Ticks, Mosquitos, and Worms, Oh My!

Ticks and mosquitoes are out in full-force this summer! This is the next post in our tick and mosquito series, and we’re looking at the most common diseases spread by ticks and mosquitoes in Wisconsin, as well as a few critters to keep your eyes on if you’re traveling abroad.

It’s the season for spending time outdoors, travel, and fun family trips, and whether you’re hopping on a plane to go someplace tropical, or road tripping to a campsite here in Wisconsin, or even hanging out in your backyard or local park, be on the lookout for bugs that could bite, burrow, and spread disease.

Illnesses Spread by Ticks in Wisconsin

Ticks can carry multiple pathogens (or germs) that may cause illness in humans. We monitor trends in these diseases to determine patterns where the risk of getting sick is high, such as geographical locations and times of the year. Our monitoring can also help our state and healthcare partners determine if current diagnosis processes and treatment courses are still effective. 

Check out our Reportable Disease Data Dashboard and select “Vector-borne” to see trends in these diseases over time.

The most common type of tick that people and animals get sick from in Wisconsin is the deer tick, also called the blacklegged tick. If you get bitten by a tick and want to know what type it is, the Wisconsin Department of Health Services (DHS) offers the ability to submit an image for identification through their Tick Identification Service. You can also download the Tick App to log any tick encounters and get personalized prevention tips.

Image credit: CDC

The early symptoms of different tickborne diseases are usually pretty similar. They often start within 30 days after a bite from an infected tick. Call your doctor if you have any of these symptoms in the month after you know you’ve been bit or you’ve spent a good amount of time outside (camping, hiking, etc.):

• Fever and/or chills
• Rash (which may look like a bullseye, but keep in mind not everyone gets this telltale rash)
• Headache
• Fatigue
• Muscle and/or joint aches

Below are some examples of diseases carried by ticks. For more information on these or other tickborne illnesses, visit the DHS webpage on Illnesses Spread by Ticks.

Lyme Disease

Lyme disease, which is spread by the deer tick, is the most commonly reported tick-borne illness in Wisconsin. It’s caused by bacteria, which means treatment involves antibiotics. An infected tick must be attached for at least 24–36 hours to spread the disease to a person, so be sure to safely remove ticks as soon as you find them.

Powassan Virus

Powassan virus is another illness spread by the infamous deer tick. In 2024, there were 12 cases reported in Wisconsin, which is the most in state history. It isn’t known exactly how long an infected tick must be attached to a person to spread the virus, but it’s likely less than 12 hours and could be as little as 15 minutes. Powassan virus can cause serious illness, and unfortunately there is no treatment. In addition to the symptoms above, an infected person could also experience nausea, vomiting, and neck stiffness in the early stages.

Anaplasmosis & Ehrlichiosis

Anaplasmosis and ehrlichiosis each occur when a tick infected with a bacteria bites a person. The difference between the two is the type of bacteria that causes illness. A tick must be attached for at least 12 hours to spread anaplasmosis or ehrlichiosis. Both diseases are treated with antibiotics, and it’s important to get treatment as soon as possible after symptoms start. Symptoms of anaplasmosis or ehrlichiosis may start as early as 5 days after being bitten.

Take action to prevent tick bites and remove ticks if you're bitten 

Check out our blog on how to prevent tick bites and safely remove ticks if bitten. And remember, if you’re diagnosed with a disease caused by bacteria and your doctor prescribes antibiotics, be sure to take the antibiotics exactly as directed, including dosage, frequency, and duration.