The guinea worm grows to a metre long in its victim's body before punching its way out – but hopefully not for much longer
(Image: CDC/The Carter Center)
Education is an important part of eradication
IT STARTS with a painful blister – a very painful blister. It feels, people say, like being stabbed with a red-hot needle. When the blister bursts, the head of a worm pops out, thin, white and very much alive.
The rest of the worm, about a metre long, remains inside your body. It can take up to two months to pull it out, inch by agonising inch, during which time it may be impossible to walk. In extreme cases, you may host up to sixty of them, anywhere on your body. The worms can cause paralysis or lethal bacterial infections, and even if you survive mostly unscathed, next year it can happen all over again.
The guinea worm (Dracunculus, or little dragon) is probably the closest living equivalent to the monsters in the Alien movies – except we’re beating this enemy. Guinea worm was once widespread in Africa, the Middle East and many parts of Asia. In 1986, there were nearly 4 million cases a year in 20 countries across south Asia and Africa. Last year, there were just 3142 in four countries in Africa. The worm could be extinct by 2012, making dracunculiasis the second human disease ever to be eradicated – the first being smallpox.
Guinea worms start out as minuscule larvae living inside water fleas of the genus Cyclops. These millimetre-long crustaceans live in stagnant water, and people can swallow them when they drink from ponds, ditches or shallow wells. Stomach acids dissolve the water fleas but can leave the larvae untouched. The free larvae then burrow out of the intestine and cross to the chest or abdominal wall, where the male and female worms mature and mate. The males eventually die, but the growing females tunnel imperceptibly to, and then under, the skin.
Even as the females grow up to a metre long, their hosts remain unaware of their presence. The worms prevent pain by secreting opiates and dodge the immune system by coating themselves with human proteins. It may be just as well people don’t know they are infected as nothing can help at this stage.
A year after being swallowed, the guinea worms change tack. They secrete a searing acid, create a blister and emerge from the skin – most often on the leg or foot, but it can be anywhere. The acid alerts the immune system, but this only makes matters worse. As the tissue around the worm swells, it adds to the pain and wedges the worm in place.
“The worms secrete a searing acid. People seek out water to relieve the burning pain, and the female worms then expel hundreds of thousands of larvae”
The horrendous pain is no accident. It causes people to seek out cool water to relieve the burning sensation, and when the females sense the water, they contract violently, expelling hundreds of thousands of larvae. If there are any water fleas in the water, they will be infected and the cycle begins again.
The fact that the worms emerge after a year is no accident either. Water flea populations peak when there is lots of stagnant water, which happens in the dry season in wet areas, such as Ghana, and in the wet season in dry areas, such as Sudan. Either way, a yearly cycle maximises the larvae’s chances of finding water fleas.
Death and paralysis
Guinea worms can cause all sorts of problems for their victims. Some worms lose their way and attack the heart or spinal cord, leading to death or paralysis. The emergence site can become infected by bacteria, leading to abscesses and tetanus. If a worm passes near a joint, it can cause stiffness. Joints can even seize up altogether, causing limbs to wither from disuse.
Worst of all, though, the guinea worm season tends to occur at times when people need to plant or harvest their crops. “A family that cannot cultivate because of guinea worm has no harvest,” says Makoy Samuel Yibi, head of guinea worm eradication for the south Sudan government. “Every village has stories of people who died after bad guinea worm outbreaks.”
There is no drug that kills guinea worm, no vaccine and no protective immunity after infection. There are, however, two simple ways to prevent infection: stopping people with emerging worms from contaminating water sources, and not swallowing water fleas, either by drinking water from clean wells or by filtering infested water. Because water fleas are relatively large, even simple cloth filters can eliminate them.
Clean drinking water alone helped eradicate guinea worm from many countries over the past century. Then, in 1986, the World Health Organization declared guinea worm eradication an official goal and The Carter Center, set up by former US president Jimmy Carter, took up the challenge.
(Image: CDC/The Carter Center)
Clean water is essential in the fight against guinea worms
Guinea worm disease is an obvious target for eradication and the only one besides polio now backed by the WHO. Only humans are infected by guinea worm, and the larvae die within months if no one swallows the water fleas carrying them. So stop human infections and the worm disappears.
The eradication programme had succeeded in India and Pakistan by 2000, but donations were flagging. Then the Bill and Melinda Gates Foundation stepped in, and progress resumed. The results are spectacular (see map). For instance, no cases were reported last year in Nigeria, which in 1986 was the worst-infected country with 700,000 cases.
It helps when governments or charities install tube wells that provide clean water, but this is expensive. Instead, The Carter Center’s main strategy is to provide cheap ways to cope with infested water. These include filters for household water stores, drinking straws with filters that people can carry with them, the pesticide Abate to kill water fleas in ponds, and “containment huts” for people to go to when a worm appears, to keep them away from water supplies.
(Image: CDC/The Carter Center)
A young girl has a adult worm removed. This painful process often takes weeks
There are now tens of thousands of containment centres across Africa, staffed by local volunteers trained to remove worms using the time-honoured method of winding them gently around a stick (see “The staff of Asclepius”). If a worm breaks and releases its larvae into the flesh, the pain is intense. The centres feed residents and provide bandages, antiseptics, painkillers and cold compresses.
“The heroes of guinea worm eradication are the 10,000 village health volunteers,” says Sandy Cairncross of the London School of Hygiene and Tropical Medicine. “The key is to organise institutions in rural communities, and give them continuing modest support.”
Cairncross pioneered the use of computer mapping systems to track progress – and to show governments and donors that their efforts are paying off. “Thorough surveillance is key, because it mobilises national leadership,” says D. A. Henderson at the University of Pittsburgh, Pennsylvania, who led the fight against smallpox. “The guinea worm campaign has also been brilliant in getting local people to understand and cooperate in the effort.”
Part of the problem is persuading people that guinea worms come from water, says Makoy. “They believe it comes from God or eating certain animals or witchcraft. They do not see the point of filtering water,” he says. But once some families try it, the effects are so dramatic that the rest soon follow.
“People were sceptical that we could eradicate the worm without drugs or vaccines,” says Don Hopkins, a parasitologist at The Carter Center who heads the eradication drive. “Changing people’s behaviour is notoriously hard.”
The World Bank has estimated that the cost of guinea worm eradication in Africa, which Hopkins puts at $250 million in total, will be recouped within four years in increased food production alone. That’s not counting other benefits like children staying at school.
As cases become rarer, each one becomes harder and more expensive to find and contain, but it is crucial to keep going. “As long as there is one worm left, it will spread and be everywhere again,” says Makoy.
Hopkins cites cases where the worms were eliminated from a country, only for someone from outside to infect a pond. Such outbreaks often feature infections with multiple worms, as people have let their guard down and stopped filtering water.
(Image: CDC/The Carter Center)
A simple pipe filter can make a huge difference
With just 452 cases in total in Ghana, Mali and Ethiopia last year, eradication now depends on southern Sudan, which had 2690, or 86 per cent of all cases. “We can stop transmission this year,” says Makoy, but it will take another year or two after that to be sure the campaign has succeeded.
The main reason Sudan still has so many cases is the civil war that has raged almost continually since independence in 1956. It could yet derail things. “It’s a race between war and the worms,” says Hopkins, “but I’m an optimist.” He does have reason: in 1995, the warring sides agreed a truce to allow guinea worm teams to work.
There has been a peace agreement between north and south Sudan since 2005, but that could be threatened in the lead-up to elections in April and to a referendum next year, in which the oil-rich south is expected to reject continued union with the north. Meanwhile, conflict is escalating between southern peoples such as the Nuer and the Dinka. Last year, guinea worm staff had to stay indoors or be evacuated due to a lack of security on 35 occasions, and two local offices were destroyed. “We have the right team and materials to succeed,” says Makoy. “All we need is peace.”
The staff of Asclepius
Guinea worms have long afflicted humanity. They are thought to have been the “fiery serpents” described as attacking the Israelites in the biblical story of the exodus, and worm tracks have been found in 3000-year-old Egyptian mummies. The only way to get them out, then as now, is to slowly wind them around a stick. While there is no definitive proof, this is widely thought to be the origin of the symbol of the Greek and Roman god of healing, Asclepius – a serpent wrapped around a staff. The staff of Asclepius is on the crest of the World Health Organization and other medical bodies, but it has sometimes been confused with the caduceus, a winged staff entwined by two snakes. The caduceus was a symbol of Mercury, god of commerce and thieves, and later became associated with alchemy.
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