Retrospective serological survey of Porcine circovirus-2 infection in Mexico.

Postweaning multisystemic wasting syndrome (PMWS) is considered a multifactorial emerging disease of which Porcine circovirus-2 (PCV-2) is the necessary infectious cause. However, retrospective studies have shown that PMWS is not a new disease and that PCV-2 has been circulating in pig farms for years. Most of these studies were performed in Europe and Asia; only a few were performed in North or South America. A PCV-2 retrospective serological survey was carried out with 659 serum samples collected from pigs in Mexico between 1972 and 2000. Serological analyses were performed with an immunoperoxidase monolayer assay (IPMA). The overall prevalence of PCV-2 antibodies was 59% (387/659); the prevalence was 27% (24/90) for the period from 1972-1979; 44% (74/169) from 1980-1989, and 72% (289/400) from 1990-2000. Antibodies to PCV-2 were detected in at least 1 pig from all tested years since 1973. This study shows evidence of enzootic PCV-2 infection in Mexico for many years before the first description of PMWS in the country (in 2001), further supporting results obtained in other parts of the world. To date, this study provides the earliest evidence of PCV-2 infection in the North and South American continents.