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In the U.S., the term “ehrlichiosis” is broadly applied to multiple different infections. Ehrlichia chaffeensis and Ehrlichia ewingii are transmitted by the lone star tick (Amblyomma americanum) in the southeastern and southcentral U.S. Ehrlichia muris-like (EML) has been diagnosed in a small number of patients from Minnesota and Wisconsin. The tick that causes EML has yet to be determined. The disease is characterized by fever, headache, chills, and muscle aches. Ehrlichiosis is diagnosed based on clinical signs and symptoms and then later confirmed using laboratory tests. The most effective treatment is doxycycline. The disease can be prevented by prompt tick removal.
Anyone who lives or recreates where the tick species may be present could become infected. The majority of reported human illnesses are due to Ehrlichia chaffeensis. Ehrlichia chaffeensis and Ehrlichia ewingii are commonly reported from the southeastern and southcentral U.S., from the eastern seaboard extending westward to Texas. Ehrlichia muris-like has been reported from Minnesota and Wisconsin.
Incidence of ehrlichiosis ranged from 0.03 to 1 case per million persons in Michigan. The frequency of disease is highest among males and individuals over 50 years of age. People can become infected throughout the entire year. However, the majority of the cases have an onset of clinical signs/symptoms in June and July which corresponds to peak tick activity for the adult and nymphal stages of the tick.
What are the signs and symptoms of Ehrlichiosis?
The signs and symptoms associated with these Ehrlichia species will typically develop 1-2 weeks after the bite from an infected tick. The general signs include fever, headache, chills, muscle aches, nausea, red eyes, and/or rash. However, a rash may not be a common clinical sign as approximately 60% of children and less than 30% of adults with Ehrlichia chaffeensis infection may develop a rash.
This disease could be fatal if not treated correctly. Those individuals who develop severe symptoms may experience difficulty breathing and/or bleeding disorders. Approximately 1.8% of patients die as a result of the infection.
How is ehrlichiosis diagnosed?
Ehrlichiosis is a difficult disease to diagnose. The disease symptoms may vary from person to person and may resemble other diseases. Diagnostic tests, especially those based on the detection of antibodies, will often appear negative for the first 7-10 days of illness. Treatment is most effective if started early in the course of the disease. Thus, there is no test available at this time that can provide definitive results during the initial stages of the disease.
The diagnosis of ehrlichiosis is based on clinical suspicion alone. The diagnosis must be made based on clinical signs and symptoms, and can later be confirmed using specialized confirmatory laboratory tests.
Additional information regarding the diagnosis of ehrlichiosis can be found at:
What should I do if I have a tick that I want to identify or test?
Knowing what kind of tick bit you may be important in knowing what your risk of disease is. The Michigan Department of Health and Human Services (MDHHS) provides tick identification at no charge to Michigan citizens. There are two ways to have a tick identified, 1) By submitting a photo of your tick, or, 2) by sending the tick to the MDHHS for microscopic identification. If you want to submit a photo of your tick, the MDHHS will make all attempts to identify the tick based on the condition of the tick and the condition of the photos. However, definitive tick identification may only be made by sending the tick for microscopic examination.
Ticks that are submitted from people to the MDHHS for microscopic identification and identified as blacklegged ticks (also known as deer tick) and are alive will be forwarded to the MDHHS Bureau of Laboratories for Lyme disease screening only, at no cost. Ticks that are dead when they are received or are from animals (dog, cat, horse, etc.) will not be tested however, they will be identified to species and life stage.
What is the treatment for ehrlichiosis?
Doxycycline is the first line treatment for adults and children of all ages and should be initiated immediately whenever ehrlichiosis is suspected. Infected individuals who are treated early and correctly may recover quickly via outpatient medication. However, those experiencing more severe symptoms may require hospitalization. Treatment should never be delayed pending the receipt of laboratory results, or be withheld on the basis of an initial negative laboratory result.
Ticks are responsible for transmitting ehrlichiosis. Two of the ehrlichial species are transmitted by the bite of an infected lone star tick (Amblyomma americanum).
How can I prevent ehrlichiosis?
The most effective way to prevent ehrlichiosis is to prevent tick attachment.
- Avoid direct contact with ticks
- Ticks are typically found in wooded and brushy areas
- Stay in the center of hiking trails
- Repel ticks with DEET or permethrin
- Use repellents containing 20 to 30% DEET (N, N-diethyl-m-toluamide) on exposed skin and clothing
- Treat clothing and gear with products containing 0.5% permethrin
- Find and remove ticks from your body
- Perform frequent tick checks throughout your day
- Conduct a full-body tick check upon return from tick-infested areas
- Wear light-colored clothing to make it easier to see the ticks
- Tuck long pants into high socks
- Wear a long-sleeve shirt
- Avoid direct contact with ticks
- The Tick Management Handbook
An integrated guide for homeowners, pest control operators, and public health officials for the prevention of tick-associated disease (Connecticut Agricultural Experiment Station)
- CDC: Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis - A Practical Guide for Health Care and Public Health Professionals
- Michigan's Five Most Common Ticks
Ticks are significant vectors (carriers) of pathogens that cause human and animal disease. In Michigan, tick-borne diseases are rare, but they do occur and can be serious if not properly diagnosed and treated.
- Michigan Tick ID Card
Pocket-sized card for identifying common ticks in Michigan. Information regarding tick removal and tick-bite prevention.
- Tickborne Diseases of the U.S. - information from the CDC
- Ticks and Your Health
Brochure describing Lyme disease and other tick-borne diseases in Michigan. Other topics covered include tick-bite prevention, preventing ticks on pets, and landscape techniques to minimize tick risk.
- Tick Removal