Guinea Worm and the Medical Practice Symbol

I have mentioned that I am reading "Parasite Rex" by Carl Zimmer. The book is just as I expected. Wonderfully written, scary stories and anecdotes about parasites. I especially like his discussion of how the term "parasite" arose.

The word literally means "beside food," and the Greeks originally had something different in mind when they used it, referring to officials who served at temple feasts. At some point the word slipped its etymological harness and came to mean a hanger-on, someone who could get the occasional meal from a nobelman by pleasing him with good conversation....

But that is neither here nor there. Let's discuss guinea worm infection and its possible association with the symbol of medical practice....the Caduceus. The study of parasitology is filled with stories concerning history and especially biblical references.


Guinea worm, or Dracunculus medinensis, is a roundworm found in India, West and Central Africa and parts of the Middle East. The worms are found in the subcutaneous tissues of humans and the female worm can be over 30 inches in length. You become infected with guinea worm by drinking water that is contaminated with small, freshwater crustaceans that are themselves infected with guinea worm larvae. (Cyclops).

When the crustacean is consumed in contaminated drinking water, the guinea worm larvae in the Cyclops is released and makes its way through the intestinal wall, crosses the abdominal mesentaries, penetrates the abdominal muscles and make their way to the subcutaneous tissues. Fertilized females release their live larvae by penetrating the skin about a year after infection. Infected individuals often wind the body of the emerging female around a small stick so as to collect the entire adult worm rather than breaking it off in the body.

Obviously, the way to prevent this infection is to provide a clean, uncontaminated, source of drinking water. Also, the live larvae of the adult female need to be released into fresh water in order to find a Cyclops to infect as an intermediate host. So please do not go swimming or wading in fresh water if you find yourself with a female guinea worm emerging from your body.

Now, what you ask does this have to do with the symbol of medical practice? Well, you need to open your bible to Numbers 21:6-9:

And the Lord sent fiery serpents among the people, and they bit the people; and much people of Israel died.

Therefore the people came to Moses and said, We have sinned, for we have spoken against the Lord, and against thee; pray unto the Lord, that he take away the serpents from us. And Moses prayed for the people.

And the Lord said unto Moses, Make thee a fiery serpent, and set it upon a pole; and it shall come to pass, that every one that is bitten, when he looketh upon it, shall live.

And Moses made a serpent of brass, and put it upon a pole; and it came to pass, that if a serpent had bitten any man, when he beheld the serpent of brass, he lived.

Here we have talk of a serpent on a pole. Guinea worm, by the way, causes intense pain (like fire) when it emerges from a blister on an arm or leg.


Where Zimmer gets it wrong is stating that "But it may be that that person's invention was remembered in the symbol of medicine, known as the caduceus: two serpents wound around a staff." [Chapt. 1, pg. 2]

Actually, the symbol of medicine is not the winged staff with two serpents. That would be the "Caduceus of Mercury" or the "Karykeion of Hermes". This is actually a symbol of commerce.


The actual symbol of medicine is the Staff of Asclepius. A staff, or stick, with a single snake wrapped around it. You can find all you want to know about the difference between a caduceus and the staff of Asclepius here at the website of New Zealand physician Dr. Blayney.

Why is the caduceus a symbol of medicine in the USA? Blame it on the US Army Medical Corps.