Swimmer’s Itch

This discovery has set about nearly a century-long quest for control and prevention of this common and troublesome malady. Attempts at killing the parasite in either the bird or snail hosts have been made to break its life cycle. However, these strategies have proven challenging, and have had unintended negative ecological consequences with limited effectiveness. For example, applying copper sulfate to kill the snail hosts kills all aquatic life forms and was shown to be ineffective at stopping swimmer’s itch in research conducted and published on South Lake Leelanau. Furthermore, a recent discovery (2021) has shown that there are more parasite hosts than previously thought, such as Canada geese, mergansers and mallards. While diversity is often celebrated as an ecological benefit, when it comes to swimmer’s itch, it makes it harder to control. This discovery has discredited attempts made to control swimmer’s itch at the lake-wide level.

Without the ability to control the swimmer’s itch causing parasite (otherwise known as the avian schistosome cercariae), efforts have now transitioned to the prevention of swimmer’s itch. There have also been new discoveries in how the cercariae move through the water. They emerge most abundantly in the morning and travel up to the water’s surface, and then can move around at the surface due to wind and current, often accumulating in shallow water when there are onshore winds. This information has helped researchers develop innovative prevention strategies that may be helpful to everyone. Shifting the paradigm from lake-wide control to individual prevention has now empowered everyone to swim itch free if proper strategies are employed.

Strategies to avoid swimmer’s itch include:

• Wear a tight-fitting, full-body rash guard (check them out online - ocean bathers wear them often to prevent jellyfish stings)
  • Larvae don’t typically penetrate fabric and bonus: less sunscreen is necessary!
• Swim later in the day
  • Larvae usually exit snails each morning and will die or be eaten during the day.
• Avoid lounging in surface waters
  • Larvae migrate to the surface and can accumulate in shallow water.
• Avoid onshore winds
  • Larvae move with the wind and can congregate near windward shores.
• Towel off after swimming
  • Some larvae are sticky and can cling to skin when you exit the water.
• Swim in deeper water if you are able
  • Larvae are released from shallow water snails so fewer are found in deeper water.
• Employ a swim baffle*
  • Baffles show promise in diverting drifting larvae away from swim areas.
• Skim the swim area surface*
  • Modified pool leaf rakes show promise in clearing a swim area of the larvae.
• Try different creams & lotions
  • Various products claim to repel larvae from entering the skin.
• Contact your lake association
  • They may have reporting tools available to avoid areas with recently reported cases. The Lake Leelanau Lake Association suggests using this reporting tool to see if others have reported cases nearby and to report your own case.

*Learn more about these methods below.