The sero-diagnosis of heartwater: a comparison of five tests.

Five serological tests, the indirect and competitive ELISA, the indirect fluorescent antibody (IFA) test with 2 different antigens and the Western blot technique were compared and applied to sera that were known to be either negative or positive against Cowdria ruminantium or that were collected from animals in heartwater-free regions. No false positive reactions were recorded with any of the tests against the known negative sera. Except for minor variations in the sensitivity of the 5 tests, there was good correlation between them. Their specificity, however, remains in dispute since in all 5 tests extensive cross-reactions were recorded with antibodies in response to an as yet unidentified agent, probably Ehrlichia.