Nigel W. Beebe

This article details a correction to: Craig, A., Panda, N., Palapu, R., Oku, G., Lifoia, C., Tatalu, J., Beebe, N., Kelly, G., Kama Jr, N., Iro’ofa, C. and Bugoro, H. (2024) ‘Citizen Science for Enhanced Dengue Vector Surveillance in Solomon Islands: A Methods Paper’, Citizen Science: Theory and Practice, 9(1), p. 3. DOI: https://doi.org/10.5334/cstp.679

The mosquito Anopheles farauti Laveran (1902) is a coastal malaria vector with a wide distribution throughout the Southwest Pacific. This species shows strong population genetic structure across Australia, New Guinea, and the Solomon Archipelago. In Queensland, Australia, its southern range limit has been the 21° latitude but, in 2023, it was detected in mosquito surveys 300 km further south, at 23° latitude. Additional collections undertaken in 2024 suggested that a population of An. farauti had established at this new southern limit. Sequencing of the mitochondrial cytochrome oxidase I (COI) gene revealed a single haplotype shared by all individuals, matching the nearest northern population. To investigate the suspected southward range expansion of An. farauti in Queensland, we performed machine learning ecological niche modeling using both MaxEnt and Random Forest approaches using historical collection data and WorldClim bioclimatic variables from that period. The model output indicated that the 23° latitude in Queensland is within the species’ projected suitability range and identified temperature-related factors as the primary drivers of its distribution in Queensland. We hypothesize that the prolonged La Niña (2020 to 2023), and the 2023 global marine heatwave, which drove warmer ocean and coastal ambient temperatures, facilitated the latitudinal expansion of An. farauti in Queensland.

Anopheles farauti (Laveran, 1902) is a major malaria vector in the Southwest Pacific region that is showing behavioural resistance to indoor insecticide-based vector control. This study utilised fluorescent dust-based mark release recapture (MRR) experiments to quantify the dispersal characteristics of An. farauti through a non-village natural ecosystem in tropical north Queensland, Australia. Good quality adult mosquitoes were collected from the field using a Fan Box Traps (FBT), with initial parity dissections of this material showing a daily survival rate of 0.68 during the wet season and 0.75 during the dry season. We then performed 51 separate mosquito MRR releases (19,889 marked An. farauti) during the wet and dry seasons between 2015 and 2017. Mosquito recaptures utilised three collection systems: human landing catches (HLC), FBTs and a bespoke mosquito catch barrier system (MCB). Most of the 308 (1.55%) marked An. farauti were recaptured by the MCB (78%), while the rest (22%) were recaptured by either our CO2 baited FBT and HLC. The longest flight distance was 3.51 km and An. farauti was estimated to travel approximately 73 m per day with HLCs collecting approximately 14 times more mosquitoes than the CO2 baited FBT. This data provides novel insights into the movement and survival of An. farauti in a natural ecosystem, suggesting longer flight distances than documented and different survival rates between the wet and dry seasons. These parameters will be important for modelling pathogen transmission dynamics, potential mosquito gene drive spread, and contribute to future malaria control strategies in the Southwest Pacific.

The Asian tiger mosquito, Aedes albopictus, is currently the most widespread invasive mosquito species in the world. It poses a significant threat to human health, as it is a vector for several arboviruses. We used a SNP chip to genotype 748 Ae. albopictus mosquitoes from 41 localities across Europe, 28 localities in the native range in Asia, and 4 in the Americas. Using multiple algorithms, we examined population genetic structure and differentiation within Europe and across our global dataset to gain insight into the origin of the invasive European populations. We also compared results from our SNP data to those obtained using genotypes from 11 microsatellite loci (N = 637 mosquitoes from 25 European localities) to explore how sampling effort and the type of genetic marker used may influence conclusions about Ae. albopictus population structure. While some analyses detected more than 20 clusters worldwide, we found mosquitoes could be grouped into 7 distinct genetic clusters, with most European populations originating in East Asia (Japan or China). Interestingly, some populations in Eastern Europe did not share genetic ancestry with any populations from the native range or Americas, indicating that these populations originated from areas not sampled in this study. The SNP and microsatellite datasets found similar patterns of genetic differentiation in Europe, but the microsatellite dataset could not detect the more subtle genetic structure revealed using SNPs. Overall, data from the SNP chip offered a higher resolution for detecting the genetic structure and the potential origins of invasions.

Background: The mosquito Culex annulirostris Skuse (Diptera: Culicidae) is an important arbovirus vector in Australasia. It is part of the Culex sitiens subgroup that also includes Cx. palpalis and Cx. sitiens. Single locus mitochondrial and nuclear DNA sequencing studies suggest that Cx. annulirostris consists of a complex of at least two species. We tested this hypothesis by analysing both nuclear microsatellite data and additional mitochondrial sequence data to describe the population genetics of Cx. annulirostris through Australia, Papua New Guinea (PNG) and the Solomon Archipelago. Methods: Twelve novel microsatellite markers for Cx. annulirostris were developed and used on over 500 individuals identified as Cx. annulirostris by molecular diagnostics. Ten of the 12 microsatellites then used for analysis using Discriminant Analysis of Principal Components, a Bayesian clustering software, STRUCTURE, along with estimates of Jost’s D statistic that is similar to F_ST but better suited to microsatellite data. Mitochondrial cytochrome oxidase I (COI) DNA sequence were also generated complementing previous work and analysed for sequence diversity (Haplotype diversity, Hd and Pi, π), Tadjima’s D, and pairwise F_ST between populations. An allele specific molecular diagnostic with an internal control was developed. Results: We confirm the existence of multiple genetically and geographically restricted populations. Within mainland Australia, our findings show that Cx. annulirostris consists of two genetically and geographically distinct populations. One population extends through northern Australia and into the south-east coast of Queensland and New South Wales (NSW). The second Australian population occurs through inland NSW, Victoria, South Australia, extending west to southern Western Australia. These two Australian populations show evidence of possible admixture in central Australia and far north Queensland. Australia’s Great Dividing Range that runs down southeast Australia presents a strong gene-flow barrier between these two populations which may be driven by climate, elevation or river basins. In PNG we find evidence of reproductive isolation between sympatric cryptic species occurring through PNG and Australia’s northern Cape York Peninsula. A PCR-based molecular diagnostic was developed to distinguish these two cryptic species. Conclusion: This study adds to the growing body of work suggesting that the taxon presently known as Cx. annulirostris now appears to consist of at least two cryptic species that co-occur in northern Australia and New Guinea and can be distinguished by a ITS1 PCR diagnostic. The Solomon Islands population may also represent a distinct species but in light its geographic isolation and lack of sympatry with other species would require further study. Additionally, the mitochondrial and nuclear DNA evidence of population structure between geographic regions within Australia appears latitudinal and elevational driven and may suggest an additional subspecies in that hybridise where they overlap. Graphical

Indoor insecticide applications are the primary tool for reducing malaria transmission in the Solomon Archipelago, a region where Anopheles farauti is the only common malaria vector. Due to the evolution of behavioural resistance in some An. farauti populations, these applications have become less effective. New malaria control interventions are therefore needed in this region, and gene-drives provide a promising new technology. In considering developing a population-specific (local) gene-drive in An. farauti, we detail the species’ population genetic structure using microsatellites and whole mitogenomes, finding many spatially confined populations both within and between landmasses. This strong population structure suggests that An. farauti would be a useful system for developing a population-specific, confinable gene-drive for field release, where private alleles can be used as Cas9 targets. Previous work on Anopheles gambiae has used the Cardinal gene for the development of a global population replacement gene-drive. We therefore also analyse the Cardinal gene to assess whether it may be a suitable target to engineer a gene-drive for the modification of local An. farauti populations. Despite the extensive population structure observed in An. farauti for microsatellites, only one remote island population from Vanuatu contained fixed and private alleles at the Cardinal locus. Nonetheless, this study provides an initial framework for further population genomic investigations to discover high-frequency private allele targets in localized An. farauti populations. This would enable the development of gene-drive strains for modifying localised populations with minimal chance of escape and may provide a low-risk route to field trial evaluations.

During preliminary mosquito surveys at Cowley Beach Training Area in north Queensland, Australia, it was found that the utility of the standard encephalitis virus surveillance (EVS) trap for collecting the malaria vector Anopheles farauti (Laveran) adults was compromised by the harsh tropical conditions. With the aim of increasing the survival rate of mosquitoes, we designed a downdraft fan box trap (FBT) that incorporated a screened fan at the bottom of the trap, so mosquitoes did not have to pass through a fan. The FBT was tested against the EVS and Centers for Disease Control (CDC) light traps, where mosquitoes do pass through a fan, and a nonpowered passive box trap (PBT). We conducted 4 trials to compare the quantity and survival of An. farauti and culicine mosquitoes were collected in these traps. Although not significant, the FBT collected more An. farauti than the EVS trap and PBT and significantly less An. farauti than the CDC light trap. However, the FBT improved on the CDC light trap in terms of the survival of An. farauti adults collected, with a significantly higher percentage alive in the FBT (74.6%) than in the CDC light trap (27.5%). Thus, although the FBT did not collect as many anophelines as the CDC, it proved to be superior to current trap systems for collecting large numbers of live and relatively undamaged mosquitoes. Therefore, it is recommended that FBTs be used for collecting An. farauti adults in northern Australia, especially when high survival and sample quality are important.

Arthropod-borne arboviral diseases—including dengue, Zika, and chikungunya—place a substantial burden on the health of populations, globally. Dengue alone is endemic in more than 100 countries and causes more than 96 million symptomatic cases and approximately 40,000 deaths annually. The recent surge in arboviral disease outbreaks, coupled with the World Health Organization’s newly published vector control guidelines, accentuates the imperative to understand the dispersion of disease-carrying mosquitoes across diverse spatial and temporal scales. However, traditional surveillance mechanisms often fall short because of workforce limitations, logistical complexities, jurisdictional boundaries, and budgetary constraints, especially in low- and low-middle-income countries. In this article, we systematically report the design, implementation, and iterative enhancement of a groundbreaking school-based citizen science initiative for augmenting mosquito surveillance in the Solomon Islands. Key reflections encompass the initiative’s role in supporting routine government-led disease vector monitoring, sustainability through integration and fostering participant engagement, and the amalgamation of citizen-collected data with government surveillance activities. The article also discusses the impact of the citizen science initiative with regard to the Solomon Islands’ pursuit of the Sustainable Development Goals. Our findings underscore the potential of citizen science methods to support and extend public health surveillance activities and to serve as a community-engagement-for-behaviour-change tool in resource-constrained contexts.