On the brink of becoming extinct

Guinea worm is a parasite of Asia and Africa, which lives in lakes and stagnant waters, carried by microscopic water fleas. It infects mainly humans but also some wild and domestic animals.

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When people drink contaminated water, the fleas are digested the and the worms released. These burrow through the stomach wall and migrate towards the person’s back to mate. The male worms then die, while the females grow to a metre long.

Guinea worms make a painful blister on the leg or foot when they burrow out. People often put their affected foot into cool water to soothe the pain from the wound. When they do the end of the worm comes out and releases a burst of tiny larvae, ready to enter water fleas and start the life-cycle again.

You cannot vaccinate against Guinea worm. The main way to treat the person (or dog, as in the photo) is to carefully pull out the worm a few centimetres each day until it is gone. Spurred on by the eradication of smallpox, a huge international effort was started in 1980 to try to eliminate this parasite, through improved sanitation and healthcare.

In 1976 there were 10 million cases of Guinea worm. By 2024, there were only 15 known patients worldwide. Guinea worm could become the second ever human infection, after smallpox,  and the first ever parasite to be eradicated globally.