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How to eradicate a disease

A generation ago, guinea-worm disease was bringing misery to millions; now it is down to two cases a week

Tom Whipple | November/December 2014

It is just possible that the most important guinea worm in history has already found its home. Its host does not know it yet, but inside his or her body this long white parasite is reproducing and growing. Through the next few months, as millions of her ancestors have done before, she will feed and strengthen. Then slowly, excruciatingly, she will break through the skin of her host’s foot and release her larvae.

Humans and guinea worms have coexisted like this for millennia. The worm is described in ancient Egyptian texts, and its calcified remains have been found in mummies. The Rod of Asclepius, the snake wrapped around a staff that is the symbol of medicine, is believed to be a depiction of the only mechanism for speeding its exit: twirling it around a stick. Yet of all the hundreds of millions of worms that have burrowed their way out of African feet, this one is special: it could well be the last.

In 1986 there were 3.5m cases of guinea worm. Last year, there were 148. This year, up to late September, just 80 had been recorded: 68 in South Sudan, two in Ethiopia, nine in Chad and one in Mali. For only the second time ever, we could be about to eradicate a disease in humans.

Throughout human history, guinea-worm disease has been a fact of life across sub-Saharan Africa and parts of Asia. It received its common name from European traders who found it endemic in west Africa—and were liable to return with it themselves. Its Latin name, Dracunculus medinensis, which it gained in the 19th century, shows that it was equally prevalent on the opposite side of Africa and beyond: the name means “fiery little serpent of Medina”.

Whether on the Arabian Peninsula or the Gold Coast, in 2000AD or 2000BC, the guinea worm has always been a curse. Whole villages would go down with it, year after year, the farmers unable to farm, the children unable to go to school. This is a disease without a cure, and with a particularly pernicious life cycle. From microscopic beginnings, living inside water fleas, the guinea worm enters humans through infected water supplies. For a year it grows inside its host. We normally think of a disease as something caused by an unseen agent, like the virus that lies behind the alarming spread of Ebola. But a disease—a dis-ease—can be anything that causes pain or dysfunction. When this worm emerges, it is a metre long and by this stage in its life cycle it may well feel closer to a wildlife attack than a disease. Bursting through the flesh, usually the foot, it creates an intensely painful boil—so painful that the most natural thing to do is put your foot in water to cool it. At which point it releases its larvae to begin the journey again. 

It is crippling, both literally and economically. The US Centres for Disease Control and Prevention (CDC) describes it as “a disease of poverty and also a cause of poverty” because of the disability it brings. “Parents with active guinea-worm disease might not be able to care for their children,” the CDC says. “The worm often comes out of the skin during planting and harvesting season. Therefore, people might also be prevented from working in their fields and tending their animals.” So people stay at subsistence level or below, without the education or resources that would rid them of the disease. The worm feeds on this vicious cycle as much as it feeds on its human host. But there is a way to break it.

In 1980 Dr Donald Hopkins, then at the CDC, recognised that guinea worm had one weakness: its reliance on humans. It cannot reproduce outside an animal, and no other animal reliably carries it. So getting rid of this disease does not require expensive vaccinations or sophisticated laboratories. Stop humans putting their infected feet in water, get those living in infected areas to filter water—often with just a cloth—and you stop the worm.

Hopkins’s realisation came at a time when disease control had just claimed its greatest victory. Thanks to a massive effort, involving teams working across countries and continents, smallpox had been eradicated. It is still one of the greatest feats of public-health policy. “It was a tremendously exciting time,” says Hopkins, who headed the CDC’s Sierra Leone smallpox operation 1967-69. To have been partly responsible for eradicating one disease and largely responsible for the near-eradication of another is extraordinary.

Hopkins was born in the deep South in 1941, when it was still segregated. One of ten children of a carpenter, he knew he wanted to be a doctor from a young age. It was during a trip abroad that he decided on his specialism. “I was playing the tourist in Egypt in 1961 when I saw all these children and adults get flies around their eyes and have problems with their eyes—I now know it was trachoma. I went to medical school determined I would work on tropical disease.”

In Sierra Leone, where he was sent on the global smallpox programme, he found his cause. Rushing to infected areas before the disease spread, he and his team pioneered rapid-response tactics, encircling outbreaks with vaccination programmes and isolating patients, often within hours of the first reports. “I can’t tell you how motivating it was for us,” he says, “to see how we were saving people’s lives.”

Smallpox is a terrible disease. As with guinea worm, the earliest evidence of it probably comes from the Egyptians: its tell-tale pustules were found on the mummified skin of Pharaoh Ramses V. Unlike guinea worm, it is a killer; spread by a virus, it is credited with half a billion deaths in the 20th century. Yet this scourge of humanity was eradicated in just a few years.

Flushed with success, Dr Hopkins turned his energies and the same techniques to the next eradicable disease. Guinea worm was an obvious target: because of its unusual life cycle it merely required an effective education programme and water filtration, coupled with speedy isolation of infected people. All of which makes Hopkins’s job sound far too easy.

For a disease to be eradicable there are certain useful preconditions. “You want it to be found only in humans,” says Professor John Edmunds of the London School of Hygiene and Tropical Medicine (LSHTM). “If there is an animal reservoir you have to deal with that too,” he says, from his central London office, above the cellars where thousands of mosquitos are bred for research, some species fed directly from the blood of laboratory assistants.

Ideally, you would also like to know where the disease is at all times. “When people are infectious, what fraction is clinically apparent? How many go on to develop symptoms at all?” With guinea worm, infectiousness coincides with the worm emerging, so it is obvious. There is another vital criterion by which guinea worm does not do so well: it is just not quite serious enough. “It sounds brutal, but from an epidemiological perspective you want people to be really sick,” says Edmunds. “You can’t have them pottering around going to work.” This goes some way to explaining why smallpox was the first disease to fall: it occurred only in humans, there was a vaccine, infectious people were symptomatic and—crucially—they were so sick that they were bedridden. 

But even these factors are merely helpful prerequisites. The real challenge of eradicating a disease is seldom purely medical. When embarking on an eradication programme—a battle that is currently being waged against polio, measles, mumps, rubella and the tropical bacterial infection yaws—the teams involved tend to know in theory exactly what needs to be done. In practice, although some scientific problems will emerge along the way, the barriers they face are more likely to be political, cultural and logistical.

It is no coincidence that the countries where guinea worm remains are some of the most unstable and inaccessible. For all the team’s scientific knowledge, Donald Hopkins says, “We are dealing with human beings. They are in traditional, suspicious communities.” Reaching them often requires not just medical, but political intervention. And the most dramatic example of that has been guinea worm. 

By the mid-1990s, when Dr Hopkins says he had naively hoped guinea worm would be long gone, Sudan had probably the least conducive politics, culture and logistics in the world for health workers. In the south, where a huge reservoir of the disease remained, a civil war was entering its 12th year. No aid agencies were reaching patients. With brutal bush warfare between the Muslim government and Christian separatists, complicated by disputes over oil and an insurgency by the Lord’s Resistance Army on the Ugandan border, worm-education programmes were hardly a priority.

By now, though, Hopkins had the backing of Jimmy Carter’s foundation, the Carter Centre, which had hired him to lead its guinea-worm programme. In 1995 Carter flew to Nairobi to meet the head of the south Sudanese forces, John Garang. “He said he was getting ready to go to Khartoum,” Hopkins says. “Before he went, he asked Garang whether, if he could persuade the northern government to agree to a ceasefire in order to get health workers in, the southern forces would also accept. Garang said yes. The speculation is that he only did so because he thought it unlikely the north would agree; the dry season was approaching and that was the best time for fighting.”

This was enough for Carter, who left for Khartoum. On the way, his plane stopped in Nairobi to pick up a CNN correspondent, Gary Striker. “In Khartoum, Carter was able to let President Bashir know that CNN was there and that one way or another there was going to be a news story,” Hopkins says. “He could either hold up Bashir and his government as obstructive and warmongers, or as having agreed to this wonderful thing. Of course they agreed to that wonderful thing.”

An uneasy, but unprecedented, six months of peace followed, in which health workers scrabbled to reach all of the country before time ran out. It became known in Sudan as the Guinea Worm Ceasefire.

It is easy to see why, despite independence, South Sudan remains one of the last redoubts of the disease—and not only because almost as soon as the war with the north ended a new conflict in the south began. In 2010, just before the referendum on independence, I travelled with members of the health ministry to a town to the east of the capital, Juba, to inspect and re-stock one of the clinics they were due to inherit. On paper theirs was a shiny new department, ready to offer whatever help it could. On paper, though—more specifically on our maps—there were also roads.

For two days, our Land Cruiser shuddered along dirt tracks and ditches. By night we used the indicators—finding a vehicle that worked was enough of an achievement, let alone one with working headlights—to illuminate the edge of the poorly demarcated road, beyond which lay minefields. By day we continued often at less than walking pace, rolling in and out of man-deep potholes like a fishing boat in a storm. 

When we arrived at our destination, a member of our party was beaten over the head by a man wielding a plank of wood. There was no particular reason for the attack. We had travelled just 60km from Juba—in a country 1,000km wide. In the face of this, it is a brave health worker who orders people in pain to keep their feet out of stagnant ponds.

That presupposes there is even a health worker to do the ordering. In countries coming out of civil wars the stock of qualified clinicians is often rather stretched. To give an idea of the scale of the problem, at independence, South Sudan had 19 registered midwives covering a country of 10m. The woman I travelled with was very senior in the newly formed health ministry, and tasked with rectifying this. Her first target was superstition. Arriving in one village, I was told to avoid a nearby hill because bad spirits lived there and anyone who walked on it died. I nodded solemnly, trying to be sensitive to the local culture. My companion scolded the people for being silly and pledged to climb the hill that evening. However shrewd, she was also the product of a country where there had been little in the way of a schooling system in 30 years. So although her courage and dedication were astonishing, her scientific knowledge was in many areas pre-Enlightenment. That night we camped in the bush and ours was the only light for 30km around. As foot-long stick insects swayed out of the gloom and hulking great beetles buzzed clumsily towards the bare bulb, it felt as if the whole of the jungle was coming to greet us. There was a clear sky and I stepped out to look at the stars, explaining we did not see them like this in Britain. “Why is that?” my companion asked. “Is it because they are farther away?” 

Much like an insurgency against an occupying army, a campaign against any disease relies on the co-operation of the population. The way Donald Hopkins achieves his results differs from country to country, but the principle is the same: encourage the locals to do the job for themselves. 

“The disease is the world’s problem, but at a local level it’s their problem too,” he says. “They don’t want to have these diseases, and we need to show them that they don’t need to. Ultimately it’s not about someone having to fly out to detect every case; what we need is for local reaction to be immediate. If someone has guinea worm, they need to make themselves known and be isolated.” The Carter Centre’s goal is to work with national health ministries to train local volunteers to continue their work—they have trained 30,000 in South Sudan alone. In an ideal world, Hopkins and his colleagues would just co-ordinate the initial approach and then sit in their headquarters in Atlanta, collating the results.

If that sounds like the sort of consensual aid programme that would make a marvellous case study in a charity brochure, it is worth pointing out that Hopkins does not much care how this co-operation is achieved. It could be because people are enthused by the eradication programme; it could also be because the government of South Sudan is offering $100 to anyone who turns themself in—or their neighbour.

It is working. This year only a fraction of South Sudan’s 68 cases were not caught in the first 24 hours—and it looks set to go the way of Ivory Coast, Egypt and Nigeria, all declared guinea worm free. Hopkins’s real worry is the swathe of the Sahara which after the Arab spring has become ungovernable. Mercifully, so far, the eradication programme’s problems with Islamism have been restricted to instability. If only the same were true of a far more high-profile eradication programme: polio. 

Viewed on a graph, polio looks as if it should be vying with guinea worm as the next disease to be eradicated. Recorded cases have dropped from hundreds of thousands, in 125 countries, in 1990, to fewer than 500 last year—and in just three countries. But nobody is talking about imminent eradication. Those three countries are Afghanistan, Nigeria and Pakistan. And polio persists in Pakistan largely because of something no one could possibly have foreseen when the programme began: the death of Osama bin Laden. 

On May 2nd 2011, two stealth helicopters entered Pakistani airspace, en route to Abbottabad. It was the beginning of Operation Neptune Spear; within hours Osama bin Laden would be dead. Barack Obama was confident enough to risk such a raid thanks to the assurances of the CIA, which was pretty sure that bin Laden was there. A team had collected DNA samples from family members inside the compound—by pretending to be offering vaccinations.

When the details of this covert programme emerged, all health workers in Pakistan became, by association, suspected spies. Taliban commanders in two districts vowed to use violence to enforce a boycott of polio vaccinations until drone strikes stopped. They have been true to their word. Polio has been the major beneficiary. “Right now in polio eradication the absolutely dominant issue is this political one,” says Dr Heidi Larson, an anthropologist who works with the LSHTM. “We simply aren’t going to have eradication confirmed with this fountain of the disease coming out of northern Pakistan.”

International health programmes are often met with suspicion. In the West middle-class parents are most likely to oppose vaccination, on the false ground that it causes autisma campaign of misinformation that has stalled the 40-year measles-eradication programme. Larson works for the LSHTM’s Vaccine Confidence Project, applying an anthropologist’s skills to monitor and combat public concerns. She says such reactions are not surprising. “There’s something about the nature of these programmes. They are population-wide, government-driven and often involve a needle. For anyone with issues with distrust, or control, or governments, that breeds suspicion.”

For all the cross-cultural opposition to eradication programmes, in the Islamic world there has been a deeply worrying new development. “There have been 50 or 60 people killed, explicitly targeted because of their involvement in the polio programme,” Larson says. “That’s a new phenomenon, we have never had violence before.”

Experience has shown that, as a country approaches elimination, getting rid of the final few cases can be wearing. It is, more than anything, about patience and tenacity. You keep going, and going, until the tally stands at zero. Zero is a number that, in disease terms, is arguably further from 80 (the number of guinea-worm cases so far this year) than 80 is from 3.5m. Zero infections can never become 80, but for 80 to become 3.5m just takes time and bad luck.

In polio, having come within a comparable distance of zero, Professor Edmunds now thinks there is a chance they might not even succeed, that this final stage may be too much. “It is apparent that as we get close to the polio endgame,” he says, “in some ways it gets further and further away.”

Donald Hopkins is far from complacent that the end is nigh for the guinea worm. He still goes into the field several times a year and monitors progress from his home office in Chicago, where a statue of the Hindu smallpox goddess (no longer so busy) sits alongside a glass jar containing a preserved guinea worm. At the age of 73, he is not planning his retirement; there have already been too many setbacks. Some have been simply bad luck. “In 2006 a young Koranic student walked from south Mali to an area around Kidal, in the north,” he says, his low soft voice occasionally slipping into the deep-South vowels of his childhood. “There had not been guinea worm there for a generation, but a year later all these people began going down with the disease. It was one of three or four dramatic examples of a single person contaminating the water supply and giving rise to 60, 70, 80 cases. That is what keeps me up at night.”

In Chad, there is a worry that the campaign’s entire modus operandi—that health workers need only rid humans of the diseasecould be subverted. The water fleas that carry the guinea-worm larvae can exist in fish, but cannot reproduce in them. They can reproduce in warm-blooded mammals, but the only ones into which they reliably find their way are humans—largely, it turns out, because we drink from vessels. “The way dogs drink water, lapping it up with their tongues, causes the water fleas to flee,” Hopkins says. On the Chari river in Chad, however, at the end of the dry season, there is a mass harvesting of fish, which are left out to dry. Their entrails are discarded, to be eaten by dogs. 

“If dogs eat uncooked fish entrails,” Hopkins goes on, “then the fish can serve to concentrate a lot of these infected larvae. And that way the infection can be passed sporadically to humans.” Spotting this is detective work in itself—it takes a year for an infected dog to show symptoms, which would ordinarily be missed in any case, and another year for any humans it infects to show up in the Carter Centre’s data. 

This is another difficulty of eradicating guinea worm: time spent fighting a disease should not be measured in human years, but in the disease’s lifespan. With smallpox, the incubation period was two weeks, and every fortnight Hopkins could collect data and assess progress. With guinea worm it takes a year to know if you have been successful—or to learn if a missed case has infected the pond that supplies a town’s water. In these terms, Hopkins’s decades fighting guinea worm are the same as just over a year spent tackling smallpox. 

“I started this in October 1980,” he says of the job that has occupied most of his working life. “I don’t think I would have been courageous enough if I had thought we would still be going now.” For all his caution, he allows himself a moment of hope. “This could be the year. We can’t be sure yet, but we can pray. Then, 12 months after the last case, we can exhale.”

And when that day comes, Donald Hopkins, the man at the centre of two of the greatest enterprises in the history of human health, will be able to retire.  


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