Lyme Disease and Related Tick-Borne Infections - Ehrlichiosis

Highlights	Diseases with Similar Symptoms	Babesiosis
Introduction	Diagnosis	Resources
Symptoms	Treatment	References
Risk Factors	Prevention
Complications	Ehrlichiosis

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Ehrlichiosis

Ehrlichiosis refers to several tick-borne diseases caused by very small organisms called Ehrlichiae, which affect both humans and animals. Ehrlichiae are gram negative bacteria that infect and destroy white blood cells. Two human diseases are caused by varieties of Ehrlichiae found in the U.S.

Human monocyte ehrlichiosis (HME) infects white cells known as monocytes. More than 1000 cases of HME have been reported since it was first identified in 1986. It is caused by the bacterium Ehrlichiachaffeensis and is carried by the Lone Star tick, found primarily in the southcentral and southeastern U.S.
Human granulocytic ehrlichiosis (HGE) infects granulocyte white blood cells. It is more likely than HME to be carried by adult Ixodes ticks and so is most often found northeastern and upper midwestern states.

Ehrlichiosis caused by other or unspecifiedorganisms is a new category that was added in 2000 to account for other cases of these bacteria that have been detected.

Both HGE and HME have been reported in Europe. In fact, a Swedish study reported an almost equal prevalence of ehrlichiosis and Lyme disease in one population group. The European form of HGE appears to be a less severe condition than in the U.S. HME has also been reported in Africa.

Some studies indicate that middle-aged and elderly men are most likely to be infected with either form of ehrlichiosis.

Symptoms of Ehrlichiosis

Ehrlichiosis usually develops rapidly. Patients who are infected with ehrlichiosis will begin to feel symptoms between3to 16 days after being bitten by an infected tick. A patient may feel fine early in the day only to experience very severe, debilitating symptoms a few hours later. While ehrlichiosis is often very mild, with only flu-like symptoms, in some cases, symptoms can be severe:

Rash -- about one-third of HME patients and a smaller proportion of HGE patients develop a rash; the rash does not form a circle as it does in Lyme disease
Fever

Other common symptoms may include:

Malaise
Confusion
Severe headache
Muscle and joint aches
Chills
Cough
Nausea, vomiting, and lack of appetite

In serious cases, the patients may develop mental abnormalities, breathing difficulties, and kidney problems. Symptoms that affect the central nervous system, including seizures, coma, a stiff neck, sensitivity to light, and others, may be mistaken for meningitis. There does not appear to be a chronic phase for the ehrlichiosis, although much is still unknown about the disease.