Ehrlichia and Anaplasma
المؤلف:
Cornelissen, C. N., Harvey, R. A., & Fisher, B. D
المصدر:
Lippincott Illustrated Reviews Microbiology
الجزء والصفحة:
3rd edition , p200-201
2025-08-04
516
Ehrlichia and Anaplasma resemble Rickettsia in appearance and behavior. However, these organisms parasitize monocytes and neutrophils, respectively, and grow exclusively within host-derived cytoplasmic vacuoles, creating characteristic inclusions called morulae.
A. Clinical significance
Human monocytic ehrlichiosis (HME) is caused by Ehrlichia chaffeensis. Human granulocytic anaplasmosis (HGA) is caused by the organism Anaplasma phagocytophilum (Figure 1). The symptoms of HME and HGA are similar and often nonspecific. Common symptoms include fever, chills, headache, myalgia, and arthralgia. HME often presents with nausea, which is rare with HGA. More severe manifestations of HME include meningoencephalitis, myocarditis, and acute renal failure. Serious manifestations of HGA include severe leukocytopenia and thrombocytopenia due to damage of the infected cell populations. Rash is seldom seen for either HME or HGA, and deaths from HGA and HME have occurred. HME has been confirmed in some thirty states in the southeastern and south-central United States and has been most commonly associated with bites of the Lone Star tick. HGA has been associated with the bites of deer and dog ticks and has been reported in North and South America, Europe, and Asia.
Fig1. Diseases caused by Ehrlichia and Anaplasma.
B. Laboratory identification
Antibody assays and a PCR method have been diagnostically useful in investigative laboratories. Occasionally, the characteristic morulae can be seen in peripheral blood smears during acute illness.
C. Treatment
The treatment of choice is doxycycline.
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