Early warning effect of antibody monitoring on prevention and control of porcine reproductive and respiratory syndrome in large-scale pig farms
In order to reveal the variation rule of PRRS antibody levels in immunized and non-immunized pigs,two self-propagated pig farms of similar scale were selected in Longyan city,Fujian province.One farm was immunized with TJM-F92 strains from a do-mestic manufacturer,while the other was not immunized.PRRS antibody was detected and analyzed in commercial pigs of different weeks of age in two farms by ELISA method.ORF5 gene of two PRRSV strains detected in clinical samples was sequenced by RT-PCR method,and sequence analysis was performed in combination with reference strains.The antibody detection results showed that the positive rate of PRRS antibody in 248 sera from the unimmunized field decreased from 70.0%at 4 weeks of age to 26.7%at 10 weeks of age,and the positive rate of PRRS antibody began to rise after 14 weeks of age until 18 weeks of age,maintaining 97.1%-100%.Among 170 sera from the immunization field,the antibody level was higher at 2 weeks of age and the positive rate was 100%.After immunization,the antibody levels were 80%,70%and 90%at 6 weeks of age,8 weeks of age and 10 weeks of age,respectively,and the other weeks of age were 100%.The genetic evolution analysis of ORF5 gene showed that the strain detected in immune field was HP-PRRSV,which had 70.5%～93.8%homology with HP-PRRSV(JXA1,HuN4,etc.)and vaccine strains HP-PRRSV TJM-F92,and was in the same subbranch with JXA1,HuN4,etc.The homology between the strain detected in non-immune field and NADC30 was 87.2%,belonging to NADC30-like clade.Therefore,when the positive rate of PRRS antibody is low and individual S/P values are high and the dispersion degree is large,treatment measures should be taken immediately to prevent secondary infection caused by PRRSV infection in pig farms.This study indicated that regular antibody monitoring could play an effective early warning role in the prevention and control of PRRS in vaccine immune field and positive stable field.
Porcine reproductive and respiratory syndromeELISA RT-PCRMonitoringEarly warning
国家科技期刊平台
NSTL
万方数据
