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Malaria No More

A common fungus could be the weapon needed to fight malaria.

by Hugh Sturrock

Photo by Hugh Sturrock

Anopheles stephensi, the mosquito responsible for spreading malaria in Asia.

It’s called Beauveria bassiana and it’s probably found in your soil. This common fungus is known to be an insect killer: when the skin of locusts and beetles comes into contact with it, it enters their body, feeds off their insides and eventually kills them.

Its reputation as an insecticide is what led a team of scientists from Imperial College and Edinburgh University, headed by Dr. Matt Thomas and Professor Andrew Read, to investigate its effect on malaria-carrying mosquitoes. If it could kill these mosquitoes before they infected a human, then it would be a huge step forward in controlling the spread of malaria, of which there are more than 300 million new cases globally each year and about a million deaths.

Mosquitoes often get into people’s homes, resting on ceilings, walls and bed netting after a bloody meal. Researchers wanted to recreate this environment for their study, so to simulate the inside of a house, they placed mosquitoes in old ice cream pots covered in bed netting. The inside surfaces of the pots were sprayed with oil containing Beauveria bassiana fungus and mosquitoes were allowed to rest inside for 24 hours.

After their 24 hours of confinement, the mosquitoes were still alive and were released into large cages. Would they drop like flies in the coming days?

The results were what they had hoped for: within two weeks, 90% of the mosquitoes were dead. The timing of their deaths was crucial since the malaria parasite takes 2 weeks to become infectious in mosquitoes. Since they were killed within this time period, those carrying malaria would never be able to transmit it to humans.

Photo by Hugh Sturrock

A female anopheles mosquito killed by the Beauveria bassiana fungus.

In addition to this impressive killing power, insects don’t seem to develop a resistance to the fungus. This is now a problem with pyrethroids, the chemicals most commonly used to get rid of mosquitoes.

And contrary to chemical insecticides like DDT, which is effective but has been banned in most countries for fear that it might have adverse effects on humans and the environment, sprays containing Beauveria bassiana are an environmentally-safe alternative.

Further work will have to be done to investigate how long the fungal spray stays effective once it has been applied to surfaces, but these results do give hope that a green and economical addition to the anti-malarial arsenal may be on its way.

For more info:

The Read Group: Institutes of Evolution, Infection and Immunology Research http://readgroup.icapb.ed.ac.uk/

Hugh Sturrock's blog

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First Science 2014