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Biology of ehrlichiae

Daniel J Sexton, MD
J Stephen Dumler, MD
Section Editor
Stephen B Calderwood, MD
Deputy Editor
Jennifer Mitty, MD, MPH


Ehrlichiae, which include bacteria in the family Anaplasmataceae, have been known to cause diseases of interest to veterinarians for over 100 years. However, their role as agents of human disease was not recognized until 1987. Since then, the number of ehrlichiae recognized to cause human disease has rapidly expanded, as has our knowledge about the epidemiology, clinical characteristics, and treatment of the diseases caused by these organisms.

The biology of ehrlichiae will be reviewed in this topic. A discussion of the diseases caused by these bacteria is presented separately. (See "Human ehrlichiosis and anaplasmosis".)


The taxonomy of the Rickettsiales order and the two major families (Rickettsiaceae and Anaplasmataceae) underwent a radical change during the last two decades [1,2], based mostly on genomic data, but also on phenotypic features. A detailed discussion of Rickettsiaceae is presented separately. (See "Biology of Rickettsia rickettsii infection".)

The current configuration of the genus Anaplasmataceae provides for four to five clades that represent individual genera: Ehrlichia, Anaplasma, Neoehrlichia, Neorickettsia, and Wolbachia. These Anaplasmataceae can be divided into tick and non-tick transmitted bacteria:

Tick-transmitted – All members of the genera Ehrlichia, Anaplasma, and Neoehrlichia are transmitted by the bites of ticks. These include:

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Literature review current through: Nov 2017. | This topic last updated: Jul 06, 2017.
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