INFECTION WlTH SCHISTOSOMES

pathologically important Platyhelminthes include the digenetic trematodes Opisthorchis, Clonorchis, Paragonimus, Fasci%psis and Fascio/a and the cestodes (tapeworms). Ali the schistosomes that mature in man belong to the genus Schistosoma of the family Schistosomatidae, which contains Il other genera, some of which cause cercarial dermatitis (Rollinson & Southgate, 1987). The genus Schistosoma contains 19 species (WHO, 1993), five of which (Schistosoma haematobium, S. mansoni, S. japonicum, S. mekongi and S. interca/atum) are of major pathological importance, while the others are essentially parasites of non-human mammals, although sorne zoonotic transmission to man does occur. An estimated 600 million people are at risk for schistosomiasis; 200 million are currently infected in 74 countries (WHO, 1993). Pròbably more than 95% ofhuman infections are due to S. mansoni and S. haematobium. Several of the 'non-human' species, including S. mattheei and S. bovis, are of veterinary importance, and both domestic and ferai animais are major reservoirs of infection with S. japonicum (but not wi th any of the other species) (Taylor, 1987). This monograph is restricted to S. haematobium, S. mansoni and S. japonicum.