Deer ticks, Lyme disease carriers, found in Montana
Laura Lundquist
(Missoula Current) Montana appears to have a new invasive species, and this one could come with a few nasty parasites.
The Montana Department of Public Health and Human Services announced last week that three blacklegged ticks, also called deer ticks, have been found in eastern Montana over the past year. While the ticks aren’t necessarily pleasant, the real problem is that they’re known to carry Lyme disease, in addition to several other parasites that can infect people and animals.
The first blacklegged tick was found in Dawson County around Glendive earlier in 2024. A man found the tick on his hunting dog and sent it to the Montana State University Extension's Schutter Diagnostic Lab, where diagnostician Marni Rolston identified it. Rolston collaborated with scientists at the National Institutes of Health’s Rocky Mountain Laboratory in Hamilton to confirm the identification.
"This discovery is incredibly important because it greatly expands the geographic range of the blacklegged tick, a carrier of the pathogen that causes Lyme Disease,” said Bob Peterson, an MSU entomologist in a release. “The implications of finding this tick in Montana cannot be overstated."
In the fall of 2024, two more ticks were found in Sheridan County in far northeast Montana, an area popular for bird hunting, and DPHHS, along with the Centers for Disease Control and Prevention, confirmed they were blacklegged ticks.
The percentage of blacklegged ticks that are infected with Lyme disease ranges from none to more than 50% of a population, depending on the area and life stage. Lyme disease infection occurs mostly in the northeastern, mid-Atlantic, and north-central United States, according to the CDC. Blacklegged ticks found in most areas of the southeastern United States are almost never infected.
Lyme disease can produce a wide range of symptoms, depending on the stage of infection. These include fever, rash, facial paralysis, an irregular heartbeat and arthritis.
No pathogens were found on the ticks in Montana, according to the DPHHS. But their presence means Montanans should be alert, particularly in Dawson and Sheridan counties, said Devon Cozart, DPHHS vector-borne disease epidemiologist.
“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,” Cozart said in a release. “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.”
Blacklegged ticks are not native to Montana. Research indicates they survived the Ice Age in the southeastern U.S. and then steadily expanded northward during the 20th century, spurred by reforestation, a warming climate and animal hosts moving north. In addition, blacklegged ticks have subsequently been spreading west, followed by the lone star tick.
Research has shown that several species can serve as migration vectors for ticks, including deer and migratory birds. People can also factor in, because they move animals around, including horses and dogs. In recent years, the number of nonresidents using eastern Montana to train their dogs in the winter and hunt in the fall has surged. Just like ticks can be carried into your house, one or two ticks could hitch rides to Montana on nonresident dogs from the hotbeds of Minnesota, Iowa and Wisconsin.
If anything, dog owners should be concerned because pets can get Lyme disease too. In most cases, a tick must be attached for more than 24 hours before the Lyme disease bacterium can be transmitted, according to the CDC. If you remove a tick within 24 hours, you can greatly reduce the chances of you or your pets getting Lyme disease.
According to the CDC, the established populations currently closest to Montana are in the eastern portions of the Dakotas and throughout Minnesota. A November 2023 CDC scientific review concluded that, because black-legged ticks have established in counties in the far eastern parts of Nebraska and the Dakotas, “it is reasonable to assume that (blacklegged ticks) invaded in recent decades from the eastern neighboring states of Minnesota and Iowa.”
The map showing tick presence could change to include Montana if researchers find more ticks. To that end, DPHHS is launching a citizen-scientist program and is requesting the public’s help in tick surveillance, especially in Dawson and Sheridan counties. Anyone who thinks they have found a blacklegged tick is encouraged to fill out this online form.
Montana is home to the Rocky Mountain wood tick and the American dog tick, which can also spread diseases such as Rocky Mountain spotted fever and Colorado tick fever. These ticks tend to be brown and are much larger than the dark-red deer tick.
Contact reporter Laura Lundquist at lundquist@missoulacurrent.com.