Mosquito Control Research Articles

Chromobacterium biopesticide overcomes insecticide resistance in malaria vector mosquitoes.

Vector mosquito control is an integral part of malaria control. The global emergence of insecticide resistance in malaria-transmitting Anophelines has become an impediment and has created an urgent need for novel mosquito control approaches. Here, we show that a biopesticide derived from the soil-dwelling bacterium Chromobacterium sp. Panama (Csp_P) kills insecticide-resistant Anopheles mosquitoes, regardless of their resistance mechanisms. In addition, sublethal dose of Csp_P acts as a synergist to now used chemical insecticides across multiple classes. Moreover, Csp_P reduces host-seeking behavior and malaria parasite infection in vector mosquitoes in ways that further decrease transmission. Mosquito glutathione S-transferases are essential for Csp_P's mosquito-killing mechanism. Enclosed field trials in Burkina Faso, conducted in diverse ecological settings and supported by a mathematical model, have now demonstrated its potential for malaria control in settings with widespread insecticide resistance.

Development of a controlled-release mosquito RNAi yeast larvicide suitable for the sustained control of large water storage containers

Large household water storage containers are among the most productive habitats for Aedes aegypti (Linnaeus, 1762), the primary mosquito vector for dengue and other arboviral pathogens. Increasing concerns for insecticide resistance and larvicide safety are limiting the successful treatment of large household water storage containers, which are among the most productive habitats for Aedes juveniles. The recent development of species-specific RNAi-based yeast larvicides could help overcome these problems, particularly if shelf stable ready-to-use formulations with significant residual activity in water can be developed. Here we examine the hypothesis that development of a shelf-stable controlled-release RNAi yeast formulation can facilitate lasting control of A. aegypti juveniles in large water storage containers. In this study, a dried inactivated yeast was incorporated into a biodegradable matrix containing a mixture of polylactic acid, a preservative, and UV protectants. The formulation was prepared using food-grade level components to prevent toxicity to humans or other organisms. Both floating and sinking versions of the tablets were prepared for treatment of various sized water containers, including household water storage tank-sized containers. The tablets passed accelerated storage tests of shelf life stability and demonstrated up to six months residual activity in water. The yeast performed well in both small and large containers, including water barrels containing 20-1000 larvae each, and in outdoor barrel trials. Future studies will include the evaluation of the yeast larvicide in larger operational field trials that will further assess the potential for incorporating this new technology into integrated mosquito control programs worldwide.

Boosting the efficacy of fungal biocontrol: miRNA339-5p-mediated mosquito immunity regulation.

Aedes mosquitoes are vectors for numerous viral diseases, including dengue, zika, chikungunya, and yellow fever. Therefore, underscoring the urgent need for eco-friendly alternatives to combat insecticide resistance and the scarcity of effective vaccines. Entomopathogenic fungi present a sustainable alternative to chemical insecticides; however, their widespread application is limited by their relatively low virulence. Here, we investigated the immunological interactions between Metarhizium anisopliae and Aedes albopictus, demonstrating that fungal infection significantly up-regulated immune-related genes in the Toll and melanization pathways, thereby enhancing antifungal and antibacterial defenses at 48 h post-infection (hpi). Small RNA sequencing identified miR339-5p as a crucial modulator, targeting the immune genes Gram-Negative Binding Protein 1 (GNBP1) and CLIP-domain Serine Protease B15 (CLIPB15), which are critical for Toll and phenoloxidase (PO) pathway activation. The administration of a synthetic miR339-5p mimic increased fungal virulence, resulting in a higher mortality rate among adult mosquitoes and a significant increase in the mortality rate of mosquito larvae within 24 hpi. GNBP1 was found to regulate both Toll and PO pathways, while CLIPB15 specifically modulated the PO system by cleaving prophenoloxidase (PPO). This research highlights the potential of leveraging Ae. albopictus-encoded miR339-5p through advanced genetic engineering techniques to bolster the efficacy of existing fungal-based mosquito control strategies, providing a promising approach in the fight against mosquito-borne diseases. © 2024 Society of Chemical Industry.

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.

Characterization of Culicoides and mosquito fauna at the National Zoological Garden of Rabat, Morocco

Zoos are considering to be essential places for the conservation of wild animal species. It is essential to prevent their infection by pathogens especially for those belonging to threatened or extinct species. Zoo captive animals are susceptible to several Culicoides and mosquito borne-viruses. In order to further evaluate the risk of pathogen transmission in zoos, it is essential to identify the presence of potential vector species, as well as the animals bitten by those vectors.For this purpose, Culicoides and mosquito species composition was investigated in ten sites from March to June 2021 for Culicoides (18 collection nights) and in four sites from April to June 2022 for mosquitoes (16 collection nights) at the National Zoological Garden of Rabat (ZGR), Morocco. Culicoides (Diptera: Ceratopogonidae) were collected using Onderstepoort Veterinary Institute traps (UV-light/suction traps (OVI type)), every two weeks. Mosquitoes (Diptera: Culicidae) were collected using BG-Pro mosquito trap (BGP) combined with a CO2 source as an attractant, on two consecutive days every two weeks. The blood meal of engorged Culicoides was amplified by PCR, sequenced, and blasted for host species identification.In total, 1584 individuals belonging to the Culicoides genus were collected (88.25 % females and 11.75 % males) belonging to at least 13 different species. Among the species collected, Culicoides newsteadi (33.28 %), C. imicola (23.74 %), C. circumscriptus (18.88 %) and C. obsoletus/C. scoticus (7.96 %) constituted the majority of the total catches. These species are proven or suspected vector species of bluetongue and African hose sickness viruses in the Mediterranean basin. For mosquitoes, 455 individuals belonging to four species of three genera were collected (97.58 % females and 2.42 % males): Culex pipiens s.l. (94.29 %) (vector species of West Nile and Rift Valley fever viruses), Culiseta longiareolata (4.81 %), Aedes detritus s.l. and Ae. caspius (representing together less than 1.00 %). The results of blood meal analyses revealed that Culicoides fed on humans (n = 7), camels (n = 2), and common eland (n = 2).The composition of Culicoides and mosquito fauna is characteristic of the Rabat region. The composition is thus mostly determined by the environment rather than by the animal species presence. The results highlighted that Culicoides fed on humans and ruminants. It is therefore likely that the zoo's animals could be threatened by arboviruses transmitted by domestic animals in the region. Particular attention must be paid to the prevention of vector-borne diseases to ensure the proper conservation of species.

Wolbachia-Based Approaches to Controlling Mosquito-Borne Viral Threats: Innovations, AI Integration, and Future Directions in the Context of Climate Change

Wolbachia-based mosquito control strategies have gained significant attention as a sustainable approach to reduce the transmission of vector-borne diseases such as dengue, Zika, and chikungunya. These endosymbiotic bacteria can limit the ability of mosquitoes to transmit pathogens, offering a promising alternative to traditional chemical-based interventions. With the growing impact of climate change on mosquito population dynamics and disease transmission, Wolbachia interventions represent an adaptable and resilient strategy for mitigating the public health burden of vector-borne diseases. Changes in temperature, humidity, and rainfall patterns can alter mosquito breeding habitats and extend the geographical range of disease vectors, increasing the urgency for effective control measures. This review highlights innovations in Wolbachia-based mosquito control and explores future directions in the context of climate change. It emphasizes the integration of Wolbachia with other biological approaches and the need for multidisciplinary efforts to address climate-amplified disease risks. As ecosystems shift, Wolbachia interventions could be crucial in reducing mosquito-borne diseases, especially in vulnerable regions. AI integration in Wolbachia research presents opportunities to enhance mosquito control strategies by modeling ecological data, predicting mosquito dynamics, and optimizing intervention outcomes. Key areas include refining release strategies, real-time monitoring, and scaling interventions. Future opportunities lie in advancing AI-driven approaches for integrating Wolbachia with other vector control measures, promoting adaptive, data-driven responses to climate-amplified disease transmission.

Larvicidal and enzyme inhibition effects of Phoenix pusilla derived Methyl oleate and malathion on Aedes aegypti strains

This study explores the larvicidal potential of methanolic flower extracts from Phoenix pusilla (Pp-Fe), its major compound, and malathion (MLT), against laboratory strain (LS) and field strain (FS) of Aedes aegypti, the dengue mosquito vector. We identified thirty-one derivatives, with methyl oleate (MO) comprising 28.5% of Pp-Fe. Comparative efficacy evaluations were performed using peak dosages of Pp-Fe (500 ppm), MO (5 ppm), and MLT (5 ppm) on LS and FS larvae. Both LS and FS second instars showed higher susceptibility to Pp-Fe (95% and 93%, respectively) and MO (85% and 83%, respectively). MLT resulted in significant mortality rates among LS larvae (98%) and notable reductions among FS larvae (71%). The expression levels of key biomarker enzymes (carboxylesterase, GST, and CYP450) exhibited a consistent decrease and subsequent upregulation in LS and FS larvae following exposure to Pp-Fe and MO, contrasting with the significant expression variations observed in LS and FS larvae exposed to MLT. LS larvae demonstrated heightened susceptibility and evident midgut cell damage following all treatments, suggesting potential disparities in susceptibility and adaptive responses between LS and FS strains towards MLT. These observations underscore the promising larvicidal attributes of Pp-Fe and MO, emphasizing the need for further exploration of their mechanisms of action in the development of environmentally sustainable mosquito control strategies and resistance management.

Mosquito diversity, abundance and phenology in Mexico City: A heavily urbanized environment

We need to understand how zoonotic diseases make their way in urbanized areas, and one way is via gathering well-structured temporal and spatial accounts of zoonotic disease vectors. Due to its large biotic and abiotic heterogeneity, Mexico City provides favorable environmental conditions for the proliferation of mosquitoes including vector species of medical importance. Hereby we present the results of one year sampling (May 2023-April 2024) in eight contrasting locations in Mexico City. In total, 4,861 mosquitoes belonging to 11 species were captured, with Culex stigmatosoma and Culex restuans emerging as the most dominant, while Anopheles aztecus, Culex erythrothorax and Aedes trivittatus were the least abundant. Monthly fluctuations in the composition and abundance of species were observed at each site, highlighting cemeteries as the places with the highest mosquito density, making them key areas for monitoring. This research should serve local health authorities to guide mosquito control strategies, and two key candidates are Culex quinquefasciatus and Cx. restuans, particularly from June to November which is when their abundance reaches a peak.

Forecasting the relative abundance of Aedes vector populations to enhance situational awareness for mosquito control operations.

Aedes-borne diseases represent a major public health threat and mosquito control operations represent a key line of defense. Improving the real-time awareness of mosquito control authorities by providing reliable forecasts of the relative abundance of mosquito vectors could greatly enhance control efforts. To this aim, we developed an analytical tool that forecasts Aedes aegypti relative abundance 1 to 4 weeks ahead. Forecasts were validated against mosquito surveillance data (2,760 data points) collected over multiple years in four jurisdictions in the US. The symmetric absolute percentage error was in the range 0.43-0.69, and the 90% interquantile range of the forecasts had a coverage of 83-92%. Our forecasts consistently outperformed a reference "naïve" model for all analyzed study sites, forecasting horizon, and for periods with medium/high Ae. aegypti activity. The developed tool can be instrumental to address the need for evidence-based decision making.

Gallium-doped titania nanotubes as advanced photocatalysts and biopesticides: a path to water purification and vector control

AbstractThe release of Rose Bengal (RB) dye poses a significant threat to aquatic ecosystems, necessitating sustainable water treatment solutions. This study introduces a novel photocatalytic approach utilizing titania nanotubes (TNTs) doped with varying contents of gallium oxide (Ga₂O₃, 0–5%) via a hydrothermal method. Characterization techniques, including FTIR, XRD, TEM, SEM, EDX, and XPS, confirmed the formation of nanotubular structures with enhanced surface area and defect states. The total organic carbon (TOC) measurement indicated effective mineralization of RB dye. Among the synthesized photocatalysts, the 1% Gallium-doped titania nanotubes (Ga-doped TNTs) achieved optimal RB degradation, decomposing 97% of the dye within 110 min under UV illumination, owing to improved charge separation and synergistic effects between Ga and TNTs. Furthermore, Ga-doped TNTs demonstrated superior efficacy in mosquito control, with 100% larvicidal mortality observed at 400 °C compared with only 57.2% for TNTs. Similarly, the pupicidal mortality rate at 72 h increased from 26.2% (TNTs) to 60.8% (Ga-doped TNTs-400). The findings emphasize the dual functionality of Ga-doped TNTs as efficient photocatalysts for water purification and eco-friendly biopesticides, presenting a promising strategy for environmental remediation and vector control.

EFFECT OF SEX AND AGE ON SURVIVAL OF ADULTCULEX TARSALISFROM A SUSCEPTIBLE LABORATORY STRAIN EXPOSED TO PERMETHRIN IN THE CDC BOTTLE BIOASSAY

ABSTRACTThis study investigates the effect of mosquito sex and age on the survival and resistance determination of adult Culex tarsalis exposed to permethrin, a pyrethroid commonly used for mosquito control, using the Centers for Disease Control and Prevention (CDC) bottle bioassay method. A permethrin-susceptible strain of Cx. tarsalis (Bakersfield strain) was used in this study. Survival was compared for young adult females (2–5 days old) relative to older adult females (7–10 days old) and separately for female and male mosquitoes of the same age (2–5 days old). Mortality was slightly higher for males than females during the first observation period (0–5 min) following permethrin exposure, and higher for older females relative to younger females from 5 to 10 min following permethrin exposure, with no differences in mortality by either sex or age for observation periods during the remainder of the diagnostic period. When evaluated over the full diagnostic period, survival varied with mosquito age but not sex. However, all mosquitoes, regardless of sex or age, died within the 30-min diagnostic period for this species, confirming their permethrin susceptibility per the CDC bottle bioassay. This research contributes valuable insight into the potential impact of sex and age on mosquito susceptibility to insecticides in the context of insecticide resistance determination.

Investigating the Potential of X-Ray-Based Cancer Treatment Equipment for the Sterile Insect Technique in Aedes aegypti Control Programs.

The sterile insect technique (SIT) stands as an eco-friendly approach for mosquito control, but it is impeded by the limited availability of γ-ray radiation source. This research sought to investigate a different radiation source-the Varian Clinac 23EX linear accelerator, which is frequently used for X-ray therapy in cancer treatment. Evaluation parameters including emergence rate, average survival time, induced sterility (IS), male mating competitiveness of irradiated males and fecundity (the number of eggs per female per batch), and the egg hatch rate of females mated with irradiated males were assessed to gauge the application potential of this cancer treatment equipment in the realm of the SIT. The results indicated that X-rays from radiation therapy equipment can effectively suppress the hatch rate of offspring mosquitoes without adversely affecting the emergence rate of irradiated males or the fecundity of females. In addition, at an X-ray dose of 60 Gy, the induced sterility in Ae. aegypti was comparable to the sterility induced by 40 Gy of γ-rays with both treatments resulting in 99.6% sterility. Interestingly, when a release ratio of 7:1 (irradiated males:unirradiated males) was used to competitively mate with females, the IS results resulted by 60 Gy X-rays and 40 Gy γ-rays were still at 70.3% and 73.7%, respectively. In conclusion, the results underscored the potential of the Varian Clinac 23EX linear accelerator as an X-ray source in SIT research.

A qualitative analysis of perceived risks and benefits of mosquito abatement and bite prevention strategies in Northeastern U.S. communities.

Mosquito-borne disease (MBD) incidence is increasing in the United States (U.S.), presenting an evolving health threat. Assessments of public perceptions have revealed limited awareness of MBDs among the U.S. population. Our team used focus groups to gain an in-depth understanding of risk perceptions regarding mosquito exposure and pesticide use, and benefit perceptions and motivators for bite prevention strategies. A total of 37 individuals participated in focus groups across 3 states: New Jersey (n = 14), New York (n = 15), and Massachusetts (n = 8). Most participants were unfamiliar with public mosquito control services and felt they were not at high exposure risk to any MBDs. Overall, participants were supportive of investing public funds for mosquito surveillance. However, participants across all focus groups expressed concerns over ecosystem health and long-term consequences of pesticide use for mosquito control. Participants in every focus group referenced a risk assessment that weighed the risk of MBD exposure against the use of chemical control: once participants perceived MBDs as negatively impacting human and/or animal health in their area, sentiment swung largely to supporting the use of pesticides. In the absence of an obvious MBD threat, participants preferred nonchemical control interventions. Participants felt communication from mosquito control agencies should be accessible, disseminated across multiple venues, and should include instructions for the public during spray events, resources for individual bite prevention, and information on control products used. Our research results can inform the development of improved, evidence-based MBD outreach and educational resources that are acceptable, actionable, and relevant to Northeast communities.

Preparation for targeted sterile insect technique to control invasive Aedes aegypti (Diptera: Culicidae) in southern California: dose-dependent response, survivorship, and competitiveness.

Aedes aegypti is fast spreading across California, with over 300 cities within 22 central and southern counties being infested since its introduction in 2013. Due to its cryptic breeding habitats, control efforts have not been successful so far. This calls for innovative tools such as sterile insect technique (SIT) to reinforce the existing integrated pest management (IPM). Here, we assessed fitness, survivorship, and dose response of X-ray irradiated male Ae. aegypti in California. Locally acquired Ae. aegypti eggs were hatched and reared in temperature-controlled laboratory setting at the West Valley Mosquito and Vector Control District in Ontario, California. Freshly emerged adult male mosquitoes were manually separated using motor-operated aspirators and treated with X-ray radiation at different dosage (42-60 Gy). Dose response of irradiated males was analyzed and induced sterility determined. Survivorship of males treated with different X-ray doses was compared. Fecundity of females that mated with irradiated males at different X-ray doses was generally comparable. Overall, induced sterility increased with higher X-ray doses. Nulliparous females that mated with male Ae. aegypti treated with 55-60 Gy laid eggs with over 99% sterility. Non-irradiated male mosquitoes had higher survivorship (mean = 0.78; P = 0.0331) than irradiated mosquitoes (mean range = 0.50-0.65). The competitiveness index of irradiated males decreased with increasing X-ray treatment doses, 1.14 at 55 Gy and 0.49 at 60 Gy, and this difference was significant (P < 0.01). Irradiated males showed high survivorship and competitiveness-key for the anticipated SIT application for the control of invasive Ae. aegypti in California.

Comparison of different spectral ranges of UV-LED lighting for outdoor mosquito trapping in forested area in Thailand.

Mosquito surveillance is critical for actively tracking the location and monitoring population levels and the threat of mosquito-borne disease. Although light-emitting diodes (LEDs) light traps have grown in popularity, there is still a limited understanding of the application of light wavelengths for trapping nocturnally active wild mosquitoes in forest ecotypes. This study evaluated the performance of different UV wavelengths in trapping mosquito populations in a forested mountainous area in Nakhon Ratchasima province, Thailand. Traps with different UV wavelengths were deployed in 6 locations, following a 6 × 6 Latin square replicated 6 times over a total of 36 nights. Light traps were operated between 18:00 and 06:00 h from October 2022 to August 2023. Mosquitoes were separately collected from individual traps every 4 h at 22.00, 2.00, and 6.00 h. Mosquitoes were killed by placing in a freezer (- 20 °C) for at least 30 min and then were morphologically identified using illustrated keys for adult females. Traps fitted with the LED 365 wavelength light source were the most effective in capturing 790 (23.66%) of the total mosquitoes collected, followed by the UV fluorescent 632 (18.93%), with the other 4 LED wavelengths collecting between 16.89% (LED 385) and 12.64% (LED 375) of the mosquitoes. Culex was the most common genus, representing 56.00% of total mosquito abundance. LED 365 and LED 385 were comparable to the UV fluorescent traps (the standard reference). Optimal trapping times were during 18:00-22:00 h. Compared to the other wavelengths, LED 365 was significantly more effective at capturing Coquillettidia and Culex mosquitoes than the UV-based traps.

Carry-over effects of Bacillus thuringiensis on tolerant Aedes albopictus mosquitoes

BackgroundThe biological larvicide Bacillus thuringiensis subsp. israelensis (Bti) represents a safe and effective alternative to chemical insecticides for mosquito control. Efficient control of mosquitoes implicates continuous and extensive application of Bti. This massive use of Bti imposes strong selective pressure, but the complex mode of action of the numerous synergistic Bti endotoxins lower the risk of the emergence of resistance. Although resistance to Bti has not been identified at the population level in nature, some larvae can survive Bti exposure, suggesting tolerance mechanisms. Here we investigated whether Bti-tolerant Aedes albopictus larvae experience any fitness costs. We also studied how this tolerance affects different aspects of the phenotype of the emerging adults that could be relevant for arboviral transmission.MethodsWe exposed Ae. albopictus larvae to lethal concentration of Bti and studied the fitness and gut microbiota of tolerant larvae and their adult counterparts. We further compared the transcript abundance of nine key immunity genes in the gut of Bti-tolerant larvae and their emerging adults versus those not exposed to Bti.ResultsOur results showed that Bti exposure has multifaceted impacts on Ae. albopictus mosquitoes during both larval and adult stages. The carry-over effect of Bti exposure on tolerant larvae manifested in reduced adult emergence rate, shorter lifespan, and decreased fecundity. Bti also alters the gut microbiota of both larvae and adults. We observed higher microbial diversity in Bti-tolerant larvae and changes in the richness of core microbiota. Bti infection and the altered microbiota triggered immune responses in the larval and adult guts.ConclusionsThe observed reduction in mosquito fitness and changes in the composition of the microbiota of adults emerging from tolerant larvae could negatively influence mosquito vectorial capacity. Understanding these impacts is crucial for evaluating the broader implications of Bti-based insecticides in mosquito control programs.Graphical

Detection of the 1016Gly and 989Pro Knockdown Resistance Mutations in Florida, USA Aedes aegypti.

Aedes aegypti is a major arboviral disease vector and is therefore a critical target for control by public health programs. Early eradication efforts have shown that Ae. aegypti can rapidly build insecticide resistance, and, now, resistance to pyrethroids, the major class of adulticides used for operational control, is common in many populations. A major contributor to this resistance is a group of knockdown resistance (kdr) SNPs that normally exist in distinct ensembles in the Western Hemisphere and the Indopacific with little known mixing. In this study, we detected, and confirmed, using multiple methods, the Indopacific kdr SNPs, both V1016G and S989P, in three recent collections from Osceola County, Florida. This represents a large expansion of the geographic range of the Indopacific kdr SNPs. We consider the implications of this finding on future insecticide resistance surveillance studies, including assessing the ability of our current screening tools to detect these SNPs. We find that the presence of the Indopacific SNPs requires the modification of existing resistance screening protocols and requires further work to understand the operational implications for mosquito control.

Target-site mediated insecticide resistance in major mosquito (Diptera: Culicidae) vectors: A systematic review

The use of insecticides remain the most effective vector control approach for mosquito borne diseases like malaria, dengue fever, chikungunya, and Zika virus disease; however, their increasing resistance has complicated the management. Mutations in kdr, ace-1/ace-2, rdl, and nAChR, are involved in target-site mediated resistance and prevent the binding of pyrethroids and dichlorodiph enyltrichloroethane, organophosphorus pesticide, carbamates and cyclodienes, respectively. Here, we review the current knowledge on target-site mediated insecticidal resistance mechanisms in major mosquito vectors and the techniques used to identify these mutations. The results showed that kdr mutations are frequently reported in mosquito species, indicating the overuse of pyrethroid in mosquito control. Report on ace mutations is very limited, primarily detected in Anopheles and Culex, with extremely low detection rate in Aedes, despite the wide application of organophosphates in their control. Notably, reports of rdl mutations and changes in nAChR are rare, which provides an opportunity to exploit these target sites, particularly in the event of disease outbreaks. Among various detection methods such as RFLP, TaqMan, Multiplex PCR and FRET, allele-specific PCR is mostly employed, especially in detecting kdr mutation. However, allele-specific PCR cannot detect novel mutation. As a result, there is an urgent need to develop a scalable, cost-effective tool that can be widely applied especially as these mutations are genetic markers for early detection of insecticide resistance. Robust monitoring methods remain critical to manage insecticide resistance and effective control of mosquito-borne diseases.

Using models and maps to inform Target Product Profiles and Preferred Product Characteristics: the example of Wolbachia replacement.

The global prevalence of diseases transmitted by Aedes aegypti mosquitoes, such as dengue, Zika and Yellow Fever, is increasing, but development of promising new mosquito control technologies could reverse this trend. Target Product Profiles (TPPs) and Preferred Product Characteristics (PPCs) documents issued by the World Health Organization can guide the research and development pathways of new products and product combinations transitioning from proof of concept to operational use. We used high resolution global maps of the case and economic burden of dengue to derive programmatic cost targets to support a TPP for Wolbachia replacement. A compartmental entomological model was used to explore how release size, spacing and timing affect replacement speed and acceptability. To support a PPC for a hybrid suppress-then-replace approach we tested whether Wolbachia replacement could be achieved faster, more acceptably or at a lower cost if preceded by a mosquito suppression programme. We show how models can reveal trade-offs, identify quantitative thresholds and prioritise areas and intervention strategies for further development. We estimate that for Wolbachia replacement to be deployable in enough areas to make major contributions to reducing global dengue burden by 25% (in line with 2030 WHO targets), it must have the potential for cost to be reduced to between $7.63 and $0.24 (USD) per person protected or less. Suppression can reduce the number of Wolbachia mosquitoes necessary to achieve replacement fixation by up to 80%. A hybrid approach can also achieve fixation faster and potentially improve acceptability, but may not justify their cost if they require major new investments in suppression technologies. Here we demonstrate the value dedicated modelling can provide for interdisciplinary groups of experts when developing TPPs and PPCs. These models could be used by product developers to prioritise and shape development decisions for new Wolbachia replacement products.

Effectiveness of Essential Oils from Leaves of Two Plant Species in the Control of Anopheles gambiae

Background: The current method of controlling malaria vectors using synthetic chemicals has caused serious problems for human health and the environment. Hence, a need for alternative, cheap, readily available, and acceptable mosquito control methods. Objective: To evaluate the bioinsecticidal efficacy of Ocimum gratissimum and Mesosphaerum suaveolens against Anopheles gambiae using the bioassay method. Methods: Oil extracts in 5 ml, 25 ml, and 75 ml serially diluted twice in 100 ml of olive oil formed 0.05%, 0.25%, and 0.75%, while 1 m in 100 ml formed 1%. Olive oil only served as a control. Twenty-five female Anopheles mosquitoes, aged 2-4 days, were blown into tubes containing filter paper-coated essential oils of various concentrations in quadruplicates. Results: Over 50% mortality was recorded in mosquitoes exposed to 0.75% and 1% O. gratissimum compared to others (p &lt;0.05). Knockdown time (KDT) was higher in mosquitoes exposed to 1% O. gratissimum compared to others (p &lt;0.05). Generalized linear regressions showed that the essential oils of O. gratissimum and M. suaveolens contributed 4% (f2 = 0.042) and 14% (f2 = 0.167) to the variability of mortality with time. KDT50 (9.34 - 131.5 minutes) and KDT95 (77.6 - 275 minutes) of O. gratissimum as well as KDT50 (162.8 - 233.6 minutes) and KDT95 (302.8 - 415 minutes) of M. suaveolens were recorded. Stigmastane; 4,22-Stigmastadiene-3-one (Area: 45.88%) in O. gratissimum and gamma-Sitosterol (16.02%) in M. suaveolens were identified by Gas Chromatogram as the highest dose of chemical compounds. Conclusion: The low bioinsecticidal activities of these plant extracts could be attributed to the low occurrence of terpenoids and alkaloids.