Chlamydial abortion and vaccination

Chlamydia psittaci induces several diseases in ruminants, among them abortions are the most common, the most important economically, and the most dangerous for human health, specially for pregnant women. Diagnosis is performed by microscopic examination of placental smears and serological analysis. The transmission of the disease occured at the time of abortion when chlamydiae are discharged profusely in infected uterine fluids, placentas and fetuses. Venereal transmission is possibly a mode of infection. Killed vaccines reduced the incidence of abortions but could not prevent the excretion of chlamydiae. Systematic use of such vaccines could allow the selection of antigenic variants. We developped a live thermosensitive vaccine which is stable, safe and efficient since it prevents abortion and chlamydial shedding at lambing. A new vaccine as efficient as live vaccine and which allow the detection of infected animals, even in vaccinated flocks, is in progress.