Effectiveness and durability of insecticide mixtures for pyrethroid resistance in sub-Saharan Africa

Abstract

Pyrethroid (PY) resistance is now rampant in most malaria-endemic countries, threatening to lower the effectiveness of standard long-lasting insecticide nets (LLINs) treated with PY only. Of the 88 countries that reported data on insecticide resistance monitoring to the WHO for the period 2010–2020, nearly all of them confirmed resistance to at least one insecticide in one malaria vector species.1 The next generation of LLINs that combine a PY with a synergist or another active ingredient promises to preserve the utility of LLINs in malaria prevention. There is evidence that these novel combinations are effective in reducing malaria incidence and achieving required entomological outcomes. Two recent landmark trials in Tanzania2 and Benin3 showed superiority of chlorfenapyr plus α cypermethrin compared with α cypermethrin either alone or in combination with other active ingredients. In the two studies, outcomes were reported at 24 months of follow-up. The long-term durability of this protection is critical, especially given that LLIN are intended to last a 3-year cycle in most national distribution cycles before they are replaced.