Tuesday, August 09, 2005

We too are manipulated by our parasites

Manipulative Malaria Parasite Makes You More Attractive (to Mosquitoes) - New York Times

It is becoming clear that many, if not all, parasites alter the behaviors of their hosts. Research shows malaria-infected mosquitoes vary their biting behavior depending on the parasite's life cycle. Now we learn that infected human children smell more attractive to mosquitoes:
After studying 12 sets of children, the scientists discovered a striking pattern. 'Gametocyte-infected children attracted about twice as many mosquitoes as either uninfected ones or ones infected with nontransmissible stages,' Dr. Koella said. 'The results really jump out.'

The infected children did not show symptoms like fever, a common situation in Africa. Nevertheless, the researchers treated them with anti-malaria drugs on the day of their study. Two weeks later, after the medicine had cleared the parasites, the scientists repeated the experiments with the same three children. They found that the cured children were no more attractive to the mosquitoes than the others.
I'm starting to worry that the 'toxoplasma alters personality' claim may be valid.

Throughout most of human history we carried a very large number of parasites in our bodies -- particularly worms. How has losing those worms changed our behavior?

Update 8/10: Still thinking about our friends the worms. Some think the absence of worms is the cause of some inflammatory bowel diseases (ulcerative colitics especially). So if worms would make their hosts careless about hygeine, and probably careless about many things, would removing our parasitic worms give rise to obsessive-compulsive disorder? Does being wormless make some people unusually rigid and puritanical? Does having worms promote careless behavior?

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