Biology subjects

Paine, M. J. I.

Publications and source records attributed to Paine, M. J. I..

5 recordsLinked to original sources

bioRxiv2026

Transcriptomic profiling reveals multiple mechanisms of insecticide resistance in Aedes aegypti from Angola

Control of arboviruses remains heavily reliant on insecticide-based vector control targeting adult Aedes aegypti, especially during outbreaks, but the effectiveness of these tools can be compromised by insecticide resistance. While the mechanisms underlying resistance have been widely studied in Latin American and South East Asian Ae. aegypti, knowledge from African populations is limited, particularly regarding metabolic resistance. To address this knowledge gap, we sequenced the transcriptomes of Ae. aegypti collected in Angola, from both unexposed individuals and survivors of exposure to the organophosphate fenitrothion, alongside two insecticide-susceptible laboratory reference strains. Many overexpressed genes belonged to the major detoxification enzyme families, including 96 cytochrome P450 monooxygenases (CYP450s), 18 glutathione S-transferases (GSTs), and 35 carboxylesterases, with multiple genes previously detected as upregulated in Latin American and Asian populations. These included frequently reported, functionally-validated, metabolic resistance genes such as CYP9J24, CYP9J26, and CYP6BB2. However, expression of auxiliary resistance families including hexamerins, heat shock proteins, and odorant binding proteins were linked to the insecticide resistance phenotype, whilst numerous cuticular genes differentiated the Angolan population from both susceptible laboratory strains. A novel candidate, CYP6AG7, that was overexpressed after fenitrothion exposure was experimentally validated, and surprisingly metabolised fenitrothion into its toxic oxon form, which it did not subsequently break down. The antioxidant response element (ARE) motif, to which the transcription factor Maf-S binds, was detected in all CYP450 overexpressed in the fenitrothion treatment suggesting their potential coordinated induction. Analysis of genetic differentiation revealed several resistance-linked genes under potential selection, and SNP screening identified both known and novel non-synonymous mutations in the voltage-gated sodium channel (VGSC) gene, the target for pyrethroid insecticides. This is the first RNAseq dataset for Ae. aegypti from Africa in the context of insecticide resistance, providing insight into the complexity of resistance mechanisms, including some shared, and others potentially novel, compared to better studied populations from other geographical regions. Author summaryDengue, chikungunya, yellow fever, and Zika are diseases that exert an increasing public health burden across Africa, primarily transmitted by the mosquito Aedes aegypti. We rely heavily on insecticides to control these mosquitoes, but populations are increasingly developing resistance, making control efforts less effective. While resistance mechanisms have been well-studied in the Americas and Asia, comparatively little is known about how African Ae. aegypti resist insecticides. We collected Ae. aegypti mosquitoes from Angola and compared the genes expressed in fenitrothion resistant versus susceptible mosquitoes using RNA sequencing. We identified overexpressed candidate insecticide resistance genes from the detoxification enzyme families that mosquitoes use to break down insecticides, including several genes previously linked to resistance in other regions. One novel enzyme identified, CYP6AG7, was experimentally validated and found to convert the pro-insecticide fenitrothion into its harmful form but interestingly not break down this harmful metabolite further. Mutations potentially linked to insecticide resistance were also detected in detoxification genes and insecticide target site genes. Our study provides the first comprehensive molecular characterization of insecticide resistance mechanisms in African Aedes aegypti, offering crucial data to inform vector control strategies and insecticide resistance management across the continent as dengue and related diseases continue to spread.

bioinformatics↗

bioRxiv2026

Synergistic action of different molecular mechanisms causes striking levels of insecticide resistance in the malaria vector Anopheles gambiae

Intensifying insecticide resistance in the malaria vector Anopheles gambiae poses a serious threat to the hard-won gains in reducing malaria deaths in Africa. The genetic basis of insecticide resistance is often complex, involving multiple genes and mutations. However, we still lack a clear understanding of how each mechanism contributes to overall resistance and how highly resistant phenotypes arise. In this study we generated a suite of transgenic An. gambiae strains carrying either individual mechanisms or combinations that frequently co-occur in nature. We show that co-overexpression of different classes of detoxification enzymes (CYP6P3, CYP6M2, CYP9K1, ABCH2, GSTE2 and COEAE6G), as well as the overexpression of detoxification enzymes in the presence of target site resistance mutations, can lead to substantially greater levels of resistance. Our findings suggest that increased resistance strength is a primary driver for selection of multi-mechanism resistance and are transformative for the scientific insight required to design robust molecular diagnostics for timely and reliable resistance detection in the field. We further show that P450 based resistance can constitute an Achilles heel for highly resistant mosquitoes, making them more vulnerable to pro-insecticides; compounds that typically require P450 activation. Our results advance our understanding of the mechanistic basis of insecticide resistance and have important implications for the design and implementation of effective and evidence-based resistance management strategies.

genetics↗

bioRxiv2026

Widely circulating pyrethroid resistance mechanisms reduce the efficacy of transfluthrin and pose a risk for mosquito-borne disease control with spatial emanators

Spatial emanators (SE) are a promising complement to existing tools for preventing mosquito transmitted diseases. In 2025, the WHO updated the WHO Guidelines for Malaria to include a conditional recommendation for the indoor use of prequalified SE products in malaria control. Both prequalified, and many other SE products contain the volatile pyrethroid transfluthrin, which shares the same target site as other (contact/solid phase) pyrethroids. Therefore, an assessment of cross resistance is critical to predict effectiveness against mosquitoes with existing pyrethroid resistance. Our results show that resistance to solid phase pyrethroids is correlated with resistance to transfluthrin in Anopheles and Aedes species. Moreover, commonly-selected resistance mechanisms including target site mutations and over-expression of P450 detoxification enzymes can confer resistance to transfluthrin. Furthermore, we show that resistant mosquitoes are less impacted by transfluthrin in terms of flight activation (irritancy) and reduced blood feeding inhibition, with the response correlating with resistance strength. Transfluthrin did not elicit an electroantennography response in Anopheles gambiae and surgically ablating mosquitoes antennae did not result in differences in flight activation upon transfluthrin exposure, suggesting the antennae are not required for transfluthrin to elicit behavioral responses. These results provide new insight regarding the mode of action of transfluthrin and the risk of resistance reducing transfluthrins efficacy in vector control interventions.

pharmacology and toxicology↗

bioRxiv2026

Generational selection, transcriptomics and functional characterization reveal the impact of environmental pollutants on the evolution of insecticide resistance in malaria vectors

Insecticide resistance is threatening malaria control. While the evolution and spread of resistance has been linked to scale-up in the distribution of public health insecticides, the role of environmental pollutants such as the polyaromatic hydrocarbons (PAHs) from industrial and agricultural use remains largely uncharacterized. The PAHs are potent ligands of the aryl hydrocarbon receptor (Ahr) transcription factors involved in the regulation of xenobiotic metabolizing enzymes, and potentially involved in insecticide resistance. Here, using field insecticide-resistant (Auyo) An. coluzzii and a laboratory-susceptible colony (Ngousso), we conducted a multi-generational selection experiment using naphthalene, fluorene and a mixture of both PAHs. After ten generations, the changes in susceptibility to insecticides were monitored using WHO bioassays and whole-transcriptome analysis (RNASeq) was conducted. Compared with the non-selected colony lines, PAH exposures significantly reduced pyrethroid and DDT resistance in the field population, suggesting fitness cost associated with established resistance. In contrast, Ngousso showed a significant increase in DDT resistance (p = 0.01) at the tenth generation. A significant increase in permethrin resistance was also observed at the seventh generation (p = 0.03). Several candidate genes from the major detoxification classes were overexpressed in the selected lines (including GSTe2, CYP6Z1, and CYP6P4); the most consistent were CYP6M4 and CYP4C27, as well as those from the Ahr pathway. Heterologous expression of CYP6M4 revealed its ability to metabolise pyrethroids, including permethrin, deltamethrin, and -cypermethrin, as well as PAHs (naphthalene and fluorene). These findings establish the role of environmental pollutants as additional drivers of metabolic insecticide resistance in An, coluzzii.

ecology↗

bioRxiv2025

Significant variations in tolerance to clothianidin and pirimiphos-methyl in Anopheles gambiae and Anopheles funestus populations during a dramatic malaria resurgence despite sustained indoor residual spraying in Uganda

A dramatic malaria resurgence occurred in areas of Uganda between 2020 and 2022 coincident with the switch to clothianidin-based formulations for indoor residual spraying. During the resurgence, Anopheles funestus numbers increased but when an alternative insecticide, pirimiphos methyl, was reintroduced in 2023, both malaria cases and An. funestus mosquito density fell. In this study, we investigated possible causes of the resurgence by assessing; 1) whether sufficient quantities of insecticide were sprayed; 2) the residual insecticide bioefficacy against wild mosquitoes and; 3) the insecticide susceptibility of vector populations using standard test tube assays and wall cone assays. In 2023, after adjusting for extraction efficiency, 70-80% of the houses had optimal residual concentrations of insecticides (clothianidin >0.3g/m2; pirimiphos methyl >0.5g/m2) with significant variations between sampling rounds and wall types. Mud walls had the lowest residual concentration of insecticides, and the lowest observed mortality in wall cone assays, compared to fired bricks with plaster/cement/paint. In the studies of residual bio efficacy, by World Health Organization (WHO) definitions, An. funestus showed resistance to clothianidin (<80% mortality) up to 11 months and susceptibility to pirimiphos methyl (>90% mortality) when exposed to wall surfaces up to 7 months post-spray. In WHO tube tests, variations were observed in susceptibility to clothianidin in An. funestus populations using dose- and time-response assays (80-98% mortality). In 2022, An. gambiae was largely susceptible to the clothianidin-based formulation Sumishield (85-90% mortality) although the levels dropped slightly in 2023 (60-85% mortality) mainly in mud and pole houses. In contrast, An. gambiae was mildly susceptible to the pirimiphos methyl-based formulation Actellic ([~]80% mortality) and time response assays showed An. gambiae populations had very low knockdown and mortality at lower exposure time compared to An. funestus. Regression models showed a positive association between residual insecticide concentration (RIC) and mortality in houses sprayed with Sumishield but not Actellic houses. Despite the possible variations observed in spray operations, the study revealed that An. funestus exhibited a higher tolerance to clothianidin-based formulations compared to An. gambiae, and this might have driven the malaria resurgence observed in Uganda. However, there are signals of An. gambiae resistance to pirimiphos-methyl which will require further investigation and monitoring.

zoology↗