Effect of porcine reproductive and respiratory syndrome virus infection onthe ovary and progesterone levels in third trimester pregnant sows

Porcine reproductive and respiratory syndrome virus (PRRSV) is a common cau se of reproductive failure and abortion in swine. The mechanism of abortion is not fully defined, and the effect of the virus on luteal function has n ot been explored. In this study, we exposed late-term pregnant swine to var ied doses of PRRSV strain NADC-8 and evaluated effects on ovarian function by serial determination of plasma progesterone levels and by microscopic ev aluation of ovarian pathologic alterations combined with immunohistochemist ry and in situ hybridization to detect PRRSV antigen. We identified no spec ific trend in plasma progesterone level associated with PRRSV infection sta tus and no microscopic ovarian lesions, PRRSV antigen was not demonstrated in ovarian tissues by immunohistochemistry or in situ hybridization at necr opsy 21 days postexposure. Based on these findings, it does not appear that either a direct or an indirect effect on luteal function contributes to PR RSV-induced abortion. (C) 2001 by Elsevier Science Inc.