What is guinea worm? Is it a real worm?

Ask the expert
25 May 2016

Q: What is guinea worm? Is it a real worm?

A: Guinea worm is, in fact, a real worm. It is a large nematode, Dracunculus medinensis, which is ingested through drinking contaminated water. The condition is known as dracunculiasis or guinea-worm disease. The worm eventually causes a debilitating and painful infection that begins with a blister, normally on the leg. Around the time of its eruption, the person may experience itching, fever, swelling, severe pain and a burning sensation.

Infected people often try to relieve the pain by immersing the infected part in water. If it is immersed in open water sources such as ponds and shallow step wells the worm emerges and releases thousands of larvae. The larva is ingested by a water flea (cyclop), where it develops and becomes infective in two weeks. When a person drinks the water, the cyclop is killed by the acidity of the stomach and the larva is freed and penetrates the gut wall. After about one year, a blister forms and the mature worm, one metre long, emerges thus repeating the life-cycle.

At the beginning of the 20th century, guinea-worm disease was widespread in many countries in Africa and Asia. Out of 20 countries that were endemic worldwide in the early 1980s, only Chad, Ethiopia, Mali and South Sudan – all from the African continent – are currently endemic. In 2015, only 22 cases were reported to WHO.