Medical Encyclopedia


Medical Encyclopedia

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Contents of this page:



Alternative Names    Return to top

Human monocytic ehrlichiosis; HME; Human granulocytic ehrlichiosis; HGE; Human granulocytic anaplasmosis; HGA

Definition    Return to top

Ehrlichiosis is an infectious disease transmitted by the bite of a tick.

Causes    Return to top

Ehrlichiosis is caused by bacteria that belong to the family called Rickettsiae. Rickettsial bacteria cause a number of serious diseases worldwide, including Rocky Mountain spotted fever and typhus. All of these diseases are spread to humans by a tick, flea, or mite bite.

Scientists first described ehrlichiosis in 1990, and have identified two types in the United States:

Ehrlichia bacteria can be carried by the Lone Star tick, the American dog tick, and the deer tick, which can also cause Lyme disease.

In the United States, HME is found mainly in the southern central states and the Southeast. HGE is found mainly in the Northeast and upper Midwest.

Risk factors for ehrlichiosis include:

Symptoms    Return to top

The time between the tick bite and when symptoms occur is about 7 - 9 days. This is called the incubation period.

Symptoms may seem like the flu (influenza), and may include:

Other possible symptoms:

A rash appears in less than half of the cases. Sometimes, the disease may be mistaken for Rocky Mountain spotted fever. The symptoms are often quite general, but patients are sometimes sick enough to see a doctor.

Exams and Tests    Return to top

The doctor will do a physical exam and check your vital signs, including:

Other tests include:

Treatment    Return to top

Antibiotics (tetracycline or doxycycline) are used to treat the disease. Young children should not take tetracycline by mouth until after all their permanent teeth have grown in, because it can permanently discolor growing teeth.

Outlook (Prognosis)    Return to top

Ehrlichiosis is rarely deadly. With antibiotics, patients usually improve within 24 - 48 hours. Recovery takes 3 weeks.

Possible Complications    Return to top

When to Contact a Medical Professional    Return to top

Call your health care provider if you become sick after a recent tick bite or if you've been in areas where ticks are common. Be sure to tell your doctor about the tick exposure.

Prevention    Return to top

Ehrlichiosis is spread by tick bites. Preventing tick bites will prevent this condition, as well as other tick-borne diseases. Common measures include:

Studies suggest that a tick must be attached to your body for at least 24 hours in order to cause disease, so early removal will prevent infection. If you are bit by a tick, write down the date and time the bite happened, and bring this information to your doctor if you become sick.

References    Return to top

Bratton RL. Tick-borne disease. Am Fam Physician. 2005; 71(12): 2323-30.

Mandell GL, Bennett JE, Dolin R. Principles and Practice of Infectious Diseases. 5th ed. London: Churchill Livingstone; 2000:2310-2315.

Update Date: 1/22/2008

Updated by: Kenneth M. Wener, MD, Department of Infectious Diseases, Lahey Clinic, Burlington, MA. Review provided by VeriMed Healthcare Network.

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