Ehrlichia chaffeensis andEhrlichia ewingii are transmitted by the lonestar tick in the southeastern and southcentral United States. In addition, a thirdEhrlichia species provisionally called Ehrlichia muris-like (EML) has been identified in a small number of patients residing in or traveling to Minnesota and Wisconsin; a tick vector for the EML organism has not yet been established. The symptoms caused by infection with these Ehrlichia species usually develop 1-2 weeks after being bitten by an infected tick. The tick bite is usually painless, and about half of the people who develop ehrlichiosis may not even remember being bitten by a tick.
Treatment: Doxycycline is the first line treatment for adults and children of all ages and should be initiated immediately whenever ehrlichiosis is suspected. Use of antibiotics other than doxycycline and other tetracyclines is associated with a higher risk of fatal outcome for some rickettsial infections.