About Ehrlichiosis
Ehrlichiosis is an illness spread by ticks. It is preventable and treatable. In Wisconsin, ehrlichiosis is caused by the bacterium Ehrlichia muris eauclairensis. This type of ehrlichiosis is spread by the deer tick, also known as the black-legged tick. In the southeastern and south-central United States, ehrlichiosis is caused by the bacteria Ehrlichia chaffeensis and Ehrlichia ewingii. Ehrlichia chaffeensis and Ehrlichia ewingii are spread by the lone star tick. Lone star ticks are rare in Wisconsin.
Anyone can get ehrlichiosis. People who spend more time outdoors are at a higher risk of being bitten by an infected tick. Ticks are found in areas with woods, brush, or tall grass. In Wisconsin, ticks are most active from May to November but they can be active anytime temperatures are above 40° F.
Map description
The map to the right shows the annual average number of cases of ehrlichiosis caused by Ehrlichia muris eauclairensis per 100,000 people by county. Ehrlichiosis in Wisconsin is rare, and is more common in the northern region of the state. The deer tick, which spreads ehrlichiosis in Wisconsin, is also more common in northern Wisconsin.
Protect yourself with Tick Bite Prevention
Ehrlichiosis 101
In Wisconsin, ehrlichiosis is spread to humans through the bite of an infected deer tick.
A tick must be attached to a person for a certain amount of time, likely at least 12-24 hours, before it’s able to spread ehrlichiosis. To help prevent illness, remove ticks as soon as you find them.
Most people are infected by immature ticks, called nymphs. Nymphs are very small, about the size of a poppy seed. They’re hard to see. Most people don’t feel their bites. This makes them harder to remove right away. Nymphs are most active during the spring and early summer.
Adult ticks also spread ehrlichiosis. Adults are larger than nymphs. They’re more likely to be found and removed before the bacteria spread to the person. The image to the right shows an adult deer tick. Adult ticks are most active during the cooler months in early spring and fall.
Ticks can attach to any part of the body. They often are found in hard-to-see areas, such as:
- Behind the knees.
- In the armpits.
- On the scalp.
- In and around the ears.
- Inside the belly button.
- On the groin.
Ehrlichiosis is preventable and treatable. Learn about Tick Bite Prevention and how to properly remove any ticks you find.
Symptoms can show up between five days to two weeks after being bitten by an infected tick. Early signs and symptoms are usually mild. If antibiotic treatment is delayed, more severe symptoms can occur. It’s important to get treatment as soon as possible to avoid serious illness.
The following symptoms may be seen with ehrlichiosis. However, few people will have all the symptoms listed. The combination of symptoms varies for each person.
Early signs and symptoms
- Fever
- Chills
- Severe headache
- Muscle aches
- Tiredness
- Nausea, vomiting, diarrhea
- Confusion
Late signs and symptoms
- Damage to the brain or nervous system
- Respiratory failure
- Uncontrolled bleeding
- Organ failure
Ehrlichiosis can be treated with antibiotics. Doxycycline is the most effective antibiotic for adults and children of all ages. Treatment should begin as soon as the doctor suspects you have ehrlichiosis. Most people treated with oral antibiotics during the early stages of ehrlichiosis fully recover.
It’s important to get treatment as soon as symptoms start. Delaying treatment can be dangerous.
Antibiotic treatment following a tick bite (also called tick bite prophylaxis) isn’t recommended to prevent ehrlichiosis. There is no evidence this practice is effective. It may only delay onset of disease. Instead, if you’re bitten by a tick, be alert for the symptoms listed above. Call a doctor if you develop a fever or other symptoms.
Resources from the Wisconsin Department of Health Services (DHS)
- Signs and symptoms, treatment, and prevention—Ehrlichiosis caused by Ehrlichia muris eauclairensis Fact Sheet, P-03323 (PDF)
- Signs and symptoms, treatment, and prevention—Anaplasmosis and Ehrlichiosis Fact Sheet, P-42045
- Education on the risk of illnesses spread by ticks—Tickborne Diseases Risk in Wisconsin, P-01751 (PDF)
- Educational tri-fold card about ticks in Wisconsin, proper removal, and tick bite prevention—Tick Safety Guide Tri-Fold Card, P-01434
- Fact sheet with simple steps to take—Protecting Your Family From Mosquitoes and Ticks, P-02080
Resources from the CDC
- Signs and symptoms, treatment, prevention, and more—CDC Ehrlichiosis Page
- Preventing Ticks on Your Pets
- Fact sheet on tick bite prevention for hunters.—It's Open Season on Ticks (PDF)
- Plastic trail sign used to remind hikers that there are ticks in the area—Prevent Tick Bites (PDF). Order the sign from CDC Publications on Demand.
- Fact sheet on steps to take after a tick bite—Tick Bite: What to Do (PDF)
- Educational comic for kids—Don't Let a Tick Make You Sick Comic (PDF)
- Educational crossword for kids—Don't Let a Tick Make You Sick Crossword (PDF)
Partner resources
- Information from the University of Wisconsin-Madison Medical Entomology Laboratory—Wisconsin Ticks and Tick-borne Diseases
- Information on ticks found in the Midwest, surveillance resources, and tick biology and development from the Midwest Center of Excellence for Vector-Borne Diseases—Ticks
Contact us
Questions about illnesses spread by ticks? We’re here to help.
Bureau of Communicable Diseases
Phone: 608-267-9003
Fax: 608-261-4976