When in 1988 former US President Jimmy Carter toured Denchira and Elevanyo, two villages near Accra, Ghana, he noticed a young woman who appeared to be cradling a baby. Carter approached her for a chat, but was stopped in his tracks by a disquieting sight.
“It was not a baby. It was her right breast, which was about a foot long, and it had a guinea worm coming out of its nipple,” Carter later recalled. During his tour of Ghana that year, Carter saw hundreds of people affected by the guinea worm, an infection known as dracunculiasis — a disease caused by the nematode parasite Dracunculus medinensis. It’s a condition that can cause fever, severe pain, and even permanent damage to affected limbs.
In the late 1980s the country reported as many as 180,000 cases of guinea worm disease per year. Across the globe, that number was a staggering 3.5 million. However, by 2020, the world was down to just 27 cases, all of them in Africa.
This enormous reduction in prevalence is a direct effect of campaigns by endemic countries assisted by organizations such as the Centers for Disease Control and Prevention, the World Health Organization (WHO), and the Carter Center (a not-for-profit founded in 1982 by Jimmy Carter), which have strived since the 1980s to eradicate dracunculiasis, hoping to make it the second human disease purposefully wiped off the face of Earth. (Smallpox was the first.)
“That’s an extraordinary public health achievement,” said David Molyneux, parasitologist at the Liverpool School of Tropical Medicine, in an interview with Medscape Medical News. Yet the eradication goal, currently set for 2030, seems unlikely to be met. What’s more, some experts argue that chasing eradication may be altogether a misguided idea.
Humanity has known dracunculiasis for millennia. Well-preserved specimens of Dracunculus medinensis were discovered in Egyptian mummies, while some researchers claim that the Old Testament’s “fiery serpents” that descended upon the Israelites near the Red Sea were in fact guinea worms, as the parasite was endemic to the area in the past. Even the serpent coiled around the staff of Asclepius, the god of medicine, might have been a guinea worm, according to some historians.
This would make sense considering how the disease is treated. When an adult worm emerges through the skin, a painful and crippling occurrence, it is wound up around a stick or a piece of gauze, a little at a time, to slowly draw it out of the skin. As the worm can be over 3 feet long, this procedure may take weeks. What you end up with is a stick with a long, snake-like animal coiled around it. Asclepius’s staff.
The first step in the infection is when a person drinks water contaminated with copepods, or water fleas, which contain the larvae of Dracunculus medinensis. Next, the larvae are freed in the stomach and start migrating through the body, looking to mate. The fertilized female worm is the one that causes the debilitating symptoms.
About a year after the initial infection, the pregnant female worm looks for exit points from the body, usually through legs or feet, ready to release new larvae. If the unlucky sufferer steps into a pond or a river, the immature larvae escape into the water, where they are eaten by water fleas. “People are fetching water to drink, and they walk into the water thinking they can get cleaner water not along the edge,” said Adam Weiss, director of the Carter Center’s Guinea Worm Eradication Program, in an interview with Medscape. The vicious cycle begins anew.
Dracunculiasis may not be a killer disease, but it is painful and disabling. A study on school attendance in Nigeria showed that in 1995, when guinea worm infection prevalence among schoolchildren was as high as 27.7%, it was responsible for almost all school absences. As the result of the infection, children were seen wandering and sitting around the village helplessly. If it was the parents who got infected, children stayed out of school to help around the home. The dracunculiasis’ impact on work and earning capacity is so profound, in fact, that in Mali the infliction is known as “the disease of the empty granary.”
When in 1986 the Carter Center took the reins of the global dracunculiasis eradication campaign, India was the only country with a national program to get rid of the disease. Yet, once other nations joined the struggle, the results rapidly became visible. By 1993, the American Journal of Tropical Medicine and Hygiene published a paper titled, “Dracunculiasis Eradication: Beginning of the End.” The cases plummeted from 3.5 million in 1986 to 221,000 in 1993 and 32,000 in 2003, then to a mere 22 cases in 2015. What worked was a combination of surveillance, education campaigns, safe water provision, and treating potentially contaminated water with a chemical called Abate, a potent larvicide.
Today, many endemic countries, from Chad and Ethiopia to Mali and South Sudan, follow similar procedures. First and foremost is the supply of clean drinking water. However, Weiss says, this is not a “silver bullet, given how people live.” Those who are semi-nomadic or otherwise take care of livestock often fetch water outside of the village, from ponds or rivers. This is why dracunculiasis eradication programs include handing out portable water filters, which can be worn around the neck.
But if you don’t know why you should filter water, in all likelihood you won’t do it — cloth filters distributed for home water purification sometimes ended up as decorations or sewn into wedding dresses. That’s why education is key, too. Poster campaigns, comic books, radio broadcasts, instructions by volunteers, even t-shirts with health messages slowly but surely did change behaviors.
Cash rewards for reporting cases of dracunculiasis, which can be as high as $100, also work well to boost surveillance systems. Once a case is identified, patients may be moved to a containment center, both to treat the wound and to prevent patients from spreading the disease. Local water sources, meanwhile, may be sprayed with Abate.
1995 was the first year set as a target date for the eradication of dracunculiasis. Yet the goal wasn’t met — even though the total number of cases did decline by 97%. Next goals followed: 2009, 2020, and now, finally, 2030. For well over a decade now the world has been down to a trickle of cases per year, but the numbers don’t seem to want to budge lower. Weiss calls it a “limbo period” — we are almost there, but not quite. The final push, it seems, may be the one that’s the most difficult, especially now that we have two further complications: increasing conflicts in some endemic areas and zoonotic transmission.
According to WHO, in places like the Democratic Republic of the Congo, Mali, South Sudan, and Sudan, insecurity “hinders eradication efforts.” Not only does this insecurity make it difficult for health workers to reach endemic areas, but wars and violence also displace people, pushing those infected with guinea worm to walk far distances in search of safety, and spreading the disease during their travels. Case containment and contact tracing become challenging. A recent study by Molyneux and his colleagues showed that in the 3 years since 2018, conflicts in the endemic areas have increased dramatically.
And then there are the animals. Up until 2012, eradication of guinea worm seemed fairly simple, at least from a biological perspective: stop infected humans from contaminating drinking water and the parasites won’t be able to continue their life cycle. But in 2012, news came from Chad that a significant number of local dogs were found infected with the Dracunculus medinensis parasite, the very same one that attacks humans. In 2020, close to 1600 dogs were reported to be infected with guinea worm, most of them in Chad. This left scientists scratching their heads: dracunculiasis was supposed to be a purely human infliction. How were the dogs getting infected? Did the parasite jump to a new species because we were so efficient at eliminating it from humans?
“I have first seen a guinea worm transmission in dogs back in 2003,” said Teshome Gebre in an interview with Medscape. Gebre is regional director for Africa at International Trachoma Initiative and has spent more than 40 years fighting to eradicate various diseases, including smallpox and guinea worm. Yet in 2003, Gebre’s report was dismissed: it couldn’t have been the same species of the parasite, the reasoning went, since Dracunculus medinensis was exclusive to humans.
“I think it’s fair to say that there were infections in dogs before 2012. I find it difficult to believe, logically, that it just came out of nowhere,” Weiss said. A 2018 genetic study showed that a novel host switch is an unlikely scenario — the parasites must have been infecting dogs in the past, we just haven’t been looking. By 2012, Chad had a very efficient guinea worm surveillance system, with generous cash rewards for human cases, and people started reporting the dogs, too. Soon money was also offered for news on infected animals, and the cases exploded. This was then followed by accounts of afflicted cats and baboons.
To announce the eradication of dracunculiasis in 2030, the requirement will be no more transmission of the parasite for at least 4 years prior anywhere in the world — not only zero human cases, but also no infections in dogs, cats, or baboons. Seven countries remain to be certified as guinea worm–free, all of them in Africa. “We have to be a 100% sure that there is no transmission of the parasite in a country,” said Molyneux, who participated in country certification teams — a rigorous process to validate country reports. He believes that the presence of animal hosts as well as growing insecurities in the region make such certification extremely challenging over the next few years.
“Eradication as it is defined does not seem feasible by 2030 as things stand, [considering] political and resource constraints, the unknowns of the ecology of dogs, and the possible impact of climate change and geopolitical instability and with countries having other health priorities, including COVID,” Molyneux said. For Weiss, dogs are not that much of a problem — since they can be tethered to prevent the spread of the disease. But you can’t tether baboons. “That does raise that more existential threat–related question of: is this scientifically possible?” he said. Weiss and his colleagues at the US Centers for Disease Control and Prevention are currently working on a serologic assay to test whether baboons are important for human transmission.
For some experts, such as Gebre, the current struggles to bring cases down to zero put a spotlight on a bigger question: is it worthwhile to strive for eradication at all? That last stretch of the eradication campaign can appear a bit like a game of whack-a-mole. “There were times when we’ve achieved zero cases [in Ethiopia]. Zero. And then, it just reemerges,” Gebre says. Programs aimed at certification are costly, running up to $1.6 million per year in Nigeria. The funds, Gebre points out, often come from the same donor pockets that pay for the fight against malaria, HIV, polio, as well as other neglected tropical diseases. He believes it would be more cost- and time-efficient to switch the effort from total eradication to elimination as a public healthcare problem, a point he argued in a 2021 paper in International Health.
Of course, there is the risk that the cases would go up again once we ease up on the pressure to eradicate dracunculiasis. “Do we want to be fighting guinea worm in perpetuity?” Weiss asks. However, Gebre believes the cases are unlikely to explode anymore.
“The situation in the countries is not the way it was 30 years ago,” Gebre said, pointing out increased awareness, higher education levels, and better community-based health facilities. “You can cap it around a trickle number of cases a year — 10, 15, 20 maybe,” he says.
The keys, Gebre and Molyneux both say, include the provision of safe drinking water and strengthening the healthcare systems of endemic countries in general, so they can deal with whatever cases may come up. “Water, sanitation, surveillance, good public education — and the maintenance of the guinea worm–specific reward system to maintain awareness, as well as continuing research” are all needed, Molyneux says.
Getting out of the dracunculiasis limbo period won’t be easy. We certainly need more data on animal transmission to better understand what challenges we might be facing. The experts agree that what’s important is to follow the science and stay flexible. “We have made an incredible progress, our investment has been worthwhile,” Molyneux says. But, he adds, “you have to adapt to the changing realities.”
Gebre received no financial support for the review article and has no other conflicts of interest to declare. Molyneux is a member of the WHO International Commission for the Certification of Dracunculus Eradication (ICCDE), an independent body appointed by the director general of WHO. He acts as a rapporteur for the ICCDE as a paid consultant. He declared he does not receive any financial support for other related activities. Weiss receives support from the nonprofit Carter Center.
Marta Zaraska is a science journalist based in France and the author of “Growing Young: How Friendship, Optimism and Kindness Can Help You Live to 100.”
Content Source: https://www.medscape.com/viewarticle/964437?src=rss