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Hosts of avian schistosomes can be either year-round resident or migratory birds, including seagulls, shorebirds, ducks, and geese. Adult worms are found in the blood vessels 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 .  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 .  Humans are inadvertent and inappropriate hosts; cercariae may penetrate the skin but do not develop further .  A number of species of trematodes with dermatitis-producing cercariae have been described from both freshwater and saltwater environments, and exposure to either type of cercaria will sensitize persons to both.