by emad » Mon Jan 23, 2006 2:25 pm
Can cat parasites alter human personalities? <br> January 17, 2006 <br>The Return of the Puppet Masters <br>Posted by Carl Zimmer <br><br>Are brain parasites altering the personalities of three billion people? The question emerged a few years ago, and it shows no signs of going away.<br><br>I first encountered this idea while working on my book Parasite Rex. I was investigating the remarkable ability parasites have to manipulate the behavior of their hosts. The lancet fluke Dicrocoelium dendriticum, for example, forces its ant host to clamp itself to the tip of grass blades, where a grazing mammal might eat it. It's in the fluke's interest to get eaten, because only by getting into the gut of a sheep or some other grazer can it complete its life cycle. Another fluke, Euhaplorchis californiensis, causes infected fish to shimmy and jump, greatly increasing the chance that wading birds will grab them.<br><br>Those parasites were weird enough, but then I got to know Toxoplasma gondii. This single-celled parasite lives in the guts of cats, sheddding eggs that can be picked up by rats and other animals that can just so happen be eaten by cats. Toxoplasma forms cysts throughout its intermediate host's body, including the brain. And yet a Toxoplasma-ridden rat is perfectly healthy. That makes good sense for the parasite, since a cat would not be particularly interested in eating a dead rat. But scientists at Oxford discovered that the parasite changes the rats in one subtle but vital way.<br><br>The scientists studied the rats in a six-foot by six-foot outdoor enclosure. They used bricks to turn it into a maze of paths and cells. In each corner of the enclosure they put a nest box along with a bowl of food and water. On each the nests they added a few drops of a particular odor. On one they added the scent of fresh straw bedding, on another the bedding from a rat's nests, on another the scent of rabbit urine, on another, the urine of a cat. When they set healthy rats loose in the enclosure, the animals rooted around curiously and investigated the nests. But when they came across the cat odor, they shied away and never returned to that corner. This was no surprise: the odor of a cat triggers a sudden shift in the chemistry of rat brains that brings on intense anxiety. (When researchers test anti-anxiety drugs on rats, they use a whiff of cat urine to make them panic.) The anxiety attack made the healthy rats shy away from the odor and in general makes them leery of investigating new things. Better to lie low and stay alive.<br><br>EDIT:<br><!--EZCODE AUTOLINK START--><a href="http://www.corante.com/loom/archives/2006/01/17/the_ret...">www.corante.com/loom/arch...the_ret...</a><!--EZCODE AUTOLINK END--> <br><br> <br> <p></p><i>Edited by: <A HREF=http://p216.ezboard.com/brigorousintuition.showUserPublicProfile?gid=emad@rigorousintuition>emad</A> at: 1/24/06 11:01 am<br></i>