Using polymerase chain reaction to obtain PRRSV-free piglets from endemically infected herds

pidemiological studies have confirmed the presence of porcine reproductive and respiratory syndrome virus (PRRSV) in Canada since 1979(Dea S, et al. Proc Mystery Swine Dis. Comm Meet. 1990; 67–72) and in the United States since 1985(Joo HS, et al; SIRS Comm Mtg, LCI. 1992; 245–249. Owen WJ, et al; SIRS Comm Mtg, LCI. 1992; 243–244). Porcine reproductive and respiratory syndrome virus is now endemic in most pig producing countries. Once it has entered a herd, PRRSV tends to remain present and active in the herd indefinitely (Muirhead M, et al. Managing pig health and the treatment of the disease. 5M Enterprises Ltd. 1997;94–101,173– 177). A number of management strategies have been used in the industry to try to control and/or eradicate PRRSV in herds.1,2 Early weaning3 and Isowean4—a modification of early weaning in which the sows farrow at the source farm—have been used to obtain weaned piglets free from certain infectious agents that are endemic in the herd.5 In this paper we describe three different management procedures: