Factors contributing to emergence of Ehrlichia and Anaplasma spp. as human pathogens

Ehrlichioses and anaplasmoses are caused by α-proteobacteria within the family of Anaplasmataceae. These diseases have been known for a long time in veterinary medicine and recently in human medicine. These tick-borne zoonoses are considered as emerging diseases. The first case of human monocytotropic ehrlichiosis occurred in 1986. Human granulocytic anaplasmosis was described as a separate entity in 1994 and ehrlichiosis caused by Ehrlichia ewingii was reported in humans in 1999. The number of cases has been rising steadily due to better diagnostic techniques and better surveillance worldwide. In this review, we will present human and animal ehrlichioses and anaplasmoses as emerging diseases and present candidate(s) for the future.