Mozzie sex key to malaria

Interfering in mosquitoes' sex lives could help halt the spread of malaria, British scientists said.

A study on the species of mosquito mainly responsible for malaria transmission in Africa, Anopheles gambiae, showed that because these mosquitoes mate only once in their lives, meddling with that process could dramatically cut their numbers.

Researchers from Imperial College London found that a "mating plug" used by male mosquitoes to ensure their sperm stays in the right place in the female is essential for her to be able to fertilise eggs during her lifetime.

Without the mating plug, sperm is not stored properly and fertilisation is disrupted, they wrote in the study in the journal PLoS Biology.

Reproductive success

"The plug plays an important role in allowing the female to successfully store sperm in the correct way inside her, and as such is vital for successful reproduction," Flaminia Catteruccia of Imperial's life sciences department wrote.

"Removing or interfering with the mating plug renders copulation ineffective. This discovery could be used to develop new ways of controlling populations of Anopheles gambiae mosquitoes, to limit the spread of malaria."

Billions at risk of malaria

Around 40% of the world's population is at risk of malaria, a potentially deadly disease which is transmitted via mosquito bites.

It kills more than a million people worldwide each year and children account for about 90% of the deaths in the worst affected areas of sub-Saharan Africa and parts of Asia.

Catteruccia's team analysed the composition of the male mosquito's mating plug, and found it is formed when an enzyme called transglutaminase interacts with proteins in the male mosquito's seminal fluid. This interaction causes the fluid to clot into a gelatinous solid mass, known as the mating plug.

When the researchers knocked out the enzyme in male mosquitoes in the lab, the plug could not form, meaning reproduction failed when they mated.

Sterile females

If this process could be developed for use in the field, perhaps in a spray form like an insecticide, it could "effectively induce sterility in female mosquitoes in the wild," Catteruccia wrote, offering potential as "one more weapon in the arsenal against malaria".

Health experts want more effort to go in to a multi-pronged approach to fighting malaria, combining prevention measures like insecticides and bed nets with improved access to the best drug treatments in highest risk areas.

The World Health Organisation said last week that increased funding was starting to pay off in the battle against the killer disease. - (Kate Kelland/Reuters Health, December 2009)