The mosquito at work © CDC / James Gathany / Wikipedia
Reading Mosquitoes are less fertile, but they live longer if they are affected by the virus of avian malaria. This is the result of a study by French researchers from the National Center for Scientific Research. This shows that the pathogen manipulates the mosquitoes largely selfishly - because the longer the mosquitoes live, the higher the probability of parasite transmission, the scientists conclude. The causative agents of malaria are single-celled parasites that are transmitted by mosquitoes to other animals. There are several types that infect different animals. The best known is Plasmodium falciparum, which causes malaria tropica in humans. For their study, however, scientists around Julien Vézilier selected Plasmodium relictum, a variant that mainly affects birds. They performed two different experiments: the first one was just to investigate a possible impact on the life expectancy of the insects. They gave one mosquito-infected and the other? Clean? Blood as food. Then they counted the dead mosquitoes on the cage floor every day. In the second experiment, the mosquitoes were again infected or pure blood. This time, the researchers observed not only the mortality but also the fertility of female mosquitoes by counting the number of eggs laid.

It turned out: mosquito females infected with plasmodia had a significantly reduced fertility compared to healthy animals. But they lived much longer. The scientists conclude that this is a kind of redistribution of energy between propagation and survival. This redistribution is caused by the pathogens, as it is important for the disease spread that the mosquitoes live as long as possible. The resources are available to them because they spend less energy for reproduction.

For the pathogens it is very important that the mosquito lives long, the researchers say. Because the parasites need 10 to 14 days of incubation. This is the time between the infection of the mosquito and the multiplication of the parasite. In addition, the longer the mosquito can fly around, the more mammals it can sting, and the greater the chance that the plasmodia will actually be transmitted. Because only when an animal has been stung at least twice by the mosquito, the parasites can infect the new host. A better understanding of Plasmodium, its mode of action and distribution can help in the long run to better control the other Plasmodium species as well and thus find new approaches against malaria, the researchers hope.

Julien Vézilier (Center national de la recherche scientifique) et al .: Proceedings of the Royal Society B; doi: 10.1098 / rspb.2012.1394 © science.de - Gesa Seidel advertisement

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