ISOLATION OF CIRCOVIRUS FROM LESIONS OF PIGS WITH POSTWEANING MULTISYSTEMIC WASTING SYNDROME

Postweaning multisystemic wasting syndrome (PMWS), an apparently new d isease, has been recognized in swine herds in western Canada. Young pi gs with this disease have progressive weight loss, tachypnea, dyspnea, and jaundice, accompanied by interstitial pneumonia, lymphadenopathy, hepatitis, and nephritis. We examined more than 400 pigs from more th an 70 herds in Alberta, Saskatchewan, and Manitoba with cases of PMWS. A small virus was isolated from a range of tissues from 8 of 8 affect ed pigs examined. The agent was identified as a circovirus-like virus using electron microscopy, immunohistochemical staining with porcine a nd rabbit immune serum, and in situ hybridization. Immunohistochemical examination of tissues from more than 100 affected pigs has revealed widespread viral antigen, often contained in circovirus-like inclusion bodies, in lesions from numerous organs. Although Koch's postulates r emain to be fulfilled, these results demonstrate a high degree of asso ciation between the presence of the circovirus-like virus and PMWS in affected swine.