Humans are inadvertent and inappropriate hosts cercariae may penetrate the skin but do not develop further. The parasite develops in the intermediate host to produce free-swimming cercariae that are released under appropriate conditions and penetrate the skin of the birds and migrate to the blood vessels to complete the cycle. Life CycleĪdult worms are found in the blood vessels of definitive hosts and produce eggs that are passed in the feces On exposure to water, the eggs hatch and liberate a ciliated miracidium that infects a suitable snail (gastropod) intermediate host. Cercarial dermatitis occurs on the exposed skin outside of close-fitting garments. The areas of skin affected by seabather’s eruption is generally under the garments worn by bathers and swimmers where the organisms are trapped after the person leaves the water. These schistosomes all use different snail intermediate hosts, commonly those from the families Nassariidae, Lymnaeidae, and Physidae.Ĭercarial dermatitis should not be confused with seabather’s eruption, which is caused by the larval stage of cnidarians (e.g., jellyfish). ( =Orientobilharzia) turkestanicum) occur occasionally. Cases involving mammalian schistosomes Heterobilharzia americana, Bivitellobiharzia spp., Schistosomatium spp., and some aberrant zoonotic Schistosoma spp. ), Bilharziella polonica, and Gigantobilharzia huronensis. Other avian schistosomes that cause cercarial dermatitis include Ornithobilharzia spp., Austrobilharzia spp. Several genera/species are known to cause cercarial dermatitis the most commonly implicated genus globally is the waterfowl schistosome Trichobilharzia spp. Skin penetration by these zoonotic cercariae causes dermatitis, but the cercariae do not mature into adults in the human body. These cercariae seem to have a chemotrophic reaction to secretions from the skin and are not as host-specific as other types of human-infecting schistosomes. Cercarial dermatitis (“swimmer’s itch”, “clam-digger’s itch”, “duck itch”) is caused by the cercariae of certain species of schistosomes whose normal hosts are birds and mammals other than humans.
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