Introduction and history of the disease

Schistosomal dermatitis, cercarial dermatitis or swimmers' itch is caused by penetration of larvae, cercariae, of blood flukes (schistosomes) into human skin which are released from infected snails (Figure 22.1). Being a global problem, the disease is widespread, for example, in northern and central Europe, in Russia, and in North America.

Depending on the geographic location, it is variously known as 'swimmers' itch', 'bather's dermatitis', 'cercarien dermatitis', 'sawah', 'rice paddy itch', 'lake side disease', 'clam-diggers itch', etc. (Hunter 1975).

The cause of swimmers' itch in temperate and northern regions is usually avian schistosomes. Swimmers' itch is also an initial symptom of schistosomiasis caused by several species of tropical, human schistosomes like Schistosoma mansoni, S. haematobium, and S. japonicum. In addition, swimmers' itch can be caused by schistosomes infecting mammals other than man, such as cattle. The symptoms of cercarial dermatitis were described already more than 150 years ago when Fujii (1847) described the initial symptoms of the 'Katayama disease'. Cort (1928) made the first description of cercarial dermatitis caused by an avian schistosome. While collecting molluscs (Lymnaea emarginata-angulata) at Douglas lake in Michigan, US, he accidentally noticed that cercariae of Cercaria elvae [first described by La Valette St George (1855), mentioned as Trichobilharzia ocellata in Europe (McMullen and Beaver 1945)] produced a severe prickly sensation on the wrists and that this was followed by the appearance of papules which evolved into a pustular eruption with intense itching within 48 h. Since then, the dermatitis produced by cercariae of bird and mammalian schistosomes has been described by several workers over the years (e.g. Christenson and Green 1928; Matheson 1930; Vogel 1930; Wesenberg-Lund 1934; Olivier 1949; Cort 1950; Pirila and Wikgren 1957; Berg and Reiter 1960; Hoeffler 1974, Hoeffler 1977; Kirschenbaum 1979; Shimizu et al. 1981; Kimmig and Meier 1985; Sevcova et al. 1987; Beer and German 1993; Kullavanijaya and Wongwaisayawan 1993; Thune 1994; Kolarova et al. 1999).

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