Background: Insecticide resistance monitoring is key for evidence-based control of Anopheles and Aedes disease vectors in particular, since the vast majority of insecticide-based public health adult vector control tools are reliant on pyrethroids. While widespread pyrethroid resistance in Anopheles species and Aedes aegypti has been described in many countries, data for Papua New Guinea are scarce. Available data indicate the local Anopheles populations remain pyrethroid-susceptible, making regular insecticide resistance monitoring even more important. Knowledge on Aedes insecticide resistance in PNG is very limited, however, high levels of Aedes aegypti resistance have been described. Here we present insecticide resistance monitoring data from across PNG generated between 2017 and 2022. Methods: Mosquito larvae were collected in larval habitat surveys and through ovitraps. Mosquitoes were reared to adults and subjected to insecticide treated filter papers in WHO insecticide susceptibility bioassays. Subsets of Aedes mosquitoes were subjected to sequencing of the voltage-sensitive sodium channel (Vssc) region to identify resistance mutations. Results: Overall, nearly 20,000 adult female mosquitoes from nine PNG provinces were used in the tests. We show that in general, Anopheline mosquitoes in PNG remain susceptible to pyrethroids but with worrying signs of reduced 24 h mortality in some areas. In addition, some Anopheles populations were indicated to be resistant against DDT. We show that Ae. aegypti in PNG are pyrethroid, DDT and likely bendiocarb resistant with a range of Vssc resistance mutations identified. We demonstrate that Ae. albopictus is DDT resistant and is likely developing pyrethroid resistance based on finding a low frequency of Vssc mutations. Conclusion: This study represents the largest overview of insecticide resistance in PNG. While Ae. aegypti is highly pyrethroid resistant, the Anopheline and Ae. albopictus populations exhibit low levels of resistance in some areas. It is important to continue to monitor insecticide resistance in PNG and prepare for the widespread emergence of pyrethroid resistance in major disease vectors.

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