Retrospective study of porcine circovirus 2 infection in Japan: Seven cases in 1989

Retrospectively, we demonstrated that seven pigs necropsied in 1989 had cha racteristic porcine circovirus 2 (PCV-2) lymphoid tissue lesions of severe lymphoid depletion, syncytial giant cell formation, and intracytoplasmic in clusion bodies in macrophages. Immunohistochemically, PCV-2 antigen was det ected in these tissues and the distribution of positive staining correspond ed to the distribution of inclusion bodies. Electron microscopy demonstrate d viral particles compatible with porcine PCV-2. Therefore, the disease occ urred in Japan as early as 1989.