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Alternative Names Return to topHuman 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.