Ehrlichiosis is an infectious disease transmitted by the bite of a tick.
Alternative NamesHuman monocytic ehrlichiosis; HME; Human granulocytic ehrlichiosis; HGE; Human granulocytic anaplasmosis; HGA
Causes, incidence, and risk factorsEhrlichiosis 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.
Signs and testsThe doctor will do a physical exam and check your vital signs, including:
Other tests include:
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.
Expectations (prognosis)Ehrlichiosis is rarely deadly. With antibiotics, patients usually improve within 24 - 48 hours. Recovery takes 3 weeks.
ComplicationsCall 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.
PreventionEhrlichiosis 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.
ReferencesWalker 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.
Ehrlichiosis is an infectious disease transmitted by the bite of a tick.
Alternative NamesHuman monocytic ehrlichiosis; HME; Human granulocytic ehrlichiosis; HGE; Human granulocytic anaplasmosis; HGA
Causes, incidence, and risk factorsEhrlichiosis 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 time between the tick bite and when symptoms occur is about 7 - 14 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 general, but patients are sometimes sick enough to see a doctor.
Signs and testsThe doctor will do a physical exam and check your vital signs, including:
Other tests include:
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.
Expectations (prognosis)Ehrlichiosis is rarely deadly. With antibiotics, patients usually improve within 24 - 48 hours. Recovery takes 3 weeks.
ComplicationsCall 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.
PreventionEhrlichiosis 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 to cause disease. Early removal will 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 doctor if you become sick.
ReferencesDumler JS, Walker DH. Ehrlichia chaffeensis (human monocytotropic ehrlichiosis), anaplasma phagocytophilum(human granulocytotropic anaplasmosis), and other anaplasmataceae. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa : Churchill Livingstone Elsevier; 2009: chap 193.
Reviewed ByReview Date: 08/24/2011
Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine; Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
There are two forms of ehrlichiosis in the United States; human monocytic ehrlichiosis and human granulocytic ehrlichiosis
Many patients with ehrlichiosis are admitted to the hospital for treatment
Monocytic ehrlichiosis is caused by Ehrlichia chaffeensis
Granulocytic ehrlichiosis is probably spread by the blacklegged tick Ixodes scapularis
The bacteria that causes granulocytic ehrlichiosis is not known, but suspected to be either Ehrlichia equi or Ehrlichia phagocytophila
Monocytic ehrlichiosis
Yes
Yes
Yes
Yes
Yes
About 100 cases of granulocytic ehrlichiosis have been reported in Connecticut, Massachusetts, Rhode Island, Minnesota, New York, and Wisconsin