Human ehrlichiosis and anaplasmosis, of all types, are nationally notifiable diseases.
Seasonality is due to higher likelihood of tick exposure/bite when people spend more time outdoors in warmer months.
Presumptive diagnosis is made in patients with potential tick exposure/demonstrated tick bite combined with fever and other characteristic constitutional symptoms plus leukopenia and/or thrombocytopenia and elevated LFTs. Serology or polymerase chain reaction confirms diagnosis.
Treatment with antibiotics should be started immediately if the diagnosis is suspected clinically. Doxycycline is the drug of choice.
Tick-borne emerging infections of white blood cells are most commonly caused by 3 different gram-negative bacteria from the Anaplasmataceae family: Ehrlichia ewingii, E chaffeensis, and Anaplasma phagocytophilum. Ehrlichia muriseauclairensis (formerly known as Ehrlichia muris-like agent, EMLA) also causes symptomatic infection and is the most recently recognized form of human ehrlichiosis. The type of infection that develops depends on the infecting bacteria and includes human monocytotropic/monocytic ehrlichiosis (HME), human granulocytotropic/granulocytic anaplasmosis (HGA), and human ewingii ehrlichiosis (HEE). The clinical manifestations of each type are generally the same. This topic deals with human infection only. CDC: ehrlichiosis Opens in new window CDC: anaplasmosis Opens in new window
History and exam
Key diagnostic factors
- history of tick bite/exposure
- history of immunosuppression
- small erythematous lesion with or without necrotic center
- nonspecific rash
Other diagnostic factors
- abdominal pain
- stiff neck
- secondary infections
- tick bite/exposure
- age over 60 years
- male sex
1st investigations to order
- peripheral blood smear
Investigations to consider
- immunofluorescence antibody assay
- polymerase chain reaction
- Western immunoblotting
- Pneumonia, bacterial or viral
- Gastroenteritides, bacterial or viral
- CDC yellow book health information for international travel: rickettsial diseases
- Tickborne diseases of the United States: a reference manual for health care providers
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