Ehrlichia species
MICROBIOLOGY
- Cause of tick-borne infection in humans; obligate intracellular pathogens that infect human macrophages and monocytes.
- Species described as causing human infection:
- Human monocytic ehrlichiosis (HME): due to Ehrlichia chaffeensis, transmitted by Amblyomma americanum (lone star tick, Fig 1) and possibly other tick vectors such as Dermacentor variabilis (American dog tick).
- Lone star is the most common cause of tick bites in the southern U.S. Ticks are generally found in woodland habitats with white-tail deer (considered the main reservoir).
- E. ewingii (Ee): a canine pathogen that rarely infects humans, an infection now termed "human ewingii ehrlichiosis [HEE]."
- Human cases are increasingly described from a broader range (10 states range similar to E. chaffeensis), though most to date have been in Missouri.
- ~20-30 cases are reported in the U.S. annually.
- E. muris: human infection noted in Europe, Russia, Japan/Asia, and described in the Western U.S.
- This occurs via tick vector Ixodes persulcatus complex.
- Ehrlichia species, E. muris eauclairensis
- Previously termed E. muris-like (EML) agent.
- Recently identified[14] in Wisconsin, this organism is a close relative of E. muris; the likely vector is the Ixodes scapularis tick (the same as HGA and B. burgdorferi).
- Sero-crossreactivity is seen with antibodies to E. chaffeensis, which may confuse an accurate diagnosis.
- For reporting purposes, it remains categorized in CDC reporting as "Undetermined ehrlichiosis/anaplasmosis."
- Existing PCR primers for E. chaffeensis and E. ewingii may fail to detect EML.
- Cases to date have been described in Minnesota, Wisconsin, and Michigan.
- Human monocytic ehrlichiosis (HME): due to Ehrlichia chaffeensis, transmitted by Amblyomma americanum (lone star tick, Fig 1) and possibly other tick vectors such as Dermacentor variabilis (American dog tick).
- See separate module for human granulocytic anaplasmosis [HGA] (formerly called human granulocytic ehrlichiosis) caused by the distantly related organism, Anaplasma phagocytophilum, transmitted by Ixodes scapularis (deer tick) and on the West Coast, the western black-legged tick (Ixodes pacificus) in the same distribution as Lyme disease (Borrelia burgdorferi).
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Last updated: May 17, 2024
Citation
Auwaerter, Paul. "Ehrlichia Species." Johns Hopkins ABX Guide, The Johns Hopkins University, 2024. Pediatrics Central, peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540185/3.1/Ehrlichia_species.
Auwaerter P. Ehrlichia species. Johns Hopkins ABX Guide. The Johns Hopkins University; 2024. https://peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540185/3.1/Ehrlichia_species. Accessed November 9, 2024.
Auwaerter, P. (2024). Ehrlichia species. In Johns Hopkins ABX Guide. The Johns Hopkins University. https://peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540185/3.1/Ehrlichia_species
Auwaerter P. Ehrlichia Species [Internet]. In: Johns Hopkins ABX Guide. The Johns Hopkins University; 2024. [cited 2024 November 09]. Available from: https://peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540185/3.1/Ehrlichia_species.
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