Ehrlichiosis (air-lick-ee-oh-sus) is a tick-borne disease of white blood cells caused by very small bacteria. The bacteria invade white blood cells called monocytes and so ehrlichiosis is also called human monocytic ehrlichiosis (HME). Ehrlichiosis occurs primarily in the southeastern United States and has been reported rarely in California.
The bacteria that cause ehrlichiosis are carried by certain kinds of ticks and can be transmitted to a person when a tick bites them. In the south central U.S., the lone star tick (Amblyoma americanum
) is known to carry and transmit the agent of ehrlichiosis. The tick vector in California has not been identified.
Taking appropriate precautions to avoid tick bites can reduce the risk of infection with ehrlichiosis, as well as other diseases transmitted by ticks. If possible, avoid areas where ticks are known to occur. When in these areas, wear light-colored long pants and long sleeve shirts. Insecticides with pyrethrin can be applied to clothing to further deter ticks from attaching. When outdoor activities are completed, thoroughly examine yourself and promptly remove any ticks that may be attached.