Swimmer’s Itch

Swimmer’s Itch

What you can do

There is a product available called Swimmer’s Itch Guard. The Glen Lake Association is not endorsing it, but it has been tested and shown to be effective against Swimmer’s Itch. Check the local pharmacies for availability, or swimmersitchguard.com. Apply liberally before entering the water & reapply after 90 minutes of water activity.

Another product to consider using is a sunscreen lotion called Bullfrog.

We’d also like to know about local swimmer’s itch cases. Please click here to report any case of swimmer’s itch. With your help, we can monitor and track cases of swimmer’s itch — and progress in eradicating it.

History of our Swimmer’s Itch programs

The Glen Lake Association has a 30-plus year effort in the research and control of Swimmer’s Itch. Our research in the mid-80s helped define the life-cycle of Swimmer’s Itch on Glen Lake, i.e., one snail species and one bird species.

The Glen Lake Association was one of the first lake associations in the nation to live trap and relocate Merganser broods (two campaigns spanning 10 years) with the help of SICON, LLC, which was able to obtain the necessary state and federal permits.

We were also the first lake association to obtain a major grant ($200,000) from the State of Michigan Department of Commerce (mid-80s) to support these programs. We have the longest working relationship with SICON, LLC, the world leader in Swimmer’s Itch research, education and control.

Where are we now?

Common Mergansers are now a federally protected migratory species (U.S. Fish and Wildlife Service), and a moratorium was placed on trapping and relocating broods on Glen Lake from 2009 to present.

Part of the reason was SICON, LLC went temporarily out of business and the permits were denied pending further research, thus interrupting our control strategy using SICON as our strategic partner.

From 2010 to present, the Glen Lake Association’s approach was limited to recommending topical creams (“Itch Guard”), swimmer education and Common Merganser harassment. The harassment was aimed at reducing the number of broods coming on the lake in the summer along with preventing bird loafing on any particular shoreline.


The Glen Lake Association’s only means of controlling the merganser population is during spring and fall with the use of pyrotechnics. We hope the “screamers and bangers” force the ducks off the land and prevent them from loafing along shorelines.

If you see a brood of Merganser ducklings in the lake, please call the Glen Lake Association at 231-334-7645. The ducks swim with a brood of 10-16 ducklings. They swim/scoot across the top of the water for 8-10 feet, stop, and sometimes dive for food.

Where are we headed?

We feel that we have been fortunate to date, especially in comparison to other neighboring lakes, having benefited from all the diligent time, energy and money ($350,000) invested over the last two decades. However, we are concerned that our current harassment strategy could be losing its effectiveness. Consequently, we are working with a state coalition of 15 lake associations and SICON (now back in business) to find the money needed for research required by the state before it will lift the moratorium on trapping mergansers.

Conducting this research on Glen Lake will drastically mitigate the risk posed by more common mergansers on our lake.

Brief tutorial

Cercarial larva is the parasite that causes swimmer’s itch on Glen Lake. (NOTE: there are nine species of parasites that cause swimmer’s itch in Michigan.) Cercariae are shed by Stagnicolous snails that are infected by parasites transmitted by avian hosts — the common Merganser in our case (presently).

The key to success in our treatment of swimmer’s itch is to break the lifecycle of the parasite in one of the two hosts. Historically, we tried to kill the snails by copper sulfate treatment, but that was ineffective (snails repopulated after expiration of the two hours of chemical potency). However, this was the only treatment for more than 30 years, from the 1950s to the 1980s.

After much debate, the Glen Lake Association conducted three years of research (with SICON’s founder) in the mid-80s. With three years of fecal analysis data from a wide variety of bird species on Glen Lake, the Common Merganser was identified as the primary bird host and constituted the vast majority of swimmer’s itch cases.

Recent action and results

With the Glen Lake Association unable to obtain highly restricted trapping permits, we’ve been relying on a harassment strategy that began in 2010.

Our only metric to measure effectiveness has been brood/bird count, and we have been able to keep the number of broods between one and two per summer. However, last summer, the brood number increased to three and each brood had a higher number of young bringing the new resident Common Merganser population to a total of 30, compared to nine in the prior year.


Given Common Merganser counts are increasing despite increased harassment, we believe the risk of Swimmer’s Itch on Glen Lake could be increasing. Other lakes in northern Michigan, such as Higgins Lake, that have not had a strong deterrent history like Glen Lake, have witnessed dramatic problems. That is why we are participating in a coalition of 14 other lakes to seek the necessary funds to support research and control efforts, ideally on Glen Lake.