Experimental infection of pregnant ewes with enteric and abortion-source Chlamydophila abortus

Two groups of pregnant ewes were experimentally infected oronasally in midp regnancy. A faecal and an abortion-source isolate of Chlamydophila abortus were used. They were derived from a healthy ewe from a flock with no histor y of abortion, and from an aborted factus in a farm with enzootic abortion. As assessed by modified Ziehl-Neelsen (MZN) staining, egg culture, antigen ELISA, the Clearview((R)) test and immunohistochemistry, inoculation resul ted in placental and/or foetal infection in all ewes. Histopathology reveal ed placentitis in two and four ewes inoculated with the enteric or abortion -source isolate, respectively, in addition, these samples were immunohistoc hemically positive for chlamydial antigen. All six ewes infected with the e nteric isolate and five of seven ewes infected with the abortion-source iso late showed evidence for a serological response by an indirect ELISA or CFT . Neither chlamydiae nor lesions were detected in the placentae and lambs o f the uninfected control ewes, which remained seronegative. Our results sug gest that enteric C. abortus can be associated with placental and foetal le sions in sheep. (C) 2001 Elsevier Science B.V. All rights reserved.