Phylogenetic position of Cowdria ruminantium (rickettsiales) determined by analysis of amplified 16S ribosomal DNA sequences

Abstract

The 16S ribosomal DNA sequence of Cowdria ruminantium, the causative agent of heartwater disease in ruminants, was determined. An analysis of this sequence showed that C. ruminantium forms a tight phylogenetic cluster with the canine pathogen Ehrlichia canis and the human pathogen Ehrlichia chaffeensis. Although a close relationship between the genus Cowdria and several members of the tribe Ehrlichieae has been suspected previously, the tight phylogenetic cluster with E. canis and E. chaffeensis is surprising in view of known differences in host preference and target cells.