Bovine abortion of unknown infectious aetiology still remains a major economic problem. In this study, we focused on new possible abortigenic agents such as Parachlamydia acanthamoebae and Waddlia chondrophila. Retrospective samples (n = 235) taken from late-term abortions in cattle were investigated by real-time diagnostic PCR for Chlamydiaceae, rachlamydia spp. and Waddlia spp., respectively. Histological sections of cases positive by real-time PCR for any Chlamydia-related agent were further examined by immunohistochemistry using specific antibodies.
Chlamydophila abortus was detected only in three cases (1.3%) by real-time PCR and ArrayTube Microarray playing a less important role in bovine abortion compared to the situation in small ruminants in Switzerland. By real-time PCR as many as 43 of 235 (18.3%) cases turned out to be positive for Parachlamydia. The presence of Parachlamydia within placental lesions was confirmed in 35 cases (81.4%) by immunohistochemistry. The main histopathological feature in parachlamydial abortion was purulent to necrotizing placentitis (25/43). All 235 cases were negative for Waddlia by real-time PCR.
Parachlamydia should be considered as a new abortigenic agent in Swiss cattle. Since Parachlamydia may be involved in lower respiratory tract infections in humans, bovine abortion material should be handled with care given the possible zoonotic risk.