A Surprising Number Of Wisconsin Ticks Now Carry Lyme Disease

It is officially tick season in Wisconsin, and if you are spending time outdoors hiking, camping, fishing, or simply working in the yard, there is something worth knowing before you head out the door.

Tick season is active, and a new study suggests the odds of encountering an infected tick in Wisconsin are higher than many people realize.

According to the Wisconsin Department of Health Services, ticks in the state are typically most active from May through November, though activity can occur any time temperatures climb above freezing.

Three tick species in Wisconsin are known to spread disease to people — the deer tick, the wood tick, and the lone star tick. Of those, the deer tick is the one that demands the most attention.

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Lyme Disease Is On The Rise In Wisconsin

Lyme disease is the most common tick-borne illness in the upper Midwest by a wide margin, and the deer tick is its primary carrier.

The same tick can also transmit pathogens that cause anaplasmosis, babesiosis, ehrlichiosis, and several other tick-borne diseases.

Reports indicate Lyme disease cases in Wisconsin have quadrupled over the past 20 years, with 6,469 confirmed cases recorded in 2024 alone, which was a record year for the state.

New Marshfield Clinic Study Reveals Lyme Disease Threat Higher Than Expected

Marshfield Clinic Research Institute puts those numbers in sharper focus. The institute's Tick Inventory via Citizen Science Project, also known as TICS, compiled results from 12,493 tick submissions from Wisconsin residents over two years.

Researchers tested 707 adult female deer ticks collected across the state and found that 51 percent carried the bacteria responsible for Lyme disease. Lead researcher Dr. Alexandra Linz noted the number was higher than expected.

The study also found higher concentrations of infected ticks in southwestern Wisconsin and in fall samples, suggesting both geography and season play a role in exposure risk.

Researchers also flagged a concerning new development: The lone star tick, typically found in warmer climates, is now appearing in Wisconsin. That tick can cause alpha-gal syndrome, a condition that triggers a red meat allergy.

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One important clarification from researchers is that a 51 percent infection rate in ticks does not translate to a 51 percent chance of getting sick from a bite.

Studies put the actual transmission risk closer to 3 percent, and a deer tick generally needs to be attached for 24 to 36 hours before the bacteria can be passed on. Prompt removal matters.

How to Protect Yourself This Season

The Oneida County Health Department and the Wisconsin Department of Health Services recommend the following steps to reduce your risk this season:

• Wear light-colored clothing so ticks are easier to spot, and tuck pants into socks when walking in wooded or grassy areas
• Use EPA-registered repellents such as DEET, picaridin, or permethrin-treated gear
• Stay on cleared trails and avoid tall grass and brush when possible
• Shower within two hours of coming indoors, and place clothing in a dryer on high heat for 10 to 15 minutes to kill any ticks
• Perform a full-body tick check after being outdoors, paying close attention to the armpits, behind the knees, the scalp, the groin, and the sock and belt lines
• Check pets thoroughly as well, because they can carry ticks inside
• If you find a tick, grasp it with fine-tipped tweezers close to the skin, pull upward slowly and steadily, and clean the area with alcohol or soap and water

The Wisconsin DHS also recommends downloading The Tick App, a free tool from the Midwest Center of Excellence for Vector-Borne Disease that allows users to report tick encounters and access prevention tips.

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If you develop a rash, fever, fatigue, joint pain, or headache in the days or weeks after spending time outdoors, contact your healthcare provider right away. Early treatment with antibiotics is highly effective, but the longer Lyme disease goes untreated, the more serious the complications can become.