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California Study Finds Lyme Disease-Carrying Ticks by the Beach

Researchers found as many ticks carrying the bacterium that causes Lyme disease in coastal areas as they did in woodlands

Grasses and coastal scrub photographed at Salt Point State Park in Northern California. This park is one of several coastal areas researchers surveyed as part of a new study of disease-carrying ticks. (Amy Meredith via Flickr under CC BY-ND 2.0)
smithsonianmag.com

A study looking for disease-carrying ticks in Northern California found the insects in an unexpected place: the seaside. Researchers found Lyme disease-carrying, black-legged ticks in the brush and grasses edging right up to the sand of the region’s beaches, reports Linda Carroll for NBC News.

“We went into new habitats and found them in numbers we didn’t expect,” Daniel Salkeld, an ecologist studying wildlife disease at Colorado State University and the study’s lead author, tells NBC News. “A few years ago, I would have said the ticks there wouldn’t have been infected because there aren’t any gray squirrels, which are the source for Lyme in California.”

Because gray squirrels are California’s main vector for Borrelia burgdorferi, the bacterium that causes Lyme disease, woodlands have headlined the list of the state’s places where ticks are cause for concern. But Salkeld’s research, published last week in the journal Applied and Environmental Microbiology, searched for ticks in new places.

“If you go to those coastal bluffs, you just get that scrub, and that’s the kind of habitat we started looking in,” Salkeld tells Paulina Firozi of the Washington Post. “I don’t think we were expecting to find many ticks, but we did, and we found heaps of ticks in big numbers. And they’re infected with diseases.”

Without gray squirrels around to spread the Lyme-causing bacteria, Salkeld tells NBC News that the reservoir of bacteria “could be voles or rabbits.”

Ticks tend to wait on leaves or blades of grass and then latch onto the bodies of a human or animal hosts when something brushes past. So, to look for ticks, the researchers conducted what are called “tick drags'' in parks in Marin, Monterey, Napa, Santa Clara, Santa Cruz and Sonoma counties. Tick dragging involves dragging a cloth over an area’s foliage. Any ticks nearby are likely to latch on to the fabric, and at the end of a survey the researchers count how many of the insects they’ve picked up.

Per NBC News, when the team then tested the ticks they collected, researchers found 4.1 percent of adult ticks collected from coastal scrub and in 3.9 percent of adult ticks from woodland areas tested positive for Lyme-causing Borrelia burgdorferi.

In a statement, Linda Giampa, executive director at Bay Area Lyme Foundation, says the study has prompted her organization to encourage people “to take preventative measures in beach areas,” as well as “encouraging healthcare providers to learn the symptoms of tick-borne infections beyond Lyme disease.”

Lyme disease is transmitted through black-legged tick bites and causes a range of symptoms from mild to debilitating. Though it is a challenging disease to diagnose, the Centers for Disease Control and Prevention estimate that around 480,000 people are diagnosed and treated for Lyme disease each year in the United States.

“I’m not trying to ruin anyone’s vacation or outdoor time,” Salkeld tells the Post. Still, he says it’s important to “always be aware that ticks are around in most of the habitats in California.” If you do find a tick on yourself, a loved one or a pet, Salkeld advises you get rid of the tick “as fast as you possibly can,” and then send it in for identification and testing.

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