J Vet Diagn Invest 2:55-58 (1990) Chlamydial infection in aborted and stillborn lambs

Abstract. Chlamydia psittaci is a major cause of ovine abortion in the fourth to fifth months of gestation. During the lambing seasons of 1986, 1987, and 1988, fetuses from 52 cases of ovine abortion, stillbirth, or perinatal death were submitted to the laboratory for necropsy examination. Placenta or fetal tissues from 34 cases were cultured on mouse L cells for C. psittaci. Chlamydia psittaci was identified by immunofluorescence on cultures in 20 of these cases. The major gross lesion consistently associated with Chlamydial abortion was placentitis with multifocal cotyledonary necrosis and accumulation of red-brown exudate in the intercotyledonary placenta Chlamydiae appeared as spherical organisms, less than 1 µm in diameter, in the cytoplasm of tropho-blasts in impression smears of cotyledons. H istologically, placentitis was sometimes accompanied by pneumonia or encephalitis in the fetus. Chlamydia psittaci was considered the cause for fetal death when Chlamydial isolation was associated with placentitis or inflammation of other fetal tissues and when other abortifacient agents were not detected. Enzootic abortion of ewes (EAE) was first described in Scotland in 1936,9 but it was 1950 before Stamp identified Chlamydia psittaci as the etiologic agent? Chlamydia is now recognized as a major cause of ovin