Comparative evaluation of a new commercial recombinant ELISA and the complement fixation test for the diagnosis of Chlamydophila abortus infection in naturally infected flocks in Tunisia

Chlamydiosis is a significant cause of abortion in goats and sheep in Tunisia. A new commercially available ELISA (ELISA-Chlamydophila abortus, ELISA-C. abortus) for detecting antibodies against C. abortus was evaluated using field sheep and goat serum samples. This ELISA is based on a recombinant antigen that expresses part of a protein from 80 to 90 kDa family that is specific to C. abortus. Serum samples collected from 219 sheep and 53 goats flock presenting abortion problems were used in this study. To assess the sensitivity of this new serological test, it was compared with the complement fixation test (CFT) using ELISA-antigen (Elisa-ag) detection and/or isolation as reference technique. Only 61.1% of the sera gave concordant results in both ELISA-C. abortus and CFT, and results were non-concordant for 22.4% due to 16.5% of doubtful results on CFT. The concordance of ELISA-C. abortus and Elisa-ag result was 65% while that of the CFT with ELISA-antigen was only 45%. This study using field material demonstrated that ELISA-C. abortus is a suitable method for diagnosis of chlamydiosis in order to implement early prophylactic measures from the first cases of abortion, both to stop the spread of infection and to prevent associated economic loss.