In the 1950s, the N.H. Department of Fish and Game began importing mallard ducks into the state to add to the game population. What they did not realize was that not only were they importing ducks, but a tiny parasite, cercarial dermatitis, in the ducks' blood stream as well.
What Causes Swimmers' Itch?
Swimmers' itch (also called cercarial dermatitis) is a skin rash caused by an allergic reaction to contact with certain parasites of birds and mammals. Snails become infected with these parasites and then release them in fresh and salt water. Swimmers' itch generally occurs during the summer months.
What are the Symptoms of Swimmers' Itch?
Symptoms include tingling, burning, or itching of the skin within minutes or days after exposure. Small reddish pimples appear within 12 hours, which may develop into small blisters. Itching may last up to a week or more, but will gradually go away.
Is Swimmers' Itch a Health Hazard?
No. The swimmers' itch parasite is not parasitic to humans and causes no human diseases. No treatment is required for the rash. The rash will go away naturally within a few days, and there are no lasting effects. The same lotions used for mosquito bites and other itching rashes can control the itching caused by the rash. Swimmers' itch cannot be spread from person-to-person.
Is Swimmers' Itch Related to Water Quality?
No. The presence of swimmers' itch is not related to pollution or poor water quality. It is a natural life cycle. Although it has been present in the state for many years, it has never been a significant nuisance problem in most New Hampshire lakes.
Is There Any Way to Prevent Swimmers' Itch?
No. The adult parasite lives in the bloodstream of infected host animals such as ducks, geese, gulls, swans, as well as in certain aquatic mammals such as muskrat and beaver. The parasites produce eggs that are passed in the feces of the host bird or mammal. So if the animal feces land in the water, the water becomes contaminated.
How Do I Avoid Swimmers' Itch?
- Avoid swimming in areas where swimmers' itch is a known problem or where signs have been posted warning of unsafe water.
- Avoid swimming near or wading in marshy areas where snails are commonly found.
- Towel dry or shower immediately after leaving the water.
- Encourage health officials to post signs on shorelines where swimmers' itch is a current problem.
- Do not attract birds by feeding them in areas where people are swimming.