Pennsylvania Leads the US
in Lyme Disease Cases
Click the image to view full-size. Illustration by Lisa Haney.
What is the most dangerous animal in Pennsylvania? The black bear? The rattlesnake? Maybe the whitetail deer, because it’s involved in so many collisions with vehicles?
In the opinion of biology professor Tom Simmons, the correct response might be Ixodes scapularis—the blacklegged tick, commonly called a deer tick.
In its nymph stage, the blacklegged tick is about the size of a poppy seed, but arguably it poses more of a danger to humans than any other creature in the commonwealth.
The blacklegged tick is the main vector—or transmitter—of Lyme disease, an infectious illness that can cause fever, fatigue, headache, joint pain, neck stiffness, loss of ability to move one or both sides of the face, heart palpitations, and other medical
complications. In the United States, Lyme disease is the most common vector-borne disease, surpassing mosquito-borne West Nile virus and Zika.
In the past, ticks and Lyme disease were concerns primarily of hunters, fishermen, hikers, campers, and others who wandered from the pavement. But now, Simmons said, the risk has shifted and broadened.
Since 2011, Pennsylvania has reported the largest number of Lyme disease cases of any state, he said. Since 2010, those cases have tripled in southwestern Pennsylvania, and Indiana County is one of the hot spots.
“If you look at the number of cases, corrected for population size, you will see middle western Pennsylvania as a whole—Indiana County included—has a higher incidence than the other counties,” Simmons said.
Blacklegged ticks at different life stages. From left: larva, nymph, adult male, and adult female. Photo by Tom Simmons
While hunters and anglers are more likely to take preventive measures, people walking in wooded parks or working in the backyard may not realize the danger lurking there, too. “Therein lies the problem,” he said.
Simmons has been on IUP’s biology faculty for 26 years, and his research, aided by some of his students, is focused on learning more about the ecology of insects and ticks that transmit pathogens to humans.
He said 95 percent of Lyme disease cases are in the Northeast—New England and the Mid-Atlantic states—and in north-central states including Minnesota and Wisconsin. In the last 10 to 20 years, Lyme disease and the tick have been spreading across Pennsylvania
and into Ohio and advancing from the north-central states as well. “Eventually, the two populations will meet in Ohio,” he said.
According to Simmons, when Europeans colonized America, they generally deforested the landscape and overhunted wildlife. “So the habitat for the blacklegged tick was mowed down or eliminated, and the hosts for the ticks [especially deer] were eliminated,”
he said. “The tick disappeared, and so did the Lyme disease.”
But infected ticks survived in pockets along the East Coast, and since 1900, forests, deer, and ticks have made a comeback. “We feel the tick is simply recolonizing where it used to be,” Simmons said, and many of those areas are now forested land, fragmented
with human development.
Simmons was born and raised on New York’s Long Island, ground zero for much of the initial research on ticks and Lyme disease in the early 1980s.
In 2011, students in his Applied Entomology and Zoonoses (diseases transmitted from animals to humans) course conducted a survey of ticks in the Whites Woods Nature Center, less than a mile from his Weyandt Hall office. Six teams of students dragged one-meter-square
pieces of white muslin over the ground and bushes in the nature center.
In two or three hours, the six teams collected close to 90 adult ticks, Simmons said. Tests conducted by the state Department of Environmental Protection showed that 67 percent of those ticks were positive for the bacterium that causes Lyme disease. His
reaction: “Holy mackerel! This is as bad as Long Island or Lyme, Connecticut,” where the disease was discovered.
Since then, students in his classes have also scoured the nature center and the adjacent Co-op recreational park to count small mammals, conduct deer density estimates, and evaluate vegetation—all factors that influence tick populations.
“The animals that are most common there are deer, white-footed mice, chipmunks, and shrews—all important for the ticks, and all important for Lyme disease. And you have a community [of humans] right up against it,” he said. “We have a laboratory right
outside our door.”
According to Simmons, blacklegged ticks like moisture and humidity in woods and forests, especially those composed of hardwood, deciduous trees. The ticks cannot tolerate dry areas, but they can survive cold temperatures.
Rusty-orange in color, the female blackegged ticks are a little larger than the males and are more likely to embed their mouthparts into the flesh of a host. “They need a blood meal for egg development,” Simmons said.
Not every tick is infectious, he said, but while blacklegged ticks are the main vector of Lyme disease, people should be wary of any tick they find crawling on their clothing or skin. “Particularly in the summer, the nymphs of different species
look a lot more similar than the adults,” he said.
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Biology professor Tom Simmons and students Shannon Tepe, left, and Anna Manges collected ticks at Blue Spruce Park, north of Indiana, in June. Photo by Keith Boyer.
Students from RUIA College in India who attended a summer biotechnology
program at IUP joined Simmons in a tick survey on the South Campus, near the president’s residence. Photo by N. Bharathan
More than 150 species of birds and animals, including humans, are hosts for ticks. Mice, chipmunks, and shrews are the most common hosts.
“The white-footed mouse is the poster child for a tick host and, more important, a reservoir for the Lyme disease bacterium,” Simmons said.
About six years ago, Simmons attended a Pennsylvania Vector Control Association meeting at which DEP specialists gave an update on ticks and Lyme disease. Simmons noticed on a map that ticks had been collected for study in only a few western Pennsylvania
counties. He thought to himself, “We could really contribute to this project.”
In the 2013-14 school year, Simmons and some student volunteers went out in the field at every opportunity to search for and collect ticks for the statewide study. The findings, published by DEP in 2015, showed that infected ticks were present in every
county of the commonwealth and that Lyme disease was a problem for more than just the Eastern Seaboard.
“That was very important,” he said. “We didn’t want the public, or the health care community, to think, ‘Oh, this is an Eastern problem.’ Because that’s the most dangerous situation—when you think it’s not a problem and it actually is.”
“The deer aren’t going anywhere, the mice aren’t going anywhere, the ticks aren’t going anyplace, and we don’t yet have a vaccine for people.”
Simmons’s trips afield with students also convinced him that ticks are “superabundant” in Indiana County. “I hate to say it—there’s no other word. The woods are infested with them here,” he said.
One theory circulating now is that a year of greater-than-normal acorn production is followed the next year by a large mouse population, which provides an abundance of hosts for larval ticks. The next year, those larval ticks develop into nymphs.
“Apparently two years ago was a big mast year,” Simmons said.
“The bad news is that it’s really bad,” and the incidence of Lyme disease is likely to spread, probably north, west, and south, he said. “The deer aren’t going anywhere, the mice aren’t going anywhere, the ticks aren’t going anyplace, and we don’t yet
have a vaccine for people. So what it comes down to is education and people taking measures to protect themselves.”
When people are outdoors working or playing near vegetation, Simmons recommends they wear light-colored clothing treated with the insecticide permethrin. They should keep shirttails tucked into pants and pant legs tucked into socks.
“You don’t have to be scared. You can still go out in the woods,” he said. “You just have to be aware, and when you get back in, you should really wash your clothes, dry them in a dryer, take a shower, and do a tick check of your entire body.”
Photo courtesy Centers for Disease Control
According to IUP biology professor Tom Simmons, ticks are alert and waiting in the outdoors. They get excited when they sense heat, carbon dioxide, lactic acid, vibrations, and shadows caused by passing humans and other animals.
When a suitable host brushes against vegetation where a tick is resting, the tick crawls on.
So what should a person do if he or she discovers a tick embedded in the skin?
If the tick is known to have been attached less than one day, the risk is low, and the person probably does not need to see a doctor, Simmons said.
“Just get the tick off,” he said. He prefers to use fine-tip tweezers or forceps. “Just grab it as close to the skin as you can and pull it off” like a splinter, but avoid crushing the body of the tick.
If the tick has been attached two or more days, the recommendation is to see a doctor, he said.
Physicians vary in how they treat patients with tick bites. Some doctors immediately prescribe a dose or course of an antibiotic such as doxycycline; others suggest waiting a couple weeks for an antibody test or for symptoms to show. The tick may also
be saved and tested for infection.
Some people will develop redness around the site of the tick bite, as they do with a mosquito bite. But not everyone bitten and infected by a tick develops the classic bull’s-eye rash around the site or elsewhere on the body.
“I consider those people who get a bull’s-eye rash with flu-like symptoms very quickly to be lucky, because under those conditions, you have a confirmed case of Lyme disease and will be treated [immediately],” Simmons said. “It’s when you don’t get the
rash and you don’t know you were bitten and then you have ailments later on—from exposure weeks, months, or years ago—that is problematic.”