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Headline of the Month:

"Suicide Grasshoppers Brainwashed by Parasite Worms." And it's quite accurate. Thanks to GeekPress for the pointer. Rated IS for Icky Science.

David Smallberg:
Carl Zimmer's wonderful book Parasite Rex has a number of fascinating cases of mind-altering parasites. One may even be law-related: the organism Toxoplasma gondii causes rats to become reckless, losing their natural cautiousness, including when cat scent is present. (This is because T. gondii's life cycle is essentially cat gut => cat feces => rat => cat gut.) A study showed a higher than average toxoplasmosis infection rate among incarcerated criminals.
I'd love to see a follow-on study. The speculation is that while the organism evolved to chemically affect rat brains, it might have an incidental effect on other mammalian brains. An infected human might feel less constrained by social strictures, thus more likely to get in trouble with the law.
9.6.2005 9:21pm
Stephen M (Ethesis) (mail) (www):
This is a great post, thanks for the link -- now to tie this into evolutionary psychology some how ;)
9.6.2005 9:55pm
MadVeternarian (mail):
I'm glad someone wrote about Toxo, I was going to mention it. Nice find
9.7.2005 12:40am
J.G. Gamble (mail):
Brain-washing worms? Hah! How about ant-decapitating fly larvae:

http://www.phorid.net/phoridae/ant_de_flies.html

Money quote:

"In Costa Rica, we have found leaf-cutting ants still wandering along trails with their nestmates, in spite of the fact that there is nothing inside their heads except for a mature, fat phorid maggot."
9.7.2005 12:06pm
markm (mail):
I can see it coming - the Toxoplasmosis Defense. AKA, "the parasite made me do it." But what I want to know is, how did these people catch it? If I understand correctly, you either have to eat cat poop or a raw rat.
9.7.2005 4:59pm
David smallberg:

But what I want to know is, how did these people catch it? If I understand correctly, you either have to eat cat poop or a raw rat.

Cows can ingest the eggs through contaminated water or soil, cysts form in their muscle, and people eat the meat not quite properly cooked. Kids play in sandboxes. People clean cat litter boxes. Because toxoplasmosis is potentially fatal to people with weak immune systems, people with AIDS and pregnant women (whose fetuses are susceptible) are advised to stay away from cat litter.
9.8.2005 3:02am