The Carter Center and the Government of South Sudan have announced the world's newest nation has been free of Guinea worm for 15 months. This is usually considered the time required to establish local elimination of this terrible parasite, although World Health Organization confirmation will take longer. Although at least two countries still have Guinea worm, South Sudan posed the biggest challenges. If transmission has been ended there, global success is very close.
Guinea worm (Dracunculiasis medinensis) infection is seldom fatal, but it is truly awful. For most parasites and diseases, the pain and suffering they inflict are a by-product of their infection. For Guinea worms, it is an essential part of their reproductive cycle. The worms' eggs are transmitted through water, and to get there worms cause a horrendous burning pain in the legs of the people they infect. Victims stand in water to ease the pain, allowing the worm to release eggs.
When people drink from egg-containing water bodies, the eggs hatch inside them, beginning the cycle again.
In the 1980s it was estimated there were 3.5 million annual cases, mostly in northern and central Africa.
However, Dracunculiasis has a weakness: it almost never infects animals other than humans. If we can stop transmission among ourselves, we can end this pest forever.
The worm has a lifecycle of about a year. If not a single case occurs over a time longer than that, then there are no living worms, or intact eggs, to restart a cycle of infection.
This realization inspired the World Health Organization to start working towards ending Dracunculiasis forever, and more recently the Carter Center, established by former President Jimmy Carter, has taken the lead. Transmission is prevented both by spreading awareness, telling victims to avoid still water bodies no matter how painful the burning gets, and distributing filtered straws that prevent the ingestion of eggs when drinking from suspect water supplies. General improvements in plumbing and sanitation have also helped.
Two years ago the Center announced what they hoped would be the final push, and it looks like they're on track.
The campaign has achieved enormous success. Most of the nations once plagued by the disease have now been declared free, and last year only 30 cases were reported. However, South Sudan, a country wracked by civil war and almost entirely lacking in infrastructure, looked like the one place the worm might survive. In 1995 Carter himself brokered a six-month ceasefire specifically to treat the worm. Now, with no cases reported since November 2016, it seems success has been achieved there.
Last year's cases were evenly divided between Ethiopia and Chad, where efforts will redouble to achieve one of the few species extinctions we actually want.