Chlamydia abortus is a species in Chlamydiae that causes abortion and fetal death in mammals, including humans.
There are approximately one or two cases of chlamydiosis diagnosis in pregnant women in the United Kingdom per year. Typically transmission occurs from contact with livestock who have recently given birth.
C. abortus is endemic among ruminants such as cows and sheep and has been associated with abortion in a horse, a rabbit, guinea pigs, mice, pigs and humans. Infected females shed bacteria near the time of ovulation, so C. abortus is transmitted orally and sexually among mammals. C. abortus infection generally remains unapparent until an animal aborts late in gestation or gives birth to a weak or dead fetus.