Scientists Say: Guinea worm | Science News for Students

Scientists Say: Guinea worm

This parasite invades people’s bodies through their drinking water, and leaves through their skin
May 20, 2019 — 6:30 am EST
a photo of a Guinea worm wound sticking out of a person's leg, and wound around a matchstick

This Guinea worm is wound around a matchstick as it is pulled out from a person’s leg. The worm has to be pulled out very slowly, and the process is very painful. 


Guinea worm (noun, “GIH-knee worm”)

The Guinea worm (Dracunculus medinensis — “drah-CUN-cue-lus MED-in-EN- is) is a parasite — an animal that lives off a host, without giving anything in return. If this worm gets inside a person’s body, it causes a painful infection called Guinea worm disease, or Dracunculiasis (drah-CUN-due-LIE-ah-sis). In fact, Dracunculiasis means “infection with little dragons” in Latin, a sign of just how much it can hurt.

Guinea worms begin their lives as larvae in the bellies of tiny water fleas. When a person drinks water and swallows the water fleas, the fleas get digested in the person’s stomach. But the Guinea worm larvae survive. They take up residence inside the unfortunate person’s body.

Over the next 100 days, those larvae grow into long, thin, white worms. Then the males and females find each other and mate. The male dies, but the female, loaded with eggs, begins moving through the person’s muscles. This can be intensely painful. Usually, the female heads toward the person’s foot. Then, she pokes through the skin of the foot. This hurts so much that the infected person often sticks their foot in water to relieve the pain. When the worm senses water, she releases her eggs. Water fleas swallow those eggs, and the cycle begins again. The whole process takes between 10 and 14 months.

After releasing her eggs, the female worm remains dangling out of the person’s foot. Often, the worm needs to be pulled out by slowly winding it around a thin stick a few centimeters (inches) at a time. Because Guinea worms can be up to one meter (3.3 feet) long, this painful process can take weeks.

Most cases of Guinea worm disease are found in a handful of countries in Africa. Luckily, people can prevent Guinea worm disease by filtering their water. This removes the water fleas that are full of Guinea worm larvae.

Scientists and doctors have worked very hard to get rid of Guinea worm disease. In the 1980s, there were 3.5 million cases of the painful infection each year. But by 2018, there were only 28 worldwide. Now, most infections are in dogs and cats, but doctors hope to get rid of the worm entirely in a few more years.  

In a sentence

Former president Jimmy Carter founded an organization to get rid of the Guinea worm.

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Power Words

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dracunculiasis     Also known as guinea worm disease, it is caused by Dracunculus medinensis , a species of nematode, or roundworm. The worms can enter someone’s body from drinking water tainted with tiny fleas that carry the parasite. The guinea worm then lives and mates inside the human body. After about a year, its victim will get a burning feeling in a leg or foot as the female worm, which had migrated there, forms a blister in the skin. If the patient puts that leg or foot into water to relieve the burning feeling, the female worm may releases her eggs into the water, starting the life cycle over again.

eradicate  To deliberately eliminate or wipe out, such as a population of vermin (rats or cockroaches, for instance) inhabiting a particular site.

egg     The unfertilized reproductive cell made by females.

Guinea worm     ( Dracunculus medinensis ) This species of microscopic nematode, or roundworm, causes dracunculiasis, also known as guinea worm disease.

host      (in biology and medicine) The organism (or environment) in which some other thing resides. Humans may be a temporary host for food-poisoning germs or other infective agents.

infection     A disease that can spread from one organism to another. It’s usually caused by some type of germ.

larva     (plural: larvae) An immature life stage of an insect, which often has a distinctly different form as an adult. (Sometimes used to describe such a stage in the development of fish, frogs and other animals.)

muscle     A type of tissue used to produce movement by contracting its cells, known as muscle fibers. Muscle is rich in protein, which is why predatory species seek prey containing lots of this tissue.

parasite     An organism that gets benefits from another species, called a host, but doesn’t provide that host any benefits. Classic examples of parasites include ticks, fleas and tapeworms.