Swimmers Itch

Swimmer’s itch, also known as lake itch, duck itch, cercarial dermatitis, and Schistosome cercarial dermatitis, is a short-term, immune reaction occurring in the skin of people that have been infected by water-borne schistosomatidae parasites. Symptoms, that include itchy, raised red bumps, usually occur within hours of infection and do not generally last more than a week.

A number of different flatworm parasites in the family Schistosomatidae parasites are what cause swimmer’s itch. These parasites use both freshwater snails and Waterfowl as hosts in their life cycles.  Mostly waterfowl are used as the vertebrate host. During one of their life stages, the larvae of the parasite, leave the water snails and swim freely in the freshwater, attempting to encounter water birds. These larvae can accidentally come into contact with the skin of a swimmer. The larva penetrates the skin and dies in the skin immediately. The larvae cannot infect humans, but they cause an inflammatory reaction. This reaction causes initially mildly itchy spots on the skin. Within hours, these spots become raised red bumps which are very itchy. Each bump corresponds to the penetration site of a single parasite.

 

One preventative measure that can be taken is to use copper sulfate in the shallow areas to ward off the parasite ridden snails and keep the parasites away.  You will also want to be sure you dry off good when you exit the water and be sure to wash with warm soapy water after swimming.  It would be difficult to try and keep any waterfowl out of your swimming area at all times but by treating with copper sulfate the parasites would not stick around long.