Deer ticks that cause Lyme disease and other ailments are moving north and west in Minnesota, and health officials say people should be on the lookout for the tiny critters now that spring is here.
In northwestern Minnesota, southern Beltrami County, southeastern Clearwater County, eastern Becker County and all of Hubbard and Cass counties now are considered high-risk areas for tick-borne diseases.
That means outdoors enthusiasts in many parts of northwestern Minnesota now have one more thing to worry about.
"People aren't used to thinking about ticks or tick-borne diseases" in many of those areas, Melissa Kemperman, an epidemiologist for the Minnesota Department of Health, said.
According to Kemperman, the number of Lyme disease cases in Minnesota set a record in 2007. Final numbers aren't yet available, but Kemperman said more than 1,200 people contracted the tick-borne disease last year.
The previous record was 1,023 reported cases in 2004. In 2006, the Department of Health reported 913 confirmed cases of Lyme disease in Minnesota.
Lyme disease causes joint pain and inflammation and can damage the heart and nervous system if left untreated. Kemperman said the statistics show the disease definitely is moving north and west.
Deer ticks also can transmit anaplasmosis and babesiosis, diseases that are less common than Lyme disease but potentially more serious if left untreated.
All of the diseases are treatable and produce flulike symptoms in their early stages.
Limited by habitat
Kemperman said deer ticks thrive in hardwood forest habitat with brushy areas. That likely limits the chances of finding them in less forested areas in the far northwest corner of the state and across the Red River in North Dakota.
Still, people who live or spend time in forested areas where deer ticks weren't a problem in the past definitely need to be on the lookout, Kemperman said.
That can be tricky because deer ticks are much smaller than a wood tick. An adult deer tick is about the size of a sesame seed, and the nymphs are even smaller.
"You're not going to find them in the middle of a wetland or grassy area, but where there's forest, you could find them," Kemperman said. "We're definitely worried about that."
North Dakota recorded 11 cases of Lyme disease from 2002 through 2006, according to Erin Fox, epidemiologist for the North Dakota Department of Health. She said many of the cases were attributed to out-of-state travel.
With levels of the disease that low, Fox said it's difficult to establish any information on prevalence or disease trends. Numbers for 2007 aren't yet available, she said.
Kemperman said she's already hearing reports of people finding adult deer ticks in Minnesota. The nymphs start coming out in May, and the period from May through July is the peak time for encountering deer tick nymphs. Adult deer ticks become abundant again in fall.
To reduce the risk of deer ticks, Kemperman said people should avoid walking directly into brush. It's also a good idea to wear light-colored clothing to make the ticks more visible and tuck pant legs into boots or socks.
Kemperman said people should apply repellants such as DEET or permethrin when venturing outdoors. DEET can be applied both to skin and clothing, while people only should apply permethrin to clothing, Kemperman said.
It's also important, Kemperman said, to pay attention to how you're feeling; Lyme disease symptoms usually appear within three to 30 days.
"About a month or so after you spend time in hardwood habitat, if you have flulike symptoms -- fever, muscle aches, headaches -- get yourself to a doctor," she said.
Why the increase?
Kemperman said it's difficult to know why deer ticks are expanding their range, but a handful of factors likely come into play. She said the tiny ticks likely were present historically in many parts of the U.S., before deforestation and declining deer populations reduced their numbers.
In more recent years, habitat improvements and high deer populations may have allowed the ticks to move into new areas.
Climate change also could be a factor.
"More and more people are talking about climate change these days, and I think it's becoming less and less premature to attribute some of this to climate change," Kemperman said.
Kemperman said it's difficult to predict whether deer ticks or the diseases they carry will be more abundant this year, but taking preventive measures to reduce the risk is the best approach.
"I know it's a pain putting on that repellant and taking the time (to check for ticks), but it really takes just a few moments," Kemperman said. "If you get (sick), it's time away from work or time away from school. So really, it's a few minutes now vs. days to weeks and a lot of money down the road."
- On the Web:
Minnesota Department of Health, www.health.state.mn.us.
Dokken reports on outdoors. Reach him at (701) 780-1148; (800) 477-6572, ext. 148; or send e-mail to email@example.com.