Abstract
In 1998, 36% of all test sera from Gifu Prefecture contained an antibody against the porcine reproductive and respiratory syndrome (PRRS) virus. A retrospectively serological survey employing the enzyme-linked immunosorbent assay (ELISA) on sera collected from 1982 to 1998 showed that the antibody to PRRS virus was first detected in sera collected from fattening pigs in May 1988. Thereafter, the positive rate in Gifu Prefecture increased rapidly. No significant difference were observed between positive rates obtained with ELISA and those obtained from indirect immunofluorescence assay.
