Page last updated at 09:56 GMT, Monday, 15 June 2009 10:56 UK

Birth control to combat malaria

By Bethany Bell
BBC News, Vienna

Anopheles mosquito
Anopheles mosquitoes spread malaria

Mosquito bites can be deadly.

Anopheles mosquitoes carry the parasite that causes malaria, a disease which kills around a million people every year.

Traditionally mosquito populations have been controlled by pesticides.

But scientists at the International Atomic Energy Agency (IAEA) are working on another method - using radiation to sterilize male mosquitoes.

The idea is to produce large numbers of male mosquitoes that are sexually sterile
Mark Benedict
International Atomic Energy Agency

The sterile insect technique (SIT) has worked well in reducing tsetse flies and some other insect pests, such as fruit flies.

The IAEA scientists are now trying to adapt the technique to the anopheles mosquito.

Birth control

Mark Benedict, a medical entomologist at the IAEA, says SIT is "birth control" for insects.

"The idea is to produce large numbers of male mosquitoes that are sexually sterile," he said.

"Those males will be released into the wild and find virgin female mosquitoes and they will mate with them."

A female usually only mates once in her life so if her partner has been sterilized none of the hundreds of eggs she lays will hatch.

Sterilization takes just a couple of minutes.

Mosquito pupae are gathered into a metal pot and are lowered into a machine, where they are exposed to radiation.

When they come out they are sexually sterile.

In the hot and humid laboratories at the IAEA, the team is trying to develop methods of raising male mosquitoes that are strong enough to survive the irradiation - and sexy enough to attract females out in the wild.

They are also working on ways to transport and release them in the wild.

Field project

Preparations for a pilot field project in Northern Sudan are underway to test the feasibility of SIT for mosquitoes.

The area is marked by extreme desert, but humans, livestock and wild mosquitoes live along the edge of the Nile River.

Despite a relatively small number of mosquitoes, there are high levels of malaria transmission there.

Mark Benedict says the sterilized pupae will be released along the river banks where the wild mosquitoes breed.

"That will give us a good idea of over what area we can release and what population densities we can see controlled" he says.

It is early days but Mark Benedict is optimistic about the prospects of SIT.

It is hoped that along with other tactics such as insecticide treated bed-nets, the technique can work as a tool in the fight against malaria.

The technique is "very well suited to elimination and eradication programmes."

"What we need to do now is get one or two projects off the ground, measure the potential and see where we can take it from there," he said.

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