Tuesday, July 19, 2011

Attractiveness of humans to mosquitoes

There were a couple of questions on this paper, Malaria Infection Increases Attractiveness of Humans to Mosquitoes, that I wanted to check up on, and like I said, the answer is usually more complicated and more interesting than expected.

First, children infected with malaria but NOT producing gametocytes were no more attractive to mosquitoes than uninfected children. Not even slightly. The data points are practically on top of one another.

BUT, what I hadn't realized was that when they treated the children the ones that had been infected with gametocytes were then LESS attractive to mosquitoes. Strange.

A striking aspect of our results is that former gametocyte carriers (i.e., after treatment) seem to repel mosquitoes, as only 22%, i.e., less than one third, of the responding mosquitoes prefer these children (t-test: t = −2.203, df = 11, p = 0.050; Wilcoxon signed-rank test: p = 0.040). An explanation for this result could be based on the slight anaemia in previously infected children. Mosquitoes might sense this anaemia and prefer those children with a higher concentration of red blood cells as it is these that the mosquitoes require. This would indicate a remarkable adaptation by the mosquitoes. The interpretation, however, would predict that the children previously infected with the asexual stage should also repel mosquitoes—but this was not observed.

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