Of Different PRRS Vaccine On The Immune Effect Of Swines

The purpose of this study is to study the epidemiology of PRRS in Liaoning area and to study the effect of different PRRS vaccine on the immune effect of swines,then to provide scientific basis for the development of immune program that can effectively prevent and control PRRS.In this study,a total of 1892 samples of swine's vaccinated and unvaccinated serum samples from 10 cities and counties in Liaoning area between 2015 and 2016 were detected by ELISA,and the seroepidemiological survey is conducted.The results show that the positive rate of antibody in vaccinated herds is 68.08%,and in different growth periods,the positive rate of weanling piglets is the highest,at different seasons,the positive rate of winter is the lowest.The positive rate of antibody in unvaccinated herds is 25.35%,and in different growth periods,the positive rate of weanling piglets is the highest,at different seasons,the positive rate of summer is the highest.A total of 1490 cases of suspected PRRS are collected and the etiology epidemiological investigation is carried out.The results show that the average positive rate of PRRSV in Liaoning area from 2015-2016 is 45.91%,in different growth periods,the positive rate of weanling piglets is the highest,suckling piglets is second,at different seasons,the positive rate of summer is the highest.The results show that PRRSV is most susceptible to piglets,and low temperature is an important factor affecting the immune effect of PRRSV,and high temperature could increase the infection rate of PRRSV.42 healthy and weaned piglets are randomly divided into 4 groups(A,B,C,D).Group A is control group,immunity of attenuated in group B,immunity of inactivated in group C,immunity of attenuated and inactivated in group D.Blood samples were taken from cranial vena cava on the 14th,28th,42th,56th,70th day after immunity for blood analysis,the levels of specific antibodies are detected by ELISA,detecting lymphocyte transformation rate and the levels of cytokines IFN-a,IFN-?,TNF-a are detected by ELISA.The results show that the average number of leukocytes of group D in the 70th day is significantly higher than group B(p<0.01),after 42th day the average number of leukocytes of group D is significantly higher than other groups(p<0.01);after immune 28th day,lymphocyte count of group D is significantly higher than that in group B(p<0.01);the number of each group of red blood cells and hemoglobin concentration,the neutral granular cell number and median cells shows a slow upward trend and group D higher than other three groups The level of antibodies of group B is significantly higher than group D(p<0.05)and group A(p<0.01).On the 42th day after immune,the lymphocyte transformation rate of group D is significantly higher than group A,B and C(p<0.01),after the 56th day,the lymphocyte transformation rate of group B is significantly higher than group C and D(p<0.05);The levels of cytokine of group B is higher than the other three groups on the 14th day,after enhanceing immune the levels decrease,then increase on the 70th day.The result indicates,the immunity of attenuated and inactivated could better stimulate the porcine blood cell proliferation,the effect of immunity of attenuated vaccine is higher than other two kinds of immunization.