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Did the frigid winter take a toll on ticks? Probably not

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Tick nymphs
Blacklegged tick nymphs crawl around in a test tube at an entomology lab at the University of Minnesota in St. Paul.
Jeffrey Thompson | MPR News

Sometimes, a particularly harsh winter will put a dent in Minnesota's deer tick population. Think of it as nature's way of rewarding humanity after a long, cold winter. Only deer ticks transmit Lyme disease.

This winter was pretty rough. But was it bad enough to kill off the ticks?

The short answer: probably not.

Cold temperatures only kill ticks if they're exposed to the frigid air, said Dave Neitzel, an epidemiologist with the Minnesota Department of Health.

"So far, we're having no trouble finding the adult stage of the blacklegged tick," he said, "what most people know as deer ticks."

Ticks were insulated under a thick blanket of snow this winter, so the bitter cold didn't reach them.

Using a drag cloth, Dave Neitzel collects ticks.
Using a drag cloth, Dave Neitzel collects blacklegged tick samples in May 2016 at the Rice Creek Park Reserve in Lino Lakes.
Matthew Hintz for MPR News 2016

Now that the snow has melted, Neitzel and his survey crew at the Minnesota Department of Health have been conducting field surveys in historically tick-infested areas to count tick hitchhikers.

"We have a little piece of cloth that we drag behind us in the woods," said Neitzel, "and we stop every 15 to 20 meters and we pull ticks off of ourselves and pull ticks off of the cloth. A very simple sampling method, but it works really well."

Early survey results, he said, have shown increased deer tick numbers, compared to this time last year.

More deer ticks means there's a greater likelihood of more Lyme disease cases. The condition causes fever and fatigue, then joint damage — and if left untreated, heart and neurological problems.

"In the adult stage of the blacklegged tick, it's not unusual to find that about 40 percent of the adults are infected," said Neitzel. "If you have two or three blacklegged ticks on you, there's probably one that's infected for sure."

Neitzel has been studying tick-borne diseases since the 1980s. In that time, Minnesota has gone from seeing a handful of Lyme cases a year to more than a thousand annually.

Dave Neitzel finds an adult blacklegged tick.
Dave Neitzel locates an adult female blacklegged tick that had climbed on to his pant leg in May 2016 at the Rice Creek Park Reserve in Lino Lakes.
Matthew Hintz for MPR News 2016

The Health Department urges people who spend time in brushy or wooded areas to protect themselves from ticks by applying repellents that contain DEET, the same ingredient that wards off mosquitoes.

Even more effective are products that contain permethrin.

"It can be applied to clothing before you go out," said Neitzel. "It not only kills ticks effectively, but it's a strong repellent too."

Regular tick checks are also recommended. One tip for finding the tiny deer ticks is to step into sunlight and look for reflections off of their backs, said Neitzel.

May, June and July are typically the worst months for Lyme disease exposure. But don't relax when August rolls around. Neitzel said it's also expected to be a bad year for mosquitoes and that raises the risk of West Nile virus, especially later this summer.