Wednesday, 1 January 2014 09:27
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Reuters: Scientists in California believe they are close to producing mosquito repellents that are less expensive and more effective than any currently available. Their goal is to reduce the incidents of mosquito-borne diseases like malaria in the developing world, while also providing relief in countries where the insects are a seasonal pest.
In a laboratory at the University of California, Riverside, scientists believe they are close to developing the next generation of mosquito repellents... chemical compounds that shut down the mosquitoes’ ability to detect the presence of humans. Mosquitoes are initially attracted to humans by carbon dioxide in the breath, but Dr. Anandasankar Ray says the neurons that trigger that long distance attraction have a secondary function once the insect gets closer.
“The same receptor that detects carbon dioxide is also detecting odours from our skin and when the mosquito comes close to us, the dual receptor is triggered by odours coming from skin and the mosquito is able to effectively find its way to us.” After testing more half a million chemical compounds, Ray’s team has found one that shuts that receptor down. Called ethyl pyruvate, it occurs naturally in fruits and inhibits the mosquito’s ability to detect carbon dioxide and the odours commonly emitted by humans,” Dr. Ray.
“When we apply ethyl pyruvate to a human arm and offer it to hungry mosquitoes in a cage, then very few of the mosquitoes are attracted to the human arm because only a few of them are able to smell it out. The majority of the mosquitoes are no longer interested in it, so we are able to mask the human arm from hungry mosquitoes by applying this fruity smelling odour called ethyl pyruvate.” Another compound, called cyclopentanone has the opposite effect. It attracts mosquitoes, a quality Ray says could be exploited for mosquito traps. But the discoveries did not come easily. First, fellow researcher Genevieve Tauxe, had to find the neurons activated by chemical smells. Not so easy in a mosquito.
“With this apparatus we are able to insert a very small electrode into the part of the mosquito’s nose, effectively, where its olfactory neurons are and where the smell is happening. So then we get a readout in real time of the electrode activity of the neurons that are right there. So what you’re seeing in those spikes is that each one represents the action-potential of the neuron, which is a signal that’s being sent to the brain that it’s detected something. So the more frequently those spikes occur, that means the more strongly that neuron is being activated and the more of the signal is getting to the brain,” Tauxe said.
The key to producing better repellents and attractants lies in the ability to manipulate those signals… something conventional repellents like DEET can’t do. DEET has long been regarded as the most effective option, but in developing nations where tropical diseases like malaria and dengue fever are rife, it is too expensive and usually inaccessible to most people.
Dr. Ray said: “Perhaps by finding designer odours, better odours that can attack other target receptors, we will be able to improve upon DEET and finally have the next generation of insect control product.” Ray and his team say they’re on the right track and that less expensive, more effective solutions are now within reach.
