Beat the Mozzie with Grapes

By Alice Orszulok

Scientists have found an alternative to the smelly bug spray that we rely on to keep mosquitos at bay.

Summer’s almost here, and with it we can expect plenty of fun and exciting things: holidays, sunshine, days at the beach and plenty of barbecues. What we’re not looking forward to is hoards of pesky mosquitos that like to crash our outdoor parties, dinners and play time. These pests not only like to snack on our blood and leave an itchy bite in its place, in some countries they can carry a parasite that causes the deadly disease Malaria.

The main ingredient in the insect sprays we currently use is called DEET. The chemical is great at repulsing biting insects like mosquitos and fleas, however it is also expensive, and can even cause health problems. For many people in third-world countries like in Africa, having access to bug repellants is a life or death situation. Malaria kills over 500,000 people every year, most of these are children in poor African countries. This is why scientists have developed a cheaper (and less smelly) alternative to the DEET-based bug sprays.

“Cost stops it from being used in the areas of the world where it is most needed,” Anandasankar Ray, an entomologist (a scientist who studies insects) from the University of California told Science News.

Although it was originally believed that DEET meddled with the insect’s olfactory senses (their ability to smell) it is now understood that they just don’t like the smell. If you’ve ever used mozzie spray before, you can understand why. Just imagine that but much, much worse—even without bug spray mosquitos can smell you from 30 metres away!

To find a replacement for DEET, scientists needed to find out exactly what it was about the chemical that insects didn’t like. The team inserted special genes into fruit flies that made their nerve cells glow when active. Fruit flies are similar to mosquitos, but much easier to work with. Then they exposed the flies to DEET, and watched as some of the nerve cells in the flies’ antennae lit up. These cells contained a receptor called Ir40a. Receptors are what sends signals to the brain so that we can respond to the situation. For instance, if you put your hand on a hot stove, pain receptors in your hand send signals to your brain to let you know that you’re in danger so that you lift it off. In this same way, the flies’ receptors send messages to the brain to move away from the smell.

Once the scientists figured this out, they needed to find a new chemical compound that would activate Ir40a in the same way. It needed to be cheap, easily accessible and safe to use. They ended up finding three compounds in grapes, plums and orange flowers. Not only are these deemed safe and affordable, they smell good enough to eat!

Source [Science News]

Malaria: A disease caused by a parasite that invades the red blood cells. The parasite is transmitted by mosquitoes, mostly in tropical and subtropical regions such as in Africa.