Schistosomiasis of the Western Hemisphere is an import from Africa, where 150 million people carry the parasite, dwarfing the unsolved problem in the new world.
The little worm lives comfortably in blood vessels, male and female tucked together as if in a double bed, manufacturing potential babies for many years in defiance of laws forbidding population explosion. Another form develops into cysts in fresh-water snails, each cyst spilling over with thousands of other babies.
Control of this miserable infestation could be effected in many ways. Destruction of either of the two free-living forms, going to or coming from the snail, would end the problem. Unfortunately these animalcules live but briefly, and poisons concentrated enough to kill them would be destructive of the people who must use the water in which the little fellows swim. Storing and impounding the water can help, but it is not often tried because it is
THE WORM'S TURN. JAMA. 1967;199(4):270-271. doi:10.1001/jama.1967.03120040080017