Dracunculiasis (Guinea worm disease): causes, symptoms and eradication

Dracunculiasis is caused by a large parasitic nematode worm, Dracunculus medinensis. WHO explains in a question-and-answer item that guinea worm is, in fact, a real worm: a large nematode that is ingested through drinking contaminated water and that eventually causes a debilitating and painful infection beginning with a blister, normally on the leg.

The disease is concentrated among rural, underserved and remote communities that rely on open, stagnant water such as ponds for drinking water. WHO describes it as a crippling disease on the verge of eradication.

This page relies on WHO, as no UK-specific patient guidance on dracunculiasis was found among UK health sources. It is included here as general information on a disease that is rarely encountered in the UK.

WHO describes a life cycle that depends on drinking water. A person swallows water containing tiny crustaceans (copepods, commonly called water fleas) that carry infective larvae. The water fleas are dissolved by stomach acid, and the larvae are released, pass through the intestinal wall and migrate through the body.

After around 100 days male and female worms mate, and the male dies in the tissues. The female, measuring 60 to 100 cm, settles under the skin and, 10 to 14 months after infection, emerges at an exit site, typically the lower leg or foot.

When a blister forms and the worm emerges, people often immerse the affected area in water to relieve burning pain. WHO says this lets the worm expel thousands of larvae into the water, where they are eaten by new water fleas, and the cycle repeats.

WHO says there are usually no symptoms for about a year after infection. Around the time of emergence the person may have a fever, swelling, itching, severe pain and a burning sensation, and WHO's regional office says about 90% of worms emerge from the legs and feet.

• A painful blister that ulcerates as the worm emerges.

• Painful swelling (oedema), blistering and intense generalised itching around the time of emergence.

• Secondary bacterial infection of the ulcer, which WHO says invariably develops and worsens inflammation and pain, causing temporary disability.

• Permanent disability, which WHO says can occur when worms emerge near joints.

• Serious allergic reactions if the worm ruptures in the tissues.

WHO's regional office says there is no drug to treat guinea-worm disease and no vaccine to prevent re-infection, and that removing the worm can take several days to several weeks. When the worm comes out it can be very painful, slow and disabling, and open wounds often become infected with bacteria.

Care in affected communities focuses on case containment: isolating the person from water sources, caring for the wound and preventing further spread. WHO lists case containment, wound care and the tethering of infected domestic dogs and cats as part of its eradication strategy.

Medical advice is important for anyone who has been in an area where guinea worm occurs and develops a painful blister or an emerging worm. Wound care and treatment of secondary infection are managed by a clinician, and anyone in the UK with such a history should contact the GP or NHS 111.

WHO says transmission can be stopped because humans alone are responsible for maintaining it. The measures it lists include surveillance to detect all cases within 24 hours of worm emergence, safe drinking water from protected wells and boreholes, filtering water through finely meshed cloth or a 0.15 mm nylon mesh filter, treating unsafe water sources with temephos to kill water fleas, and health education.

The numbers show how far the campaign has come. WHO says approximately 3.5 million cases occurred in 20 countries in the mid-1980s, falling to fewer than 10,000 in 2007, 542 in 2012 and 13 provisional human cases in 2024, all in villages in Chad and South Sudan.

A remaining challenge is infection in animals, mainly dogs and cats. WHO reports 661 infected animals in 2024 (provisional), mostly in Angola, Cameroon, Chad and Mali, which means surveillance and containment of animals are now as important as human case finding.

Transmission depends on drinking contaminated, stagnant water in a small number of remote areas, which WHO identifies as Angola, Chad, Ethiopia, Mali and South Sudan. A traveller or someone who has lived in such an area is the main route by which a person in the UK could come across it, and the disease has a long delay before symptoms, so a diagnosis may come long after leaving.

Travellers to rural parts of affected countries are advised generally to drink only safe, filtered or treated water. For tailored travel advice, the NHS and the TravelHealthPro service provide country guidance.

In the UK, suspected parasitic infections acquired abroad are assessed by a GP and, where needed, an infectious diseases or tropical medicine specialist, with wound care and treatment of secondary infection provided through the NHS.

Travel clinics, including private ones, can advise on safe water practices before travel. The most reliable current information on case numbers and eradication progress comes from WHO.