Linda Grigoraki

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 summary: Dengue, 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.

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.

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 transfluthrin’s efficacy in vector control interventions.

Insecticide resistance in mosquitoes, largely mediated by cytochrome P450 monooxygenases (CYPs), compromises the efficacy of vector control tools. In this study, chemically-wise selected natural extracts and compounds were screened for their CYP inhibition potential. Among 37 tested plant extracts and fractions, a decarboxylated acidic fraction of industrial hemp ( Cannabis sativa Linnaeus var. ‘Futura 75’) emerged as a promising hit, and phytochemical profiling identified cannabidiol (CBD) as its major component (IC₅₀ = 18.37 μM for CYP9K1). CBD was used as a scaffold to generate semisynthetic analogues; of which a piperazinyl analogue outperformed the natural scaffold demonstrating significantly greater potency (IC₅₀ = 2.50 μM for CYP9K1). Docking studies using homology-derived CYP9K1 models also supported a stronger binding affinity of the piperazinyl analogue relative to CBD. Toxicity assays using pyrethroid-resistant Anopheles gambiae Giles adults confirmed that neither CBD nor the piperazinyl analogue had intrinsic toxicity, yet the semisynthetic analogue significantly enhanced deltamethrin efficacy, showing a threefold synergistic effect. The safety profile of the cannabis compounds for non-target organisms was evaluated through human cell line cytotoxicity tests and bee toxicity assays, suggesting low non-target organism toxicity. Our study describes the identification of a plant-derived synergist lead with strong potential as an insecticide additive to combat metabolic resistance in malaria-transmitting mosquitoes.

Sustaining malaria control in Africa is imperilled by the rapid evolution of insecticide resistance in the major vector Anopheles gambiae. Although current genomic and transcriptomic approaches map known resistance alleles, they often lack predictive power to anticipate liabilities to new insecticides. We present a predictive functional chemoproteomic framework integrating competitive activity-based protein profiling with functional validation to identify enzyme-mediated resistance mechanisms before they arise in field populations. Applied to a susceptible Anopheles gambiae strain, fluorophosphonate probe profiling with pirimiphos-methyl-oxon, the bioactive metabolite of the organophosphate pirimiphos-methyl, revealed 18 active serine hydrolases. The carboxylesterase Coeae6g was selected for further functional analysis because it had previously been shown to be associated with pyrethroid and carbamate resistance. Functional assays confirmed Coeae6g confers resistance to pirimiphos-methyl and mediates cross-resistance to malathion, bendiocarb, and permethrin. These findings bridge genotype–phenotype gaps, align with emerging field genomic signatures, and establish a scalable framework to complement genomic surveillance and guide insecticide management in malaria vector control.

Purpose Cutaneous leishmaniasis (CL) is an endemic disease in Algeria. In southeastern regions, data concerning this infection are limited. Therefore, we aimed to assess the epidemiological status and identify the causative Leishmania spp. in El Meghaier province. Methods A retrospective study was conducted between 2023 and 2024. Diagnosis was confirmed by microscopic examination. For patients with positive results, clinical and demographic data were recorded. Molecular analysis was then carried out on DNA extracted from Giemsa-stained slides to identify the Leishmania species. Results In total 722 suspected cases were analyzed and only 118 were positive cases. A predominance in males was detected, and the most affected group age was [≥ 20] years old (N = 51; 43.2%). The statistical analysis showed strong association between age group and the positivity rate (X² = 37.59, P < 0.0001). Multiple lesions were observed in 72 patients (61.1%), most frequently located on the feet (76 cases; 64.4%) and hands (15 cases; 12.7%). Among the 118 microscopically positive samples, 53 were included for molecular analysis. Of these, 29 yielded a positive PCR amplification. Initial parasite typing was performed using PCR-ITS1, which detected Leishmania DNA in 14 samples (26.4%), predominantly L. major (92.8%). Samples negative by PCR-ITS1 were subsequently analyzed using nested ITS1-PCR, which identified 15 additional positives (38.5%). Sequencing of the amplified products confirmed the presence of L. major (66.6%) and L. infantum (13.3%). Conclusion These findings confirm, for the first time, the occurrence of both L. major and L. infantum in the study area. Further studies are needed to investigate the potential vectors and reservoirs involved.

Pyrethroid insecticide resistance in the primary malaria vector, Anopheles gambiae, poses a substantial challenge to ongoing control efforts in sub-Saharan Africa, where most malaria cases and deaths occur. To combat this challenge, newer chemicals, including pirimiphos-methyl (PM) are being used. To gain insight into how future resistance may develop to these compounds, a proactive chemical proteomics approach was developed using activity-based protein profiling (ABPP) in susceptible An. gambiae to identify enzymes interacting with pirimiphos-methyl (PM) and its toxic metabolite PMO. We discovered 18 serine hydrolases (SHs) as primary targets of PMO, including the carboxylesterase COEAE6G. Subsequent in vitro and in vivo validation confirmed that COEAE6G confers resistance to PM, as well as cross-resistance to malathion, permethrin and bendiocarb. This study underscores the utility of ABPP as a powerful tool for early detection of potential resistance markers, such as COEAE6G, enabling the development of effective resistance management strategies.

Background: A rapid, accurate method to identify and to age-grade mosquito populations would be a major advance in predicting the risk of pathogen transmission and evaluating the public health impact of vector control interventions. Whilst other spectrometric or transcriptomic methods show promise, current approaches rely on challenging morphological techniques or simple binary classifications that cannot identify the subset of the population old enough to be infectious. In this study, the ability of rapid evaporative ionisation mass spectrometry (REIMS) to identify the species and age of mosquitoes reared in the laboratory and derived from the wild was investigated. Results: The accuracy of REIMS in identifying morphologically identical species of the Anopheles gambiae complex exceeded 97% using principal component/linear discriminant analysis (PC-LDA) and 84% based on random forest analysis. Age separation into 3 different age categories (1 day, 5–6 days, 14–15 days) was achieved with 99% (PC-LDA) and 91% (random forest) accuracy. When tested on wild mosquitoes from the UK, REIMS data could determine the species and age of the specimens with accuracies of 91 and 90% respectively. Conclusions: The accuracy of REIMS to resolve the species and age of Anopheles mosquitoes is comparable to that achieved by infrared spectroscopy approaches. The processing time and ease of use represent significant advantages over current, dissection-based methods. Importantly, the accuracy was maintained when using wild mosquitoes reared under differing environmental conditions, and when mosquitoes were stored frozen or desiccated. This high throughput approach thus has potential to conduct rapid, real-time monitoring of vector populations, providing entomological evidence of the impact of alternative interventions.

Resistance to pyrethroid insecticides has evolved in Bactrocera oleae populations in Greece, threatening the efficacy of control interventions based on this insecticide class. Here we report the collection of populations from Crete with resistance levels reaching up to 331-folds, compared to susceptible laboratory strains and show that pyrethroid resistance is substantially suppressed by the PBO synergist, suggesting the involvement of detoxification enzymes. To identify specific candidate genes implicated in resistance, we performed comparative transcriptomic analysis, between the pyrethroid resistant populations from Crete and the susceptible laboratory strains, using both whole bodies and Malpighian tubules. Several genes were found differentially transcribed between resistant and susceptible flies in each comparison, with P450s being among the most highly over-expressed detoxification genes in pyrethroid resistant populations. Four of the over-expressed P450s ( Cyp6A61, Cyp6G6, Cyp4P6 and Cyp6G28 ) were recombinantly expressed in Escherichia coli and in vitro metabolism assays revealed that CYP6A61 is capable of metabolizing alpha-cypermethrin, while CYP6G6, CYP4P6 and CYP6G28 are capable of metabolizing deltamethrin. No metabolism of neonicotinoid insecticides was recorded. We further silenced CYP6G6 in vivo , via RNAi, which led to a small, but significant increase in deltamethrin toxicity. The study provides valuable information towards the development of molecular diagnostics and evidence-based insecticide resistance management strategies.

Background: A rapid, accurate method to identify and to age grade mosquito populations would be a major advance in predicting the risk of pathogen transmission and evaluating the public health impact of vector control interventions. Whilst other chemometric methods show promise, current approaches rely on challenging morphological techniques or simple binary classifications that cannot identify the subset of the population old enough to be infectious. In this study, the ability of Rapid Evaporative Ionisation Mass Spectrometry (REIMS) to identify the species, sex and age of mosquitoes reared in the laboratory and derived from the wild was investigated. Results: The accuracy of REIMS in identifying morphologically identical species of the Anopheles gambiae complex exceeded 97 % using principal component/linear discriminant analysis (PC-LDA) and 84 % based on random forest analysis. Age separation into 3 different age categories (1 d, 5-6 d, 14-15 d.) was achieved with 99 % (PC-LDA) and 94 % (random forest) accuracy, after including three species and storing samples at room temperature for up to 11 days. When tested on wild mosquitoes from the UK, REIMS data could determine the species and age of the specimens with accuracies of 91 and 90 % respectively. Conclusions: The accuracy of REIMS to resolve the species and age of Anopheles mosquitoes is comparable to that achieved by chemometric approaches. The processing time and ease of use represent significant advantages over current, dissection-based methods. Importantly the accuracy was maintained when using wild mosquitoes reared under differing environmental conditions, and when mosquitoes were stored frozen or desiccated. This high throughput approach thus has potential to conduct rapid, real- time monitoring of vector populations, providing entomological evidence of the impact of alternative interventions.