Getting ahead of insecticide-resistant malaria vector mosquitoes

In The Lancet, Manfred Accrombessi and colleagues 1 Accrombessi M Cook J Dangbenon E et al. Efficacy of pyriproxyfen-pyrethroid long-lasting insecticidal nets (LLINs) and chlorfenapyr-pyrethroid LLINs compared with pyrethroid-only LLINs for malaria control in Benin: a cluster-randomised, superiority trial. Lancet. 2023; (published online Jan 24.)https://doi.org/10.1016/S0140-6736(22)02319-4 Summary Full Text Full Text PDF PubMed Google Scholar report the results of a rigorous cluster-randomised, controlled, superiority trial in Benin, encompassing 54 030 households and 216 289 people, which confirms that the addition of the pyrrole insecticide chlorfenapyr to long-lasting insecticidal nets (LLINs), as a second active ingredient to back up the pyrethroids we have relied upon so heavily for so long, can have invaluable effects on malaria transmission and disease burden. A total of 115 323 LLINs were distributed to 54 030 households and the primary outcome of mean malaria case incidence 24 months after LLIN distribution in a cohort of children aged 6 months to 10 years showed 1·03 cases per child-year (95% CI 0·96–1·09) in the pyrethroid-only LLIN reference group, 0·56 cases per child-year (0·51–0·61) in the chlorfenapyr-pyrethroid LLIN group (hazard ratio [HR] 0·54, 95% CI 0·42–0·70; p<0·0001), and 0·84 cases per child-year (0·78–0·90) in the pyriproxyfen-pyrethroid LLIN group (HR 0·86, 95% CI 0·65–1·14; p=0·28). Together with a similar study in Tanzania by Mosha and colleagues, 2 Mosha JF Kulkarni MA Lukole E et al. Effectiveness and cost-effectiveness against malaria of three types of dual-active-ingredient long-lasting insecticidal nets (LLINs) compared with pyrethroid-only LLINs in Tanzania: a four-arm, cluster-randomised trial. Lancet. 2022; 399: 1227-1241 Summary Full Text Full Text PDF PubMed Scopus (10) Google Scholar these findings decisively confirm that dual-ingredient LLINs containing chlorfenapyr can improve on the epidemiological effect of pyrethroid-only nets in contemporary Africa, where resistance to pyrethroids has become ubiquitous 3 Hemingway J Ranson H Magill A et al. Averting a malaria disaster: will insecticide resistance derail malaria control?. Lancet. 2016; 387: 1785-1788 Summary Full Text Full Text PDF PubMed Google Scholar over the 15 years since WHO embraced LLIN scale-up to universal coverage targets. 4 WHOInsecticide treated mosquito nets: a position statement. Global Malaria Programme; World Health Organization, Geneva2007 Google Scholar Efficacy of pyriproxyfen-pyrethroid long-lasting insecticidal nets (LLINs) and chlorfenapyr-pyrethroid LLINs compared with pyrethroid-only LLINs for malaria control in Benin: a cluster-randomised, superiority trialOver 2 years, chlorfenapyr-pyrethroid LLINs provided greater protection from malaria than pyrethroid-only LLINs in an area with pyrethroid-resistant mosquitoes. Pyriproxyfen-pyrethroid LLINs conferred protection similar to pyrethroid-only LLINs. These findings provide crucial second-trial evidence to enable WHO to make policy recommendations on these new LLIN classes. This study confirms the importance of chlorfenapyr as an LLIN treatment to control malaria in areas with pyrethroid-resistant vectors. Full-Text PDF Open Access