Guinea worm, formally called Dracunculus medinensis, is a type of nematode that’s long been a thorn in our sides, likely having been documented as far back as Biblical times. Its complicated life cycle starts out in freshwater, when larvae are eaten by tiny crustaceans known as copepods. When we unknowingly ingest these copepods through drinking water (or eating undercooked fish that ate the copepods), the worms burst free and reach our intestines, where they fully mature and mate. The males then die and the pregnant females migrate to a spot underneath our skin, usually along our legs. About a year post-infection, the females cause a blister to form. And when this blister breaks, the worm slowly begins to emerge from our skin, triggering a painful burning sensation that drives the infected to cool their wound off in the nearest water source. Once this happens, the worm releases thousands of larvae into the water, starting the whole thing again.

© Image: CDC/Dr. Mae MelvinDracunculus medinensis larvae

This chain of events isn’t just a gruesome act of puppetry; it’s often very harmful to the host. The worm can take days to weeks to safely remove, usually by slowly wrapping a stick around it. This painful process leaves kids unable to go to school and adults unable to work. And if things go wrong, such as the worm breaking open during removal, it can lead to permanent disability caused by secondary infections or inflammation. The worm can also get stuck before it even reaches the skin, causing other problems like arthritis.

For millennia, Guinea worm was an unavoidable fact of life in much of the world. Even in the modern era, it remained common in poorer countries with limited access to sanitation. But in the 1980s, a dedicated eradication program was started by the Carter Center, a non-profit organization founded by former U.S. president Jimmy Carter. The Carter Center, along with partners including community leaders and the World Health Organization, have steadily driven the Guinea worm back. Before the program began, as many as 3.5 million people contracted Guinea worm disease annually in over 20 countries across Africa and Asia. But in 2021, according to the Center Center’s latest tally, there were just 14 cases reported in four countries (Chad, Ethiopia, Mali, and South Sudan), down from the 27 cases reported in 2020.

© Photo: Louise Gubb/Corbis (Getty Images)A patient with a guinea worm emerging from the leg, at the Savelugu Case Containment Center.

“Rosalynn and I are encouraged by the continued commitment and persistence of our partners and the citizens in the villages to eradicate Guinea worm,” Jimmy Carter said in a statement. “Because of their persistence, this dreadful disease will be eradicated. Today we are closer than ever, and I am excited at the prospect of seeing the job finished.”

If and when it does happen, Guinea worm disease would be only the second disease in humans to be eradicated, following smallpox. And it’d be the first disease to be killed off without the use of vaccination. Instead, the program has largely relied on the cooperation of affected villages to adopt measures like using filtered water containers and reporting possible sightings of Guinea worms before they can contaminate drinking water, along with some larvicide treatment of stagnant water sources.

Unfortunately, the last few years have provided added hurdles toward eradicating the worm. While humans are the primary host for the Guinea worm, it’s now known that it can also infect other animals. These are usually dogs, but cats and baboons have been hosts as well. So eradication won’t be possible until there are no cases in humans or animals. There does seem to be some good news there, though. In 2021, there were fewer reported dog cases of Guinea worm in Chad (790), where the problem has been the worst, than there were in 2020.

It will take years of seeing no cases in humans or animals to truly confirm the eradication of Guinea worm disease. And even after the Guinea worm is vanquished, there may yet be related species out there still capable of infecting humans. But in our pandemic times, it’s nice to see at least one disease on the run.