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American scientists have discovered a specific odour produced by malaria-infected cells which attracts mosquitoes. This might explain why malaria mosquitoes are more likely to bite infected individuals. The study was published in mBio, the online open-access journal of the American Society for Microbiology.

When mosquitoes get infected with malaria, they become less fit and are less likely to reproduce. One would expect that this selective pressure enriches for mosquitoes with a decreased tendency to bite infected humans. However, this does not seem to be the case. Instead, the mechanism may be counteracted by the mosquito-attracting compound terpene which is excreted by the malaria-infected cells. This force of attraction might overrule the proposed negative selection.

In the study, human red blood cells were infected with the malaria virus and grown in airtight bags. Subsequently, the air on top of the cultures was analysed and compared with the air composition of non-infected cells. This resulted in the discovery of terpene, which is normally produced in plants preferred by malaria mosquitoes. The malaria virus mimics this effect by causing the production of the same chemoattractant luring mosquitoes to the infected host.

According to the authors, these results may give rise to new diagnostic procedures: “We have studies ongoing to see if we can detect these compounds in children with malaria, because obviously a breathalyser test would be a lot nicer than the blood-based tests that are currently used," says senior author Audrey Odom, an assistant professor of paediatrics and molecular microbiology at Washington University School of Medicine, St. Louis. Additionally, she sees possibilities for future malaria control: "Understanding the molecular basis of mosquito attraction and host choice is important for figuring out how you might prevent people from getting bitten in the first place."

Sources: mBio and Eurekalert

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