Electronphotomicrograph of morulae in a bone marrow leukocyte in a patient with ehrlichiosis.
Arrows indicate individual ehrlichiae.
The genus Ehrlichia is currently classified as a member of the tribe Ehrlichieae, of the family Rickettsiaceae, in the order Rickettsiales. The names of the latter organisms are enclosed in quotation marks because they have not been formally proposed and accepted according to the rules of the International Code of Nomenclature of Bacteria, Bacteriological Code. However, this type of classification may be misleading because some of the Ehrlichia species have been found in cells other than their chief target cell type. The pathogen is often referred to as the agent of HGE or the HGE agent. This species is very similar, or likely identical, to E. phagocytophila and E. equi.