ABSTRACT
INTRODUCTION On the basis of the taxonomic reorganization of the family Anaplasmataceae proposed in 2000 (1), ehrlichial pathogens affecting humans include Ehrlichia chaffeensis, E. ewingii, and sporadic reports (Olano and McBride, Unpublished data) of E. canis infections in humans (2). This chapter will discuss in detail human monocytotropic ehrlichiosis (HME), caused by E. chaffeensis, and ehrlichiosis ewingii, a form of granulocytotropic ehrlichiosis, caused by E. ewingii. Before the taxonomic reorganization of the Anaplasmataceae family occurred, a pathogen formerly known as the HGE agent or E. equi/E. phagocytophila was identified as the cause of human granulocytotropic ehrlichiosis. Such pathogen is now in the genus Anaplasma and is known as Anaplasma phagocytophilum. The disease it causes is now known as human granulocytotropic anaplasmosis, described in another chapter.
