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.
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