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After a 30-year campaign, only 126 people in the world were known to be infected with the waterborne guinea worm in 2014, down from 3.5 million in 1986. If this trend continues, guinea worm disease could become only the second disease in history to be eradicated, after smallpox. It would be the first parasitic disease to be wiped out and also the first to be defeated without the use of vaccines or medicine.
Former Pres. Jimmy Carter announced the provisional year-end count at the American Museum of Natural History in New York City on Monday. His nonprofit organization, The Carter Center, has led the campaign to eradicate the pest since 1986. Back then the guinea worm could be found in a band of 21 countries that stretched across central Africa and into Asia.
“The first time I saw a guinea worm was in a small village in Ghana. The village had about 400 people in all and two thirds of them had a guinea worm,” said Carter during a press event at the museum. Today, Ghana is free of guinea worms and the Carter Center counts only 70 cases in South Sudan, 40 in Mali, 13 in Chad and three in Ethiopia. “We hope that in the next few years we’ll have zero guinea worm cases anywhere in the world,” Carter said.
Unlike most maladies, guinea worm disease is a prime candidate for eradication because it is only transmitted to humans when they drink water containing the larvae of the nematode (roundworm) Dracunculus medinensis from infested sources. “If you can stop that, you can stop infection,” said Donald Hopkins, vice president for health programs at The Carter Center, during a panel organized by the museum.
The center’s strategy has been simple: educate at-risk populations about the worm and pass out filters that residents can use to rid their drinking water of the parasite. The filters range from cloth nets that cover 50-gallon drums to slim pipe filters about the size of a cigar that nomads can carry around their necks to sip water.
If ingested, the larva grows for a year within the host’s stomach or intestines. When an adult female worm is ready to lay its eggs, it must exit the host to find a source of water. “It’s like a salmon run—the female worm is trying to eject eggs into water before it dies,” says Craig Withers, program support director at the center. The meter-long worm then makes its way to the surface of the skin and breaks out in a slow, painful egress typically lasting more than 30 days. Many times, a victim will inadvertently help the worm infect others by splashing water over the wound to soothe the pain and providing it with a chance to deposit its eggs and start the cycle anew.
Withers estimates about half of the patients they tracked in the campaign’s earliest days harbored more than one worm—and in rare cases, a single person could have 50 to 80. It is only just before the worm starts to penetrate the skin from within that victims may suffer symtoms including fever, soreness and swelling and realize they are infected. Many victims wind the worm around a stick as it emerges, although this method typically speeds its removal by only a few days.
The World Health Organization declares a disease officially eradicated once three years have lapsed from the last known case. To encourage patients to come forward for treatment and monitoring, the center offers a $100 reward for reporting a case of guinea worm, which Carter said equates to several months of pay for some villagers. Hopkins estimates that eradication efforts have so far cost $350 million to $400 million. “There’s a lot of work to be done for that last 126 cases still,” Hopkins said. The remaining few infections are often in the most rural or challenging spots—ongoing conflict between Islamic militants and counterterrorism forces in Mali, for example, has made it difficult for public health advocates to safely work in the area.
Carter’s visit was scheduled in anticipation of today’s opening of “Countdown to Zero,” a special exhibit at the museum focused on the possibilities for elimination and eradication of diseases including guinea worm, river blindness, malaria and Ebola—the latter of which holds great challenges because it is transmitted to humans by so many types of animals including fruit bats, chimpanzees, porcupines and antelopes.