Chemical coated mosquito nets could drastically improve malaria situation: Lancet

India has one of the largest numbers of malaria cases – in 2017 there were 5,33,481 cases and 107 deaths

The good old mosquito net with a little innovation could still be the best ally against malaria.

Mosquito nets coated with a long-lasting chemical – called piperonyl butoxide (PBO) – combined with pyrethroid insecticide reduced the prevalence of malaria in children by 44% over one year, and 33% over two years, compared to the mosquito nets currently used, according to a randomised controlled trial published in The Lancet. Based on this evidence, the World Health Organisation (WHO) recommends increasing coverage of PBO bed nets in areas where resistance to pyrethroids is developing.

India has one of the largest numbers of malaria cases – in 2017 there were 533481 cases and 107 deaths. This, according to some international reports could just be the tip of the iceberg with the country’s public health system failing to reach most patients.

Progress in malaria control is under threat by wide-scale resistance to the pyrethroid insecticide class currently used in indoor spraying and on current bed nets. This has resulted in a need for new types of insecticide for nets and indoor spraying.

Alongside effective treatment, these interventions previously reduced deaths from malaria by 62% worldwide between 2000 and 2015, however, there is a risk that these improvements could begin to reverse due to resistance

Indoor spraying of walls and ceilings kills mosquitoes that enter the home, while mosquito nets prevent them from reaching and biting people during the night, and the insecticide coating the nets kills the mosquitoes. Alongside effective treatment, these interventions previously reduced deaths from malaria by 62% worldwide between 2000 and 2015, however, there is a risk that these improvements could begin to reverse due to resistance.

“Our study is the first randomised control trial to report that PBO nets were more effective than standard nets against malaria infection and transmission by pyrethroid resistant mosquitoes. It also provides the strongest evidence so far of the effect of pyrethroid resistance on the use and efficacy of standard nets,” says lead author Dr Natacha Protopopoff, London School of Hygiene & Tropical Medicine, UK.

In this study, the authors compared standard and PBO bed mosquito net and indoor spraying of another insecticide – called pirimiphos-methyl – in 40 villages in Muleba (Tanzania). The PBO chemical is expected to last for up to two years when applied to nets, while pirimiphos-methyl indoor spraying lasts for approximately one year. The randomised trial included four groups: households either received a PBO net with no indoor spraying, a PBO net and indoor spraying, a standard net with no indoor spraying, or a standard net and indoor spraying. Previously, there was inadequate evidence to justify swapping from standard nets to PBO nets across all areas, and concerns that the PBO chemical could interact and reduce the benefits of pirimiphos-methyl indoor spraying.