Cercarial dermatitis

**Definition:** A disease caused by an infection with the parasitic worm Schistosoma. This disease is characterised by tingling, burning, itching of the skin, small reddish pimples, or small blisters. Transmission is by direct contact with contaminated water. Confirmation is by identification of Schistosoma eggs in a faecal, urine, or blood sample.

**Long definition:** Cercarial dermatitis is caused by the cercariae of certain species of schistosomes whose normal hosts are birds and mammals other than humans. They attempt to, and, sometimes may actually, enter human skin. The penetration causes a dermatitis which is usually accompanied with intense itching, but the cercariae do not mature into adults in the human body. Implicated schistosome species include Austrobilharzia variglandis (normal host ducks) and Nassarius obsoletus (normal host snails). Cercarial dermatitis (swimmer’s itch) occurs on the exposed skin outside of close-fitting garments [CDC].