Mosquitoes infected with the malaria parasite are more attracted to human odours than uninfected ones, according to a study by a team of scientists.

Reporting in the journal PLOS ONE, they said the malaria parasite, Plasmodium falciparum, altered the host mosquito’s olfactory system. A heightened attraction to human odours causes it to fly more frequently to humans to feed on their blood, thereby increasing transmission of the pathogen responsible for the tropical disease.

The scientist heading the study, Renate C. Smallegange, an entomologist at Wageningen University in the Netherlands, has investigated mosquitoes’ attraction to human scent for years.

Human malaria is transmitted only by females of the genus Anopheles; they suck blood, needing it to nurture their eggs. Dr. Smallegange and her Dutch, US and British colleagues are the first to demonstrate that the parasite has power over mosquito behaviour.

Primary evidence

For her research, Dr. Smallegange put scraps of both worn and clean stockings in cages which contained infected and uninfected females.

All the mosquitoes landed more often on the surfaces emanating human odour. But the mean landing rate on the worn stockings was more than three times greater in the case of infected mosquitoes.

Some 3.3 billion people worldwide live in high-malaria-risk areas, mainly in sub-Saharan Africa, South America and Southeast Asia. The authors hope the findings will lead to improved mosquito traps using attractive smells.

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