Former President Jimmy Carter was joyful, candid and the farthest thing from maudlin disussing his melanoma diagnosis and plans for treatment.

He talked about work still to be done and, in particular, an enemy he hopes to vanquish before his own time is up. "I would like the last Guinea worm to die before I do," Carter said Thursday.

The Carter Center has spent the past 30 years trying to eradicate guinea worm, a parasitic disease that is both painful and grotesque. "It is about the most awful thing you can imagine in terms of a non-fatal ailment," says David Baron, who interviewed Jimmy Carter about guinea worm in 2010 in South Sudan while on assignment for PRI's The World.

Guinea worm starts with a burning blister, usually on your arm or leg. "Soon what emerges is a worm, that eventually, when it comes out, could be three feet long. It looks like a long strand of angel hair pasta and it's excruciatingly painful as it comes out."

"When the worm comes out, you've got that burning blister. Your instinct is to want to immerse the skin in water," says Baron. But that's how the problem spreads. "When you do that, the worm puts out thousands and thousands of larvae that infect the drinking water. If anyone drinks the water, it gets into their system and, a year later, they develop a blister and out comes another worm."

A guinea worm emerges from the leg of a South Sudanese girl in Juba in this picture taken in 2007. After living inside its host for up to 14 months, the long Guinea worm, a spaghetti-like waterborne parasite up to three feet long, releases chemicals to soften the flesh, making a blistering, pus-filled wound. It then pushes out so it can deposit around a million larvae. Credit: Skye Wheeler/Reuters

It turns out that eradicating Guinea worm comes down to something very simple: filtering water. For several decades now, the Carter Center has been distributing millions of water filters to people in affected areas.

"This is an eradication program without any vaccine, without any drug, without any cure. It's purely preventative." Baron says the fact that Guinea worm can be eradicated is what partly motivated Carter in the first place. "There are very few diseases one can even imagine eradicating. But with Guinea worm, it was possible if one just put the effort and the money into it. And he decided to do it," Baron says.

Carter got involved in Guinea worm eradication after an encounter in Ghana in the early 1980s. "He told me about being in Ghana and seeing a young woman who was cradling her breast. He thought she was nursing a child and went over to the woman. He wanted to meet the child. When he went to her, he realized she was in excruciating pain. There was a worm emerging from her breast." Eventually it turned out she had 11 worms emerging from her body.

Besides prevention, the Carter Center is also focusing on early treatment. "As soon as the worm emerges, that person can be treated." It's a one-year cycle. "You get infected, it grows in your body and then it comes out. And once it comes out, then it's left your body, unless you get re-infected," Baron says.

The Carter Center's efforts to eliminate Guinea worm have been impressive. When their program started in the mid-1980s, there was an estimated 3.5 million cases in over 20 countries around the world. In 2014, there were just 126 cases for the entire year affecting just four countries: Chad, Ethiopia, Mali and South Sudan.

At that rate, Jimmy Carter may just get his final wish after all.

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