"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

May 3, 2010

May 3 - Capillaria hepatica

Capillaria hepatica is a parasitic nematode that has an utter death wish for its host - it's the only way that it can be transmitted. Larvae are ingested by a host - normally a rodent, but occasionally man, and they make their way from the intestine to the liver. There they mature and begin to lay eggs, but unlike many parasites, these eggs don't go anywhere just yet. They just wait, paused in their development until they get a little fresh air. The adults eventually die and all of these eggs and dead worms cause some nasty damage to the liver, which can kill the host - or make it easy prey to another animal. If the animal dies and rots, the eggs will eventually be released and become infective L1 larvae. Or, if the original host is eaten or scavenged, the eggs pass through that host, out into its feces, and then become ready to infect their new hosts. In some parts of the world, such as southeast Asia, this parasite is extremely common in rodents, but luckily it's very rare in people and fewer than 40 cases have ever been reported.


  1. It has long been the practice (and I am as guilty as others) to call any infection in which capillarid eggs are found in the liver Capillaria hepatica. Consequently, dozens, if not hundreds, of mammal species are listed as hosts. I have a strong hunch that when DNA is extracted, a species complex will appear, similar to Trichinella. I recommend it to someone as a PhD dissertation topic.

  2. Sounds like a very good project! Any budding students out there?