| Porcine Reproductive and Respiratory Syndrome(PRRS)is a porcine infectious disease caused by Porcine Reproductive and Respiratory Syndrome Virus(PRRSV).It is mainly characterized by respiratory symptoms in piglets and reproductive disorders in sows.It is one of the most popular porcine infectious diseases worldwide.,The economic loss caused every year is huge.At present,the prevention and control of the disease mainly relies on vaccines,and the widely used types of vaccines mainly include inactivated vaccines and attenuated vaccines.Inactivated vaccines have high safety,but poor immunogenicity.Attenuated live vaccines have good immunogenicity,but there is a risk of returning to strong virulence.Both vaccines have poor cross-protection against heterologous strains.In addition to immunization,other comprehensive prevention and control measures can be taken,including monitoring and phasing out diseased pigs and drug control,among which virus monitoring and antibody monitoring are the key to establishing a PRRS stable field.This article analyzes the correlation between sow PRRSV antibody level and production performance,and monitors the changes of PRRSV antigen and antibody after negative pigs are immunized,and provides technical data for the later stage of PRRSV hazard evaluation and antigen and antibody monitoring in pig farms.The research obtained the following results :(1)Correlation analysis between sow PRRSV antibody level and production performance.Select 39 pregnant sows not immunized with PRRS vaccine but antibody-positive to track their production,record the qualified number of sows in each group,number of live piglets,number of live piglets,total number of piglets,litter weight,number of stillborns,and mummified fetuses Use SPSS23.0 for data analysis,perform natural logarithmic transformation on data that does not obey the normal distribution,and count live weak,deformed,stillbirth,and mummified fetuses.Conversion of(appearing value is 1,not appearing value is 0);using 9 indicators as dependent variables,antibody value as independent variable,measurement data to establish a linear regression model(using partial regression coefficient β to represent the quantitative relationship);count data Establish a logistic regression model(express the quantitative relationship with the odds ratio OR).The results showed that there was no significant correlation between the level of antibody value of virulent sows and the number of qualified piglets,number of live piglets,total number of piglets,litter weight,number of deformities,number of stillbirths,number of mummies,and number of weak piglets.(2)Analysis of PRRS attenuated vaccine time after inoculation.Select PRRS-negative reserve pigs,and collect blood 14-84 days after the injection of the attenuated PRRS vaccine,at an interval of 14 days,with 20 pigs each time.The RT-PCR technology was used to detect PRRSV.The results showed that the positive detection rate of PRRSV reached a peak 28-42 days after the injection of the attenuated vaccine,and the detection rate of the antigen at 84 days after vaccination was 0.The law of PRRSV vaccine attenuation in pigs The curve appears as a single peak.(3)Changes in antibody levels in pigs vaccinated with PRRS attenuated vaccine.Test the N protein antibody and neutralizing antibody of each group.The results show that the dispersion of N protein antibody is large at the initial stage of vaccination;when the positive rate of N protein antibody reaches 100%,the dispersion is small,and the dispersion in the later period does not change much.At this time,use the dispersion It is more accurate to evaluate the ability of immunized pigs to resist wild virus infection.The neutralizing antibody 100% positive time lags behind the N protein antibody 100% positive time by 14days;only 15% of the pig PRRSV neutralizing antibodies are positive at 28 days after immunization.The neutralizing antibody level varies greatly among individuals.The neutralizing antibody induced by attenuated vaccine And the overall antibody titer is not high.In summary,there is no significant correlation between the PRRSV antibody level of virulent sows and the number of piglets passing,number of live piglets,total number of piglets,litter weight,number of stillbirths,number of mummies,number of weak piglets and other production performance,and the production performance is high or low(Reproductive indicators)cannot be directly related to the level of PRRS antibodies;the detection rate of PRRSV after injection of attenuated vaccine reaches a peak at 28-42 days after vaccination,which is about 30%;at 84 days after immunization,the detection rate of PRRSV is 0.The positive rate of N protein antibody reached 100% 42 days after immunization with the attenuated PRRS vaccine,and the dispersion became stable;the time for neutralizing antibody to reach 100% positive was 14 days later than the time of 100% positive for N protein antibody,and the overall neutralizing antibody titer At a low level,and individual differences are obvious. |
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