Targeting ticks

A Medical School, Duluth Campus scientist and his students collect blacklegged (deer) ticks to track their expanding range in Minnesota — and map the Lyme disease they spread
By Greg Breining

No one wants ticks.

Except Benjamin Clarke, Ph.D. If you have any, please mail them to him.

Clarke is an associate professor in the Department of Biomedical Sciences at the Medical School, Duluth Campus. He and his undergraduate students are trying to determine where ticks — especially the blacklegged ticks that harbor the bacteria that causes Lyme disease — are most prevalent in the state and where the risk of contracting Lyme is greatest.

In his pursuit of tick knowledge, Clarke has mailed out some 500 tick kits so folks can collect the ticks they acquire during their outdoor activities. The kits include a “tick key” for raking the tick off the skin, an ID card to determine whether it is a blacklegged tick (otherwise known as a deer tick), and a plastic vial for sending the specimen, with information about time, location, temperature, and a rough guess of humidity, to Tick Outreach at the Medical School. In addition, he gives “tick talks” to community groups once a month.

Clarke also collects specimens during “tick drags” he leads with University of Minnesota Duluth (UMD) undergrads and students from local community colleges. The goal of his tick project is twofold: to learn more about Minnesota ticks and tick-borne diseases, and to encourage students from rural areas and reservations to learn more about science and consider pursuing a science degree.

Benjamin Clarke, Ph.D. and one of his tick teams: medical student Chris Little; Emily Hartman, University of Minnesota Duluth Class of ’17; and Jubran Jindeel, a biology major at UMD.

Benjamin Clarke, Ph.D. (second from left), and one of his tick teams: medical student Chris Little; Emily Hartman, University of Minnesota Duluth Class of ’17; and Jubran Jindeel, a biology major at UMD. (Photo: Brett Groehler)

Ticks on the march

Third-year Medical School student Chris Little checks for ticks on a “tick drag” in Duluth’s Hartley Park.

Third-year Medical School student Chris Little checks for ticks on a “tick drag” in Duluth’s Hartley Park. (Photo: Brett Groehler)

As blacklegged ticks have spread through Minnesota, so have the bacterium and the disease.

Clarke caught the tick bug after a local doctor came to his office about 10 years ago to find out more about the spreading range of blacklegged ticks and Lyme. The health risk maps of the day showed the disease centered largely from Pine County south. “We’re up in Duluth, and he had a bunch of patients hit with this disease,” says Clarke.

“So I mixed the two things — my interest in actual disease and this idea of the epidemiology about it spreading — and made that into what we call a problem-based learning project for the students in the summer. They would get together and read up on it, formulate ideas that they would like to do,” Clarke explains. “In other words, this project was really generated at the level of community college and university students getting together.”

It’s not surprising that a project on Lyme disease would stem from community concern. The tick and the bacteria it carries were virtually unknown 50 years ago. Since then, it has become one of the most prevalent infectious diseases in the nation and state. The federal Centers for Disease Control and Prevention officially records about 35,000 cases nationally each year. However, because the disease is so difficult to diagnose, the CDC estimates the real incidence is nearly 10 times that high. The epicenter of the epidemic lies in New England, New York, and Pennsylvania, though Minnesota and Wisconsin are not far behind.

Lyme is caused by the bacterium Borrelia burgdorferi, carried by the blacklegged tick, a root beer–colored tick smaller and more almond-shaped than the familiar wood tick (also called a dog tick). Historically in Minnesota, blacklegged ticks were confined to the St. Croix River Valley. But during the last 30 years, they have spread across the forested areas of the state. 

“Climate change is the easy answer. But it’s more complicated than that,” says Jonathan Oliver, Ph.D., assistant professor of entomology in the University’s School of Public Health. Also driving the tick migration are changes in forest pattern and density and changes in populations of creatures that host the tick, including the white-footed mouse, which is a reservoir for the bacterium.

The disease itself was unheard of until 1975, when it was identified in Old Lyme, Connecticut. (However, a similar bacterium and disease are known in Europe and Asia; in fact, Ötzi, the 5,300-year-old hiker found mummified in the Italian Alps, had traces of Borrelia bacteria in his tissues.)

As blacklegged ticks have spread through Minnesota, so have the bacterium and the disease. “They’re marching north,” says Clarke. “They didn’t see deer ticks 10 years ago, and now they’re seeing them.”

A living hypodermic Needle

Ticks at various life stages climb stalks of vegetation, stretch out their front legs, and in a pose called “questing,” wait for a target, whether a mouse, white-tailed deer, or human. After the tick latches onto a passing victim, it crawls to a suitable source of blood and bites in. The trickle of blood arouses the Borrelia bacteria that live in the tick’s gut. They proliferate and move toward the tick’s mouth. After 18 to 24 hours, bacteria move into the victim as the tick alternately sucks in blood and spits out saliva to keep the blood flowing. Says Clarke, “The best way to think of a tick is that it’s a living hypodermic needle.”  

That delay in the arousal of the bacteria is the reason it’s important to do a daily tick check. “If you find the tick early enough, you’re way less likely to get sick, especially from Lyme disease,” says Oliver.

Once established in humans, the bacteria often cause a red bull’s-eye rash surrounding the bite site, but as many as 30 percent of victims never get a rash. The bacteria causes flu-like symptoms such as fever, chills, fatigue, body aches, headache, neck stiffness, and swollen lymph nodes. In its early stages, Lyme is successfully treated with antibiotics. Untreated, an infection can lead to long-lasting joint pain, temporary facial paralysis, numbness in the limbs, severe fatigue, and even heart problems. 

Budding student scientists

Clarke, an enrolled member of the Grand Portage Reservation – Minnesota Chippewa Tribe, recruits interested students through two science enrichment programs. One is the Bridges to the Baccalaureate Degree, a partnership between Lake Superior College, Fond du Lac Tribal and Community College, and UMD that encourages community college students to pursue four-year degrees in the sciences. He also engages students through Pathways to Advanced Degrees in Life Sciences, a summer program designed to serve Native American, low-income, and other underserved students.

The National Institutes of Health and the Medical School have funded the programs. Lynne Bemis, Ph.D., professor of medicine, codirector of the Native American Mentoring Program, and past chair of the Department of Biomedical Sciences on the Medical School, Duluth Campus, says she supported Clarke’s program because she wanted to do something that mattered to Minnesota people. “The research that you do should be something of a priority to them.”

Says Bemis, who studies Bartonella, another group of pathogenic bacteria transmitted by ticks, “I think the real stellar part of what he’s doing is getting undergraduates involved in something that they’re probably going to interact with all their lives if they’re from this area.”

Clarke’s students themselves identified some of the issues they wanted to explore. They devised the tick collection. They also thought up the tick kits. “I wish I could take credit for all this,” says Clarke. “It’s really from their work.”

Working in teams of three, the students walk 100-yard transects, dragging yard-wide white fabric flags. Every 10 yards, they stop, pick ticks from the fabric, and drop them in a vial.

“We’re looking for ticks from several different life stages,” says Clarke. “If you can see more than one life stage, you can make the argument that the tick population is established. It didn’t just by random chance hop onto a deer and fall off.” The team examines specimens to determine whether they are actually carrying the Lyme bacteria. Clarke and his students are also trying to determine the kinds of microhabitats the ticks prefer — woods vs. fields, uplands vs. lowlands, humid environments vs. arid ones.

Jubran Jindeel, a graduate of Lake Superior College, entered UMD through the Bridges to the Baccalaureate Degree program and began work on Clarke’s tick project two years ago. The biology major has scoured the woods for ticks, tucking his pant legs into his socks and duct taping his pant legs and shirtsleeves to repel the pests. 

Now, Jindeel is testing ticks mailed in by the public and collected during the tick drags for the Borrelia bacteria. The public’s tick contributions have come from all over Minnesota and Wisconsin, he says. About one in three, so far, have been infected with Borrelia, as is the norm in Minnesota.

Benjamin Clarke, Ph.D., headshot

Benjamin Clarke, Ph.D., collects tick specimens from around Minnesota to track areas of greatest Lyme disease risk. (Photo: Bob King, formerly of the Duluth News Tribune)

There’s a map for that

A hand holding specimen tubes.

(Photo: Bob King, formerly of the Duluth News Tribune)

Within a year, says Clarke, the project will have collected enough specimens to publish an online map showing areas of greatest Lyme disease risk. The map will focus on northeastern Minnesota but will also include information from much of Minnesota and Wisconsin. It will be updated and available to the public. Tick collecting runs from early April (when the snow recedes) through early October (first snowfall). The map will represent ticks collected each season, updated after the tick season in the fall. 

Scientists will use the map to study how Lyme is sustained in the region by investigating the role of disease reservoirs such as field mice and deer, and to look for genetic variants of the Borrelia bacteria that may cause illness, says Clarke.

Mapping high-risk areas won’t eliminate Lyme disease, but it may help people avoid the most troublesome areas and heighten awareness so people take effective precautions, such as spraying their clothes with insect repellent and doing daily tick checks. Because neglect, as many Minnesotans have discovered, can be miserable. 

Says Clarke, “People who have persistent Lyme — they’re suffering.”

Published on October 15, 2019

A tricky diagnosis

Lyme disease is devilishly hard to diagnose. 

The characteristic bull’s-eye rash does not always appear. Other symptoms — fever, chills, fatigue, body aches, headache — accompany everything from the flu to a hard day at the gym.

Standard lab tests for Lyme detect the body’s production of antibodies against Borrelia burgdorferi, not the bacterium itself. That means if you go to the doctor soon after a tick bite — when antibiotics would be most effective — you may test negative because your body has not yet produced many antibodies. And, if you’ve been successfully treated for Lyme once and come in later with another tick bite, you may test positive whether you’re infected or not because antibodies from the first infection remain in your body.

So researchers are looking for a better test.

Benjamin Clarke, Ph.D., associate professor in the Department of Biomedical Sciences at the Medical School, Duluth Campus, is studying two approaches: looking for metabolic byproducts of the bacteria in the bloodstream, and developing techniques for finding Borrelia that’s hiding in circulating lymphocytes, the white blood cells that reside in the lymph nodes.

Jonathan Oliver, Ph.D., assistant professor of entomology in the School of Public Health, is trying to obtain funding for a test that would identify the bacteria proteins that trigger an antibody reaction. 


Tick-borne diseases in Minnesota 

Lyme disease is by far the most common tick-borne disease in Minnesota, but it’s not the only one, says Jonathan Oliver, Ph.D., assistant professor of entomology in the School of Public Health. The blacklegged tick, which carries Lyme, is also responsible for:

Human granulocytic anaplasmosis, a bacterial disease that appeared in Minnesota in 1990. It causes fever, severe headache, muscle aches, chills, and shaking. In recent years, about 500 cases have been reported annually in Minnesota.

Powassan virus disease, first reported in the state in 2008. It causes inflammation of the brain (encephalitis). Minnesota sees fewer than a dozen cases a year.

Ehrlichiosis, caused by Ehrlichia muris bacterium. First reported in Minnesota in 2009, it appears in about a half-dozen people a year here. Symptoms include muscle pain, headache, fever, chills, nausea, and diarrhea.

Borrelia mayonii disease, similar to Lyme, first identified in Minnesota in 2013.

Babesiosis, an infection by a tick-borne parasite. The state records fewer than 100 cases a year. About 20 percent of patients with the infection also have Lyme disease.

The American dog tick (aka wood tick) can carry Rocky Mountain spotted fever, a deadly bacterial disease treatable with antibiotics. Symptoms include rash, fever, headache, muscle aches, nausea, and vomiting. It is rare in Minnesota.

The lone star tick, endemic to the southeastern United States, has been found in scattered locations through Minnesota. “We expect it to become an established parasite here at some point,” says Oliver. “It’s a real aggressive tick. Lone star ticks will actually seek out hosts.” The lone star tick can cause ehrlichiosis as well as an allergy to red meat.

Another emerging threat to Minnesotans is the Asian longhorned tick. Native to Asia, where it carries several diseases, this aggressive tick has been reported in 11 states in the eastern United States. “We don’t know what they might carry here,” says Oliver, “probably Powassan virus, Babesia, hopefully not Lyme.”