At present, despite extensive laboratory investigations, most cases of porcine abortions remain without an etiological diagnosis. Due to a lack of recent data on the abortigenic effect of Chlamydiales, 286 fetuses and their placentae of 113 abortion cases (1 to 5 fetuses per abortion case) were investigated by polymerase chain reaction (PCR) methods for Chlamydiaceae and selected Chlamydia-like-organisms such as Parachlamydia acanthamoebae and Waddlia chondrophila. In 0.35% of the cases (1/286 fetuses) the Chlamydiaceae real-time PCR was positive. In this Chlamydiaceae-positive fetus, Chlamydia
abortus was detected by a commercial microarray and 16S-ribsomal RNA PCR followed by sequencing. This fetus had a porcine circovirus type 2 co-infection. By the Parachlamydia real-time PCR, 3.5% (10/286 fetuses of nine abortion cases) were questionable positive (Ct values between 35.0 and 45.0). In two of these ten cases, a confirmation by Chlamydiales specific real-time PCR was possible. All samples were tested negative by the Waddlia realtime PCR. It seems unlikely that Chlamydiaceae, Parachlamydia and Waddlia play an important role as abortigenic agents in Swiss sows.