New Discoveries in Swimmer’s Itch
Prevention is the Key
“An ounce of prevention is worth a pound of cure” so the saying goes. This certainly rings true for Swimmer’s Itch. Prevention is the key to itch free enjoyment of our waters.
Listed below are suggested preventative strategies based on GLA Swimmer’s Itch research on the behavior and life cycle of Swimmer’s Itch. If carefully employed, these methods will work to greatly reduce the total number of or even eliminate itch cases for an entire swim season. Please note that these strategies should be used together to be most effective at preventing Swimmer’s Itch.
- Cover your skin with swimwear that covers the area you want to be itch free (SI rarely affects a person’s hands, feet, and face)
- Towel off vigorously after swimming
- Swim in the afternoon or early evening vs. morning
- Do not swim when the wind is blowing onshore.
- Do not swim/wade in shallow water without using prevention measures
- Install a swim baffle in your swim area (two years of research indicates this works!)
- Use a parasite skimmer (watch the video link below for more info)
- Use a kid friendly wading or “kiddy pool” vs. using shoreline lake water for small kids to swim more safely and itch free.
Be aware that there is never a case, even using all these tactics, that Swimmer’s Itch risk can be reduced to zero. But there is so much we can do to have our best chance at preventing the itch. Check out this informative Swimmer’s Itch Prevention Video on what we learned from our 2017-2019 research and for more details about what you can do! And if you do experience Swimmer’s Itch, please click here to report a case. With your help, we can monitor and track cases of Swimmer’s Itch —and progress in managing it.
Brief tutorial and history of Swimmer’s Itch
Cercarial larva is the parasite that causes Swimmer’s Itch on Glen Lake. (NOTE: there are multiple species of parasites that cause Swimmer’s Itch in Michigan.) Cercariae are shed by multiple snail species that are infected by parasites transmitted by avian hosts —such as the Common Merganser, Canada Geese and Mallard ducks.
Historically we tried to break the lifecycle of the parasite in one of the two hosts. 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. We tried to remove and harass the resident mergansers which at the time were thought to be the exclusive avian hosts on our lake from the 1980’s-2019. Despite these efforts, numbers of mergansers and cases of swimmer’s itch increased, and we discovered through DNA testing that mergansers were not the exclusive SI hosts we had once thought them to be.
Where are we now?
The Glen Lake Association has a 30-plus year effort in the research and management 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. Research from 2017-2019 again revolutionized the scientific understanding of Swimmer’s Itch. Through use of DNA testing, multiple species of itch were identified (including a never before discovered species) cycling through multiple bird hosts in addition to the Common Merganser, all contributing to Swimmer’s Itch on Glen Lake. Given what we now know, it is clear that attempts to control Swimmer’s Itch by interrupting this complex life cycle are ineffective.
Given the newly understood, increasingly complex nature of Swimmer’s Itch and clear and overwhelming evidence that copper sulfate application and Merganser harassment, trapping and relocation are ineffective and even harmful, what is there left to do? The Glen Lake Association has learned and continues to make new discoveries that lead us to new approaches for combatting Swimmer’s Itch. The key to future success in our treatment of Swimmer’s Itch is to prevent humans from coming into contact with the Cercarial larva. Using what we have learned about the behavior of Swimmer’s Itch, we can arm our ourselves against exposure to the Itch.
Prevention is the key! Research has demonstrated that there are methods and technologies available to effectively control individual swimmer exposure to Swimmer’s Itch. But we need your help! Ongoing research including the use of data from Swimmer’s Itch case reporting will be keys to furthering our ability to protect against and prevent Swimmer’s Itch.