Over the July Fourth weekend, the Tanana Lakes Recreation Area in Fairbanks was crowded with folks trying to beat the heat. Swimmers powered through laps. Kids squealed as they splashed in the shallows. But one local stayed ashore.
“Swimmer’s itch is horrendous,” Mirabel Estrada said. “It feels like the worst mosquito bite you've ever had, except it's everywhere, in all the worst places.”
Estrada said she got swimmer’s itch at the Tanana Lakes swim beach as a kid. Over-the-counter remedies didn’t make the rash go away, so she had to see a doctor.
“I looked like I was covered in chicken pox,” she said. “Then they gave me a shot in the butt, and it did go away.”
The science behind the scratch
The itch comes from a tiny parasite that lives in local swimming holes. Fairbanks scientists are trying to figure out if climate change is making infections more common, and they’re asking for help from folks who have been bitten.
University of Alaska Fairbanks biology student Pirada Anderson is heading up the project — which involves a tank full of infected snails that Anderson says turns into a “swimmer’s itch hotspot.” .
“It's like a mega-itch tank,” she said. “If I reach my arms in to change out the snail food, sometimes I'll get swimmer's itch up and down my arms.”
The infection is caused by a tiny worm that’s barely visible to the naked eye. It burrows into your skin and often triggers an allergic reaction before it eventually dies and gets absorbed.
According to Anderson’s supervisor, UAF parasitologist Don Larson, that’s because it’s mistaken you for its natural host. People are essentially innocent bystanders in a lifecycle where the parasite typically moves from snails to ducks.
“They look for motion and heat to tell where a duck is,” Larson said. “We're swimming, and we get mistaken for a duck.”
A warming world could make swimming itchier
Larson said the worms become most active when lakes and ponds are at their warmest, and climate change could make those conditions last longer each year.
“Those snails will be warmer and the parasites will be warmer,” he said. “If they're warmer, they'll grow faster, and will be more active.”
Or climate change could eventually do the opposite. If warmer temperatures arrive too early, Larson said that could throw off the parasite’s life cycle by disturbing the host species it needs to survive.
Larson stressed that swimmer’s itch is not lethal, and it will usually go away on its own. Through his many years of work with the worms, he’s even found something to appreciate about them.
“The male has this groove that the female lays in, and they breed and mate for life,” he said. “And that can be decades of just living in somebody happily in little bliss, I guess.”
Larson even has a t-shirt from Etsy with two swimmer’s itch worms coiled in matrimony, in the shape of a heart.
Waterproof sunscreen can protect you, but mind the gaps
In Alaska, the worms are most active from July to September. They’re most often found in deep or shallow ponds and lakes, and less commonly in creeks, rivers and the ocean.
According to the CDC, most cases can be treated like an allergic reaction, with antihistamines and things like calamine lotion and hydrocortisone. A layer of waterproof sunscreen will help block the worms from burrowing into your skin, but it must be applied everywhere.
“They like to find little spaces I forget,” he said. “In the little gap between our fingers. If I forget underneath my watch, I'll get a little swimmer’s itch there.”
Meanwhile, the scientists are preparing an online survey that will ask people about their swimmer’s itch — questions like where they think they got it, what they were doing at the time, and the intensity of the reaction. It’s set to launch early next summer.