"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

April 11, 2010

April 11 - Taenia solium

Having a pork roast for Sunday dinner? Then, you probably don't want to think about today's parasite, Taenia solium, the pork tapeworm. Humans can acquire these worms by eating undercooked pork and if so, then the tapeworms mature into adults and take up residence in the intestine, where they can grow up to 7 meters long and will release eggs in shed proglottids. However, sometimes humans are infected after ingesting eggs directly, which means the human turns into the intermediate host. In these cases, cysticerci or bladder worms can infect other tissues, including the brain, producing a very serious and potentially even fatal disease and sometimes must be surgically removed. A recent study has suggested that humans have been hosts to T. solium for 10,000 years and picked up the tapeworms from scavenging on ungulates, passing it on to pigs when they later domesticated these animals.


  1. It's interesting to read 17th and 18th century medical texts concerning human parasites and to realize how confused everyone was by tapeworms. The discussions and arguments about whether tapeworms were one long animal or many small, seed shaped creatures went on for many years. That some early texts call tapeworms (really their proglottids) cucurbitini is one example.

  2. Hi Susan et al.,

    I am a huge fan of "Parasite of the Day" and I constantly recommend it to many friends. As per your request for theme week suggestions... how about weeks based on common animals we interact with and the parasites they can carry... People may be amazed to hear about 7 parasites that their pet dog can carry, 7 that their cat can carry, 7 that chicken can carry, Squirrel, goldfish, etc. One week per host, each day a different parasite? Hamster Week!!

    On a more important note, the info you guys are gathering in these blogs represent a stunning user-friendly resource. Will it still be available once the year has ended? I would love to see this as a coffee table book or at least a full PDF I can print out and bind myself.

    Keep up the great work. Reading this makes me want to become a parasitologist (maybe I shall). I guess I should start by joining the society.


  3. Hi Felipe -
    First, I like the pets idea. There have been a few for dogs and cats already, but perhaps I can find 5 or 7 hamster parasites.

    When the year is over, I am hoping to move the site to a permanent home that people can have access to. Too bad it's a little past the prime of the popularity of page-a-day calendars!

  4. I was just thinking about asking for permission to mock up a page-a-day calendar from the Daily Parasite (just for myself and a select few friends, that is). There could be a (probably smallish!) market for a real one though - and I'm sure that quite a few popular bloggers like Carl Zimmer would pimp it for you...