Marshfield Clinic Research Institute Finds More Than Half of Ticks Collected in Study Had the Bacteria that Causes Lyme Disease

Thursday, May 21st, 2026 -- 10:00 AM

More than half of deer ticks tested by Marshfield Clinic Research Institute from its citizen science tick study were found to carry the bacteria that causes Lyme disease.

The Marshfield Clinic Research Institute launched the Tick Inventory via Citizen Science (TICS) in the spring of 2024 to investigate tick species ranges in the upper Midwest, as well as the pathogens carried by I. scapularis, also known as the deer tick or black-legged tick.

Deer ticks, which may only be the size of a poppy seed, are commonly found in Wisconsin in wooded areas and grasslands. They make contact as people brush past, latch onto their host and engorge in blood.

The ticks can potentially carry pathogens that can lead to different diseases. Reported Lyme disease cases have quadrupled over the past 20 years, according to the Wisconsin Department of Health Services. The TICS study shows the vital importance for Wisconsin residents and visitors’ awareness of ticks and knowing the signs and symptoms of Lyme disease.

“Ticks may be small, but the illnesses they carry are not,” said Jennifer Meece, PhD, Marshfield Clinic Research Institute senior vice president of research. “Knowing the symptoms of tickborne illnesses can mean the difference between early treatment and long‑term health complications.”

Meece and Alexandra Linz, PhD., a staff scientist at Marshfield Clinic Research Institute, published a pre-print paper May 15 that outlines the TICS study’s early findings. A preprint is an early posting of a research article before peer review by independent scientists or accepted at a journal.

New tick species are becoming more prevalent or detected for the first time as climate conditions shift. In the upper Midwest, Lyme disease is the most common tickborne disease, by far.

The deer tick, which carries Lyme disease, can also transmit the pathogens causing anaplasmosis, babesiosis, ehrlichiosis, and several more tickborne diseases in this region.

“Having a clear understanding of tick species’ endemic ranges is critical,” Linz said. “Knowing where and how these ranges are changing, including each species’ local pathogen prevalences, will be crucial to a public health response to tickborne diseases.”

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