Scientists find weak link in 'earth's most dangerous animal'

Scientists believe that they are close to finding the weak point of the deadly Anopheles mosquito, which has been described as the most dangerous animal on the planet because of its role in spreading malaria.

Researchers have drawn up a detailed anatomical and molecular map of the key sensory organ that the female mosquito uses to locate her next meal of human blood – which is how malaria is transmitted.

Findings from the study could eventually lead to new methods of either blocking the mosquito's exquisite sense of smell, of luring it to its death, or of developing powerful chemical repellents that people could rub on their skin to avoid mosquito bites.

About 40 per cent of the world's population are at risk of being exposed to malaria, which affects about 500 million people annually with severe illness. Each year, more than 700,000 children in Africa alone are estimated to die of malaria.

An international team of scientists that has been investigating the mosquito's strong sense of smell for several years has now mapped a specialised sensory organ that the insect uses to zero-in on the scent of its human victims.

The researchers have found that the organ, called the maxillary palp, contains a unique array of receptor cells that detect carbon dioxide and an ingredient of human sweat called octenol. "We haven't proven it yet, but the implication is that if you took away the maxillary palp the mosquito would not do nearly as well at finding human prey," said Tan Lu, from Vanderbilt University in Nashville, Tennessee. The study is published in the journal Current Biology.

It was also known that the mosquito uses two other sensory organs, the feathery antennae that serve as general purpose olfactory organs, and the proboscis, which is designed to recognise odours and tastes close up to the skin. Compared with the mosquito's antennae, which are designed to detect hundreds of different chemical compounds, the maxillary palp is highly specialised – each of its microscopic sensory hairs is attached to just three nerve cells, one tuned for detecting carbon dioxide, one for octenol and one to enhance the general sense of smell, said Professor Laurence Zwiebel at Vanderbilt.

"The amazing thing that we found was that all the sensory hairs that line the bottom of the maxillary palps are identical," he said.

"This research... provides a biological context and then strips it down to a few molecular targets that we are using to develop chemical modifiers that should have direct impacts on the mosquito's behaviour," he said.