Ehrlichiosis is a bacterial infection transmitted by the bite of a tick.
Human monocytic ehrlichiosis; HME; Human granulocytic ehrlichiosis; HGE; Human granulocytic anaplasmosis; HGA
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. There are two types of the disease in the United States:
Ehrlichia bacteria can be carried by the:
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:
The incubation period between the tick bite and when symptoms occur is about 7 to 14 days.
Symptoms may seem like the flu (influenza), and may include:
Other possible symptoms:
A rash appears in fewer than one third of cases. Sometimes, the disease may be mistaken for Rocky Mountain spotted fever, if the rash is present. The symptoms are often mild, but people are sometimes sick enough to see a health care provider.
Antibiotics (tetracycline or doxycycline) are used to treat the disease. Children should not take tetracycline by mouth until after all their permanent teeth have grown in, because it can permanently change the color of growing teeth. Doxycycline that is used for 2 weeks or less usually does not discolor a child's permanent teeth. Rifampin has also been used in people who cannot tolerate doxycycline.
Ehrlichiosis is rarely deadly. With antibiotics, people usually improve within 24 to 48 hours. Recovery may take up to 3 weeks.
Untreated, this infection may lead to:
In rare cases, a tick bite can lead to more than one infection (co-infection). This is because ticks can carry more than one type of organism. Two such co-infections are:
Contact your provider if you become sick after a recent tick bite or if you have been in areas where ticks are common. Be sure to tell your provider about the tick exposure.
Ehrlichiosis is spread by tick bites. Measures should be taken to prevent tick bites, including:
After returning home:
Studies suggest that a tick must be attached to your body for at least 24 hours to cause disease. Early removal may prevent infection.
If you are bitten by a tick, write down the date and time the bite happened. Bring this information, along with the tick (if possible), to your provider if you become sick.
Published Date: September 01, 2021
Published By: Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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Fournier PE, Raoult D. Rickettsial infections. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 311.