Human monocytic ehrlichiosis; HME; Human granulocytic ehrlichiosis; HGE; Human granulocytic anaplasmosis; HGA
Ehrlichiosis is an infectious disease transmitted by the bite of a tick.
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:
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 fewer than half of 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.
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. Doxycycline used for 2 weeks or less typically does not cause discoloration of a child's permanent teeth.
Ehrlichiosis is rarely deadly. With antibiotics, patients usually improve within 24 - 48 hours. Recovery takes 3 weeks.
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.
Ehrlichiosis is spread by tick bites. Preventing tick bites will prevent this, and other, tick-borne diseases. Common measures to prevent tick bites 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 bitten by a tick, write down the date and time the bite happened, and bring this information, along with the tick (if possible), to your doctor if you become sick.
Walker DH, Cumler JS. Ehrlichia chaffeensis (human monocytotropic ehrlichiosis), anaplasma phagocytophilum (human granulocytotropic anaplasmosis), and other ehrlichieae. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 6th ed. Philadelphia, Pa : Churchill Livingstone Elsevier; 2005: chap 190.
© 2011 University of Maryland Medical Center (UMMC). All rights reserved.
UMMC is a member of the University of Maryland Medical System,
22 S. Greene Street, Baltimore, MD 21201. TDD: 1-800-735-2258 or 1.866.408.6885