Tricking the mosquito’s “nose”  pg. 3

The bulk of the money—$450 million—was provided by the Gates Foundation, with an additional $27.1 million coming from the Wellcome Trust of the United Kingdom and $4.5 million from the Canadian Institutes of Health Research. The three organizations jointly administer the initiative along with the Foundation for the NIH.

The grants fell into several broad areas: developing improved vaccines to prevent diseases like malaria, tuberculosis and HIV; discovering ways to prevent the development of drug resistance; growing more nutritious crops to combat malnutrition; developing better methods for diagnosing and tracking disease in poor countries; and developing new ways to prevent insects from transmitting diseases.

Zwiebel’s group received an initial grant of $8.5 million for five years to develop ways to disrupt malaria transmission by chemical manipulation of the malaria mosquito’s sense of smell.

Theirs was one of seven grants that targeted the mosquito, reflecting the fact that the tiny insect is considered to be the deadliest animal on the planet. Malaria kills somewhere between 700,000 to 2.7 million people every year; two other mosquito-transmitted diseases, dengue fever and yellow fever, kill another 630,000. The World Health Organization estimates that a child dies of one of these diseases every 30 seconds.

“I was very impressed with the seriousness of the effort and the way they are trying to be circumspect in addressing what clearly are very complex issues,” says Zwiebel.

“Malaria control is not going to be a unilateral process,” he says. “We see vector control as one component in an overall multi-lateral strategy with more than one arrow… bed nets, vaccine development, vector control, water treatment, housing improvement—these are the elements that are going to bring malaria into a controllable strategy.”

The arrow in the Zwiebel group’s quiver is applying knowledge about how the mosquito’s “nose” works in order to identify chemical compounds that act as “super-repellants” and “super-attractants.”

The mosquito’s “nose” is located in its antennae and other head appendages. Studies at Vanderbilt and elsewhere have shown that its olfactory system consists of an array of different odorant receptors, each of which responds to a very narrow range of chemical signals.

These findings suggest that it should be possible to identify the specific human odorants and their respective receptors that allow female mosquitoes to identify their hosts when they need blood to reproduce. They also raise the possibility of identifying other chemicals that interact with these receptors in combinations that either attract or repel these highly selective insects.

Super-repellants

Previous studies have shown that human sweat contains about 350 different aromatic compounds, but not much research has been done on them, so researchers do not know much about individual variations in these odorants. Recent evidence indicates that mosquitoes use a blend of many odorants in targeting prey. So the researchers realize that they are faced with deciphering a highly complex system.

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View Related Article: How to trick the mosquito's nose: Malaria control at the molecular level