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Division of Epidemiology and Health Planning
275 East Main Street
Frankfort, KY  40621
502-564-3418 or 3261 

What Is Ehrlichiosis?

Ehrlichiosis is caused by several bacterial species in the genus Ehrlichia that affect humans and animals. Currently there are four ehrlichial species that are known to cause disease in humans. Human monocytic ehrlichiosis (HME) from infection with Ehrlichia chaffeensis is the ehrlichial disease most often reported in Kentucky and other southeastern and midwestern states. Six or fewer confirmed cases per year have been reported in Kentucky since 1991.


How Ehrlichiosis Is Spread?

Human monocytic ehrlichiosis is spread by the bite of an infected tick. The lone star tick, Amblyomma americanum is the primary vector for HME. Other known vectors of ehrlichiosis in the United States are the blacklegged tick (Ixodes scapularis) and the western blacklegged tick (Ixodes pacificus). Ticks become infected with ehrlichiae while feeding on blood from the host animal in their larval or nymphal state. Whitetail deer are the major host of the lone star ticks. The tick develops into the next stage and the ehrlichiae are then transmitted to the following host during the feeding process. Both the nymphal and adult stages are probably capable of transmitting the ehrlichiae to the next host.
The Symptoms Of Ehrlichiosis
The incubation period for ehrlichiosis is usually 5-10 days following the tick bite, but can be up to 21 days. The most common symptoms include fever, headache, loss of appetite, muscle aches, and fatigue. Other symptoms sometimes reported are nausea, vomiting, diarrhea, cough, joint pains, confusion and rash. Rash is uncommon in adult patients, but about 60% of pediatric patients exhibit rash. Ehrlichiosis can be a severe illness and many patients require hospitalization. Severe cases may have prolonged fever, kidney failure, blood clotting disorders, meningoencephalitis, adult respiratory distress syndrome, seizures, or coma. It is possible that many infected persons have no symptoms or symptoms so mild that they do not seek medical attention.

How Eehrlichiosis Is Diagnosed

Diagnosis is based on clinical and laboratory findings. Routine laboratory tests indicative of ehrlichiosis include low white blood cell count, low platelet count, and elevated liver enzymes. Confirmation of ehrlichiosis can be difficult as some of the tests have limited availability and interpretation can be complex.

The Treatment For Ehrlichiosis

Appropriate antibiotic treatment with tetracyclines should be initiated immediately by a health care provider when ehrlichiosis is suspected based on the clinical signs and the possibility of exposure to the tick vector. Treatment should not be delayed waiting for laboratory confirmation. Fever usually subsides within 24-72 hours after treatment with the proper antibiotic. Preventive therapy in non-ill patients who have had recent tick bites is not warranted.

How To Prevent Ehrlichiosis





Last Updated 12/16/2008
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