"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

December 14, 2010

December 14 - Fasciola hepatica

This parasite can be baaaaad, to sheep - and to humans. Fasciola hepatica, or the common liver fluke, is a trematode parasite with a typical complex life cycle like so many that we have seen here before, involving snails that are common around pastures. Metacercariae are ingested by grazing animals and then they seek out liver tissue and feed for a month or two, causing anemia and other symptoms in the animal. Eventually, they mature into adults and settle down in the bile ducts and just churn out eggs - about half a million a day! Humans can become infected with this parasite through accidental ingestion of the metacercariae in water, on water plants, through contact with livestock and perhaps from ingesting raw liver from infected animals.


  1. And unlike most of the flukes featured on POTD, this one is not microscopic- it's as big as a silver dollar- not a pleasant thing to have crawling around in your liver!

  2. I wonder how one is treated medically for this fluke? Is the liver damage permanent?

  3. There are anthelminthic drugs available for treating infection by parasitic worms such as liver flukes. A medical doctor or veterinarian would know more details about specifically what drugs are appropriate.

  4. I think it was reading about this one that put me off eating watercress from a stream running through sheep meadows.