(Undated) -- The Iowa Department of Natural Resources is starting to get reports of swimmer's itch from natural lakes in north central and northwest Iowa. Daniel Kendal of the Iowa DNR says it's caused by parasitic flatworms. The flatworm eggs are transferred to water by bird droppings. The eggs hatch and infect snails, from which the free swimming form of the flatworm larvae emerges. In the absence of a suitable host, such as a bird, the parasite will attempt to penetrate the skin of humans, after which it quickly dies, causing an allergic reaction below the skin resulting in welts and itching. He says there may be more parasites in marshy areas, but water current can also move them into non-marshy spots of the water.
He says to avoid swimmers itch there are some steps to take.
First, if possible, avoid swimming in areas containing aquatic plants because marshy areas often contain snails, which are the parasite’s intermediate host. Swimmers can also reduce the amount of time in the water, avoid beaches that are being pounded by waves and dry off quickly when getting out of the lake.
The welts and itching caused by the parasitic little pest can last for several days to about a week and usually don't require a visit to the doctor. An antihistamine along with calamine lotion can be used to treat the affected areas.
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