Discovery is hard cheese for killer mosquitoes

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June 10, 2005

Discovery is hard cheese for killer mosquitoes

By Mark , Science Correspondent

http://www.timesonline.co.uk/article/0,,2-1647983,00.html

A FUNGUS similar to cheese mould could become a valuable weapon in

the fight against malaria, scientists report today.

British research has revealed that a common fungus can reduce

malarial transmission by 98 per cent in the laboratory, by killing

the mosquitoes that pass the parasite on.

The findings, from a team at the University of Edinburgh and

Imperial College, London, suggest that spraying living quarters with

the fungus, which is harmless to humans, could help to prevent

infection with a disease that kills up to 2.7 million people a year.

A second study, in Tanzania, has indicated that the fungus is likely

to be a practical method of malaria control in the field.

Ernst-Jan Scholte of Wageningen University in the Netherlands, who

led the field research, said: " The results are extremely

encouraging. The fungi provide another tool in the fight against

malaria. "

The approach to malaria prevention uses the fungus Beauveria

bassiana as a biological pesticide. Many malarial mosquitoes have

evolved resistance to chemical pesticides. Some pesticides that

remain effective, such as DDT, are banned for health and

environmental reasons.

Inert fungal spores are sprayed on walls and ceilings, or

impregnated into bedclothes and mosquito nets. When the insects come

into contact with the spores, the fungus germinates and grows within

them. The mosquitoes usually die from fungal infection before they

can spread malaria.

Details of both studies are published today in the journal Science.

Professor Read of the University of Edinburgh said: " When

mosquitoes have taken a big amount of blood they rest up on house

walls and ceilings to digest it. They are so big and fat that they

cannot fly off for around six hours.

" We have shown that if they are sitting among spores, the fungus

penetrates the mosquito and kills it. It takes two weeks for malaria

to develop in a mosquito before it can pass it on to another human.

But this way, we can kill the insect before that.

" As they get sicker, they are less likely to blood-feed or fly well

so they run out of steam and grind to a halt. Many mosquitoes are

becoming resistant to chemical pesticides so this is a different way

to kill them. "

A further advantage of the fungal approach is that mosquitoes have

never been seen to evolve resistance to fungal infections. Matt

, of Imperial College, said that even if they did develop

this, it is unlikely that they would also be immune to chemical

pesticides.

Gerry Killeen, of the Ifakara Health Research and Development Centre

in Tanzania, said: " If this fungus can kill mosquitoes and prevent

malaria, then it merits serious investigation. We need alternatives

to chemical insecticides, especially DDT. "

Any agreement to assist Africa at the G8 Gleneagles summit will fail

unless steps are taken to tackle malaria as a global crisis, a

parliamentary report said yesterday.

The All-Party Parliamentary Malaria Group said that the scale of the

challenge from the disease will put any package of aid and trade

assistance in jeopardy. It called for " increased and sustained

resources " from the rich world, saying that the chief obstacle to

progress is not a shortage of knowledge about how to deal with the

illness but a lack of political will to put this into practice.