On 11 June 2026 WHO updated insecticide-resistance monitoring: discriminating concentrations for two indoor residual-spray active ingredients, broflanilide and isocycloseram, and how to read susceptibility to chlorfenapyr.
Main points
- WHO said a multi-centre study was set up to determine discriminating concentrations for broflanilide and isocycloseram (Praulins and colleagues, a preprint on bioRxiv). The test is the WHO bottle bioassay: bottles dried for 24 hours, mosquitoes exposed for 1 hour, held, and read after 24 hours.
- For Aedes aegypti, with acetone and MERO at 1,500 ppm: broflanilide 10 µg/bottle, isocycloseram 15 µg/bottle.
- For Anopheles, acetone and MERO at 800 ppm. Broflanilide: An. gambiae 10 µg/bottle, An. funestus 15, An. stephensi 25. Isocycloseram: An. gambiae 30, An. funestus 60, An. stephensi 50.
- Susceptibility to chlorfenapyr is confirmed when mortality is 98% or higher in a test, and the susceptible control also dies at 98% or higher at the same time point in that test. These levels are to be included in a later update of the resistance-monitoring manual (WHO 2022).
VPMA’s note
These are thresholds for a laboratory to read resistance. They are not a field spray dose and not a recommendation to change the chemical in use. Do not mix them with CDC bottle thresholds or WHO tube thresholds for other active ingredients.
- Source
- World Health Organization (WHO)
- Published
- 11 June 2026
- Section
- Research · Chemicals, Insects
Editorial note: This is a short summary and comment by VPMA, not a full copy. The original text and copyright belong to the source cited. The illustration is symbolic and is not a photograph of the event.
Source: Tổ chức Y tế Thế giới (WHO) (summarised in English by VPMA). Read the Vietnamese page.