Image caption Mosquitoes are increasingly resistant to insecticides

A new report says targeting mosquito breeding sites is likely to be increasingly necessary to reduce cases of malaria in Africa and Asia.

Researchers say that with mosquitoes becoming ever more resistant to insecticides, different approaches will be needed to help control the disease.

They include flushing out stagnant water where mosquito larvae grow and treating water with chemicals.

More than 600,000 people died from the malaria in 2010, most African children.

The number of deaths from malaria has fallen by a quarter in the last decade, largely thanks to the widespread distribution of mosquito nets treated with insecticides and the use of indoor insecticides sprays.

But the insects are becoming increasingly resistant to these chemicals, so a new report by researchers at the London School of Hygiene and Tropical Medicine says authorities should also use a method called "larval source management".

This is where mosquito larvae found in stagnant water like paddy fields or ditches are killed off by draining or flushing the land before they get a chance to develop. It also involves something called larviciding where chemicals are added to standing water.

The study found evidence that the method may significantly reduce both the number of cases of malaria by up to 75% and the proportion of people infected with the malaria parasite by up to 90% when used in appropriate settings.

The report's authors trawled through thousands of studies looking at the effectiveness of this method and found 13 which reached a high enough standard to draw their conclusions. The research came from countries including The Gambia, Kenya, Mali and the Philippines.

The report's author Lucy Tusting says the findings have important implications for malaria control policy

"The tremendous progress made in malaria control in the last decade is now threatened by mosquito resistance to the insecticides available for long-lasting insecticide treated nets and indoor residual spraying." she says

"Thus additional methods are needed to target malaria-transmitting mosquitoes.

Our research shows that larval source management could be an effective supplementary intervention in some places."

The World Health Organization says the research is not robust enough to support this method, and it is not recommended for use in rural areas where breeding grounds are hard to find.

A WHO spokesperson said: "Until there is more compelling evidence, larval control should continue to be viewed as a supplementary measure for malaria control in carefully selected settings. Promoting the widespread use of larval source management in rural areas of sub-Saharan Africa would be premature."

The WHO says larval source management should only be used alongside insecticide sprays and nets.