Recent advances on ovine chlamydial abortion.

This paper reviews new findings on ovine chlamydial abortion. Concerning chlamydial taxonomy, with the recent advances due to the analysis of the ribosomal genes, nine genotypic groups were identified separated into two lineages. It also describes the transmission of the disease, the site of entry of the organism and chlamydial shedding by underlying the role of latent infections. Recent results also concern the pathogenesis, with the kinetics of placental colonization and placental pathology leading to abortion in ruminants. Studies using experimental infection in a pregnant mouse model have allowed the identification of target placental cells and have shown the differential evolution of the infection according to the stage of pregnancy. Different diagnosis techniques are compared (ELISA, PCR and immunofluorescence for the direct diagnosis) but also the possibilities of distinction between antibodies against Chlamydia pecorum and Chlamydia psittaci (for serodiagnosis). The recent advances on prophylaxis are presented, as well as the research efforts needs for the next century.