Controlling Swimmer’s Itch
Since the life cycle of the flatworm depends on the presence of both of its two intermediate hosts, the elimination of either will block reproduction. The traditional method of controlling Swimmer’s Itch has been to attempt to kill the host snails with copper sulfate. A permit from Michigan Department of Natural Resources (MDNR) in Lansing is required prior to any aquatic use of the compound.
Copper sulfate is a nonspecific poison which means that it is toxic not only to snails, but also to many non-target aquatic plants and animals. Copper, a toxic heavy metal, accumulates in lake sediments and can bioaccumulate in the living tissues of aquatic animals. Long term heavy applications of copper sulfate can pose a significant threat to the health of aquatic environments.
Copper sulfate treatments rarely kill enough of the target snails to eliminate Swimmer’s Itch. There is also some evidence that snails may be capable of developing resistance to copper sulfate. Despite the application of tens of thousands of pounds of copper sulfate in some lakes during the past 50 years, the occurrence and severity of Swimmer’s Itch has not noticeably diminished.
NOTE: The Tip of the Mitt Watershed Council does not endorse or encourage the use of copper sulfate to prevent or control Swimmer’s Itch.
Experimental Alternatives to Copper Sulfate
One highly promising approach to controlling Swimmer’s Itch has been developed by Dr. Harvey Blankespoor of Hope College in Holland, Michigan. His method involves determining which waterfowl are involved in the flatworm life cycle and treating them with a drug to kill the parasite. This does not harm the birds, but does interrupt the life cycle of the flatworm, eliminating the need for adding a persistent toxic chemical to the lake environment.
Initial research/control programs utilizing this method have been carried out on several lakes. The incidents of Swimmer’s Itch was greatly reduced compared to pre-treatment levels. For more information about this program visit http://www.swimmersitch.org.
Another control method being used in our service area is Merganser Control Programs. As part of the Walloon Lake Association's Swimmer's Itch Initiative, the association hired a wildlife management company to hunt Mergansers during the 2009 fall hunting season. They removed 60 Mergansers that were primarily resident birds to Walloon Lake. Wildlife biologists were also hired to harass Mergansers in the spring of 2010, before they nested on Walloon Lake. This helped reduce the number of Mergansers on the lake, this year and in subsequent years, thus reducing the level of the parasite that causes Swimmer's Itch.
What can our lake association do about swimmer's itch?
It can do several things including the following: educate members about Swimmer's Itch, assess the problem of Swimmer's Itch on its lake, make recommendations for relieving the itching, and begin a control program if Swimmer's Itch is a regular problem.
Tip of the Mitt Watershed Council Recommends…
There are several means by which you can significantly reduce your chances of contracting the Swimmer’s Itch parasite
- Since itch-causing larvae usually live in the shallows near shore, it is best to avoid this area as much as possible. This is especially important when the wind is blowing toward the shore.
- Towel off thoroughly as soon as you leave the water, and at frequent intervals. The fragile cercaria of some species can sometimes be rubbed off before they fully penetrate the skin.
- Do not feed waterfowl! Feeding waterfowl may aggravate the problem by concentrating potential hosts in a limited area.
- Maintain a healthy greenbelt along your shoreline property with a variety of native plants (including trees, shrubs, and herbaceous plants) to prevent waterfowl from congregating on your property. Shading of near-shore areas as a result of a shoreline greenbelt will also help reduce the amount of bottom-dwelling algae growth, which is a primary food source for the type of snails that are commonly hosts in the schistosome cycle.
- If you get Swimmer’s Itch, ask your doctor or pharmacist for the best treatment available to help reduce the itching sensation.
Click here for our What You Should Know About Swimmer's Itch informational flyer.