It’s a great time to be a tick. Climate change is doing wonderful things for the little bloodsuckers. Since the 1990s, for example, the number of U.S. counties where Lyme disease has been reported has increased by more than 320 percent, according to The Week, a British news magazine that also publishes a U.S. version. Global warming has extended the tick’s range into states—Maine and Vermont, for example—once considered too cold for ticks. Weather changes have also reduced the time it takes for ticks to mature and also extended the summer period when they’re most active.
The size and range of populations of ticks carrying different diseases can expand like volcanic eruptions. They seem to be impossible to predict. There is a lot more that we don’t know than we do. The tick-borne Powassan virus, for example, discovered in 1958, still affects people in tiny numbers. The bad news is that, like virtually all other tick-borne diseases, it may well have the ability to flare up like Kilauea. And as the CDC notes, Powassan can infect the central nervous system and cause meningitis and encephalitis, which can be fatal, and it can lead to long-term neurologic problems.
So, what can you do? Depends on who you talk to. The CDC recommends you treat clothing and gear with .5 percent permethrin, which is the highest concentration available for this use—and you don’t want to use, say, agricultural permethrin because it’s frequently petroleum-based and not designed to adhere to clothing, meaning it could turn you into a tractor or something. But then they also recommend a bewildering number of repellents. While DEET is almost universally known and recognized, CDC tosses in picaridin, oil of lemon eucalyptus, something called IR3535 (a Dewey decimal–based repellent), PMD, and 2-Undecanone. I don’t recall having read anything about these others. I doubt they’re in wide use. You’d have a hard time finding most of them at the store.
Meanwhile, the DOD chemical protection system (against ticks and mosquitoes) is simple and straightforward: permethrin on your duds, DEET in concentrations of about 33 percent or less on your skin. One of the DOD’s recommendations is 3M’s Ultrathon. It notes that DEET in higher concentrations only marginally extends the product’s efficacy. The 33 percent solution is good for about 4 hours, while 60 percent might go five. “It is more effective to use lower concentrations of DEET with more frequent applications than to assume the higher contractions to be longer lasting. They are not.”
Permethrin kills ticks on your clothing, provided they travel at least 10 inches, during which journey they accumulate a lethal dose. DEET kills neither ticks nor mosquitoes. Paula Smith’s take is this: “Listen, honey. DEET’s like weed to ticks. It slows ’em down some, makes ’em a little woozy. But they still have the munchies if they make it to your skin.”
Be careful out there.