PMWS: an emerging disease identified in archived porcine tissues

Postweaning multisystemic wasting syndrome (PMWS) is a disease caused by porcine circovirus type 2 (PCV-2). The disease was present as early as 1986 in Spain, 1989 in Japan and 1993 in Thailand. In view of this, we considered it possible that the disease may also have been present in Switzerland prior to its first description in 2001. A retrospective investigation was performed on paraffin-embedded lymphoid organs and ileum from 496 pigs aged 5–13 weeks collected between 1976 and mid-2001. The sections were investigated immunohistochemically using a monoclonal antibody specific for PCV-2 capsid antigen encoded by ORF2. Virus antigen was detected in tissue samples of 39 pigs from 28 farms. The earliest positive sample originated from 1986. After 1989, positive pigs were found almost every year among the 20–40 cases investigated annually. These results indicate that PCV-2 has been present in Switzerland for some time, and at least since 1986.