The Effect Of Porcine Reproductive And Respiratory Syndrome Vaccine On The Immune Efficacy Of Classical Swine Fever Vaccine Or Porcine Circovirus Associated Diseases Vaccine

Porcine reproductive and respiratory syndrome(PRRS),commonly known as 'Blue ear disease',is a highly contagious infectious disease that causes reproductive disorders,high fever and respiratory symptoms in pigs.It spreads around the world and seriously threatens the development of pig breeding industry.This disease was first reported in 1996 in China,and the highly pathogenic PRRS disease characterized by high morbidity and mortality broke out in 2006,which caused huge economic losses to pig industry in China.Porcine circovirus associated diseases(PCVAD)is mainly an immunosuppressive disease caused by PCV2 infection.The epidemiological survey data showed that PCV2 infection was prevalent in pigs in China.The main clinical manifestations of the diseases is postweaning multisystemic wasting syndrome(PMWS)of piglets,and dermatitis and nephrotic syndrome,interstitial pneumonia and congenital tremor are the main manifestations in pigs aged over 12 weeks.In recent years,PRRS and PCVAD vaccines have been widely used for immunization in clinic,which has played a promoting role in alleviating clinical symptoms and controlling the occurrence of these two diseases.The mixed infection of classical swine fever virus(CSFV)and PRRSV is very common in clinic.PRRSV can replicate in macrophage and leads to immunosuppression.During PRRSV infection,the immune system of pigs is impaired and the immune response to classical swine fever(CSF)vaccine may be inhibited.At present,there are still many controversies about whether PRRS vaccine can interfere with CSF vaccine elicited antibody production and how to deal with PRRS vaccination and PCVAD vaccination.The purpose of this study was to survey the antibody level and changes of PRRS vaccination in large-scale pig farms,and to study the influence of domestic PRRS attenuate live vaccine on the immune response of both CSF and PCVAD vaccines,so as to provide theoretical basis for the prevention and control of clinical epidemic diseases.1.Serum antibody monitoring of PRRS in pig farmsIn order to understand the antibody level and dynamic of PRRS vaccination in large-scale pig farms,serum samples of pigs from 5 pig farms at different stages were collected for PRRS antibody detection.The results showed that the average positive rate of antibodies in serum samples was 72%,with the highest being 95%and the lowest being 45%,indicating that there were some differences in antibody levels among pig farms.Among them,the average positive rate of antibodies in the two farms of No.2 and No.5 without vaccination with PRRS vaccine were 45%and 50%,respectively,indicating the natural infection of PRRSV existed in these two pig farms.The average positive rate of PRRS vaccination and positive serum acclimatization was 95%and 85%respectively,indicating that both measures could provide good immune protection for the pig population.The dynamic of antibody response of PRRS vaccination in pigs were basically consistent,which showed as follows:the antibody level of newborn pigs was relatively high,and then the antibody level gradually decreased.At the age of 55-60 days,the antibody level decreased to the minimum,and then the antibody level increased again.This study provided a reference for prevention and control of PRRS through the detection of PRRS antibody level in large-scale pig farms.2.Effect of domestic PRRSV live-vaccine on immunity of CSF and PCVAD vaccinesWe further evaluated the effect of domestic PRRSV live-vaccine on the immunity of CSF and PCVAD vaccines.In this study,sixty 14-day-old piglets were randomly divided into 12 groups with 5 piglets in each group.Pigs from group A-G were inoculated PRRSV vaccine at age of 14 days.Meantime,piglets from group A were inculated PCVAD vaccine at age of 14 days and CSF vaccine at age of 28 days.Groups B,C and D were vaccinated with CSF vaccine at age of 14,21 and 28 days,respectively.Group E and F were vaccinated with PCVAD vaccine at age of 21 and 28 days,respectively.Group G was not inoculated with PCVAD and CSF vaccines.In addition,pigs in the H-L groups were not inoculated with PRRS vaccine,and the H,I and J groups were inoculated with CSF vaccine at age of 14,21 and 28 days,respectively.Group K and Group L were inoculated with PCVAD vaccine at age of 21 and 28 days,respectively.Clinical manifestations of pigs were observed and rectal temperature was recorded every day after vaccination.Daily body weighing was recorded to calculate the average daily body weight-gain.PRRSV,PCV2,and CSFV specific antibodies were detected in immunized pigs at age of 28,42,and 56 days.After vaccination,the body temperature of all experimental pigs was basically maintained in the normal range,with no significant difference in average daily body weight gain and no obvious clinical symptoms.The results of antibody detection showed that PRRS vaccine had no effect on the humoral response elicited by PCVAD vaccine.PRRS vaccine has a significant interference with CSF vaccine if they were inoculated simultaneously.However,the PRRSV vaccine has no influence on the antibody production triggered by CSF vaccine at 7 days or 14 days intervals.