Montana Health Officials Monitoring Deer Ticks After 2024 Discovery

by Sophie Tsairis

For the first time in the state’s recorded history, blacklegged ticks — the tiny, dark parasites known for spreading disease — are out for blood in Montana. 

Three ticks, confirmed to be of the blacklegged variety and commonly known as deer ticks, were found last year in Dawson and Sheridan counties in eastern Montana. Smaller and darker than the more familiar Rocky Mountain wood ticks often encountered by outdoor enthusiasts in the state, this species is harder to detect on clothing, skin and pets. 

While three may seem like a small number, their presence is significant. Deer ticks can transmit Lyme disease, anaplasmosis and other illnesses that, until now, have not been a concern in western states like Montana.

In an email, Marni Rolston, a diagnostician in Montana State University Extension’s Schutter Diagnostic Lab told Mountain Journal that scientists believe this species of tick has been expanding its range for a few decades in part due to warmer, shorter winters, allowing them to live in areas which were previously thought to be too cold for them to survive.

Montana is home to a variety of tick species that carry pathogens dangerous to human health, including diseases such as Rocky Mountain spotted fever, Colorado tick fever, soft tick relapsing fever and an infectious disease known as tularemia that affects the skin, eyes, throat, lungs, and intestines. If the deer tick becomes established in the state, Lyme disease and other pathogens will join that list. 

“The presence of this new type of tick in the state could mean that Montanans have an increased risk of exposure to diseases that weren’t previously a threat in Montana,” said Vector-borne Disease Epidemiologist Devon Cozart in a May press release from the Montana Department of Public Health and Human Services.

DPHHS officials say it’s too early to know whether the ticks are isolated cases or signs of a growing problem.

Neighboring states offer a mixed picture. In Wyoming, there are no confirmed records of deer ticks, and reported cases of Lyme disease have to date been linked to travel outside the state. According to the University of Wyoming, the state has not historically conducted formal tick surveillance. However, a new program through Teton County Weed and Pest aims to begin monitoring ticks in the future.

To the west, Western blacklegged ticks, a related species found along the Pacific Coast that also transmits Lyme disease, have been confirmed in Idaho.

Lyme, the most common vector-borne illness in the United States, is caused by a bacterial infection transmitted through the bite of an infected deer tick. Early symptoms often include a circular “bullseye” rash at the bite site, fever, fatigue and headaches. If untreated, it can affect the joints, heart and nervous system, according to MSU’s Schutter Lab.

“Currently, tick experts do not think that the blacklegged tick is present throughout Montana,” Cozart said. “These ticks could have been carried into the state by a host animal, or they could be active and reproducing here — we just don’t know yet. We will be conducting further investigations this spring.”

DPHHS is asking the public to help with tick surveillance by submitting a report through an online form if they believe they’ve found a deer tick. The data will help determine whether the species is becoming established in Montana or simply passing through with migrating wildlife.