"So, naturalists observe, a flea has smaller fleas that on him prey; and these have smaller still to bite ’em; and so proceed ad infinitum."
- Jonathan Swift

March 24, 2010

March 24 - Dracunculus medinensis

Dracunculus medinensis is a creature in the phylum Nematoda that is behind the dreaded Guinea Worm Disease. The disease is actually caused by the significantly bigger female nematode. Their life starts off with the larvae living inside of small crustaceans (copepods). When a human drinks unfiltered water, they are incidentally ingesting these small crustaceans and this is the beginning of Guinea Worm Disease. Shortly after being ingested, the small crustaceans die and release the nematode larva, which then penetrates the host stomach, intestinal wall, and enters the abdominal cavity. After reaching maturity, which takes about a year, the males die and the females survive and start to migrate through the subcutaneous tissue layer towards the surface of the skin. At this point, the female can emerge from any part of the body including the head, torso, upper body, buttocks, and genitalia, although the bottom of the foot is where they emerge from most of the time. On the bottom of the foot, the female causes painful blisters which cause the host to look for a form of relief by placing their foot into water. When the female parasite comes into contact with water, she will release her larvae which are then injested by small crustaceans and after two weeks the larvae become infectious and the cycle is ready to begin again. As a side note, the only way to remove the parasite is to pull it out through the hole it has made in the surface of the skin. OUCH!!!




Contributed by Tracey Brooks, Bucknell University.


  1. Gross factor: 9 out of 10. Well done!

  2. Once the worm emerges from the wound, it can only be pulled out a few centimeters each day and wrapped around a small stick. Sometimes the worm can be pulled out completely within a few days, but this process usually takes weeks or months (average 3 months).

    3... Months...

  3. There are woodcuts going back to the Medieval period showing the worms being extracted, as the above poster says, by wrapping around a stick slooowly. Some things never change!

  4. I'll never feel the same about drinking crustacean-rich water again. I did so enjoy the crunch.

    Good work Tracey!


  5. Some believe that the guinea worm wrapped around a stick (as one must do to extract it from the skin) is the true inspiration behind the Rod of Asclepius [popular medical symbol]. No proven origin has yet been found, but something to think about...