Clearing the water: Watershed association using science to combat swimmer’s itch

By Colin Merry

Pioneer News Network

BENZIE COUNTY — The Crystal Lake and Watershed Association is continuing its battle against swimmers itch, using a science-based method that breaks the life cycle of the parasite that causes it.

Swimmer’s itch, also known as cercarial dermatitus, is a skin rash caused by an allergic reaction to

Tom Thorr (back) and Tim Reznich (front) catch mergansers for the Crystal Lake and Watershed Association as part of an effort to reduce swimmer’s itch in Crystal Lake.

microscopic parasites that infect birds and mammals, according to the Centers for Disease Control.

The parasites are released from infected snails into the water, and if they come in contact with a swimmer, instead of a bird, they can burrow under the skin and die, causing the characteristic red rash, burning and itching.

Infected birds continue the cycle by passing the eggs of the parasite, which then hatch and infect snails, using them as an intermediary host. Herscher said swimmer’s itch has long plagued Crystal Lake, making swimming a gamble, and leading some visitors to swear off visiting the area.

In the case of Crystal Lake, the avian carriers are common mergansers, a type of duck that dives to catch its prey, which include small fish, crustaceans and invertebrates.

Swimmers itch was controlled with chemical agents in the past, but as the public became more wary of what goes into the water, and its effects on the environment and people, treatment stopped.

So for the third year in a row, the association is removing the parasite’s host from the lake, instead of treating for the parasite itself. A team traps broods of mergansers, and relocates them to lakes that do not have the type of snail that carries the parasites that cause swimmers itch. The trapping team captured the year’s first brood on June 12, and will continue as long as broods appear on the lake.

The Michigan Department of Environment, Great Lakes, and Energy has granted CLWA a permit to conduct this work.

“We started working with Swimmer’s Itch Solutions three years ago,” said Dave Wynne, president of the CLWA. “We were taught how to capture the broods, and now we’re doing it on our own.”

Tim Reznich and Tom Thorr, both teachers at Frankfort Area Schools, trap the birds, and then take them to a location to be released. Wynne said the birds are being taken to the Tippy and Hodenpyl Dam area. During the previous two years, the ducks were released in Suttons Bay.

The released chicks will imprint on the new lake, and not return to Crystal Lake. However, the hens will return.

While the CLWA works independently of Swimmer’s Itch Solutions since owner Curtis  Blankenspoor taught Reznich and Thorr know how to catch the broods, Wynne said Blankenspoor must be present when the broods are released. He also bands the birds, and occasionally fits them with a radio collar.

“One of our goals was to be able to train members of the association to catch the ducks without us,” Blankenspoor said. “We accomplished that pretty quickly. They’re good at catching broods.”

According to a press release from the watershed association, Crystal Lake showed positive results in 2018 due to the successful removal of all broods in 2017.

“Both rates and severity of swimmer’s itch were down, and a full-lake snail assessment showed a 65 percent reduction in their infection rate,” the release read. “Again in 2018, all 16 broods were removed and relocated.

“It does seem to be working,” Wynne said. “People have been telling me they’ve been able to go swimming again, when they haven’t in the past. People have also said if they’ve gotten swimmer’s itch, the ‘infection’ doesn’t seem to be as bad.”

Blankenspoor also said cases of swimmer’s itch was down, and that there was improvement, but that it would never be gone completely.

“We’re expecting the progress to continue, but we can’t ever eradicate swimmer’s itch,” Blankenspoor said. “Fall and spring migrants spend a few days on the lake, and there will always be a residual background level.”

He also said that the association will have to remain vigilant and continue removing ducks.

“It’s moved from a treatment to a maintenance program,” Blankenspoor said.

Wynne said the association is also working with the Michigan Swimmer’s Itch Partnership, which helps them assess the effectiveness of their efforts.

“We are being trained in QPCR protocol,where we filter out DNA in water samples to see the infection rate in snails,” he said. “With QPCR, you can sample virtually anything. If there is an E. coli outbreak, we can take a sample and find out if it comes from animals, and is runoff from farming, or if it comes from people, and might indicate a leaking septic system.”

Wynne said the association spent $65,000 in 2017 to combat swimmers itch, and $45,000 last year.

For more information on the CLWA and its programs, visit its website: www.CrystalLakeWatershed.org

The local community can assist by reporting sightings of merganser broods via the CLWA website (www.CrystalLakeWatershed.org) where a link from the home page opens a special reporting form (also used for reporting swimmer’s itch cases).

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