Dracunculus medinensis

Dracunculus medinensis is a parasitic worm that causes a condition known as dracunculiasis, or Guinea worm disease. This worm is the largest of the tissue parasite affecting humans. The adult female, which carries about 3 million embryos, can measure 600 to 800 mm in length and 2 mm in diameter. The males are much smaller (40 mm by 1 mm) and their lifespan is short.

Life Cycle

The life cycle of Dracunculus medinensis begins when a person drinks water contaminated with copepods (small crustaceans) that are infected with the larvae of the worm. The copepods die in the stomach, releasing the larvae, which penetrate the host's stomach or intestinal wall and enter the abdominal cavity and retroperitoneal space.

Over the next year, the female worm grows to a full size. When it is ready to release its larvae, it creates a painful blister in the skin, usually on the lower limbs. When the blister bursts, the female worm emerges and releases thousands of larvae. This is often accompanied by intense pain and a burning sensation.

Transmission

Transmission of Dracunculus medinensis occurs when larvae are released into water from the emerging female worm. The larvae are ingested by copepods and develop into infective larvae within the copepods. These copepods are then ingested by humans, and the cycle begins again.

Prevention and Control

Prevention and control of dracunculiasis involves providing safe drinking water; filtering water through a cloth if it is not known to be safe; and preventing people with emerging worms from entering water sources.

Treatment

There is no drug to treat dracunculiasis or vaccine to prevent infection. Once the worm begins to emerge, it can only be pulled out a few centimeters each day and wound around a small stick. This process, which is painful, can take weeks.

See Also

• Parasitic diseases
• Waterborne diseases
• Tropical diseases

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