Schistosomiasis is a chronic disease that infects an estimated 200 million persons, leading to an estimated 800,000 to 1 million annual deaths. It ranks second only to malaria in terms of morbidity and mortality caused by a parasitic disease. In addition, there is increasing evidence that schistosome infection may have profound effects on growth in children (de Lima e Costa et al., 1988; Corbett et al., 1992; McGarvey et al., 1993). Three species of schistosomes account for the vast majority of human infection: Schistosoma mansoni, found in South America, the Caribbean, Africa, and the Middle East; S. haematobium, found in Africa and the Middle East; and S. japonica, found in Asia and Southeast Asia. In addition, there are other species of schistosomes that infect humans with varying degrees of success such as S. intercalatum and S. mekongi. Disease is caused by the host immune response to parasite eggs that become trapped in tissues, forming granulomas. Granulomatous responses then lead to the development of fibrotic lesions, which in turn lead to portal hypertension, shunting, and esophageal varices. One or more of these serious disease manifestations are found in S. japonicum- and mansoni-infected patients who have developed hepatosplenic disease.