An experimental model for post-weaning multisystemic wasting syndrome (PMWS) in growing piglets.

Post-weaning multisystemic wasting syndrome (PMWS) is a comparatively new disease of swine, and known to occur in France since 1996. A porcine circovirus type 2 (PCV2) is found in the lesions of affected piglets. Six piglets aged 10-13 weeks were obtained from a French PMWS-affected farm. Two showing characteristic signs of PMWS (palor, weakness and emaciation) remained in poor condition and were finally killed 6 and 9 days after their arrival in the experimental unit. Tissue homogenates from these two piglets were used to reproduce mild PMWS in specific pathogen-free (SPF) piglets. This mild PMWS consisted of pyrexia (up to 41.7 degrees C) and growth retardation (up to 30% of weight reduction compared with controls) commencing 1 week after infection and lasting 3 weeks. In seven additional trials, pyrexia, growth retardation and lesions characteristic of PMWS were consistently produced in SPF and conventional piglets. However, only four of 55 inoculated SPF piglets (7.2%) showed severe wasting disease. One died and the others had to be killed 3 to 4 weeks after inoculation. None of the inoculated animals developed antibodies to any common swine viruses or bacteria, but clear evidence of PCV2 seroconversion was obtained. Our results therefore strongly suggest that PCV2 is the primary aetiological agent of PMWS. Copyright Harcourt Publishers Ltd.