General Description
Cercarial dermatitis, also known as “swimmer’s itch”, an ailment caused by the penetration of human skin by the cercariae of non-human schistosome parasites, is a common, recurrent phenomenon in freshwater, brackish and marine habitats worldwide. Adult schistosomes typically live in the mesenteric blood vessels of birds and mammals, and produce eggs that pass from their host’s body in the feces, then hatch and release miracidia that penetrate and develop in snail intermediate hosts. Snail infections culminate in the production of numerous cercariae that are regularly released into the water where they seek to penetrate the skin of a vertebrate definitive host. Cort (1928) working at Douglas Lake, Michigan was the first to associate schistosome cercariae emerging from freshwater snails as the causative agent of a dermatitis known around Michigan lakes as swimmer’s itch. He and others showed this ailment to be caused by the cercariae of several genera of schistosomes that normally use aquatic birds and non-primate mammals as their definitive hosts.
However, the situation is complicated both by a poor understanding of the identity and number of species present and by the incidence of other schistosome genera that also contribute to outbreaks.
Recognizing Cercarial Dermatitis
Symptoms: itchy, raised papules that usually occur within several hours post exposure and generally last about a week
Resources:
PDF of relevant literature
Us in the media:
Alameda County Vector Control summer newsletter 2007
Contra Costa Times 2008
Links:
American Osteopathic College of Dermatology
Swimmer's Itch.org
CDC
© copyright 2011 Sara V. Brant, University of New Mexico