infectious diseases
Ehrlichiosis and Anaplasmosis
Introduction
Ehrlichiosis and anaplasmosis are caused by rickettsial-like bacteria. Ehrlichiosis is caused mainly byEhrlichiachaffeensis; anaplasmosis is caused byAnaplasma phagocytophilum. Both are transmitted to humans by ticks. Symptoms resemble those of Rocky Mountain spotted fever except that a rash is much less common. Onset of illness, with fever, chills, headache, and malaise, is abrupt. (See also Overview of Rickettsial and Related Infections .) Ehrlichiosis and anaplasmosis are related to rickettsial diseases. E. chaffeensiscauses human monocytic ehrlichiosis. Most cases of monocytic ehrlichiosis have been identified in the southeastern and south central United States, where its arthropod vector (the lone star tick) is endemic. (SeeCenters for Disease Control and Prevention: Ehrlichiosis–epidemiology and statistics.) ) causes human granulocytic anaplasmosis, which occurs in the Northeast, mid-Atlantic, upper Midwest and West Coast of the United States, where its arthropod vector (ixodid ticks) is endemic. Lyme Disease , Because Lyme disease, babesiosis, and Powassan virus have the same tick vector and endemic area as anaplasmosis, ticks (and thus the people they bite) may be infected with more than one type of organism at the same time. The difference in the primary target cell (monocytes for ehrlichiosis and granulocytes for anaplasmosis) results in only minor differences in clinical manifestations. 