Going, going...

IT LOOKS like something out of a Gothic movie: a metre-long monster that emerges slowly through blistered human skin, its victim writhing in agony. No one is spared. It can creep out from between the toes of a child or from the belly of a pregnant woman. In the mid-1980s Dracunculus medinensis, the Guinea worm, as this horror is called, afflicted 3.5m people a year in 20 countries in Africa and Asia. But last year that number was down to just 22, all of them in Chad, Ethiopia, Mali and South Sudan. Dracunculiasis is thus poised to become the second human disease to be eradicated, after smallpox.

This blessed state of affairs is thanks to a 30-year campaign led by the Carter Centre, a charity set up by Jimmy Carter, a former president of America. Mr Carter picked his target well. Most Guinea worms grow in human beings, and their only other host is the domestic dog. Both humans and dogs can be monitored closely, in ways wild animals cannot. This means, in principle, that every case of dracunculiasis can be tracked and the worm involved prevented from reproducing. The task the Carter Centre set itself was to turn this principle into reality.