Now more than ever, those seemingly harmless trips to the forest preserve or even a particularly lush backyard could result in an uninvited -- and potentially dangerous -- guest.
Experts are reporting an upswing in ticks, those bloodsucking, disease-transmitting arachnids that don't usually leave their hosts willingly.
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The trend is particularly true for lone star ticks, which have been making their way up North after long being relegated to the Southeast and south-central part of the U.S.
"They seem to be extending their range, particularly to the Chicago metropolitan region and northern Illinois," said entomologist Phil Nixon of the University of Illinois Extension. "We've even seen them in Wisconsin."
The torrential rains this spring -- the 8.54 inches reported at O'Hare International Airport made April the wettest on record in Chicago -- didn't help. Ticks thrive in wet and humid conditions, Nixon said.
Numerous other factors could be contributing to the increase in recent years, experts say, including the use of fewer insecticides and a push to replant trees and preserve open spaces.
Nixon also said winters need to be brutally cold to kill off ticks, which can hide in soil and under leaf litter. Researchers say it takes a string of days with subzero temperatures to do the job. But the coldest week this past winter was in late January, when the average high temperature was 22 degrees, according to Weather Underground.
"They survive quite well in winter," Nixon said.
Additional factors leading to more ticks could be an increase in white-tailed deer, which carry the blacklegged tick, also known as the deer or bear tick. According to the U of I Extension, it wasn't common to see deer in the state as late as the 1970s. Since then, however, the population has exploded.
As a result of the growing tick population, the incidence of tick-borne diseases in humans is up, as well.
The Illinois Department of Public Health reported 204 cases of Lyme disease and 151 cases of Rocky Mountain spotted fever last year, compared to 47 and 12 cases, respectively, in 2002.
Spokeswoman Melaney Arnold said there are a number of possible reasons for the trend, including more electronic reporting of lab results because of more physician testing and better reporting compliance.
But Arnold also pointed to the deer tick's expansion to more counties in Illinois. In 1998, only eight counties had "established" or "suspected" deer tick populations. In 2012, there were 34 counties.
"Now we have a massive deer population to support the deer tick, and the tick is following its required adult tick host (deer) into new habitat," Arnold said. "So in that sense (of) invasion of new habitat, the deer tick is increasing over time."
Several preventive measures can be taken.
For one, always wear protective clothing such as long-sleeved shirts, long pants, socks and shoes when visiting wooded areas or places with tall grass and weeks.
Ticks don't fall from trees, contrary to popular belief; they climb upward. So Nixon said it's a good idea to tuck pants into socks or tape the area.
Insect repellent containing 10 percent to 30 percent DEET can be applied sparingly to exposed skin. Repellents with permethrin can be used on clothes.
The Illinois Department of Public Health also recommends people walk in the center of trails to avoid brushing up against weeds and brush. Ticks found crawling on clothing can be removed with masking or cellophane tape.
When prevention doesn't work and a tick latches onto you or a pet, experts recommend removing it promptly with tweezers, focusing on where the mouth meets the skin, and then washing hands and the bite area.
It's also important to check your pets for signs of ticks after they've been outside, said Dr. Marcelle Ridgway, a clinical associate professor of small animal internal medicine at the University of Illinois College of Veterinary Medicine.
"Most dogs that are exposed don't get sick, but owners can prevent disease because there's a period of hours that pass before the bacteria is transmitted," Ridgway said.
Dr. Jennifer Boland of the Banfield Pet Hospital in South Elgin said she's seen an "explosion" in the past couple of months of animals coming in with ticks.
"There's definitely an increase compared to last year," Boland said. "With the way the winter has been, it being a fairly mild winter, ticks are enjoying the weather."
She said pet owners typically wait until summer is in full swing to apply a topical flea and tick prevention product, but she's been recommending they start earlier. There's also a vaccine for Lyme disease veterinarians can administer.
Signs a dog or cat has been infected by a tick could include joint swelling, loss of appetite or lethargy, Boland said.
She also recommends checking dogs every time they come inside.
"Run your hands through their coats because you usually won't see the ticks," Boland said. "Around their ears is a favorite place."