Bed nets treated with a new kind of insecticide cut malaria cases in children by almost half in a large trial in Tanzania, according to a study in The Lancet, raising hopes of a new weapon in the fight against the age-old killer.

Bed nets have been instrumental to the vast progress the world has made in recent decades against malaria, with millions of lives saved. But progress has stalled in the last few years, in part because the mosquitoes which spread the infection have increasingly developed resistance to the insecticide used in existing nets.

In 2020, 627,000 people died of malaria, mainly children in sub-Saharan Africa.

Now, researchers at the London School of Hygiene and Tropical Medicine in the UK (LSHTM), the National Institute for Medical Research and Kilimanjaro Christian Medical University College in Tanzania, and the University of Ottawa in Canada have shown that a new insecticide –– the first in 40 years –– is both safe and effective in a real-world randomised trial.

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Chlorfenapyr, pyrethroid treatment

The nets, treated with chlorfenapyr as well as pyrethroid, the usual chemical used, reduced malaria prevalence when compared with the existing nets by 43 percent in the first year and 37 percent in the second year of the trial.

The study involved more than 39,000 households and followed over 4,500 children aged 6 months to 14 years old. The nets, developed by BASF in Germany and LSHTM, are marginally more expensive than the current nets, at around $3 per item, but the researchers said the savings in preventing cases outweighed the initial increased outlay.

Chlorfenapyr works differently than pyrethroid, effectively grounding the mosquitoes by causing wing cramps and making them unable to fly, and therefore bite, spreading the infection. The chemical was first proposed for use against malaria 20 years ago, and has been used for pest control since the 1990s.

The World Health Organisation has already pre-qualified the use of the new nets, but the trial, funded by the British government and the Wellcome Trust, could lead to more widespread recommendations for their use.

"This is the first evidence in real-life conditions," Dr Jacklin Mosha, the study's lead author from the National Institute for Medical Research, Tanzania, told Reuters news agency.

Alongside progress on a malaria vaccine, which was approved by the World Health Organisation last year, the team said the net could be another tool in the malaria toolbox.

However, they warned that it is important to ensure that mosquitoes do not also quickly develop resistance to chlorfenapyr if used widely.

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