Characterization of sodium channel mutations in the dengue vector mosquitoes Aedes aegypti and Aedes albopictus within the context of ongoing Wolbachia releases in Kuala Lumpur, Malaysia

Specific sodium channel gene mutations confer target site resistance to pyrethroid insecticides in mosquitoes and other insects. In Aedes mosquito species, multiple mutations that contribute to resistance vary in their importance around the world. Here, we characterize voltage sensitive sodium channel (Vssc) mutations in populations of Aedesaegypti from Kuala Lumpur, Malaysia, and look at their persistence in populations affected by ongoing Wolbachia releases (a dengue control measure). We also describe a Vssc mutation in Aedesalbopictus (F1534L) found for the first time in Malaysia. We show that there are three predominant Vssc haplotypes in Aedesaegypti in this region, which all persist with regular backcrossing, thereby maintaining the original genetic composition of the populations. We identify changes in genotype frequency in closed populations of Ae. aegypti maintained for multiple generations in laboratory culture, suggesting different fitness costs associated with the genotypes, some of which may be associated with the sex of the mosquito. Following population replacement of Ae. aegypti by Wolbachia in the target area, however, we find that the Vssc mutations have persisted at pre-release levels. Mosquitoes in two genotype classes demonstrate a type I pyrethroid resistance advantage over wildtype mosquitoes when exposed to 0.25% permethrin. This resistance advantage is even more pronounced with a type II pyrethroid, deltamethrin (0.03%). The results point to the importance of these mutations in pyrethroid resistance in mosquito populations and the need for regular backcrossing with male mosquitoes from the field to maintain similarity of genetic background and population integrity during Wolbachia releases

Establishment of Wolbachia strain wAlbB in Malaysian populations of Aedes aegypti for dengue control

Dengue has enormous health impacts globally. A novel approach to decrease dengue incidence involves the introduction of Wolbachia endosymbionts that block dengue virus transmission into populations of the primary vector mosquito, Aedes aegypti. The wMel Wolbachia strain has previously been trialed in open releases of Ae. aegypti; however, the wAlbB strain has been shown to maintain higher density than wMel at high larval rearing temperatures. Releases of Ae. aegypti mosquitoes carrying wAlbB were carried out in 6 diverse sites in greater Kuala Lumpur, Malaysia, with high endemic dengue transmission. The strain was successfully established and maintained at very high population frequency at some sites or persisted with additional releases following fluctuations at other sites. Based on passive case monitoring, reduced human dengue incidence was observed in the release sites when compared to control sites. The wAlbB strain of Wolbachia provides a promising option as a tool for dengue control, particularly in very hot climates

Wolbachia screen of female Aedes aegypti wMelPop-CLA strain in antibiotic trial

Wolbachia-screening data from female Aedes aegypti infected with wMelPop-CLA (McMeniman et al. 2009) strain. High Resolution Melt Assay on Roche LightCycler480

Wolbachia screen of Aedes aegypti wAlbB females in antibiotic trial

Wolbachia-screening data from female Aedes aegypti infected with wAlbB (Xi et al. 2005) strain in antibiotic trial. High Resolution Melt Assay on Roche LightCycler480

Data from: Environmental concentrations of antibiotics may diminish Wolbachia infections in Aedes aegypti (Diptera: Culicidae)

Wolbachia-infected Aedes aegypti (L.) mosquitoes for control of dengue transmission are being released experimentally in tropical regions of Australia, south-east Asia, and South America. To become established, the Wolbachia Hertig (Rickettsiales: Rickettsiaceae) strains used must induce expression of cytoplasmic incompatibility (CI) in matings between infected males and uninfected females so that infected females have a reproductive advantage, which will drive the infection through field populations. Wolbachia is a Rickettsia-like alphaproteobacterium which can be affected by tetracycline antibiotics. We investigated whether exposure of Wolbachia-infected mosquitoes to chlortetracycline at environmentally relevant levels during their aquatic development resulted in loss or reduction of infection in three strains, wAlbB, wMel, and wMelPop. Wolbachia density was reduced for all three strains at the tested chlortetracycline concentrations of 5 and 50 µg/liter. Two of the strains, wMel and wMelPop, showed a breakdown in CI. The wAlbB strain maintained CI and may be useful at breeding sites where tetracycline contamination has occurred. This may include drier regions where Ae. aegypti can utilize subterranean water sources and septic tanks as breeding sites

Antibiotic trial development data for Aedes aegypti

Count data from Aedes aegypti antibiotic trial - cumulative pupae counts, number of emerged adults from each treatment

Antibiotic trial male Aedes aegypti data - ddPCR for Wolbachia

Male Aedes aegypti from four lines in antibiotic trial. Wolbachia-screening data obtained via QX100™ Droplet Digital™ PCR (ddPCR™) system (Bio-Rad Laboratories Pty., Ltd. Hercules, CA USA) with a hydrolysis probe assay (PrimePCR™, Bio-Rad Laboratories, Inc. Cat. No. 10031261)

Data from: A comprehensive assessment of inbreeding and laboratory adaptation in Aedes aegypti mosquitoes

Modified Aedes aegypti mosquitoes reared in laboratories are being released around the world to control wild mosquito populations and the diseases they transmit. Several efforts have failed due to poor competitiveness of the released mosquitoes. We hypothesized that colonized mosquito populations could suffer from inbreeding depression and adapt to laboratory conditions, reducing their performance in the field. We established replicate populations of Ae. aegypti mosquitoes collected from Queensland, Australia, and maintained them in the laboratory for twelve generations at different census sizes. Mosquito colonies maintained at small census sizes (≤100 individuals) suffered from inbreeding depression due to low effective population sizes which were only 25% of the census size as estimated by SNP markers. Populations that underwent full-sib mating for 9 consecutive generations had greatly reduced performance across all traits measured. We compared the established laboratory populations with their ancestral population resurrected from quiescent eggs for evidence of laboratory adaptation. The overall performance of laboratory populations maintained at a large census size (400 individuals) increased, potentially reflecting adaptation to artificial rearing conditions. However most individual traits were unaffected, and patterns of adaptation were not consistent across populations. Differences between replicate populations may indicate that founder effects and drift affect experimental outcomes. Though we find limited evidence of laboratory adaptation, mosquitoes maintained at low population sizes can clearly suffer fitness costs, compromising the success of “rear and release” strategies for arbovirus control

Pooled ddRADseq library_R2.7z

Raw sequencing data archived here represents raw Read1 and Read2 paired-end Illumina data from a single sequencing run. Original R1 and R2 *.fastq files have been compressed using 7Zip (available at https://www.7-zip.org/download.html)

Wolbachia screen of Aedes aegypti wMel females from antibiotic trial

Wolbachia-screening data from female Aedes aegypti infected with wMel (Walker et al. 2011) strain. High Resolution Melt Assay on Roche LightCycler480