Tick activity is growing in Illinois as multiple species converge on the state: ‘Every year is a bad tick year’
One by one the nymphs climbed up the researcher’s bright blue boot, looking like little more than specks of dirt as they searched out another meal of blood.
Those nymphs, young lone star ticks skittering toward flesh, are just one species of potential disease vectors in Illinois. And their unsettling climb in Grundy County, captured on video last year, was just one of many tick encounters for Holly Tuten, whose work requires collecting thousands of the bloodsuckers.
While most people spend their lives trying to avoid ticks, Tuten, a vector ecologist who leads the state’s tick surveillance program with the Illinois Natural History Survey, seeks them out, hoping to understand where and what they’re spreading in an effort to reduce future damage.
“People always want to know around this time of year: Is it going to be a bad tick year?” Tuten said. “The way I think about that is, every year is a bad tick year.”
As spring settles in, tick activity is growing in Illinois, a state where researchers say the arachnids are now widespread. In the last 30 years, reports of diseases transmitted by ticks have increased tenfold in the state. The rise coincides with growing ranges of multiple species that have converged on Illinois as they find hospitable habitat, an explosion of hosts and a changing climate.
Ticks can live in grassy or wooded areas, as well as on animals, according to the Illinois Department of Public Health. Time outdoors — hiking, camping, gardening or even walking the dog — could lead to close contact with ticks, the health department says. People can pick them up in their own yards.
May is the national awareness month for Lyme disease, the most common vector-borne disease in North America. That’s also true in Illinois, where the range of the blacklegged tick, which can carry the bacteria that causes the sometimes debilitating disease, is expanding.
But there’s still much scientists don’t understand about the bloodsucking bothers. Tuten said examining ticks under the microscope is a mix of fascination and repulsion.
“We need to know what’s out there, because as environments change, as climate changes, as human behavior changes and land use changes, we could become exposed to different species,” Tuten said.
‘They’ll run across the grass for you’
There are hundreds of species globally, but the ticks to keep an eye out for in Illinois include the blacklegged tick (or deer tick), the American dog tick, the lone star tick and the Gulf Coast tick — a more recent arrival. Any of the ticks could be encountered in the state, but some are more likely to be found in certain areas than others.
The dog tick is present throughout the state. Blacklegged tick populations appear to be denser in northern Illinois and are expanding south. Meanwhile, the lone star tick and Gulf Coast tick have spread north and are now concentrated in southern Illinois.
To progress through life stages, from larva to adult, ticks feast on blood. With each meal comes another chance to pick up or transmit pathogens including bacteria and viruses. Adult ticks have had multiple feedings — meaning more chances to become infected or infect.
The Centers for Disease Control and Prevention estimates nearly a half million people are diagnosed and treated for Lyme disease annually. Incidence rates for Illinois are much lower than those for some northeastern areas, but the disease is the most prevalent of those spread by ticks in the state. Reports of Lyme disease, focused in the northern half of the state, have increased throughout Illinois in the last two decades.
In the Chicago area, blacklegged tick nymphs are likely to be active in the coming months. Although they haven’t had as many opportunities as adult ticks to pick up the bacteria that causes Lyme, the smaller ticks are considered a greater risk because they’re easy to miss during tick checks. The Lyme bacteria can generally transmit through an attached tick in 36 to 48 hours.
The dog tick and Gulf Coast tick are vectors for diseases in the spotted fever group, more common in southern Illinois and also on the rise in the last century.
A bite from a lone star tick, which has no problem seeking out humans and climbing up legs, can cause an allergy to red meat — sometimes lifelong — known as alpha-gal syndrome. The ticks can also carry Heartland virus, which is still considered rare but has been found in Illinois ticks and can lead to hospitalization.
The Illinois Natural History Survey medical entomology lab has worked with the state’s health department on tick surveillance since 2018. Data collected by researchers including Tuten is mapped and available to the public, along with disease reports.
Some ticks, such as the blacklegged tick, generally wait for hosts, reaching out with a pair of legs. Other species such as the lone star tick and Gulf Coast tick can be more aggressive in procuring their next meal, as witnessed in Tuten’s video. Gulf Coast ticks, which may be found in prairies, fields and ditches, can run nearly a foot in a few seconds.
In southern Illinois, there are some spots where it’s not a good idea to sit down, Tuten said. “They’ll just swarm you. There are places you can’t have a picnic 20 meters from the edge of the forest, because if they pick you up, they’ll run across the grass for you.”
‘Intriguing new twist’
Climate change is believed to be a driver in some ticks spreading out as they find conditions more amenable.
When it comes to climate change effects on human health, the spread of ticks is among the slower and more insidious, said state climatologist Trent Ford. As long-term shifts make the state warmer and wetter, the aftermath of tick expansion may not be immediately apparent but could cause major problems.
Ideally, Ford said, there may eventually be a model that can incorporate weather conditions in an area and project tick risk, alerting people to areas that they may want to avoid.
Ford said he’s become more careful to take preventive measures while hiking as he’s learned from researchers like Tuten.
“I really want nothing to do with ticks,” Ford said.
In recent years, researchers weren’t sure if the Gulf Coast tick was common in Illinois. But in 2020 surveillance across 16 counties, mainly in southern Illinois, nearly 800 Gulf Coast ticks were collected.
The Gulf Coast tick is not yet a familiar sight in northern Illinois, but reports have surfaced in the Chicago area on the citizen science platform iNaturalist, leading researchers to wonder if the sightings are anomalies, connected to migrating birds or other specific conditions. Gulf Coast ticks were also found in DuPage forest preserves last summer.
There were probably areas in southern Illinois where Gulf Coast ticks were established, Tuten said. “But I also think we probably have had a true invasion.”
Longer stretches of warm temperatures offer ticks more time to be active — and make for more enticing days for humans to cross tick territory. Warmer temperatures may also speed up tick development, leading to a tighter overlap of generations, potentially affecting how many ticks carry infectious agents that can lead to human illness.
In Illinois, winter is warming faster than other seasons and extreme cold is becoming less common. Although tick activity picks up in spring and summer, blacklegged ticks can be active throughout winter on days above freezing with calm weather.
Warmer winters are linked to greater tick abundance, but there are still questions about why that’s the case. It could be that more ticks survive under those conditions, or more hosts such as deer and rodents survive, or a combination of those and additional factors, Tuten said.
Tick survival may also be boosted by Illinois becoming wetter. Ticks, sensitive to drying out, struggle in severe drought and are aided by higher relative humidity. One study found warmer average winter temperatures and increased precipitation were associated with greater incidence of spotted fever group diseases in Illinois.
Scientists are also studying how ticks can withstand extremes. The parasites’ life cycle can last as long as two to three years, which means, Tuten said, “there’s a lot of opportunity there to die.” Cold snaps, for instance, could potentially increase tick mortality. But when it comes to flooding, one study found lone star ticks could survive as many as 70 days underwater.
One hypothesis attributes the northern expansion of lone star ticks to climate change. A few decades ago, the lone star tick wasn’t found in southern Indiana. By 2017, it was the most common.
But recent research offers another driver, possibly working in tandem with climate change — the proliferation of white-tailed deer and reforestation in the ticks’ natural range.
“An intriguing new twist,” Tuten said. “And unfortunately, it doesn’t lead to a simple answer.”
‘Ticks everywhere in Illinois’
Kim Fake, wildlife research coordinator with the Lincoln Park Zoo, studies the interaction between urban environments, wildlife health and human health. Conservation involves reducing conflict between humans and wildlife, Fake said, and that includes diseases transmitted between animals and people.
Researchers have been conducting surveys of ticks throughout the Chicago area. They’ve tracked mammals with motion-sensing cameras to get an idea of active wildlife and then surveyed sites for ticks with a method that involves dragging a cloth through vegetation to see which ticks latch on, Fake said.
“There’s definitely ticks present,” Fake said. Even in “some really urban green spaces.”
The researchers send their ticks to the Illinois Natural History Survey lab for identification and testing.
The surveys started in recent years, but so far blacklegged tick densities appear to be lower in more urban sites. But the prevalence of disease-causing organisms in the ticks has not yet been determined, Fake said, meaning risk could still be high — whether through what ticks are carrying or the number of people likely to pass through more urban spaces.
Whether in forest preserves or parks, you want to be aware that there could be risk of coming in contact with a tick, Fake said.
“More and more people are living in cities or altering the landscape,” Fake said. “People may not typically be thinking about their risk when they’re in a really urban area, but it can be present. So it would be really beneficial to know, what is it about certain urban areas that make them able to support tick populations?”
If you happen to come across a tick and you’re an Illinois resident, you can send photos or ticks themselves to the Illinois Natural History Survey for identification and archiving.
There’s also an app to share information. The Tick App is a citizen science effort that allows users to submit tick photos and receive tick information.
The app “has revealed that there really are ticks everywhere in Illinois,” said Rebecca Smith, an epidemiologist at the University of Illinois. “No part of Illinois is free of ticks. If we look, we find them.”
Most importantly, the app has contributed to data about where ticks are attaching to people and their pets, Smith said.
“If the ticks are out there in the middle of the forest and nobody walks by, that’s fine. But once they start attaching to people and pets, that’s when we get worried,” Smith said.
Researchers stress there are clear and routine steps people can take to prepare for time in the outdoors. That includes wearing skin-covering clothing, using repellents, staying in the center of trails and adding a tick check after outdoor activities.
Passersby during tick collections have referred to Tuten and fellow researchers — wearing chemically treated suits, head nets and boots topped with double-sided carpet tape — as “tickbusters.”
The good news, researchers say, is we’re smarter than ticks.
“Don’t be scared, be prepared,” Tuten said.
That includes keeping an eye on potential new invaders as well as emerging problems posed by familiar species.
There are geographic barriers to some species moving in, but ticks can also hitch a ride on other creatures. On the low end, one study estimated about 4 million tropical ticks are brought into the U.S. annually on migratory songbirds. There’s no evidence they’ve gained a foothold, but climate change and host distribution could make for a more suitable environment, the researchers noted.
Lone star ticks and Gulf Coast ticks could see considerable gains in suitable habitat in northern Illinois as the climate changes. The blacklegged tick has been associated with the Powassan virus, which can be deadly. There hasn’t been a human case of the disease in Illinois, but cases have been reported in Wisconsin.
Researchers are monitoring a new threat, the Asian longhorned tick, which has been spreading from the East Coast but hasn’t yet been detected in Illinois. The females can reproduce without mates.
Like other pest problems, the proliferation of ticks may be a sign of “a system out of balance,” Tuten said.
“So, maybe, the problem isn’t the ticks, but the balance.”
