Porcine circovirus 2 replication in colostrum-deprived piglets following experimental infection and immune stimulation using a modified live vaccine against porcine respiratory and reproductive syndrome virus

Porcine circovirus type 2 (PCV2) infection is now recognized as the major factor in the development of post-weaning multisystemic wasting syndrome (PMWS). Although Koch's postulates have been fulfilled for PCV2 and PMWS, the severe clinical expression of the disease observed in field cases has been difficult to reproduce experimentally. Some studies have demonstrated that immune stimulation associated with the use of some commercially available swine vaccines may trigger progression of PCV2 infection to disease and lesions characteristic of PMWS. Here we describe the effects on PCV2 infection in an experimental model following the use of a commercially available modified live vaccine to porcine respiratory and reproductive syndrome virus (PRRSV). Although none of the piglets infected with PCV2 developed clinical PMWS, the severity of microscopical lesions and the PCV2 antigen load associated with these lesions were higher in the PRRSV-vaccinated piglets compared with those detected in the PCV2 only infected animals.