Every year, during the dry season, villagers in Sub-Saharan Africa fall victim to the Dracunculiasis parasite lurking in the muddy watering holes they visit each day. Guinea worm larvae are eaten by tiny water fleas called Cyclops, which are then ingested by humans as they drink the contaminated water.

Guinea worm larvae move to their victims' abdominal tissues, where they grow and mate. The male worms die after mating, but the females make their way to other parts of the body, usually the legs and feet.

About twelve months after initial infection, the flat white worm, now as long as two or three feet, begins to emerge through the skin, emitting toxins that cause burning blisters. As victims try to ease their pain by submerging their skin in water, the blisters rupture -- releasing hundreds of thousands of new larvae, contaminating the water source, and beginning the terrible cycle all over again.

Victims must endure the worm's painful emergence for as long as three months, and are usually incapacitated not only by the pain but by fever, fatigue, and nausea as well. To speed things along, people carefully wind the worm around a stick as it emerges, being careful not to pull too hard. If the worm breaks, it will retract into the body, causing severe inflammation. Over half of all worm-emergence sites become infected, and the worst cases can result in permanent crippling or even death from tetanus.

Find out how to prevent Guinea worm disease >>