Merck Manual

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(Guinea Worm Disease)


Chelsea Marie

, PhD, University of Virginia;

William A. Petri, Jr

, MD, PhD, University of Virginia School of Medicine

Reviewed/Revised Oct 2022
Topic Resources

Dracunculiasis is infection caused by the roundworm Dracunculus medinensis, also known as the Guinea worm. It causes a painful, inflamed skin sore and debilitating arthritis.

  • People become infected by drinking water containing tiny crustaceans infected with the roundworm.

  • After mating, female worms move to the skin and create a blister, usually on the lower legs or feet, with swelling, redness, and burning pain in the area around it, and the joints near the blister may be damaged.

  • Doctors diagnose the infection when they see the worm come out through the blister.

  • Drinking only water that has been filtered, boiled, or chlorinated helps prevent the infection.

  • The worm is removed by slowly rolling it on a stick or surgically.

In the mid-1980s, 3.5 million people had dracunculiasis. The disease was widespread in many parts of tropical Africa,Yemen, India, and Pakistan. But by 2018, because of international efforts to stop dracunculiasis, only 28 cases were reported. In 2021, only 14 cases were reported in humans. Transmission remains within a narrow belt of only a few African countries—Chad, Mali, and Ethiopia, and possibly Sudan and South Sudan. The guinea worm is close to being eliminated.

Transmission of dracunculiasis

People become infected by drinking water containing tiny infected crustaceans. The immature Dracunculus worms (larvae) live inside the crustaceans. After the crustaceans are ingested, they die and release the larvae, which penetrate the wall of the intestine and enter the abdominal cavity. Inside the abdomen, larvae mature into adult worms in about 1 year, and the adult worms mate. After mating, female worms leave the abdomen and move through tissues under the skin, usually to the lower legs or feet. There, they create a blister. The blister causes severe, burning discomfort and eventually breaks open. When people attempt to relieve the burning by soaking their leg in water, the pregnant worm releases larvae into the water. Once the larvae are in the water, they find and infect another crustacean. If the pregnant worms do not reach the skin, they die and disintegrate or harden (calcify) under the skin.

Symptoms of Dracunculiasis

Dracunculiasis symptoms start when the worm begins to break through the skin. A blister forms over the worm's location. The area around the blister itches, burns, and is inflamed—swollen, red, and painful. Materials released by the worm may cause an allergic reaction, which can result in difficulty breathing, vomiting, an itchy rash, and disabling pain. Soon the blister opens, and the worm can be seen. Later the worm leaves the body, and symptoms subside.

Usually, the blister heals after the adult worm leaves the body. However, in about 50% of people, bacterial infections develop around the opening for the worm.

Sometimes joints and tendons near the blister are damaged, causing joint pain and other symptoms of arthritis.

Diagnosis of Dracunculiasis

  • Appearance of a worm at the blister

Diagnosis of dracunculiasis is obvious when the adult worm appears at the blister.

X-rays may be taken to locate calcified worms.

Prevention of Dracunculiasis

The following can help prevent dracunculiasis:

  • Filtering drinking water through a piece of fine-mesh cheesecloth

  • Boiling water

  • Drinking only chlorinated water

Infected people are instructed not to enter sources of drinking water, such as open wells or reservoirs, so that these sources do not become contaminated.

Treatment of Dracunculiasis

  • Removal of the adult worm

Usually, the adult worm (which may be up to 47 inches [120 centimeters] long) is slowly removed over days to weeks by rolling it on a stick. When the head starts to come out, the person grasps it and wraps the end of the worm around a small stick. Gradually, as the worm loosens, the stick is turned, wrapping more of the worm around the stick. Eventually, the worm is pulled free and discarded. When health care workers are available, they can remove the worm through a small incision made after a local anesthetic is used.

No drugs can kill the worms. But if a bacterial infection develops around the worm's opening, people may need antibiotics.

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