Human Ehrlichiosis

Q. What is ehrlichiosis? (pronounced air lick ee OH sis)
A. Ehrlichiosis is the general name used to describe several bacterial diseases that affect animals and humans. These diseases are caused by the organisms in the genus Ehrlichia. Worldwide, there are currently four ehrlichial species that are known to cause disease in humans.

Q. How do people get ehrlichiosis?
A. In the United States, ehrlichiae are transmitted by the bite of an infected tick. The lone star tick (Amblyomma americanum), the blacklegged tick (Ixodes scapularis), and the western blacklegged tick (Ixodes pacificus) are known vectors of ehrlichiosis in the United States. Ixodes ricinus is the primary vector in Europe.

Q. What are the symptoms of ehrlichiosis?
A. The symptoms of ehrlichiosis may resemble symptoms of various other infectious and non-infectious diseases. These clinical features generally include fever, headache, fatigue, and muscle aches. Other signs and symptoms may include nausea, vomiting, diarrhea, cough, joint pains, confusion, and occasionally rash. Symptoms typically appear after an incubation period of 5-10 days following the tick bite. It is possible that many individuals who become infected with ehrlichiae do not become ill or they develop only very mild symptoms.

Q. In the United States, where do most cases of ehrlichiosis occur?
A. Most cases of ehrlichiosis are reported within the geographic distribution of the vector ticks (see map below). Occasionally, cases are reported from areas outside the distribution of the tick vector. In most instances, these cases have involved persons who traveled to areas where the diseases are endemic, and who had been bitten by an infected tick and developed symptoms after returning home. Therefore, if you traveled to an ehrlichiosis-endemic area 2 weeks prior to becoming ill, you should tell your doctor where you traveled.

Figure 20.  Areas where human ehrlichiosis may occur based on
approximate distribution of vector tick species

For further information, see Human Ehrlichiosis Information Paper or Human Ehrlichiosis Fact Sheet from USACHPPM.

Source: http://www.cdc.gov/ncidod/dvrd/ehrlichia/Q&A/Q&A.htm