BRETT FRENCH | bfrench@billingsgazette.com
A Bozeman hunter’s bird dog has alerted health officials to the possibility that the tick that carries Lyme disease — the most common disease spread by ticks in the United States, estimated at about 476,000 cases each year — may be living in Eastern Montana.
The French Brittany and its owner had been pheasant hunting north of Richey in Dawson County, not anywhere outside of the state that the tick may have hopped aboard.
After being plucked from the dog’s neck, the tick was given to the Schutter Diagnostic Laboratory at Montana State University, according to a National Institutes of Health study.
The tick was stored in alcohol and shipped off to Rocky Mountain Laboratories in Hamilton, an NIH facility, where scientist Tom Schwan identified the tick by its unique traits.
Tick carries Lyme disease
On Feb. 28, the lab issued a press release stating scientists had confirmed the tick was Ixodes scapularis, also known as the deer tick or blacklegged tick (not to be confused with the western blacklegged tick, Ixodes pacificus that lives along the Pacific Coast).
Although more often found on the East Coast and in the Midwest, the species is gradually hitching a slow ride farther west.
What’s more, a detailed DNA sequence analysis of the tick showed it may have been carrying Lyme disease or relapsing fever, another tick-borne disease, according to Marshall Bloom, a veteran RML scientist and chief of the Biology of Vector-borne Viruses Section.
He added the evidence is not definitive enough to make a solid case for Lyme disease infiltrating Montana.
“However, what it does say is, ‘Well, guess what? We should be on the lookout for these Ixodes scapularis ticks in Eastern Montana,’ which is where this tick was from, as well as other parts of the state,” Bloom said.
Unfortunately, the ticks are tiny. During the nymphal stage, when they are most likely to spread Lyme disease, they are the size of a poppy seed. Adults are about as big as a sesame seed.
Tick search this spring
A follow-up investigation is in the works. Philip Stewart, an RML scientist, hopes to return to the Richey area to search for deer ticks to see if the species has established itself in the region, Bloom said.
Devon Cozart, a communicable disease epidemiologist for the Montana Department of Public Health & Human Services, said her agency will be helping with the quest.
“Also this spring, we will look to leverage the public’s help in submitting ticks for identification,” Cozart wrote in an email. “More information will be provided about this program, and the 2024-25 tick surveillance season, in an upcoming DPHHS press release.”
Deer ticks have been identified in Montana before, Bloom said, but following detailed questioning of the infected individuals it was discerned the people likely picked them up while out of state.
However, the ticks have been documented in North Dakota and South Dakota, Montana’s neighbors to the east.
It would have been easy enough for the tick to hitch a ride from North Dakota to Eastern Montana on a deer or other animal, Bloom noted.
Or it may have scheduled a flight.
“It’s possible the tick may have ended up in Montana after attaching to a host, such as a bird, in a different state, and then was carried here,” Cozart said. “Ticks attach to hosts at multiple points in their life cycle, and this is a common method of unintentional travel for ticks.”
Right now, scientists still have several questions.
“For example, it is unknown whether blacklegged ticks are able to survive Montana winters and actively populate,” Cozart said.
According to the Centers for Disease Control and Prevention, the percentage of deer ticks infected with Lyme disease may be as high as 50% in some areas. Strangely, blacklegged ticks in the southeastern U.S. are almost never infected, the agency said.
The ticks get Lyme disease when they feed on an infected animal, often a mouse or other rodent, when they are in their larval or nymphal stage of life.
Although deer can help move the ticks around, they aren’t infected with the disease nor can they give it to ticks. Infected female ticks also don’t spread the disease to their offspring. The female’s 1,000 to 2,000 eggs hatch in the spring. The mother dies after laying the eggs.
The tick’s four-stage life cycle takes about two to three years.
Is climate change at fault?
A research paper Bloom co-authored pointed to climate change as a possible cause for the increasing incidence of tick-borne diseases in the United States. There are 18 diseases ticks carry.
“Climate change may allow ticks to populate sites previously thought too cold and also to extend the season of (tick-borne disease) risk,” the scientists wrote.
“Many of the diverse tick-borne diseases (TBD) in the U.S. appear to be increasing in incidence, leading to concern that factors such as climate change may create challenging scenarios,” according to a JAMA Network article posted last year.
Bloom noted there are several other factors that may be at play, including more people recreating outdoors and more wildlife moving into urban and suburban areas.
“You drive down the streets of Hamilton … and there are deer just about all over,” Bloom said. “So animals like deer, which can harbor the tick, are now moving into more urban areas.”
