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Science Note: Why Lyme Disease Thrives Up North

Air Date: Week of

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The blacklegged tick, also known as the deer tick, is the only kind of tick that carries Lyme disease (Photo: Lennart Tange, Flickr CC BY 2.0)

Lyme Disease-carrying ticks in the northern United States have potentially more contact with humans, while southern heat creates fewer opportunities to infect people or animals. Living on Earth’s Don Lyman explains the connection between geography and tick behavior in this week’s note on emerging science.


CURWOOD: And now, this note on emerging science from Don Lyman.


LYMAN: Lyme disease, caused by the bacterium Borrelia burgdorferi, is transmitted by ticks that bite infected animals. An infected tick can then transfer the disease to you or me, if it should happen to bite us. The typical symptoms of Lyme disease are fever, headache, fatigue, and often there’s a telltale rash. If not treated promptly, it can damage the heart, nervous system, and joints.

About 300,000 people are infected with Lyme disease every year, but it is far more common in the North than in the South. Approximately 95 percent of all reported cases occur in 14 states in the Northeast, Mid-Atlantic, and upper Midwest. Now scientists from the U.S. Geological Survey think they know why. In a recently published study, the researchers said that black-legged ticks, which transmit the disease, die of dehydration when exposed to high temperatures and low humidity.

An earlier study found that black-legged ticks in the south tend to stay hidden under a layer of fallen leaves, where, scientists hypothesize, they are able to retain moisture but are less likely to come into contact with people. And researchers found that ticks in the North often climb up plant stems, where they may more easily latch on to people who brush against them.

So, when you take a walk in the woods in the North, beware! You can be walking right through tick habitat, while in the South you’ll be walking on top of it.

That’s this week’s note on emerging science. I’m Don Lyman.




The USGS Study on the geographical distribution of Lyme disease

CDC information on Lyme disease

Tick Counter Tool

American Lyme Disease Foundation website


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