The NYT reports that Nigeria has been free of guinea worm infections for a year.
Guinea worm — or dracunculiasis — inspires universal horror. People are stricken when they drink pond water infested with microscopic fleas, in which the worm larvae live. The worms grow to resemble translucent three-foot strands of spaghetti and finally emerge by exuding acid that bursts the skin; the pain can be crippling for months.
Only four countries — Ethiopia, Ghana, Mali and Sudan — still have the worms. About 3,000 of them were found as of last month, down from three million across the globe when Mr. Carter began his effort to wipe them out.
The WHO page on dracunculiasis eradication doesn't give many more details. A lot more information can be found in a review by Cairncross and colleagues (2002), the complete text of which is free on PubMed. I went looking out of curiosity about animal infections -- it seems too easy to get rid of this thing in humans, considering the presence of dracunculiasis in other mammals. North America in particular has a big problem with the parasite in carnivores -- raccoons get it a lot.
But the human parasite is part of a larger family of nematode parasites that infect other species and often have different crustacean hosts. There seems to be occasional transfer into humans of various other forms, and transfer of the human parasite into domesticated animals, but access to filtered water is sufficient to break the human cycle. In several countries where human dracunculiasis was eliminated many decades ago, it hasn't returned, so the simple effort to provide clean water seems sufficient to eradicate it.
Cairncross S, Muller R, Zagaria N. 2002. Dracunculiasis (Guinea Worm Disease) and the Eradication Initiative. Clin Microbiol Rev 15:223-246. doi:10.1128/CMR.15.2.223-246.2002