The snail, Nassarius obsoletus, is the intermediate host for this species and can be found at marine beaches in temperate climates. One species of schistosome often implicated in cases of cercarial dermatitis is Austrobilharzia variglandis, whose normal hosts are ducks. Cases of cercarial dermatitis can occur in both fresh and brackish water environments. The penetration causes a dermatitis which is usually accompanied with intense itching, but the cercariae do not mature into adults in the human body. They attempt to, and, sometimes may actually, enter human skin. These cercariae seem to have a chemotrophic reaction to secretions from the skin and are not as host-specific as other types of schistosomes. Note the forked “tail” and a pair of “eye spots” near the anterior end (right).Ĭercarial dermatitis is caused by the cercariae of certain species of schistosomes whose normal hosts are birds and mammals other than humans. Swimmer’s itch parasite – Cercariae of Austrobilharzia variglandis – which can cause cercarial dermatitis. Swimmer’s itch should not be confused with sea bather’s eruption (caused by larval forms of the thimble jellyfish sea anenome or Portuguese Man-of-War) or seaweed dermatitis (caused by an alga).įigure 1. When infection occurs in sea water, it is sometimes called ‘Sea Lice’. In New Zealand it is called ‘Duck Itch’ and in parts of United States it is called ‘Duckworms’ or ‘Duck fleas’. In developing countries, swimmer’s itch has been called ‘rice paddy itch’, ‘clam diggers itch’, ‘sawah’ (Malaysia), ‘kubure’ or ‘kobanyo’ (Japanese) and ‘hoi con’ (Thailand). The technical name for swimmer’s itch is cercarial dermatitis. Migrating aquatic birds infected with the trematode parasite return from their winter habitats or domesticated aquatic birds return to full activity.The water temperature reaches the appropriate level for snails to reproduce and grow rapidly.Several factors may increase the risk of swimmer’s itch. Most cases of swimmer’s itch do not require medical attention. Swimmer’s itch is found throughout the world and is more frequent during summer months. While the parasite’s preferred host is the specific bird or mammal, if the parasite comes into contact with a swimmer, it burrows into the skin causing an allergic reaction and rash. Swimmer’s itch develops on exposed areas of the skin after contact with these larval forms when they mistakenly penetrate the person’s skin (rather than its usual host, a duck). Cercarial dermatitis is usually acquired in freshwater habitats, and less commonly in marine or estuarine waters. Immature larval forms (cercariae), of parasitic flatworms (schistosomes), are released from infected snails into fresh and salt water, such as lakes, ponds, and lagoons. Swimmer’s itch, also called cercarial dermatitis, is a skin rash caused by penetration of human skin by cercariae of schistosome parasites and an allergic reaction to an infestation with certain parasites that infect some birds and mammals 1). Is it safe to swim in my swimming pool?.Once an outbreak of swimmer’s itch has occurred in water, will the water always be unsafe?.What are the signs and symptoms of swimmer’s itch?. How does water become infested with the parasite?.
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