D. medinensis: Dragon Worms in Your Body

I have to agree with this one. Some extinctions might be OK. The extinction of Dracunculus medinensis, the “dragon worm,” also known as the guinea worm, is one example.

D. medinensis is almost extinct now.

Unlike smallpox, which the UN World Health Organization wiped out in 1977, the Guinea worm (D. medinensis) has been driven almost to extinction by the efforts of former President Carter and his Carter Center. The Carter Center is a non-governmental organization.

The disease is caused by the female which, at up to 800 mm (31 in) in length, is among the longest nematodes infecting humans. In contrast, the longest recorded male Guinea worm is only 40 mm (1.6 in).


The Dracunculus medinensis life cycle starts when somebody drinks water contaminated with tiny, almost invisible crustaceans known as copepods–Anna Rothschild called them “water fleas”–that have been infected with larval guinea worms. Once swallowed by a human, the copepod is digested, but the larval worms inside it live on and infect the human.

D. medinensis larvae
D. medinensis larvae

After the D. medinensis larvae are released, they migrate through the intestinal wall into the abdominal cavity, where they mature and mate. No wonder people get sick, with playful 31-inch worms crawling around inside their bellies.

When the appropriate time comes, the pregnant female worm eats her way through subcutaneous tissues, usually until she reaches an ankle, where she releases just a few larvae at first. These produce a blister on the skin that itches so badly that people usually put their feet in water to relieve the itching, whereupon she releases the rest of them into  the water to infect the resident copepods and start the cycle all over again.

The female guinea worm slowly starts to come out a little way from the host’s skin after the blister ruptures, and patients keep their feet under water to encourage her to emerge enough so they can very gently get hold of her and begin winding her around a piece of gauze, if available. More commonly, they use a small stick. They wind her very gently, so as not to break her. If they break part of her body off, the rest will stay inside and die and rot and cause serious infection. Complete extraction usually takes several days.

Winding the worm around the stick this way is thought by some to be the source of the Rod of Asclepius, the symbol of medicine.

Ex-President Jimmy Carter and his Carter Center, working with the US Centers for Disease Control and Prevention and the UN World Health Organization, began a program in the 1980s to eradicate D. medinensis. In 1986, 20 countries were affected by the worms.

The program included educating people in the affected areas to know that the disease was caused by drinking contaminated water, isolating and supporting sufferers, distributing filters for drinking water, and educating people about using them.

As of this year, D. medinensis has been reported to be almost extinct.

This is surely a very good thing, and I admire President Carter and his Carter Center tremendously for their work.

A caution

Nevertheless, this is tampering with nature. I wonder whether or not anybody knows what the effects will be? Have there been environmental studies? Do we know what water creatures may prey on the larvae that we may starve into extinction by robbing them of their food? We know the copepods do, and they may not be the only thing. Besides, what eats the copepods that may also starve if we starve the copepods? All I’m saying is that it’s complicated. Everything in nature is, and somebody probably ought to look at it. Maybe somebody did and I’m just not finding it.

On the other hand, it seems like very minor tampering compared to what we do all the time. I’m not suggesting we stop preventing infections. I’m just suggesting that next time we start to deliberately drive an organism extinct, maybe we ought to do a study while we’re getting started. Just in case.


Note: August 21, 2015 – I just heard President Carter say (on a video) that when he started his eradication program, there were 3.6 million cases of guinea worm and now we are down to 11 cases. He has recently had a cancer removed from his liver and he still has four melanomas in his brain, but he hopes the last guinea worm will die before he does. The video is here.



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