Ehrlichiosis

Figure 1 E. chaffeensis morulae in the cytoplasm of a human monocyte.  Photograph courtesy of the Centers for Disease Control.

Figure 2 Image showing E. ewingii morulae in the cytoplasm of a neutrophil. Photograph courtesy of the Centers for Disease Control

Ehrlichiosis is the general name used to describe several bacterial diseases that affect animals and humans.  Ehrlichia is an obligate intracellular gram negative bacteria of the Rickettsiaceae family.  It is transmitted by the Ixodes tick, the same vector implicated in Lyme disease and babesiosis.  There are currently two species of Ehrlichia that are known to cause disease in humans: Ehrlichia chaffeensis and Ehrlichia ewingii. Ehrlichia chaffeensis causes human ehrlichiosis also described as human monocytic ehrlichiosis (HME).

The symptoms include fever, myalgias, malaise, headache, chills, nausea, joint pains and confusion.  The absence of a rash can help to distinguish ehrlichiosis clinically from Lyme disease and Rocky Mountain Spotted Fever.  Symptoms typically appear after an incubation period of 5-10 days following a tick bite.  Ehrlichiosis can be a serious infection with a mortality rate of 3%. However, it is possible to become infected with ehrlichiae and develop only mild symptoms.

Diagnosis is based on a combination of clinical signs, symptoms  and confirmatory lab tests.   Antibiotics are the treatment of choice.

More information:

http://en.wikipedia.org/wiki/Ehrlichiosis

http://www.columbia-lyme.org/patients/tbd_ehrli-anapla.html