"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 26, 2010

May 26 - Balantidium coli

It is thought that Balantidium coli is the only ciliate (think Paramecium) that is parasitic in people (causing the disease Balantidiasis), however in humans, these protozoans are zoonotic, with pigs as the primary reservoirs. To our porcine friends, the ciliates appear to not cause symptoms, but humans can suffer severe GI distress if they become infected by ingesting contaminated water or food. This parasite has been found worldwide, but is not a common pathogen of humans, except in the Philippines. Recent work identified the same ciliate in several other kinds of mammals including other primates and rodents, so a better epidemiological understanding is clearly in order.


  1. A lovely little parasite that I see quite often in the monkeys where I work.

  2. Tulane National Primate Research Center