[Chlamydia abortion in sheep: possibilities for serological diagnosis using a competitive ELISA and insight into the...

466 sheep sera out of 19 flocks in Switzerland were examined by a competitive enzyme linked immunosorbent assay (cELISA) for antibodies against Chlamydia psittaci "serotype 1" ("ovine enzootic abortion"). Since numerous positive reactors were found in flocks without abortion history, 30 fecal samples out of two of these flocks were examined by PCR for evidence of chlamydial DNA. One of these samples turned out to contain DNA of Chlamydia psittaci "serotype 1". These results suggest, that in Switzerland "serotype 1" of Chlamydia psittaci is widespread not only as cause of chlamydial abortion but also as latent intestinal infection in sheep. The resulting difficulties for serological diagnosis of chlamydial abortion and possible solutions based on the cELISA are discussed. The complement fixation test (CFT), still considered as standard method for serological examination for Chlamydiae, has additionally been applied.