a stringy worm that is 60 to 90 centimetres erupts through the skin on the leg or foot. Its excruciatingly painful journey out of the body can take weeks. To relieve the burning sensation, many people wade into the nearest body of water — often the same pond from which they drink. When an adult worm enters the water, it releases larvae, and the cycle starts anew.
Because scientists thought the parasite required on humans for transmission, it was believed that Guinea worm could be eradicated. In 1986, The World Health Assembly endorsed a plan targeting the parasite for extinction through the use of larvicides, and by educating people to use water filters and stay out of bodies of water if infected. The plan largely worked:
An international partnership — led by the Carter Center in Atlanta, Georgia — has reduced the number of new infections from 3.5 million per year in 1986 to just 28 in 2018.
Unfortunately, new cases indicate that animals might be able to transmit guinea worms after all. Cases in Chad may be related to dogs in a way scientists don't yet understand. Other pockets of contamination have also been discovered:
The discovery in 2013 of infected baboons — a first — in a small forested area in southern Ethiopia also has researchers scratching their heads. So far, scientists have found 15 baboons with Guinea-worm disease. The eradication programme has hired hunters to find and map water sources deep in the forest, which are then treated with larvicide. Individual baboons have been collared and are being tracked to find out where they eat, drink and sleep. A key question, Cleaveland says, is whether baboons, like dogs, can sustain transmission independently.
Accordingly, the WHO has move target date for eradicating the disease from 2020 to 2030. NPR notes that the target date has already been delayed several times for the original target of 1991, and that scientists remain optimistic:
Jessica Fairley, a tropical disease epidemiologist at Emory University, told NPR in an email that the date change wasn't a big surprise.
"In the realm of disease control, targets are generally getting more realistic (and thus pushed later and later), and so it is with guinea worm," she said. "I am confident that some of the challenges, like conflict areas and the canine reservoir, will be overcome in the next decade. It is better to be realistic and deliberate."
(Photo via WHO.)