Spatial Repellents Research Articles

COMPARATIVE BEHAVIORAL RESPONSES OF Β-CARYOPHYLLENE AGAINST ANOPHELES MOSQUITO SPECIES, POTENTIAL VECTORS OF MALARIA IN THAILAND

ABSTRACT Insecticide-based mosquito control poses risks of environmental harm and resistance development. As a safer alternative, β-caryophyllene, a nontoxic compound derived from plants, was evaluated as a safer alternative for its excito-repellency against four Anopheles mosquito species. Using an excito-repellency assay, An. minimus showed the highest escape rates (100%) at 2.5% (contact) and 5% (noncontact) concentrations. An. harrisoni also exhibited strong responses at 7.5%, with 94.34% (contact) and 72.73% (noncontact) escape. In contrast, An. epiroticus showed minimal response (12–25.42%). Significant differences between contact and noncontact trials were noted only in An. minimus and An. harrisoni. No knockdown or mortality occurred. Kaplan-Meier analysis revealed faster escape in contact conditions, especially for An. minimus. Log-rank tests confirmed dose-dependent repellency effects. These findings suggest β-caryophyllene has promising potential as a natural spatial repellent against malaria vectors.

Initial community response to a novel spatial repellent for malaria prevention in Busia County, Kenya

BackgroundMalaria transmission in Africa significantly declined between 2005 and 2015 due to widespread distribution of insecticide-treated nets (ITNs). However, since 2015, transmission has increased due to insecticide resistance and biting at times when people are not using ITNs. Spatial repellents (SRs) may help address these challenges. A double-blinded cluster-randomized controlled trial (cRCT) in Busia County, Kenya, reported that Mosquito Shield™, a transfluthrin-based SR, reduced malaria infections by 33.4% during interim analysis and 32.7% by the end of the study, among children aged 6 months to 10 years. Understanding community responses to SRs is critical for their successful deployment and long-term use. This paper reports the initial community response to MosquitoShield™ as part of the Advancing Evidence for the Global Implementation of Spatial Repellents (AEGIS) project.MethodsLongitudinal qualitative data were collected from 30 households participating in the cRCT, using modified trials of improved practices (TIPs) to assess participants’ perceptions of MosquitoShield’s utility, efficacy, appearance, and user experience with monthly product replacement. This analysis focuses on initial responses recorded one week and two months post-installation. The data were analysed using thematic coding, with researchers blinded to trial arm assignment.ResultsThe participants reported a positive initial response to the SR, with a significant perceived reduction in mosquito density and activity. Some also reported concerns about the product’s effectiveness over time and its comparison with existing mosquito control methods, particularly after first replacement. Participants highlighted their perception that the SR provided continuous protection in contrast with the situational protection offered by ITNs. Improvement suggestions included modified installation methods plus a longer-lasting product that protected more space.ConclusionMosquitoShield™ shows potential as a promising malaria prevention tool among communities in Busia County, Kenya. Incorporating user feedback and addressing concerns about product installation, duration, and coverage are crucial for successful implementation. Future research exploring community perceptions, cultural factors and behavioural responses related to long-term acceptability and the impact of SRs on malaria transmission will be crucial to ensure effective SR implementation.

Enhancing protection against vector-borne diseases in forcibly displaced communities: evaluating the efficacy of spatial repellents for cutaneous leishmaniasis control in North-East Syria

BackgroundIn Syria, during the 14 years after the outbreak of civil war, 16.7 million people have been forced to flee their homes, of which 7.2 million remain internally displaced in 2025. Breakdown in waste management caused by aerial bombardment has created ideal conditions for cutaneous leishmaniasis (CL) transmission, vectored by phlebotomine sandflies. Displaced populations reside in flimsy shelters where conventional vector control tools are operationally unfeasible. A small, lightweight, portable transfluthrin-based spatial repellent (Mosquito Shield™) has been developed which may circumvent some of these logistical issues and provide improved protection from vector-borne diseases in harsh environments.MethodsA two-arm, non-randomised cluster trial was undertaken in Ar-Raqqa governorate, North-East Syria, to evaluate the efficacy of Mosquito Shield™ in reducing CL case incidence and sandfly densities in shelters. Weekly epidemiological monitoring was performed by MENTOR Initiative mobile clinics and supported health facilities. Entomological monitoring was performed fortnightly using indoor US Centers for Disease Control and Prevention light traps in 40 randomly selected households per study arm. Phlebotomine sandflies were morphologically identified; a subset were analysed for molecular species confirmation, blood-meal preferences and pyrethroid resistance. Household surveys and focus group discussions were used to assess intervention feasibility, acceptability and uptake.ResultsAssuming a 2-month diagnosis cut-off, the CL incidence rate was 9.9 and 5.2 per 1000 in the control and intervention arms, respectively; Mosquito Shield™ demonstrated a significant impact on rate of CL infection in all ages (incidence rate ratio; IRR: 0.52 [95% CI: 0.37–0.74]; p < 0.0001). Mosquito Shield™ demonstrated a significant impact on all female sandfly density (IRR: 0.22 [95% CI: 0.14–0.33]; p < 0.0001) and blood-fed female sandfly density (IRR: 0.21 [95% CI: 0.11–0.40]; p < 0.0001). Mosquito Shield™ was received positively and perceived to be easy to use, to protect from CL, sandflies and other insect bites and required minimal behaviour change.ConclusionsTrial findings provide the first demonstrable impact of spatial repellents on CL transmission, strengthening the growing evidence basis for the effectiveness of this intervention against multiple vector species and their associated pathogens. Study results strongly support the deployment of spatial repellents to control CL in humanitarian crises.Trial registrationClinicalTrials.gov, NCT06917040.

SC Johnson Guardian™ spatial repellent shows 1-year efficacy against wild pyrethroid-resistant Anopheles arabiensis, with a similar blood-feeding inhibition efficacy to Mosquito Shield™ in a Tanzanian experimental hut trial

BackgroundSpatial repellents (SRs) that passively emanate airborne concentrations of an active ingredient within a space disrupt mosquito behaviors to reduce human-vector contact. A clinical trial of SC Johnson’s Mosquito Shield™ (Mosquito Shield) demonstrated a 33% protective efficacy against malaria in Kenya. Mosquito Shield lasts for 1 month, but a longer duration product is needed for malaria control programs. SC Johnson’s Guardian™ (Guardian) is designed to provide longer continuous protection from disease-transmitting mosquitoes.MethodsWe conducted experimental hut trials to i) evaluate the efficacy of Guardian over 12 months (between May 2022 and May 2023) and ii) assess the potential public health utility of Guardian by comparing it to Mosquito Shield over 1 month (midway through the Guardian evaluation in November 2022) against wild pyrethroid-resistant malaria vector mosquitoes. The primary endpoint was the number of blood-fed Anopheles arabiensis, while secondary endpoints were the proportion of dead An. arabiensis at 24 hours and the proportion of blood-fed mosquitoes. For Guardian, the number of mosquito landings was also evaluated by human landing catch, a method routinely used in community or implementation studies.ResultsOver 12 months of continuous use, Guardian reduced the number of An. arabiensis blood-feeding by 82.7% [95% confidence interval (78.5%–86.1%)] and landing by 65.1% (59.4%– 70.0%). Guardian also induced 20.1% mortality (18.4%–21.8%). Guardian was found to be superior to Mosquito Shield in reducing the number of blood-fed An. arabiensis with similar proportions of blood-fed and dead mosquitoes at 24 hours.ConclusionGuardian was effective in reducing blood-feeding and landing of wild pyrethroid-resistant malaria vectors for 12 months and shows superior protective efficacy compared to Mosquito Shield in reducing the overall number of blood-feeding mosquitoes. Experimental hut studies are suitable for comparative evaluations of new spatial repellent products because they precisely estimate entomological endpoints elicited by spatial repellents known to significantly impact vectorial capacity and disease transmission.

Oviposition deterrent as a component of a push-pull management approach for Drosophila suzukii.

Drosophila suzukii, spotted-wing drosophila, is a major pest of berries and cherries worldwide that attacks fruits at the ripening stage shortly before harvest. Recently, a mixture of octanoic acid and decanoic acid was developed as a 2-component oviposition deterrent (2c) as an alternative to spatial repellents for the behavioral control of spotted-wing drosophila infestation. In this study, we evaluated the efficacy of the oviposition deterrent as a "push" component in a spotted-wing drosophila push-pull, in combination with a previously identified 4-component spotted-wing drosophila attractant (4c) as the "pull", and compared the effect of push (2c), pull (4c), push-pull (2c + 4c), and control on spotted-wing drosophila oviposition in the laboratory and field. In both laboratory choice and no-choice bioassays using raspberry agar as an oviposition substrate, the pull treatment alone (4c) did not result in oviposition reduction. In contrast, both 2c and 2c + 4c resulted in a similar level of reduction in spotted-wing drosophila oviposition compared to control, indicating limited efficacy of the 4c as a pull as tested in this study. Similar results were also observed in the field, where fewer spotted-wing drosophila pupae emerged from raspberries from the 2c or 2c + 4c treated raspberries compared to untreated control, for both ripening field raspberries and store-bought sentinel raspberries. No significant difference in spotted-wing drosophila infestation was observed between control and 4c treatment. Our results suggest that an oviposition deterrent has a potential use as a push component in spotted-wing drosophila push-pull.

Investigation of Essential Oil from Cumin (Cuminum cyminum) Seeds and Selected Terpenes as Repellents Against Adult Female Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae) Sand Flies.

Leishmaniasis, a parasitic disease transmitted by sand flies, poses a significant global health threat. Chemical repellents and insecticides are widely used for protection, but prolonged use has led to resistance, reduced efficacy, and environmental concerns, emphasizing the need for new repellent compounds, ideally from sustainable sources. This study investigated the chemical composition and repellent properties of cumin seed essential oil (EO) from Greece against Phlebotomus papatasi. Gas chromatography-mass spectrometry (GC-MS) identified five major constituents, including cumin aldehyde (27.0%), β-pinene (11.4%), and γ-terpinene (10.8%). In addition to cumin seed EO and its major constituents, octanol, and 1-octen-3-ol were tested for comparison, along with transfluthrin and DEET as standard repellents. Using a static air repellency bioassay, cumin seed EO, cumin aldehyde, and octanol exhibited strong spatial repellency (EC50 of 0.34, 0.07, and 0.60 μg/cm2 respectively) comparable to transfluthrin (EC50 of 0.04 μg/cm2) at 1 h, and contact repellency, both lasting up to 3 h. This is the first study to evaluate cumin seed EO and cumin aldehyde against sand flies, highlighting their potential as alternatives to conventional repellents. Further research is needed to explore their applicability in vector control strategies.

Molecular markers of reduced behavioral sensitivity to transfluthrin in Anopheles gambiae s.s. from Western Kenya

BackgroundThe emergence and spread of insecticide resistance in malaria vectors threatens vector control efforts. The use of spatial repellent products (SR) containing volatile insecticides such as transfluthrin offer a promising complementary strategy to current vector control tools. Here, we employed whole transcriptome analysis to investigate the molecular mechanisms underlying reduced behavioral sensitivity to transfluthrin in two pyrethroid-resistant populations of Anopheles gambiae s.s. Using a high-throughput screening system (HITSS), we evaluated 600 mosquitoes across three populations (Bungoma field population, the insecticide-resistant Pimperena lab strain, and the susceptible Kisumu lab strain), categorizing them as responders or non-responders based on their SR avoidance behavior. Non-responders exhibited significantly reduced repellency (spatial activity index < 0.1) at standard transfluthrin concentrations (0.0025 μg/ml).ResultsRNA sequencing of pooled samples (n = 10 mosquitoes per pool, three replicates per condition) revealed distinct transcriptional profiles between responders and non-responders. The cytochrome P450 gene CYP12F12 showed significant overexpression (FC = 36.6389, p < 0.001) in Bungoma non-responders, suggesting its potential role in transfluthrin metabolism. Additionally, we observed population-specific distributions of voltage-gated sodium channel mutations, with fixation of kdr L995F in Pimperena non-responders and elevated frequency (80–100%) of kdr L995S in Bungoma non-responders.ConclusionsThese findings provide the first molecular evidence linking both metabolic and target-site mechanisms to reduced behavioral sensitivity to transfluthrin in malaria vectors. The co-occurrence of CYP12F12 overexpression and kdr mutations suggests multiple resistance mechanisms may affect spatial repellent efficacy, highlighting the need for resistance monitoring in spatial repellent deployment strategies.Graphical

Novel Synergized Aryl Amide Spatial Repellent Significantly Reduces Collections of Aedes Albopictus in a Wooded North Florida Suburban Residential Yard

ABSTRACT Aedes albopictus is a significant vector of dengue and chikungunya to humans. Increasing evidence of resistance of this species coupled with their use of cryptic habitat pose significant obstacles to effective control. We investigated efficacy against natural populations of Ae. albopictus of a novel aryl amide spatial repellent (Compound 53) and a novel synergist (trans-chrysanthemic acid; TCA) that in previous work had shown high capability to repel Ae. aegypti in a laboratory environment. We observed a significant reduction in collections of Ae. albopictus in a wooded north Florida residential yard when synergized Compound 53/TCA was present. We conclude that this novel synergized aryl amide demonstrates potential and should be investigated further.

VECTOR CONTROL STRATEGIES FOR TROPICAL PARASITIC DISEASES

Tropical parasitic diseases, such as malaria, dengue fever, chikungunya, lymphatic filariasis, schistosomiasis, and leishmaniasis, are a significant global health issue, particularly in tropical and subtropical countries.but these diseases disproportionately affect vulnerable populations, such as the poor, rural, or marginalized, who lack access to healthcare, clean water, and sanitation. Despite decades of research and control activities, tropical parasitic diseases persist, highlighting the need for sustainable and effective solutions. Vector control has been a vital component of the global fight against these diseases, targeting the vectors of transmission to decrease infection prevalence. However, traditional tools like insecticides, indoor residual spraying, and environmental management have been progressively undermined by obstacles like insecticide resistance, vector behavioral changes, environmental determinants, and logistical hurdles. New strategies, such as genetically modified mosquitoes, Wolbachia-infected mosquitoes, and spatial repellents, have offered new options for disease management. Integrated vector management (IVM) approaches have become increasingly recognized as a more sustainable and comprehensive means of vector control. This study discusses the changing face of traditional and new vector control methods for tropical parasitic diseases, assessing their effectiveness, scalability, and sustainability. The ultimate aim is to decrease the burden of tropical parasitic infections, achieve better health outcomes, and progress towards global health milestones.

VECTOR CONTROL STRATEGIES FOR TROPICAL PARASITIC DISEASES

Tropical parasitic diseases, such as malaria, dengue fever, chikungunya, lymphatic filariasis, schistosomiasis, and leishmaniasis, are a significant global health issue, particularly in tropical and subtropical countries.but these diseases disproportionately affect vulnerable populations, such as the poor, rural, or marginalized, who lack access to healthcare, clean water, and sanitation. Despite decades of research and control activities, tropical parasitic diseases persist, highlighting the need for sustainable and effective solutions. Vector control has been a vital component of the global fight against these diseases, targeting the vectors of transmission to decrease infection prevalence. However, traditional tools like insecticides, indoor residual spraying, and environmental management have been progressively undermined by obstacles like insecticide resistance, vector behavioral changes, environmental determinants, and logistical hurdles. New strategies, such as genetically modified mosquitoes, Wolbachia-infected mosquitoes, and spatial repellents, have offered new options for disease management. Integrated vector management (IVM) approaches have become increasingly recognized as a more sustainable and comprehensive means of vector control. This study discusses the changing face of traditional and new vector control methods for tropical parasitic diseases, assessing their effectiveness, scalability, and sustainability. The ultimate aim is to decrease the burden of tropical parasitic infections, achieve better health outcomes, and progress towards global health milestones.

Gaps in protection to Anopheles exposure in high malaria endemic regencies of Papua Province, Indonesia.

Malaria in eastern Indonesia remains high despite significant reductions and local elimination in other parts of the country. Malaria control activities that have been implemented include early diagnosis and prompt treatment, provision of Long-lasting insecticide-treated nets (LLINs), and indoor residual spraying (IRS). To expedite malaria elimination in this region, a rapid entomological assessment combined with human behaviour observations (HBOs) were conducted in eight high malaria endemic regencies in Papua Province, Indonesia. The present study focuses on identifying gaps in protection against mosquito biting indoors and outdoors that may contribute to the sustained transmission and persistently high endemicity. This research was carried out alongside a rapid entomological assessment across 48 villages in all eight regencies over 150 days. It included human landing catches (HLCs) of adult mosquitoes, with human behavior recorded through direct observation during these HLCs. The human behavior observation (HBO) data concentrated on temporal (overnight) and spatial (domestic or peri-domestic) presence, in addition to bed net usage and sleeping patterns. Household surveys, which were also conducted during the entomological collections, gathered information on house construction materials, mosquito bite prevention practices, livestock presence, and other intervention usage. Behavior-adjusted exposure for unprotected individuals in 14 villages shows gaps in protection of ITN usage before sleeping. Meanwhile, an analysis of household survey in each regency identified several gaps in protection against mosquito bites. Human exposure to mosquito bites was driven by ITN usage, IRS coverage, indoor presence without protection prior to sleeping, the absence of mosquito house screens, and outdoor presence without protection. The data reveals several gaps in protection against mosquito exposure across all eight regencies of Papua assessed. There is a need to optimize indoor interventions, as current vector control efforts do not adequately address outdoor exposure. Assessing spatial and temporal exposure can help identify effective protective vector strategies for these areas while highlighting persistent exposure risks. Community-based larval source management could enhance overall exposure reduction. Additionally, innovative measures like spatial repellents may address some protective gaps, together with improved case detection and treatment. The findings indicate that the existing strategy may not suffice to eradicate malaria in the region, necessitating a reconsidered, evidence-based, and adaptive approach.

Making scents of mosquito repellents.

Making scents of mosquito repellents.

Aedes albopictus responses to transfluthrin-impregnated polyester fabric in a semi-field system at different time periods.

Aedes albopictus responses to transfluthrin-impregnated polyester fabric in a semi-field system at different time periods.

Identifying gaps in protection from malaria vector biting in rural Cambodia using an entomological assessment and human behaviour observations

BackgroundForest-exposed populations remain the last significant, and most difficult to access, high-risk populations for malaria in Cambodia. Despite the availability of long-lasting insecticidal nets (LLINs) and/or hammock nets (LLIHNs), continued malaria transmission indicates gaps in protection. This study aimed to identify these gaps among forest-exposed individuals in Plasmodium falciparum hotspots in two provinces in Cambodia, using entomological assessments and human behaviour observations (HBOs).MethodsAnopheles bionomic traits were characterized using Human Landing Catches (HLCs) in a village setting in Mondulkiri province, and in both village and forest settings in Kampong Speu province, Cambodia. Mosquitoes were collected from 17h00 to 07h00 over 540 collection nights. Human behaviour observations (HBOs) focused on monitoring activities near HLC sites and recording the use of LLINs/LLIHNs or Project BITE’s bite prevention tools: a volatile pyrethroid spatial repellent (VPSR), topical repellent (TR), and insecticide-treated clothing (ITC). Data on mosquito landing pressure and human behaviours were integrated to generate the HBO-adjusted Human Landing Rate (HBO-adjusted HLR).ResultsA total of 5,985 Anopheles mosquitoes were collected, with 608 (10%) identified molecularly to species-level. Seventeen Anopheles species were identified, including a likely novel species from the Leucosphyrus Subgroup, which was the predominant species characterized. The HBO-adjusted HLR was found to be greatest during the early evening hours, when people were outdoors awake, followed by when people were sleeping indoors without a net. Relatively few people were observed using, or correctly using, the new bite prevention tools intended for protection in the forest.ConclusionThis study demonstrates the importance of understanding spatial and temporal human exposure to mosquito bites, in the presence of proven vector control tools (LLINs, LLIHNs) and newly introduced bite prevention tools (VPSRs, ITCs, and TRs). To help achieve malaria elimination, human behaviour data on intervention use and behaviour patterns should be evaluated and integrated with entomological data towards identifying and quantifying protection conferred by current interventions, as well as remaining gaps in protection. This information supports the selection of appropriate interventions, which supplement rather than replace existing tools, to target existing gaps in protection.

Functional Characterization of an Antenna-Biased Odorant Receptor AaOr96 Involved in Tea Tree Oil Repellency Against Aedes aegypti.

Numerous essential oils have been well acknowledged as eco-friendly alternatives to combat insect pests due to synthetic insecticide-induced pest resistance and environment pollution. As a highly commercial essential oil, tea tree oil exhibits excellent insecticidal and repellent activities. However, the molecular mechanism of the olfactory system mediating the tea tree oil-induced repellency against insect pests remains unknown. In our study, mosquito was used as a suitable model to examine the molecular mechanism of tea tree oil-induced repellency against insect pests. The results showed that tea tree oil exhibited excellent spatial and oviposition repellency against Aedes aegypti adults and outstanding repellency against larvae, which were conferred by the main constituent terpinen-4-ol. The reduced repellency in the Orco-/- mutant strain revealed that tea tree oil-induced repellency against mosquitoes was dependent on odorant receptor(s). Moreover, we identified one antenna-biased odorant receptor, AaOr96, that was involved in detecting constituents of tea tree oil to elicit repellency, and the predicted protein-ligand complex indicated that AaOr96 interacted with terpinen-4-ol via van der Waals forces from five key residues. Finally, knocking out AaOr96 resulted in a reduced spatial repellency against A. aegypti by tea tree oil and terpinen-4-ol, and a reduced oviposition repellency by terpinen-4-ol, but not by tea tree oil. Our study not only reveals that tea tree oil has great potential in pest management but also provides more insights into the molecular basis of repellency of essential oils.

A Review of Aedes aegypti Control in Peru: Approaches and Lessons Learned.

Dengue is the most widespread vector-borne viral infection globally and a serious public health problem. The 2023-2024 dengue outbreak across Latin America has drastically impacted Peru, including previously unaffected areas such as metropolitan Lima and Amazonian rural communities, presumably due to climate change. Research studies conducted in Iquitos, the largest city in the Peruvian Amazon, showed that ultra-low-volume pyrethroid spray applications against the dengue vector Aedes aegypti were effective when adequate coverage and quality control were carried out. Insecticide-treated curtains were not effective at controlling dengue transmission in Iquitos, whereas the use of passive spatial repellent emanators demonstrated 34% protective efficacy against Aedes-borne virus infection. In modeling studies, targeted indoor residual spray strategies showed promising reductions in dengue transmission, which require empirical evaluation. Trials conducted in Iquitos have shown that larval control alone is not sufficient to control Ae. aegypti, urging that government programs must consider integrated vector management.

The costs and logistics of distributing ‘forest packs’ containing novel vector control tools to forest-exposed populations in Cambodia

BackgroundMalaria incidence in the Greater Mekong Subregion has been on the decline, and most remaining malaria risk in the region is concentrated among hard-to-reach populations, especially those with exposure to forested areas. New vector control tools focused on outdoor protection in forest settings are needed for these populations.MethodsThe delivery of a ‘forest pack’ containing a volatile pyrethroid spatial repellent (VPSR), a topical repellent, and pyrethroid treatment of clothing was evaluated in an operational study in Cambodia. Costs were collected using micro-costing approaches and the cost of distribution for the ‘forest pack’ was estimated using standard economic evaluation approaches and examined in sensitivity analyses.ResultsThe cost per eligible person (the target population) per malaria season for the whole pack was estimated to be 138 USD, which was nearly entirely driven by the cost of the products.ConclusionsModifications to the ‘forest pack’ including adding a longer-lasting spatial repellent product or a reduced-cost topical repellent could significantly reduce the cost of pack distribution over the course of a malaria season.

Effect of a spatial repellent on malaria incidence in an area of western Kenya characterised by high malaria transmission, insecticide resistance, and universal coverage of insecticide treated nets (part of the AEGIS Consortium): a cluster-randomised, controlled trial.

Effect of a spatial repellent on malaria incidence in an area of western Kenya characterised by high malaria transmission, insecticide resistance, and universal coverage of insecticide treated nets (part of the AEGIS Consortium): a cluster-randomised, controlled trial.

Grapefruit-derived nootkatone potentiates GABAergic signaling and acts as a dual-action mosquito repellent and insecticide.

Humanity has long battled mosquitoes and the diseases they transmit-a struggle intensified by climate change and globalization, which have expanded mosquito ranges and the spread of associated diseases.1 Additionally, widespread insecticide resistance has reduced the efficacy of current control methods, necessitating new solutions.2,3 Nootkatone, a natural compound found in grapefruit, shows promise as both a mosquito repellent and an insecticide.4,5 However, its mechanism of action remains unclear. Our study demonstrates that nootkatone acts as a potent spatial and contact repellent against multiple mosquito species. Nootkatone-induced spatial aversion, which is influenced by human odor, is in Aedes aegypti partially mediated by Orco- and ionotropic receptor (IR)-positive neurons, while contact aversion is robust and likely mediated via the proboscis and independent of TRPA1 and IRs. We further find that nootkatone potentiates γ-aminobutyric acid (GABA)-mediated signaling by modulating the broadly expressed major insect GABA-gated chloride channel resistant to dieldrin (Rdl). At low doses, the chemosensory-mediated spatial and contact repellency is likely strengthened by nootkatone's disruption of synaptic transmission in select mosquito sensory neurons. At higher doses, nootkatone induces paralysis and death, presumably through broad-range synaptic transmission disruption. These findings reveal nootkatone's unique mode of action and highlight its potential as an effective mosquito control agent. Its dual role as a repellent and an insecticide, combined with low-to-no toxicity to humans and a pleasant smell, underscores nootkatone's promise as a future tool in mosquito control efforts.

Laboratory bioassays of volatile pyrethroid spatial repellents against medically important mosquitoes in the Asia-Pacific region: A systematic review

Laboratory bioassays of volatile pyrethroid spatial repellents against medically important mosquitoes in the Asia-Pacific region: A systematic review