Description

Ehrlichiosis is a tickborne bacterial infection, caused by bacteria of the family Anaplasmataceae, genera Ehrlichia and Anaplasma. These obligate intracellular bacteria infect and kill white blood cells.

The average reported annual incidence is 0.7 cases per million population. 

Species

Five species have been shown to cause human infection:

• Anaplasma phagocytophilum (which causes human granulocytic anaplasmosis, formerly known as human granulocytic ehrlichiosis). A. phagocytophilium is endemic to New England and the north central and Pacific regions of the United States.
• Ehrlichia ewingii (which causes human ewingii ehrlichiosis). E. ewingii primarily infects deer and dogs (see Ehrlichiosis (canine)).   E. ewingii is most common in the south central and southeastern states.
• Ehrlichia chaffeensis (which causes human monocytic ehrlichiosis). E. chaffeensis is most common in the south central and southeastern states.
• Ehrlichia canis
• Neorickettsia sennetsu

The latter two infections are not well studied.

Recently, human infection by the newly discovered Panola Mountain Ehrlichia species has been reported.

Symptoms

The most common symptoms include headache, muscle aches, and fatigue. A rash occurs but is uncommon. Ehrlichiosis can also blunt the immune system, which may lead to opportunistic infections such as candidiasis. If treatment is delayed, ehrlichiosis can prove fatal. The mortality rate is less than 3%.

Treatment

Doxycycline is the drug of choice. For people allergic to drugs of the tetracycline class, rifampicin is an alternative.  Early clinical experience suggested that chloramphenicol may also be effective, however in vitro susceptibility testing revealed resistance.

Wikipedia and GNU

The content of this entry is from the Wikipedia article "Ehrlichiosis" licensed under the GNU Free Documentation License.