Four and twenty tailors went to kill a snail . . .
Run, tailors, run, or she'll kill you all e'n now.
Old Nursery Rhyme
The sluggish snail has turned out to be far more deadly than the anonymous poet knew. For years, scientists have been busier than the old song's tailors, trying to kill certain species that carry human and animal diseases, notably the microscopic parasite that causes schistosomiasis, an ancient and virtually incurable ailment common in many warm countries. Though a selective chemical capable of destroying the guilty snails is under development...