Human ehrlichiosis, an infectious rickettsial disease that’s transmitted by the bite of an infected tick, was first diagnosed in 1986. The genus Ehrlichia contains an emerging number of species that can transmit potentially life-threatening infections.
Ehrlichiosis is caused by Ehrlichia organisms, specifically E. chaffeensis and granulocytic Ehrlichia. Known vectors include the lone star tick (Amblyomma americanum), the American dog tick (Dermacentor variabilis), and deer ticks (Ixodes dammini and Ixodes scapularis).
In the United States, most cases of ehrlichiosis are reported in the south-central and southern Atlantic areas of the country, but it has also been reported in the upper midwest. Persons at highest risk include those who live in endemic and highly wooded areas, engage in activities in high grassy areas, and own a pet that may introduce a tick into the home.
The incubation period for ehrlichiosis is 9 days from the time of the tick bite. Early symptoms include fever, chills, headache, muscle pain (myalgia), and nausea. A maculopapular or petechial rash appears in about half of the cases.
Most people infected with ehrlichiosis don’t seek medical help, but it can be fatal.
Diagnosis of ehrlichiosis is based on evaluation of signs and symptoms and supporting laboratory data. A fluorescent antibody test may return positive for E. chaffeensis or granulocytic Ehrlichia. A complete blood cell count shows decreased white blood cells (WBCs), indicative of leukopenia, and a low platelet count, indicative of thrombocytopenia. Granulocyte stain shows clumps of bacteria inside the WBCs. Liver enzymes show elevated levels of transaminase.
Ehrlichiosis is treated with tetracycline or doxycycline, producing rapid improvement when used early in the disease's course. Death can occur if treatment is delayed.
PEDIATRIC TIP Oral tetracycline usually isn’t prescribed for children until all permanent teeth have erupted because it can permanently discolor teeth that are still forming.
Supportive therapy is provided to help relieve signs and symptoms.
❑Review with the patient measures to prevent tick bites when outdoors, such as wearing long-sleeve shirts and pants, tucking pants inside boots, and using insect repellent.
❑Advise the patient to stick to trails and avoid dense brush when hiking. Also tell him to avoid standing under overhanging foliage.
❑Tell the patient that he should examine himself for ticks after being outdoors and that he should remove any ticks found on his body; studies suggest that a tick must be attached for at least 24 hours in order to cause ehrlichiosis.
Review other book chapters online related to Ehrlichiosis:
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Professional Guide to Diseases (Eighth Edition) Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2005 ISBN: 1-58255-370-X 
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