Chlamydiae in porcine abortion

Formalin-fixed, paraffin-embedded fetal livers and lungs from 139 cases of swine abortion were investigated retrospectively for chlamydiae by means of immunohistochemistry. Using a genus-specific antibody, chlamydial antigen was found in eight livers obtained from five (3.6%) abortion cases from different herds. All lung sections were negative. Chlamydiae were also labeled in five of the eight positive livers using a monoclonal antibody against immunotype 1 of Chlamydia psittaci; the remaining three livers were negative. No reactivity was seen using an antibody specific for C. trachomatis. Chlamydiae should be considered a cause of abortion in sows in Switzerland. Porcine abortigenic strains identified in this study differed immunologically from intestinal strains (known to be mainly C. trachomatis) but shared similarities with abortigenic chlamydiae of ruminants.