摘要：Swimmer’s itch (cercarial dermatitis) affects people engaged in open-water activities. We report incidence and risk factors for a US lake. Water exposures and swimmer’s itch experience were reported daily for riparian household residents and guests at Douglas Lake, Michigan, in July 2000. Incidence of swimmer’s itch was 6.8 episodes per 100 water exposure days. Positive risks were (1) exposures in shallow water and in areas with onshore winds and (2) more days of lake use in July. Further epidemiological studies will help public health agencies address this bothersome problem at recreational lakes. Cercarial dermatitis, or swimmer’s itch, is a skin condition that affects people engaged in open-water activities in fresh and salt-water areas around the world. It causes intense discomfort, discourages recreational water use, and leads to economic loss for lake regions if people decide to vacation elsewhere. Since discovery of the parasites responsible for swimmer’s itch, 1 most research has focused on the schistosomes’ life cycle and biological control methods. 2– 14 The literature on humans and swimmer’s itch consists largely of clinical and outbreak reports. 15– 28 Epidemiological studies are rare. 29, 30 We conducted a prospective study at a Michigan lake to obtain an incidence rate and identify risk factors for swimmer’s itch. The schistosomes for swimmer’s itch have a 2-host life cycle, an avian definitive host and a snail intermediate host. At one point in the cycle, snails release cercariae (free-swimming larval stage of the parasite) into the water, where they may encounter and enter ducks and other birds. If instead they penetrate human skin during recreation or work in the water, an inflammatory response occurs. Mild itching and macular eruptions occur 1 to several hours after a person leaves the water. Intense itching and papules are present 10 to 15 hours later, continuing for about a week. Swimmer’s itch is not communicable. Preventive actions before or after water exposure have been proposed, but no scientific evidence exists on their efficacy.
