Man Made Lake

A group of swimmers plays in Man Made Lake.

Warm weather and the final weeks before school starts has many Valley residents searching for the best local swimming spots. But swimming outdoors in Alaska can also bring a different concern: swimmer’s itch. The red rash looks like small red bumps or even a swath of mosquito bites, depending on the person, and is caused by microscopic parasites found in some lake waters.

So how can you both stay cool and steer-clear of that miserable summer plague? It’s all about keeping an eye out for certain conditions while avoiding lakes with known problems, Alaska’s top epidemiologist advised.

“Basically here’s the low down,” said Dr. Joe McLaughlin, chief of epidemiology at the Alaska Department of Health and Social Services. “Swimmer’s itch appears as a skin rash caused by an allergic reaction to certain micro-parasites that are present in the water.”

The parasite, McLaughlin said, is found in lake water that meets a series of conditions. Brought in most typically by waterfowl, such as ducks, it first enters the water as eggs in the animal’s poop before hatching and attaching to water snails. It is then released back into the water in search of something to infect to restart the life-cycle.

That, McLaughlin said, is when it finds human skin. But because humans are not a viable host for the parasite, instead of burrowing and growing, the parasite burrows and dies. That means while it can cause some major itching, the rash typically only lasts a few days.

Swimmer’s itch might show-up on a human anywhere from a few minutes after swimming to a few days, McLaughlin warned.

“First, you often will get that itching of the skin, sometimes you’ll get burning and tingling of the skin as well,” he said. “Next, you’ll typically get small reddish bumps and small blisters will follow that sometimes.”

So how do you have fun in the water and also avoid parasites? A few preventative measures could go a long way, he said.

Swimmers can first simply avoid areas that are either likely to host the parasite or are known to do so. Marshy areas or silty and muddy bottoms with vegetation that attract ducks and snails, for example, are two signs it might be present, he said. And as water temperatures warm they are even more likely to contain it, he said.

If you do swim in an area that is likely to have swimmer’s itch, drying off well after exiting the water or showering immediately after your swim could be key to avoiding the problem.

“If you do a really vigorous drying session that is going to help a lot to help prevent those little larvae from penetrating into the skin because you’re basically rubbing them off your skin,” he said.

While some internet sites say sunscreen might help swimmers avoid the issue, he hasn’t seen any studies confirming that, he said. Treatments for the issue include topical anti-itch cream. And you should see a doctor if the area becomes infected or the itching is uncontrollable, he said.

Where to Swim Without Swimmer’s Itch

Which Valley swimming areas are known swimmer’s itch hosts varies by month, or even what part of the water you’re enjoying. For example, swimming in the deep part of any lake, far away from the grass or areas with ducks and snails, could help you avoid the problem even when the shoreline is a known problem spot.

Some lake swimming areas, like the beach at Finger Lake, are annually well-known for their swimmer’s itch. Others, like Christiansen Lake in Talkeetna, are on-again, off-again problems.

The only non-alpine swimming area in the region that is never reported as an issue is Manmade Lake off Knik River Road in the Knik River Public Use Area. That’s because that lake is created from backflow from Knik River, making it less a lake and more a part of the river with fresh water and no problematic vegetation or ducks.

Users can access Manmade Lake and the gravel bars that make up its beach area about four miles up Knik River Road. Drivers should watch for the entrance to the area on the left against the river, and can proceed to the far side of the lake by following a well-worn ATV trail that starts to the right of the entrance.

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