Ticks Are Migrating, Raising Disease Risks if They Can’t Be Tracked Quickly Enough

Biologist Grant Hokit came to this small meadow in the mountains outside Condon, Montana, to look for ticks. A hiking path crossed the expanse of long grasses and berry bushes.

As Hokit walked the path, he carried a handmade tool made of plastic pipes taped together to hold a large rectangle of white flannel cloth.

He poked fun at this “sophisticated” device, but the scientific survey was quite serious: He was sweeping the cloth over the shrubs and grass, hoping that “questing” ticks would latch on.

Along the summer trail, ticks dangle from blades of grass, sticking their legs out and waiting for a passing mammal.

“We got one,” Hokit said.

“So that came off of this sedge grass right here,” he said. “Simply pick them off with our fingers. We’ve got a vial that we pop them in.”

Any captured ticks would go back to Hokit’s lab in Helena for identification. Most of them would probably be identified as Rocky Mountain wood ticks.

But Hokit also wanted to find out whether new species are making their way into the state.

As human-driven climate change makes winters shorter, ticks are spending less time hibernating and have more active months when they can hitch rides on animals and people. Sometimes the ticks carry themselves — and diseases — to new parts of the country.

Hokit found deer ticks for the first time in northeastern Montana earlier this year. Deer ticks are infamous for transmitting Lyme disease and can infect people with other pathogens.

Knowing a new species like the deer tick has arrived in Montana or other states is important for doctors.

Neil Ku is an infectious disease specialist at the Billings Clinic in eastern Montana. He said most patients don’t come in right after they get bitten by a tick. They usually show up later, when they start feeling sick from a tick-borne illness.

“Fever, some chills, they may just feel bad, similar to many infections we may encounter throughout the year,” he said.

It’s rare that patients connect a tick bite to those symptoms, and even more rare that they capture and keep the tick that bit them. Sorting out whether someone might have a tick-borne illness can be complicated.

Knowing what kinds of ticks are in the region will help doctors know that they might start encountering patients infected with new diseases after a tick bite, Ku said.

That’s partially why the state is on the hunt for new tick species.

“The more we know about what’s in Montana, the better we can inform our physicians, the better care you can receive,” said Devon Cozart, a zoonotic illness and vector-borne disease epidemiologist with the Montana Department of Public Health and Human Services.

Cozart collects and tests the ticks from field surveys in Montana to see whether they are carrying any pathogens.

Whether a tick can get a human sick depends on the species, but the kind of mammal it feeds on also plays a role.

“Usually it’s a rodent that might be carrying, for example, Rocky Mountain spotted fever,” she said. “So, the tick will feed on that rodent, then will get the pathogen as well.”

Because the prevalence of a particular disease can vary in mammal populations, ticks in one part of the state could be more or less likely to get you sick. That’s also important information for medical providers, Cozart said.

This kind of surveillance and testing isn’t happening in every county or state. A 2023 survey of nearly 500 health departments throughout the country found that roughly a quarter do some kind of tick surveillance.

Not all surveillance efforts are equal, said Chelsea Gridley-Smith, director of environmental health at the National Association of City and County Health Officials.

Field surveys can be expensive. For numerous local and state health departments, tick surveillance relies on a less expensive, more passive approach: Concerned patients, veterinarians, and doctors must collect and send in ticks for identification.

“It does provide a little information about what ticks are actually interacting with people and animals, but it doesn’t get into the weeds of how common ticks are in that area and how often do those ticks carry pathogens,” Gridley-Smith said.

She said more health departments want to start tick surveillance, but getting funding is hard — and might get harder as federal public health grants from agencies like the Centers for Disease Control and Prevention dry up.

Montana receives about $60,000 from a federal grant annually, but the bulk of that funding goes toward mosquito surveillance, which is more intensive and costly. What’s left funds trips into the field to look for ticks.

Hokit said he doesn’t have enough funding for his small team to survey everywhere he would like to in a state as large as Montana. That means he’s unable to monitor emerging populations of deer ticks as closely as he would like.

He found those new deer ticks in two Montana counties, but he doesn’t have enough data to determine whether they have begun reproducing there, establishing a local population.

In the meantime, Hokit uses data on climate and vegetation to make predictions about where deer ticks might thrive in the state. He has his eye on particular areas of western Montana, like the Flathead Valley.

He said that will help him and his team narrow down where to look next so they can let the public know when deer ticks — and the diseases they can carry — arrive.

This article is part of a partnership with NPR and Montana Public Radio