Schistosome infections cause much suffering in millions of people living in tropical regions of Africa, Asia, and South America (Prata, 1987; Chitsulo et al., 2000). The most severe clinical symptoms affect the kidneys and urinary tract. However, schistosomes also cause various other disorders such as heart failure and neurological diseases. Three species of schistosome are responsible for most human infections (Schistosoma mansoni, Schistosoma japonicum, and Schistosoma haematobium). These species are found in different geographical locations, have different vectors, and cause different symptoms. Schistosomes are multicellular parasites that are disseminated as free swimming larvae (cercariae) in ponds, lakes, and rivers by snails. Humans become infected when they stay in contaminated water for a few minutes. The cercariae penetrate the human skin and develop into male or female adult schistosomes within 5 or 6 weeks. These small worms (Fig. 12.1A) can live in the vascular system of their vertebrate host for 2 to 5 years. Schistosomes do not multiply within their vertebrate host. The female worms, however, lay hundreds of eggs per day in the mesenteric or vesical veins of their host. Most of the symptoms associated with these infections are caused by the inflammation that is induced by the immunogenic and toxic substances produced by the eggs. The chronic cellular reaction that develops around the eggs is organised in a granuloma (Von Lichtenberg, 1962; Warren et al., 1967).