Post-weaning multisystemic wasting syndrome (PMWS) in pigs in France: clinical observations from follow-up studies on affected farms

A disease affecting weaned pigs and known as Postweaning Multisystemic Wast ing Syndrome (PMWS) is described on French farms. Follow-up studies were de signed on cohorts of pigs on a group of 12 severely affected farrow-to-fini sh operations. Three of them were free of Porcine Reproductive and Respirat ory Syndrome Virus (PRRSV) infection. Three thousand and seventy eight pigs were included in the study. Mortality, from weaning to slaughter, was 11% and weeks 11-13 were the most critical. The first clinical sign reported wa s unthriftiness, then pallor and often fever with associated respiratory or digestive disorders. Wasting could follow rapidly and when clearly establi shed in an individual the prognosis was grave especially when the sick pigs were kept with their penmates. Antibiotics were administered without real efficacy. The lesions affected several viscera including lungs, spleen, kid neys and lymph nodes with a severe lymphoid depletion. The disease did not show a collective impact. From preliminary epidemiological investigations, a strong litter effect on disease susceptibility was suspected. PRRS virus was excluded as a major agent. On the other hand, a porcine circovirus (PCV 2) was found associated to the lesions. The environment was suspected as an important determining factor for the effect of PMWS in the herds.