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Related to ehrlichiosis: Human granulocytic ehrlichiosis




Ehrlichiosis is a bacterial infection that is spread by ticks. Symptoms include fever, chills, headache, muscle aches, and tiredness.


Ehrlichiosis is a tick-borne disease caused by infection with Ehrlichia bacteria. Ticks are small, blood-sucking arachnids. Although some ticks carry disease-causing organisms, most do not. When an animal or person is bitten by a tick that carries bacteria, the bacteria are passed to that person or animal during the tick's feeding process. It is believed that the tick must remain attached to the person or animal for at least 24 hours to spread the infection.
There are two forms of ehrlichiosis in the United States; human monocytic ehrlichiosis and human granulocytic ehrlichiosis. Monocytic ehrlichiosis is caused by Ehrlichia chaffeensis, which is spread by the Lone Star tick, Amblyomma americanum. As of early 1998, about 400 cases of monocytic ehrlichiosis had been reported in 30 states, primarily in the southeastern and south central United States. The bacteria that causes granulocytic ehrlichiosis is not known, but suspected to be either Ehrlichia equi or Ehrlichia phagocytophila. Granulocytic ehrlichiosis is probably spread by the blacklegged tick Ixodes scapularis (which also spreads Lyme disease). About 100 cases of granulocytic ehrlichiosis have been reported in Connecticut, Massachusetts, Rhode Island, Minnesota, New York, and Wisconsin.

Causes and symptoms

Both forms of ehrlichiosis have similar symptoms, and the illnesses can range from mild to severe and life-threatening. Risk factors include old age and exposure to ticks through work or recreation. Symptoms occur seven to 21 days following a tick bite although patients may not recall being bitten. Fever, tiredness, headache, muscle aches, chills, loss of appetite, confusion, nausea, and vomiting are common to both diseases. A rash may occur.


Ehrlichiosis may be diagnosed and treated by doctors who specialize in blood diseases (hematologists) or an infectious disease specialist. Because ehrlichiosis is not very common and the symptoms are not unique, it may be misdiagnosed. A recent history of a tick bite is helpful in the diagnosis. Blood tests will be done to look for antibodies to Ehrlichia. Staining and microscopic examination of the blood sample may show Ehrlichia bacteria inside white blood cells. Another test, called polymerase chain reaction (PCR), is a very sensitive assay to detect bacteria in the blood sample, but it is not always available.


Antibiotic treatment should begin immediately if ehrlichiosis is suspected, even if laboratory results are not available. Treatment with either tetracycline (Sumycin, Achromycin V) or doxycycline (Monodox, Vibramycin) is recommended. Many patients with ehrlichiosis are admitted to the hospital for treatment.


For otherwise healthy people, a full recovery is expected following treatment for ehrlichiosis. Elderly patients are at a higher risk for severe disease, which may be fatal. Serious complications include lung or gastrointestinal bleeding. Two to 10 patients out of 100 die from the disease.


The only prevention for ehrlichiosis is to minimize exposure to ticks by staying on the trail when walking through the woods, avoiding tall grasses, wearing long sleeves and tucking pant legs into socks, wearing insect repellent, and checking for ticks after an outing. Remove a tick as soon as possible by grasping the tick with tweezers and gently pulling.

Key terms

Tick-borne disease — A disease that is spread to animals by the bite of an infected tick.



McDade, Joseph E., and James G. Olsen. "Ehrlichiosis, Q Fever, Typhus, Rickettsialpox, and Other Rickettsioses." In Infectious Diseases. 2nd ed. Philadelphia: W. B. Saunders Co., 1998.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


Infection with leukocytic rickettsiae of the genus Ehrlichia; in humans, especially by E. sennetsu that produces manifestations similar to those of Rocky Mountain spotted fever.
Farlex Partner Medical Dictionary © Farlex 2012


Infection with parasitic rickettsiae of the genus Ehrlichia, especially E. sennetsu, that are transmitted by ticks and produce manifestations in humans similar to those of Rocky Mountain spotted fever, including rash, muscle pain, and fever.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


Infectious disease A rare tick-borne infection, caused by Ehrlichia canis, that usually affects dogs Clinical Fever, chills, rigors, malaise, nausea, myalgia, anorexia, encephalopathy, acute respiratory failure with infiltrates, acute renal failure with ↑ creatinine Lab ↓ platelets, ↑ transaminases Treatment Chloramphenicol, tetracycline
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


A tick-borne infection of humans, dogs, and many other mammals caused by bacteria from the Neorickettsia, Anaplasma, and Ehrlichia groups; produces manifestations similar to those of Rocky Mountain spotted fever.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


A rare human infection with Ehrlichia organisms such as E. canis that normally infect animals. The first known human infection was described in Japan in 1954. The illness is usually acquired by a tick bite and resembles glandular fever (infective mononucleosis). A new species, E. chaffeensis , was isolated in 1991 and a third in 1994. The disease is largely confined to the Southeast and mid-Atlantic states of the USA.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005


Infection with leukocytic rickettsiae of the genus Ehrlichia; in humans, especially by E. sennetsu, which produces manifestations similar to those of Rocky Mountain spotted fever.
Medical Dictionary for the Dental Professions © Farlex 2012
References in periodicals archive ?
Serology of culture-confirmed cases of human granulocytic ehrlichiosis. J Clin Microbiol.
The test for ehrlichiosis looks for two versions of the ehrlichia bacteria.
Ehrlichiosis and anaplasmosis can be treated with Doxycycline for at least 21 days.
Like ehrlichiosis, babesiosis tends to affect people who are immune-compromised, and it can be fatal in older adults.
Among the canine hemoprotozoan diseases, Ehrlichiosis and Babesiosis were prevalent.
In rare cases, especially in immunocompromised patients, ehrlichiosis can present with fulminant features and multisystem organ dysfunction and sometimes result in death.
The epidemiology of canine ehrlichiosis is closely related not only to the vector distribution, which is more frequently associated with tropical and subtropical zones, but also to animal behavior, age, and its environment [27, 36, 37].
Likewise, E chaffeensis and E ewingii, the discoveries of which occurred in 1986 and 1999, respectively, are also relatively unknown agents associated with the underreported disease HME and ewingii ehrlichiosis. (24,25) Location of the diseases and their arthropod vectors are essential in informing medical health care providers, preventive medicine personnel, and the general population as to the risk of tick-borne diseases.
However, determining the stage of infection in dogs naturally infected with canine ehrlichiosis is difficult because of the possible presence of similar acute and chronic infection clinical signs (HARRUS & WANER, 2011).
Health threats are significant from this tick, and include an illness called the Heartland virus, as well as the bacterial infection human monocytotropic ehrlichiosis. Heartland virus, discovered in northwestern Missouri by Dr.