Ehrlichiosis

Ehrlichiosis is an infectious tick-borne disease caused by bacteria of the genus Ehrlichia, most commonly Ehrlichia chaffeensis (human monocytic ehrlichiosis) and Ehrlichia ewingii (Ehrlichia ewingii ehrlichiosis). It is not a genetic disorder but rather an acquired bacterial infection transmitted primarily through the bite of the Lone Star tick (Amblyomma americanum) in the United States. The bacteria infect white blood cells (monocytes and granulocytes), leading to a systemic inflammatory illness that can affect multiple organ systems including the hematologic, hepatic, renal, and central nervous systems. Key clinical features typically appear 1 to 2 weeks after a tick bite and include high fever, severe headache, malaise, myalgia (muscle pain), nausea, vomiting, and sometimes a rash (more common in children). Laboratory findings frequently reveal leukopenia (low white blood cell count), thrombocytopenia (low platelet count), and elevated liver transaminases. In severe cases, ehrlichiosis can progress to a toxic shock-like syndrome, meningoencephalitis, respiratory failure, or disseminated intravascular coagulation, and can be fatal, particularly in immunocompromised individuals or those with delayed treatment. The standard treatment is doxycycline, which is the first-line antibiotic recommended for all age groups, including children, when ehrlichiosis is suspected. Early empiric treatment is critical, as delays in therapy are associated with increased morbidity and mortality. Supportive care may be necessary for severe cases. Prevention focuses on tick avoidance measures, including use of protective clothing and insect repellents. There is currently no vaccine available for ehrlichiosis.

Common questions about Ehrlichiosis