| At present time,the vaccination is widely used in large-scale pig farms as a basic measure for the prevention and control of major infectious diseases.Regular detection of serum antibody levels after vaccination plays a very important role in evaluating the effect of vaccine immunization,optimizing immunization procedures,and scientifically preventing and controlling diseases.Classical wine fever（CSF）,porcine reproductive and respiratory syndrome（PRRS）,and porcine pseudorabies（PR）are three major infectious diseases that seriously endanger swine industry.In this study,a large-scale pig farm in Shandong was selected,and serum samples from different pig herds were collected from 2018 to 2020,and the antibodies levels of CSF,PRRS and PR were detected by enzyme-linked immunosorbent assay（ELISA）.The purpose of this study is to dynamically understand the immune status of these three viral diseases in herds,adjust and optimize the immune program according to the actual situation of the pig farm,and continuously improve the ability of epidemic prevention.In this study,470 serum samples were collected from pig farms from July to August every year.Except for 60 samples each from 90-day pregnant sows and suckling sows,70 serum samples each were collected from gilts,30-day pregnant sows,suckling piglets,40-day nursery piglets,and 60-day nursery pigs.The detection of serum antibodies of CSF,PRRS,and PR was performed by ELISA.The results showed that in 2018 and 2019,the positive rates of CSF antibody in sow herds（replacement sows,pregnant sows and suckling sows）and suckling piglets were all between 86.67% and 100.00%,and the antibody dispersion was small.The overallity is good,the antibody positive rate of nursery pigs is poor,the lowest is only 53.33%,and the antibody dispersion is large,ranging from 14.00% to 76.10%.In 2018,the positive rate of antibodies against PRRS in sows was 80.00%-100.00%,and the positive rate of suckling piglets was also 93.33%-100.00%,but the positive rate of antibodies in nursery pigs was 33.33%-86.67%,especially for 60-day pigs The positive rate of nursery pigs was only 33.33%-66.67%.Correspondingly,the PRRS antibody dispersion of nursery pigs was the largest,ranging from 56.00% to 77.00%.Further analysis of the S/P value of PRRS in suckling sows in 2018 found that the S/P values of some sows were all greater than 2.5 and the dispersion was greater than 40%,indicating that although the antibody level was high,it still faced a serious outbreak risk of PRRS.In 2019,the positive rates of porcine PRRS in gilts,pregnant sows,suckling sows and piglets were high,while the antibodies in nursery pigs,especially 60-day pigs,were still low,ranging from 33.33% to 53.33%,and The antibody dispersion in this herd was large（49.00%-88.00%）.In 2019,the analysis of the S/P value of PRRS of suckling sows showed that only some pigs was greater than 2.5,and the dispersion was less than 40%,indicating that in 2019,the ratio of PRRS in the suckling sows of the farm was relatively stable,and the outbreak risk was lower than that in 2018.In 2018 and 2019,the wild virus of pseudorabies was negative in the gilt herd,while the positive rate of g E antibody in the pregnant and suckling sows ranged from 0.00% to 100.00%.Suckling piglets and nursery pigs also have different levels of g E antibody positive rates（0.00%-80.00%）.The dispersion analysis showed that in 2018 and 2019,the dispersion of PR g E antibodies in pregnant sows and suckling sows was 5.17%-68.64%,and the dispersion of suckling piglets was 25.11%-37.80%.The dispersion of antibodies was large in nursery pigs,ranging from102.00% to 681.05%.Due to the sharp increase in the pressure of prevention and control of African swine fever in 2019 and the actual situation of the pig farm,the farm adjusted and optimized the immunization program at the end of 2019.In 2020,we collected another 470 serum samples,and the test found that the positive rate of CFS antibody in each pig herd was almost 100%,and all positive rates of PRRS in gilts,pregnant sows,suckling sows and piglets were nearly100%,and the dispersion was 10.90%-20.18%,and the uniformity is relatively uniform;the positive rate of PRRS in sows（replacement sows,pregnant and suckling sows）and suckling piglets was almost 100%,only the positive rate of nursery pigs was 73.33%-93.33%,and the S/P value of lactating sows was mostly less than 2.5,which was in line with the normal distribution law,and the dispersion was also small,indicating that the adjusted immunization program can significantly improve the immunity level of PRRS in suckling sows;the positive rate of PR g E antibody in sows was 13.33%-100%,in suckling piglets was 53.33%-100%,and the positive rate in nursery pigs was >33.33%,and the difference in dispersion was big,indicating that the infection of pseudorabies continues to increase,and the risk was high.To sum up,this study systematically monitored the antibody levels of major three viruses diseases in a large-scale breeding pig farm in Shandong Province from 2018 to 2020,and adjusted and optimized the immune programs according to the actual problems in the pig farm,in addition to pseudorabies,there were still large wild virus infection,and the immunity level of classical swine fever and porcine blue ear disease was further improved.The results of this study have certain reference significance for epidemic disease antibody monitoring and immune program optimization in large-scale breeding pig farms. |
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