Background Aedes aegypti and Ae. albopictus are important vectors of infectious diseases, especially those caused by arboviruses such as dengue, chikungunya and Zika. Aedes aegypti is very well adapted to urban environments, whereas Ae. albopictus inhabits more rural settings. Pyrethroid resistance is widespread in these vectors, but limited data exist from the Southwest Pacific Region, especially from Melanesia. While Aedes vector ecology is well documented in Australia, where incursion of Ae. albopictus and pyrethroid resistance have so far been prevented, almost nothing is known about Aedes populations in neighbouring Papua New Guinea (PNG). With pyrethroid resistance documented in parts of Indonesia but not in Australia, it is important to determine the distribution of susceptible and resistant Aedes populations in this region. Methods The present study was aimed at assessing Aedes populations for insecticide resistance in Madang and Port Moresby, located on the north and south coasts of PNG, respectively. Mosquitoes were collected using ovitraps and reared in an insectary. Standard WHO bioassays using insecticide-treated filter papers were conducted on a total of 253 Ae. aegypti and 768 Ae. albopictus adult mosquitoes. Subsets of samples from both species (55 Ae. aegypti and 48 Ae. albopictus ) were screened for knockdown resistance mutations in the voltage-sensitive sodium channel ( Vssc ) gene, the target site of pyrethroid insecticides. Results High levels of resistance against pyrethroids were identified in Ae . aegypti from Madang and Port Moresby. Aedes albopictus exhibited susceptibility to pyrethroids, but moderate levels of resistance to DDT. Mutations associated with pyrethroid resistance were detected in all Ae . aegypti samples screened. Some genotypes found in the present study had been observed previously in Indonesia. No Vssc mutations associated with pyrethroid resistance were found in the Ae. albopictus samples. Conclusions To our knowledge, this is the first report of pyrethroid resistance in Ae . aegypti mosquitoes in PNG. Interestingly, usage of insecticides in PNG is low, apart from long-lasting insecticidal nets distributed for malaria control. Further investigations on how these resistant Ae . aegypti mosquito populations arose in P...

Population genomic approaches can characterize dispersal across a single generation through to many generations in the past, bridging the gap between individual movement and intergenerational gene flow. These approaches are particularly useful when investigating dispersal in recently altered systems, where they provide a way of inferring long‐distance dispersal between newly established populations and their interactions with existing populations. Human‐mediated biological invasions represent such altered systems which can be investigated with appropriate study designs and analyses. Here we apply temporally restricted sampling and a range of population genomic approaches to investigate dispersal in a 2004 invasion of Aedes albopictus (the Asian tiger mosquito) in the Torres Strait Islands (TSI) of Australia. We sampled mosquitoes from 13 TSI villages simultaneously and genotyped 373 mosquitoes at genome‐wide single nucleotide polymorphisms (SNPs): 331 from the TSI, 36 from Papua New Guinea (PNG) and four incursive mosquitoes detected in uninvaded regions. Within villages, spatial genetic structure varied substantially but overall displayed isolation by distance and a neighbourhood size of 232–577. Close kin dyads revealed recent movement between islands 31–203 km apart, and deep learning inferences showed incursive Ae. albopictus had travelled to uninvaded regions from both adjacent and nonadjacent islands. Private alleles and a co‐ancestry matrix indicated direct gene flow from PNG into nearby islands. Outlier analyses also detected four linked alleles introgressed from PNG, with the alleles surrounding 12 resistance‐associated cytochrome P450 genes. By treating dispersal as both an intergenerational process and a set of discrete events, we describe a highly interconnected invasive system.

Genetic monitoring of biological invasions provides an opportunity to identify past and ongoing patterns of dispersal and adaptation. Recent invasions need to be investigated with approaches that are unconfounded by the high regional coancestry and rapid temporal change typical of these systems. Here we investigate a recent invasion involving Aedes albopictus (the Asian tiger mosquito) in the Torres Strait Islands (TSI), Australia. This invasion began circa 2004, and in 2008 a cordon sanitaire was established to stop the invasion progressing south to the Australian mainland. We sampled mosquitoes from 13 TSI villages simultaneously and genotyped 373 mosquitoes at genome-wide single nucleotide polymorphisms (SNPs): 331 from the TSI, 36 from Papua New Guinea (PNG), and 4 incursive mosquitoes detected south of the cordon sanitaire. Within villages, spatial genetic structure varied substantially but overall displayed isolation by distance and a neighbourhood size of 232-577. Close kin dyads revealed recent movement between islands 31-203 km apart, and deep learning inference of incursion pathways showed Ae. albopictus had crossed the cordon sanitaire from both adjacent and non-adjacent islands. Private alleles and a coancestry matrix indicated direct gene flow from PNG into nearby islands. Outlier analyses also detected four linked alleles introgressed from PNG, with the alleles surrounding 12 resistance-associated cytochrome P450 genes. By treating dispersal as both an intergenerational process and a set of discrete events, we describe a highly interconnected invasive system. The movement of mosquitoes between distant islands and potential "genetic invasion" of insecticide resistance alleles are important management concerns.

Background Insecticide resistance (IR) monitoring is essential for evidence-based control of mosquito-borne diseases. While widespread pyrethroid resistance in Anopheles and Aedes species has been described in many countries, data for Papua New Guinea (PNG) are limited. Available data indicate that the local Anopheles populations in PNG remain pyrethroid-susceptible, making regular IR monitoring even more important. In addition, Aedes aegypti pyrethroid resistance has been described in PNG. Here, Anopheles and Aedes IR monitoring data generated from across PNG between 2017 and 2022 are presented. Methods Mosquito larvae were collected in larval habitat surveys and through ovitraps. Mosquitoes were reared to adults and tested using standard WHO susceptibility bioassays. DNA from a subset of Aedes mosquitoes was sequenced to analyse the voltage-sensitive sodium channel (Vssc) region for any resistance-related mutations. Results Approximately 20,000 adult female mosquitoes from nine PNG provinces were tested. Anopheles punctulatus sensu lato mosquitoes were susceptible to pyrethroids but there were signs of reduced mortality in some areas. Some Anopheles populations were also resistant to DDT. Tests also showed that Aedes. aegypti in PNG are resistant to pyrethroids and DDT and that there was also likelihood of bendiocarb resistance. A range of Vssc resistance mutations were identified. Aedesalbopictus were DDT resistant and were likely developing pyrethroid resistance, given a low frequency of Vssc mutations was observed. Conclusions Aedes aegypti is highly pyrethroid resistant and also shows signs of resistance against carbamates in PNG. Anopheles punctulatus s.l. and Ae. albopictus populations exhibit low levels of resistance against pyrethroids and DDT in some areas. Pyrethroid-only bed nets are currently the only programmatic vector control tool used in PNG. It is important to continue to monitor IR in PNG and develop proactive insecticide resistance management strategies in primary disease vectors to retain pyrethroid susceptibility especially in the malaria vectors for as long as possible. Graphic abstract

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.