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Maybe you’ve seen one crawl up your leg after a hike through tall grass or felt one on your dog’s back while running your hand through its fur. If you’re unlucky, you might find one already burrowing into your skin, filled with your blood.
Ticks are parasitic bloodsuckers capable of spreading deadly disease, and they are becoming more and more common. Here’s what you need to know about them.
Ticks are arachnids, close cousins to mites and more distant cousins to spiders. There is more than 800 species of ticks found around the world, and 84 that have been documented in the United States. But only a handful in the United States bite and transmit disease to humans. The most common are black-legged ticks (also known as deer ticks, but they feed on many animals besides deer), lone star ticks, American dog ticks, and brown dog ticks.
After a tick egg hatches, it goes through three life stages: larva, nymph, and adult. Both male and female ticks feed on blood by inserting their barbed, straw-like mouthparts into the skin of their host (unlike mosquitoes, which only bite if they are females preparing to lay eggs). However, only female ticks drink to the point of swallowing.
“When you see a super large and engulfed female, that means she’s going to lay eggs and start that life cycle process all over again,” said Kait Chapman, an extension educator and urban entomologist at the University of Nebraska-Lincoln.
These arachnids change dramatically in size and appearance based on how old they are and how much blood they have drunk. “The nymph blacklegged tick, if you put these unfed ones on a poppy seed bagel, they blend in quite nicely,” said Dr. Thomas Mather, professor of public health entomology at the University of Rhode Island and director of that school’s Center for Vector-borne Disease and its TickEncounter Resource Center. Meanwhile, a crowded adult female of the same species can swell to the size of a pea.
Tick bites and diseases
Although there are some months when different species and life stages are more active, it is possible to be bitten by a tick at any time of the year. If you find a tick attached to you (or your pet), you should carefully remove it.
“The recommendation is that you use tweezers, get the tick by the head as close to the skin as possible and pull it straight out,” Chapman said. “We don’t want to twist, because we could leave part of that mouth part embedded in the skin. And we don’t want to grab the body, because if you squeeze the body, the tick can regurgitate more, which means you increase your chance of getting a tick-borne disease.”
Lost_in_the_Midwest/Alamy Stock Photo
Be careful when removing a tick from your skin. Use tweezers to get the tick by the head as close to the skin as possible and pull it straight out.
Your impulse may be to squeeze the freshly removed tick, but it’s better if you drown it with hand sanitizer or alcohol and save it to show to an expert or at least take a picture. That way you can identify what kind of tick it is and how long it has been feeding; University of Rhode Island’s The TickEncounter website has tools based on color, size and geographic location.
It is important to identify the tick because certain species carry different diseases. They pick up bacteria, viruses, and other microbes from the blood of infected hosts, and when they bite a new victim, they can pass these pathogens on.
Black-legged tick larvae and nymphs, for example, often feed on white-footed mice, which can carry a bacteria called Borrelia burgdorferi. When a tick that has fed on one of these infected mice then feeds on a human, it can pass the bacteria that causes Lyme disease.
Lone star ticks, on the other hand, do not feed on white-footed mice and are therefore not carriers of Lyme. (However, they carry other disease-causing microbes, and their bites can introduce a sugar molecule into the bloodstream, which makes people allergic to red meat.)
The diseases carried by ticks can be debilitating or even life-threatening, and the risk of infection increases the longer a tick has been on you. Although there are some treatments available, it is best to avoid getting bitten in the first place.
Various studies have suggested factors that may play a role in attracting ticks, including a recent paper showing a correlation between tick attraction and static electricity in a laboratory environment. And while ticks are attracted to cues such as the carbon dioxide exhaled by animals, they tend to lie in wait rather than actively seek out their prey.
“Contrary to popular belief, they do not fall from trees. They simply sit at the edge of a tall blade of grass, for example, that might hang somewhere over, and they stick out their front legs. We call that questing,” said Chapman. “They will wait for the host to brush right by them, and that’s primarily how people get ticks: They brush for it; it sticks to their legs or their clothes.”
Insect repellents containing DEET, picaridin and oil of lemon eucalyptus have become approved by the Danish Environmental Protection Agency to protect against ticks. However, these chemicals work differently against ticks than they do against mosquitoes.
For example, DEET “burns the feet of ticks and they fall off because their feet are burning,” as opposed to interfering with the tick’s ability to find its prey the way DEET affects mosquitoes, Mather said. What’s more, “once the product dries, it doesn’t burn as much, so it really doesn’t last very long on ticks.”
Zbynek Pospisil/iStockphoto/Getty Images
Tucking the bottom of your pants into your socks is one way to prevent tick bites when you’re hiking in nature.
Instead, Chapman recommends preventing tick bites by covering your skin and tucking the bottoms of your pants into your socks. Ticks are also killed by half an hour in the dryer, so throw your clothes in as soon as you get home, even before washing them.
What’s more, “we favor wearing clothing treated with permethrin – it’s far, far more effective than bug spray, Mather said. “It blocks nerve conduction in ticks, and it makes them hyperexcited, and then they just lose function pretty quickly, and it actually ends up killing them.” Depending on where you live, he said, it may also make sense to investigate exterminating ticks that live in your yard.
These precautions may seem extreme, but for Mather they are the way of the future because “we live in a ‘more ticks in more places’ world and more people are being exposed.”
Climate change may play a role in the spread of ticks, but Mather said he believes the influx of the parasites has more to do with white-tailed deer becoming more common in areas with higher human densities. As a result, he said, “More people are being exposed to the ticks that breed on white-tailed deer.”
Despite the spread of ticks and the severity of illnesses they can cause, Chapman stressed that with the right precautions (for you and your pets — ask your vet about tick preventatives), they shouldn’t hold you hostage inside your home.
“Yes, ticks exist. Yes, they can be a public health problem, but we don’t want you to let ticks keep you indoors,” she said. “You should still be able to go outside and enjoy nature, but you just have to do those cross-checks one more time. So take some time. Do it.”
Kate Golembiewski is a freelance science writer based in Chicago who geeks out about zoology, thermodynamics, and death. She hosts the comedy talk show “A Scientist Walks Into a Bar.”