It's also known as "swimmer's itch".
Ducks, geese, mergansers, and sea gulls can transport the little critters.
While all waterfowl can be affected, the condition requires snails which are also affected -- which will pass it back to the waterfowl. Lakes without the "correct" snails will not have a duck itch problem.
Snails require growing algae to feed on, and algae require nutrients (fertilizer).
Bathing in, washing the boat, or maintaining a lakefront lawn increases the nutrients in Winnipesaukee. Algae is a growing problem. I cannot recall a single case of duck itch when I went to a Lake Winnipesaukee summer camp. ("Camp Jurassic"
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As already stated, toweling off immediately after getting out is the best prevention. The water, as it evaporates, concentrates the little skin-burrowing critters responsible for the itch.
http://healthlink.mcw.edu/article/955152713.html
A day or two of a favorable wind direction will also concentrate the itch problem into shallow waters.
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