Monitoring Of The Antibody And Pathogen Of CSFV And PRRSV In Immunized Pigs Of A Pig Farm Located In Daqing

Classical swine fever(CSF),which is caused by classical swine fever virus(CSFV),is an acute and highly contagious porcine disease with a high mortality.It caused significant economic losses to many countries around the world,and was listed as a category I epidemic disease.In recent years,the epidemic of CSF haspresented several new features including persistent infection and immunization failure,raising a series of challenges to the prevention and control of CSF.Porcine reproductive and respiratory syndrome(PRRS)is also an important infectious disease which threats the development of global swine industry.In 2006,the outbreak of ahigh pathogenic PRRS in China caused significant economic losses.At present,vaccination remains the primary strategyfor preventing and controlling CSF and PRRS in China.In the present study,using commercial ELISA kits,we performed immunological surveillance of CSFV and PRRSV in a large-scale pig farm located in Qaqing.It may contribute to the optimization of scientific immunization procedures.The immunologic surveillance of CSFV showed that: i)The positive rate of CSFV antibody in the second immunization group reached 95%,much higher than that in the single-immunization group(66.1%).To further confirm the efficacy of second immunization,more piglets were immunized.The positive rate of CSFV antibody for 418 porcine serum samples reached 91.4%,which is higher than the national standard of immunization plan(70%);The coefficient of variation for CSFV antibody was in the normal range(21.15%);the immune situation of CSF in this pig farm was satisfactory.ii)The positive rate of CSFV antigen for 530 porcine serum samples was 0%,although 18 ambiguous samples were also detected.No obvious preference for specified blocking rate of CSFV antibody was found in these ambiguous samples which were further confirmed as CSFV antigen negative using RT-PCR.The risk of latent infection in this pig farm is low.Theimmunologic surveillance of PRRSV revealed that: i)The positive rate of PRRSV antibody in the second immunization group reached 98.35%,higher than that inthe single-immunizationgroup(83.93%).To further confirm the efficacy of second immunization,more piglets were immunized.The positive rate of PRRSV antibody for 418 porcine serum samples reached 98.33%,which is higher than the national standard of immunization plan(70%);Quite a few samples showed excessively high level of PRRSV antibody,leading to a high coefficient of variation for PRRSV antibody(32.84%).ii)All these samples were detected for PRRSV antigen using a RT-PCR kit.The result showed that substantial samples were positive for PRRSV antigen,indicating the prevalence of PRRSV infection in these pigs.