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United States Department of Agriculture

Agricultural Research Service

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Ticked Off!!


You’ve been out in the woods or along the edge of the woods. Or playing with your dog. Or maybe someone else in your house has been out in the woods, or playing with your dog.

A few days later, you find a bull’s eye-shaped rash on your arm.

This is when smart kids go to the doctor and get tested for Lyme disease. You can catch it when a blacklegged tick latches onto you to do what ticks do best: biting into your skin and sucking blood.

When it does, sometimes it transmits a tiny bacterium called Borrelia burgdorferi into your body. This is the bacterium that causes Lyme disease.

Lyme disease occurs mainly in suburban areas--or even in city parks--where there are lots of wild deer. Adult ticks obtain their blood meals from large or medium-sized mammals, and large deer populations make it easy for the ticks to find a quick bite!

But adult ticks usually aren’t responsible for spreading Lyme disease to people. Generally, tick larvae pick up the bacterium from feeding on infected mice or other small animals.

Then the larvae become nymphs that lurk in the grass, on fallen logs, or in other good hiding places. When any suitable animal--such as a bird, lizard, deer, dogs, or people--passes by, a nymph latches on to score a snack. When a tick is a nymph, it has already grown out of its larval stage, but it isn't quite an adult yet.

No matter how young or old a tick is, it’s pretty small--at least to humans. When they’re looking for a meal, adult blacklegged ticks are about the size of a sesame seed.

Agricultural Research Service (ARS) entomologist John Carroll works at the ARS Animal Parasitic Laboratory in Beltsville, Maryland. He’s been tracking ticks for years to see where they are--and how to keep them away from animals and people.

Carroll wanted to find out how likely people are to pick up ticks during different outdoor activities. He tick-proofed himself by wearing boots, tucking his pant-legs into his socks, and covering the exposed sock with tape. When he went out walking, tick nymphs hitched a ride on the boots, but many were brushed off as he walked along. But when Carroll switched to sneakers and left the tops of his socks exposed, fewer blacklegged tick nymphs lost their grip on his footwear.

Carroll found tick nymphs on almost 90 percent of the fallen logs he checked--and he checked only large logs that would make good seats for tired hikers or climbing kids. This adult scientist also slowly crawled on his hands and knees for 30 seconds through leaf litter (picture that!) Afterwards, he found nymphs clinging to his pant legs. A few nymphs also stuck to his hands, but there were more on his pants

Sometimes Carroll finds ticks even when he’s not looking. After taking a clean load of laundry out of his washer one day, he saw a live lone star tick sitting on top of the agitator. So he decided to find out if washing and drying clothes is a good way to make sure no ticks are lurking in your pants or socks after you come inside.

He put groups of two different tick species--blacklegged ticks and lone star ticks--into mesh bags and washed them with regular laundry loads. He used different detergents and water temperatures, and also dried the bags of ticks at different temperatures. Many of the ticks survived their adventure in the washing machine. The way Carroll was able to kill all of them was to dry them at high heat for an hour.

Carroll was also part of a team effort to find a way to protect deer against adult ticks. A female adult blacklegged tick might produce as many as 3,000 eggs during her life. If adult ticks can’t feed, they can’t lay eggs--and when there are no eggs, there are no larvae or nymphs around to bite people.

Entomologist Mat Pound, agricultural engineer Allen Miller, and technician Craig LeMeilleur were also part of this tick-control team. Working at the ARS Livestock Insects Research Laboratory in Kerrville, Texas, they developed a device called a "4-poster."

One part of this device is a trough that the scientists stocked with corn--but this was no free lunch for the deer! In order to reach the corn-filled trough, the deer brushed their heads and necks against paint rollers filled with an acaricide (a chemical that kills ticks), which rubbed off on the heads of the deer. This protected the deer against ticks the same way you protect yourself from mosquitoes by putting on some bug repellent. (Why didn’t the scientists use an insecticide? Because ticks are arachnids--not insects!)

When the adult ticks couldn’t get their blood meals from the protected deer, they couldn’t feed--and they couldn’t lay eggs. The team found the "4-poster" controlled more than 90 percent of the tick population around the devices. Depending on the size of the herd, each device will treat deer on approximately 40 to 50 acres.

But as every bird-lover knows, squirrels never pass up the chance for a free meal. For instance, they’ll gladly go upside down to raid a backyard bird feeder.

The squirrels saw the "4-poster" as an outdoor all-you-can-eat buffet--and when they had their fill, they left behind tiny bits of corn that interfered with how the devices operated. So the Texas scientists even figured out a way to deal with the squirrels.

They added a light-controlled motor that shut down the flow of corn into the feeding troughs between dawn and dusk. Since deer generally eat at night and squirrels eat during the day, this closed down the buffet when the squirrels were foraging--and opened for business at dusk to serve their nighttime deer customers.

Bottom line: Check your clothes--and your pets--for ticks. Remember that tick larvae and nymphs are quite small. Use a topical repellent on your skin when you go to areas where ticks might be waiting for you. Check yourself for rashes and watch out for flu-like symptoms if you’ve been outside. When you come back in, make sure to thoroughly wash and dry your clothes.

And watch out for those squirrels!

--Ann Perry, Agricultural Research Service, Information Staff


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Last Modified: 2/14/2011
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