common fungus could be the weapon needed to fight malaria.
by Hugh Sturrock
| Photo by Hugh Sturrock
stephensi, the mosquito responsible for spreading malaria
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
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
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