Schistosome parasites are muticellular eucaryotic organisms that have a complex life cycle. The egg stage produced by the worm pairs is important in transmission of the parasite and responsible for pathogenesis. For 1 species, Schistosoma mansoni, the female worm produces approximately 300 eggs per day (Moore and Sandground, 1956). The eggs, after they are deposited by the female schistosome, incite a granulomatous inflammatory reaction (Damian, 1987). Approximately half of the deposited eggs reach the outside environment by passing through the wall of the intestine and being voided with excreta, to continue the life cycle. The other 50% are swept up in the circulation and filter out in the periportal tracts of the liver, resulting in periportal fibrosis, portal hypertension, and the serious sequelae of intestinal schistosomiasis such as hepatosplenomegaly and esophageal and gastric varicies.
Unlike other trematodes, schistosomes (along with the Didymozoidae) are unusual in...