PCV2?PRRSV?APP In The Fattening Period Of Pigs Co-Infection Research

PCV2 and PRRSV can cause immunosuppression in animals.Pigs infect PCV2 and PRRSV during the fattening period,resulting in decreased body resistance and lung damage,and easy to be infected with APP.APP releases Apx toxin during respiratory system proliferation,which aggravates lung cell damage in pigs and can lead to acute death in pigs.ApxIVA is a structural protein of Apx toxin.ApxIVA-N-2 antigenic protein was constructed by designing primers,constructing recombinant plasmid,expressing and purifying the ApxIVA full-length ApxIV-N' end in GenBank,and constructing ApxIVA-N-2 indirect ELISA method.Through different stages of pig serum testing,it can objectively reflect the growth and decline of the antibody of the group APP and the infection.Based on the relevant production and immunization background,PRRSV-N,PCV2-Cap,APP-ApxIV indirect ELISA method was used to conduct serological investigations on three pathogens in five(A,B,C,D,E)scale farms.The results showed that:(1)PRRSV was infected with PRRSV in the delivery room and conservation stage in the three fields of A,D and E,and the average S/P value was above 2.5;the growth pigs in the two fields of B and C were infected with PRRSV in the early stage of fattening,and the average S/P The value is around 2.0.(2)The PCV2 maternal antibody in the A field can be maintained to 150 days old;the B and C fields can be maintained to 90-125 days old;D and E can be maintained to 45-60 days old.(3)The ages of APP infection in five farms A,B,C,D,and E were mostly consistent with clinical incidence at 90-120 days old.In the B field,100 nursery pigs of 45 days old and 60 days old were selected as PCV2 as test group,and pigs which were not exempted were used as control group.The results showed:(1)PRRSV did not show positive or delayed positive effects on PRRSV infection in either 45-day-old or 60-day-old trials;(2)Strengthening PCV2 immunization has a positive effect on the protection of the disease,and 60-day-old is better than the 45-day-old plus PCV2 vaccine;(3)The ApxIV assay indicated that the PCV2 test pig was able to withstand APP challenge and produce highly specific antibodies than the control pig.