The detection of antibodies cross-reacting with Cowdria ruminantium in the sera of domestic ruminants in regions of South Africa where Amblyomma hebraeum does not occur.

High levels of seropositivity, in all probability attributable to Ehrlichia, were recorded in the serum of domestic ruminants throughout districts in South Africa where Amblyomma hebraeum, the vector of the heartwater agent, does not occur. The antibodies, detected with the indirect fluorescent antibody (IFA) and the indirect ELISA tests, cross-reacted with Cowdria ruminantium, which was used as antigen in both tests. A combination of the IFA and ELISA tests, currently employed to detect antibodies to C. ruminantium, facilitates the handling of appreciable numbers of sera and ensures maximum reliability.