Parasite transmitted through drinking water expected to become only the second human disease, after smallpox, to be defeated

Guinea worm disease is reaching the end of its days. The parasitic infection, which has sickened millions, mostly in Asia and Africa, is on the verge of being done in not by sophisticated medicine but by aggressive public health efforts in some of the poorest and most remote parts of the world.

To eliminate the parasite, which is found in drinking water, hundreds of thousands of volunteers have handed out straws with cloth filters, treated water sources with larvicide, have taught villagers how to avoid infection and have scoured the countryside for new cases.

As a result, the ailment, also known as dracunculiasis, is poised to become the second human disease (the first was smallpox) to be eradicated – and the first to be eliminated without the aid of a vaccine.

Guinea worm expert Donald Hopkins, who has been involved in the campaign for nearly three decades, calls the eradication effort "uniquely grassroots".

When former President Jimmy Carter, in conjunction with the World Health Organisation and the US Centres for Disease Control and Prevention, spearheaded the effort to eradicate the parasite in 1986, there were 3.5m new cases of Guinea worm disease a year across 21 countries. So far this year there have been 391 new cases worldwide – down from 807 this time in 2011, according to the CDC. All but four of these cases were found in South Sudan.

Guinea worm has been around for centuries. Its remains have been found in Egyptian mummies, and the plight of its victims is recounted in biblical texts.

The disease is transmitted through drinking water containing Guinea worm larvae. Once ingested, these larvae can grow for more than a year, reaching up to a metre in length.

The worm exits its host through an excruciating, burning blister, often in the leg or foot. When the victim bathes the blister in water to relieve the pain, the worm releases a new batch of eggs, restarting the cycle.

The only way to get rid of the worm is to wrap it around a stick and pull it out of the skin, inch by inch, over the course of hours to months. The practice is so ancient that many suspect it is the basis of the iconic staff and intertwined serpent of Asclepius, the Greek god of healing.

A Guinea worm infection is not usually fatal, but the parasite can cause intense pain in its path of travel from the gut to the limbs. When blisters appear on the legs or feet, the pain can be so debilitating that victims can't walk. Nausea and fever are frequent, and secondary infections can result from lesions caused as worms burrow through the skin.

Hopkins, director of health programmes at the Carter Centre in Atlanta, said the Guinea worm eradication campaign is a rare success in fighting infectious disease. He attributes the progress to the strength of local volunteers' education programmes.

"In an immunisation programme, as soon as you vaccinate, you protect. It's 'touch and leave,'" he said. "For Guinea worm, the only thing you can do is persuade people – many who are very isolated and tradition-bound – to change their behaviour."

Hopkins praised South Sudan's health ministry for "tightening the noose" on the last cases during its recovery from a long civil war. In July 2011, the country, which had just won its independence from Sudan, reported 794 cases of the illness. This July, the total was less than half that.

By tracking these last infections and stopping the worms from releasing their eggs into water sources, leaders of the campaign expect that the species will eventually become extinct.

But as the number of cases dwindles, eradication becomes more challenging. "This is the last stage, the hardest time of all, because there are so many competing health priorities in countries battling Guinea worm," said Sharon Roy, a CDC medical epidemiologist. "When you're getting down to just a few cases, it takes a great deal of political will to keep the momentum to get to the very last worm."

Hopkins said that the eradication effort – which he expects will be complete in a year or two – will have cost about $375m, less than the campaign to fight smallpox, which was declared eradicated in 1980.

"There will be a particular irony when Guinea worm is eradicated," said Roy. "Maybe it'll be time for the medical profession to get a new symbol."

This story appeared in the Guardian Weekly, which incorporates material from the Washington Post