Chlamydial abortion in sheep: Possibilities of serological diagnosis with a competitive ELISA and insight into the epidemiologic situation in Switzerland

466 sheep sera out of 19 flocks in Switzerland were examined by a competiti ve enzyme linked immunosorbent assay (cELISA) for antibodies against Chlamy dia psittaci "serotype 1" ("ovine enzootic abortion"). Since numerous posit ive re actors were found in flocks without abortion history, 30 fecal sampl es out of two of these flocks were examined by PCR for evidence of chlamydi al DNA. One of these samples turned out to contain DNA of Chlamydia psittac i "serotype 1". These results suggest, that in Switzerland "serotype 1" of Chlamydia psittaci is widespread not only as cause of chlamydial abortion b ut also as latent intestinal infection in sheep. The resulting difficulties for serological diagnosis of chlamydial abortion and possible solutions ba sed on the cELISA are discussed. The complement fixation test (CFT), still considered as standard method for serological examination for Chlamydiae, h as additionally been applied.