Most are no larger than a freckle and nearly impossible to spot, but some blacklegged ticks carry bacteria in their saliva strong enough to cause debilitating disease.
Lyme disease has crept into more than half of the counties in Minnesota and into areas that were unaffected in 1996, according to a January study from the Journal of Medical Entomology
Still, most Minnesotans who spend time in the woods — like 2012 University of Minnesota graduate Matt Stoner — are familiar with the symptoms of Lyme disease.
Stoner said he first experienced symptoms — like joint swelling, stiffness and pain — about three years ago after camping in the Boundary Waters Canoe Area Wilderness in northern Minnesota.
“The first indication was a bulls-eye rash in the middle of my back. But there came a point when I couldn’t turn my head while driving,” he said.
But when he got tested for Lyme disease a month later, the blood test came back negative.
Human blood tests for Lyme disease aren’t always accurate, and these false negatives are common, said University Department of Entomology research associate Jon Oliver.
Stoner’s symptoms grew worse and worse until they were so severe he had trouble getting out of bed. After a second trip to the doctor, he finally received antibiotics.
If Lyme disease isn’t treated within a month of infection, symptoms will likely worsen and can create chronic conditions, said Dave Neitzel, a Minnesota Department of Health epidemiologist and tick-borne disease specialist.
Stoner said when he started his treatment he felt better within a day, but symptoms have since returned three times — most recently a year and a half ago — requiring antibiotics each time.
According to a study published by the International Association for Ecology and Health, more Lyme cases are identified and treated each year, and it has spread throughout northeast Minnesota where the state is most densely forested.
“There were many parts of the state where I used to have a hard time finding these ticks, and now they’re extremely abundant,” said Neitzel, who has been researching ticks since 1985. “At first we were finding ticks in east-central Minnesota, between the Twin Cities and Duluth and in northwestern Wisconsin, right across the border there. Everything has radiated out from there.”
Neitzel said he and other researchers spent the last two decades donning white painting coveralls and dragging cloth nets through forests in each Minnesota county to collect, count and eventually test ticks for Lyme disease, bacteria and other disease agents, Neitzel said.
Ticks carry the largest variety of pathogens of any arthropod, Oliver said. Lyme is the most common disease in the United States transferred by an outside carrier, he said.
University entomology professor and tick specialist Uli Munderloh said global changes — like warming temperatures caused by humans and increased human presence in nature — lead to larger tick populations and more animals for them to feed on.
“People like to build homes in areas where there are mature trees and where they are close to nature, but nature can have some unpleasant side effects … like ticks,” she said.
Neitzel said deer and white-footed mice are the main food sources for ticks in Minnesota. Increasingly, those hosts have made their way to suburbs and wooded pockets of cities like Minneapolis.
“If you go down to the river valley down by the edge of campus and that whole wooded corridor by the river, there are populations of blacklegged ticks,” Neitzel said.
Oliver said the ticks feed three times in their lives, giving them two chances to contract the Lyme bacteria before they infect a human.
Ticks need to imbed themselves in a host for at least a day in order to spread disease, he said, which makes smaller, harder-to-find nymphs so dangerous.
“Lyme disease infection occurs in the warm months, but is peaked from mid-May to mid-July during the nymph-stage feeding,” Neitzel said.
Researchers at Virginia Commonwealth University are now developing a vaccine to prevent Lyme disease in humans, Munderloh said. Currently, the only vaccine available is for dogs, and it was approved in January.
