Evaluation of a commercially available ELISA kit for detection of antibodies to Anaplasma marginale and Anaplasma centrale in cattle in Australia and Zimbabwe

Abstract

A newly available competitive inhibition ELISA kit for the serological diagnosis of anaplasmosis was evaluated in Australia and Zimbabwe. In Australia the performance of the test was compared with the card agglutination test (CAT). The assay was evaluated using negative sera collected from Anaplasma-free herds, positive sera from experimentally infected cattle and sera from Anaplasma marginale-endemic herds. The sensitivity and specificity of the ELISA in Australia were 100 and 83.3%, respectively, and the sensitivity and specificity of the CAT were both 100%. The agreement between the ELISA and CAT in the sera from endemic herds was 86.4% (kappa=0.718). The specificity of the ELISA in Zimbabwe was 100%. No meaningful estimate of sensitivity was possible in Zimbabwe because few known positive sera were available for testing, but all eight known positive sera that were available were clearly positive. We conclude that the ELISA is a useful alternative to the CAT for epidemiological studies. The ELISA kits have advantages over the CAT in that the ELISA is more robust and reagents are better standardized, but the kits are expensive.