Tuesday, August 09, 2005

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

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

Malaria is a staggeringly devastating disease, striking an estimated 300 million to 500 million people a year and killing more than a million of them. Scientists have long wondered how the parasite that causes malaria - a single-cell creature, plasmodium, carried by mosquitoes - manages to be so successful.

New research has shown an unexpected source of its success. The parasite makes infected humans smell more attractive to mosquitoes.

The research, published on Monday in the journal Public Library of Science Biology, was carried out by a team of French and Kenyan scientists led by Jacob Koella, an evolutionary biologist at Pierre and Marie Curie University in Paris. Dr. Koella is a leading expert on the ways in which parasites manipulate their hosts.

Many parasites that need to live inside two different hosts during their life cycles also manipulate their hosts. A single-celled parasite called toxoplasma lives inside cats and then inside their prey, like rats. Research shows that infection with toxoplasma makes rats lose their fear of the odor of cats. Tapeworms that live in fish can turn them white and make them jump around near the surface of the water, where the fish are more likely to be eaten by birds, which the tapeworms make their new host. "It's amazing how much manipulation is going on in parasites," Dr. Koella said. "It would be hard to find a case where there wasn't some manipulation."

Scientists consider most of these examples as products of natural selection. A parasite's reproductive success depends on its ability to be transmitted toa new host. "And manipulation appears to be an obvious way to do it," Dr. Koella said.
The evolution of malaria. Hypotheses tested.