HERD-LEVEL CRITERIA FOR EUROPEAN AND AMERICAN PRRSV SUBTYPE STATUS BASED ON SEROLOGY

摘要

The porcine reproductive and respiratory syndrome virus (PRRSV) infection has spread in pig producing countries worldwide. Antigenic variation was initially demonstrated between European and North American PRRS virus using the immunoperoxidase monolayer assay (IPMA). Since 1996 a modified live vaccine based on the American ATTC VR-2332 strain has been used in some European countries. Recently, a European strain of the virus has been identified in the US (http://www.aasp.org/news/000216qanda.html). InDenmark, an IPMA with a Danish PRRS strain (IPMA-EU) and an IPMA with the vaccine strain (IPMA-US) run in parallel have been used to discriminate between infection of a pig with the field strain or the vaccine strain by comparison of litres in blood samples. For the same purpose (at a lower cost), an ELISA procedure comprising two blocking ELISAs (ELISA-EU) and ELISA-US) run in parallel was developed. In some individuals, these methods are unable to determine whether they have been infected with only one subtype (e.g. the one subtype with the highest titre by the IPMA test), or both subtypes. In this study, we developed criteria to make this distinction at herd (or group) level.