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Ehrlichiosis

• Ehrlichiosis [air-lick-ee-OH-sis] is a newly recognized bacterial disease that is spread by infected ticks. Two types of human ehrlichiosis have been identified in the United States: human monocytic ehrlichiosis and human granulocytic ehrlichiosis.
• Most infections are mild or without symptoms, but some can be severe and life-threatening.
• Ehrlichiosis can usually be treated with antibiotics.
• Prevention centers on avoiding exposure to ticks and removing attached ticks promptly.

What is ehrlichiosis?

Ehrlichiosis is a newly recognized and potentially life-threatening disease that is spread by ticks. Since 1986, two types of human ehrlichiosis have been identified in the United States: human monocytic ehrlichiosis (HME) and human granulocytic ehrlichiosis (HGE). The illnesses differ in the types of white blood cells they attack -- either monocytes or granulocytes.

What is the infectious agent that causes ehrlichiosis?

Ehrlichiosis is caused by specialized bacteria called rickettsiae. HME is caused by Ehrlichia chaffeensis. HGE is caused by a newly identified but as yet unnamed Ehrlichia.

Where is ehrlichiosis found?

In the United States, HME has so far been concentrated in the southeast and south-central regions. HGE has been found mainly in the upper midwestern and northeastern states, but also in northern California.

How do people get ehrlichiosis?

People get ehrlichiosis from the bite of an infected tick. Evidence suggests that the lone star tick transmits HME and that the deer tick transmits HGE. The deer tick also spreads Lyme disease and babesiosis.

What are the signs and symptoms of ehrlichiosis?

The disease is similar to Rocky Mountain spotted fever and can be severe and life-threatening. The most common symptoms are sudden high fever, tiredness, major muscle aches, severe headache, and, in some cases, a rash.

How soon after exposure do symptoms appear?

Symptoms usually appear 3 to 16 days after a tick bite.

How is ehrlichiosis diagnosed?

Diagnosis is difficult, even in severe cases. Special laboratory tests can detect recent infection with Ehrlichia bacteria. Because diagnostic tests are not widely available, the diagnosis of ehrlichiosis is usually based on symptoms and a history of exposure to ticks.

Who is at risk for ehrlichiosis?

Anyone can get ehrlichiosis, although most cases have been in adults. The risk of severe illness and complications is probably highest in older persons. People who spend time outside in tick-infested areas during the spring and summer are also at increased risk for exposure.

What complications can result from ehrlichiosis?

Severely ill patients can develop abnormally low numbers of white blood cells, abnormally low numbers of platelets, and kidney failure. Deaths have been reported for both HME and HGE. Ehrlichiosis does not appear to result in the long-term, arthritis-like symptoms sometimes associated with Lyme disease.

What is the treatment for ehrlichiosis?

Ehrlichiosis can be treated with antibiotics .

How common is ehrlichiosis?

It is not known how common HME and HGE are in the United States. Approximately 200 cases of HGE and 400 cases of HME have been confirmed. It is likely, however, that many more cases are untreated or misdiagnosed.

Is ehrlichiosis an emerging infectious disease?

Yes. Ehrlichiosis was shown to cause disease in people in 1986. Since then, HME and, later, HGE have emerged as major diseases in humans. Both the number of cases and their geographic range continue to increase.

How can ehrlichiosis be prevented?

No vaccine is available to protect humans against HME or HGE. You can reduce your risk by taking these precautions against tick bites:

• During outside activities, wear long sleeves and long pants tucked into socks. Wear a hat, and tie hair back.
• Use insecticides to repel or kill ticks. Repellents containing the compound DEET can be used on exposed skin except for the face, but they do not kill ticks and are not 100% effective in preventing tick bites. Products containing permethrin kill ticks, but they cannot be used on the skin -- only on clothing. When using any of these chemicals, follow label directions carefully. Be especially cautious when using them on children.
• After outdoor activities, check yourself for ticks, and have a "buddy" check you, too. Check body areas where ticks are commonly found: behind the knees, between the fingers and toes, under the arms, in and behind the ears, and on the neck, hairline, and top of the head. Check places where clothing presses on the skin.
• Remove attached ticks immediately. Removing a tick before it has been attached for more than 24 hours greatly reduces the risk of infection. Use tweezers, and grab as closely to the skin as possible. Do not try to remove ticks by squeezing them, coating them with petroleum jelly, or burning them with a match.

This fact sheet is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health-care provider. If you have any questions about the disease described above or think that you may have ehrlichiosis, consult a health-care provider.

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