Perhaps as many as 300 million human beings are victims of snail-borne parasitic diseases: schistosomiasis (which is of primary concern), fasciolopsis, angiostrongyliasis, clonorchiasis, and paragonimiasis. Fascioliasis, a major ailment of cattle and sheep, can also infect humans, and its control may thus serve a dual purpose. Various control methodologies, including chemical, which can be applied to the mollusc hosts of these diseases frequently are related to aquatic plant control.