- Design
- Three-arm cluster-randomised trial, 33 village clusters
- Population
- About 1,650 children aged 6 months to 9 years in Côte d'Ivoire
- Primary outcome
- Malaria incidence over 12 months
- Effect
- Chlorfenapyr IRR 0.57 (0.43–0.75); PBO IRR 0.72 (0.52–0.99)
In a cluster-randomised trial in Côte d'Ivoire, 33 clusters of villages received pyrethroid-only nets, nets adding piperonyl butoxide (PBO) or nets adding chlorfenapyr. One net was given for every two people, with home visits to help hang them. The primary outcome was malaria in children aged 6 months to 9 years over the following year.
Incidence was 1.11 cases per child-year with pyrethroid-only nets, 0.84 with PBO nets and 0.65 with chlorfenapyr nets. Against the control, the incidence rate ratio was 0.57 (95% CI 0.43–0.75) for chlorfenapyr and 0.72 (0.52–0.99) for PBO.
This adds West African trial data to earlier East African results pointing the same way, and reflects widespread pyrethroid resistance in mosquitoes. For India, where pyrethroid resistance is reported in several vector species, it is relevant to programme choices; whether these nets are procured here is a programme decision this study cannot settle.
- Recommend net use every night for children in malaria-endemic areas, whatever the net type.
- Where programmes offer a choice, chlorfenapyr-pyrethroid nets had the strongest effect in this trial.
- Ask about net use and condition when a child presents with repeated malaria.
- Report clusters of malaria in children to the district programme, as they may signal vector resistance.
Why it matters
Pyrethroid resistance is eroding the protection of the standard net that most programmes still distribute.
The statistics, in plain English
An IRR of 0.57 means 43% fewer malaria episodes. The PBO result's interval reaches 0.99, so that benefit is real but could be small.
Read the rest in the app
You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.
Scan to keep reading on your phone. No account needed to start.
Tomorrow morning, before your first patient
One edition a day for infectious diseases, written by the desk, every claim tied to its paper. Six minutes.
Get the app — free