"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 21, 2010

May 21 - Paragonimus westermanni

Yesterday was an instance of an animal parasite that was recently discovered in a human. Today's parasite, Paragonimus westermanni, is another fluke that can infect both humans and animals. Commonly known as the oriental lung fluke, humans become infected when they eat undercooked crab or crayfish, which are serving as intermediate hosts. Before the crustacean, the parasite was in a snail (oh how trematodes love their snails!) and how did they get there, you ask. The eggs of the flukes are coughed up by humans -- or by cats, it turns out. The parasites are very prevalent in many parts of Asia and as many as 80% of crabs can be infected. Common preparation methods such as pickling or salting will not kill the metacercariae and thus are easy routes to vertebrate hosts. Another popular Chinese dish - "drunken crab" - made by dousing crabs in wine is another means of infection. The species name is an honorific of a zookeeper who also observed the flukes in Bengal tigers.

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