Hepatic Fibrosis in Schistosomiasis

Schistosomiasis, a disease affecting over 200,000,000 human beings, is caused by infection with one of sev­eral s cies of the Schistosoma trematodes. The in­ fectious form for mammals is the cercaria developed by passage through snails. The major cause of death in those infected results from distortion of the hepatic circulation caused by a unique kind of fibrosis In the liver. The fibrosis occurs In relation to the formation of numerous highly cellular and collagenous granulomata as part of a cell-mediated immune response to eggs deposited by worms In the portal tract. After a period of tlme, the granulomata disappear as new for­mation of broad bands of collagen appear in the liver. Because of the nature of those bands the condition is called pipestem fibrosis. The fibrosis distorts liver ar­chitecture and with that the circulation of blood in the liver. Prevention of the disease by ecological controls directed largely against the snail vector, would seem to be most important. Falling that, the disease itself is treated largely by use of a number of chemothera­ utic agents directed against the Schistosoma. The present a icle reviews the modes of treatment now In use, and describes possible means of preventing or versing the deposition of collagen that constitutes the fibrosis. Research on analogs of proline and lysine Inhibit collagen biosynthesis or stimulate collagen d radation Is described. Possible new approaches for prevention of maturation and mating of worms lodged In portal tracts is considered as a means of preventing egg formation and the consequent host immune response that causes fibrosis.