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Human monocytic ehrlichiosis; HME; Human granulocytic ehrlichiosis; HGE; Human granulocytic anaplasmosis; HGA DefinitionEhrlichiosis is a bacterial infection transmitted by the bite of a tick. CausesEhrlichiosis 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:
SymptomsThe 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. Exams and TestsYour provider will do a physical exam and check your vital signs, including:
Other tests include:
TreatmentAntibiotics (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. Outlook (Prognosis)Ehrlichiosis is rarely deadly. With antibiotics, people usually improve within 24 to 48 hours. Recovery may take up to 3 weeks. Possible ComplicationsUntreated, 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:
When to Contact a Medical ProfessionalContact 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. PreventionEhrlichiosis 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. ReferencesDumler JS, Walker DH. Ehrlichia chaffeensis (human monocytotropic ehrlichiosis), Anaplasma phagocytophilum (human granulocytotropic anaplasmosis), and other anaplasmataceae. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 192. Fournier PE, Raoult D. Rickettsial infections. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 302. | |
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Review Date: 8/26/2023 Reviewed 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 C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. No warranty of any kind, either expressed or implied, is made as to the accuracy, reliability, timeliness, or correctness of any translations made by a third-party service of the information provided herein into any other language. © 1997- A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited. | |