Using a new bug spray on bed nets that blocks mosquitoes resistant to current insecticides almost halved malaria infections among children in Tanzania in a study that has boosted hopes of protecting more people from the killer disease.

A trial by the London School of Hygiene & Tropical Medicine involving 15,000 children found that using a bed net treated with piperonyl butoxide reduced malaria infections by 44 percent in the first year compared to nets only treated with pyrethroid.

The study comes amid concerns that mosquitoes' ability to resist insecticides is evolving rapidly and spreading across Africa, where tools such as insecticide-treated bed nets and insecticide spraying have helped cut malaria cases since 2000.