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The Asian Citrus Psyllid (ACP), Diaphorina citri, severely threatens citrus production worldwide by transmitting the greening (= Huanglongbing)-causing bacterium Candidatus Liberibacter asiaticus. There is growing evidence that the push-pull strategy is suitable to partially mitigate HLB by repelling ACP with transgenic plants engineered to produce repellents and attracting the vector to plants with a minimal disease transmission rate. Species that pull ACP away from commercial citrus plants have been identified, and transgenic plants that repel ACP have been developed. The concept of a repellent-producing plant was first demonstrated with an Arabidopsis line engineered to overexpress a gene controlling the synthesis of ß-caryophyllene and other sesquiterpenes. We have analyzed the volatile organic compounds released by this Arabidopsis line and identified α-humulene, α-copaene, and trace amounts of ß-elemene, in addition to ß-caryophyllene. Behavioral measurements demonstrated that α-copaene repels ACP at doses ca. 100× lower than those needed for ß-caryophyllene repellence. In contrast, α-humulene is innocuous at the level emitted by the transgenic plant. We confirmed that a mixture of the three sesquiterpenes in the ratio 1:100:10 repels ACP. Likewise, a commercial sample of copaiba oil containing the three sesquiterpenes, in a proportion similar to that in the transgenic plant, repelled ACP.

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Mentha arvensis is an herbaceous plant commonly known as peppermint or Japanese mint. This study investigated the toxic potential and repellent efficacy of M. arvensis essential oil (MaEO) at varying concentrations (15.625-250 mg/mL) in Nauphoeta cinerea, along with its impact on biochemical parameters in N. cinerea. The potential of the major compounds as a new analgesic target was investigated using molecular docking. The essential oil was analyzed by gas Chromatography-mass spectrometry (GC-MS) and the toxic potential, repellent property, and changes in lipid peroxidation (LPO) levels were evaluated as markers of oxidative stress. GC-MS results revealed that the main components were oxygenated monoterpenes such as menthol (71.31%), mentone (13.34%) and isomentone (5.35%). MaEO significantly reduced lipid peroxidation (LPO), the levels of non-protein thiols and iron(II) at the concentration of 125 mg/mL in N. cinerea. Furthermore, the major components, L-(-)-Menthol and menthone demonstrated high gastrointestinal absorption and high affinity with the target protein, suggesting possible links that contribute to the analgesic effect of MaEO.

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PURPOSE: The flea Ctenocephalides felis (Siphonaptera: Pulicidae), parasitizes dogs and cats globally, acting as a vector for various pathogens affecting both animals and humans. Growing interest in environmentally friendly, plant-based products prompted this study. The aim of the study was to determine the chemical composition of essential oils (EOs) from Copaifera reticulata, Citrus paradisi, Lavandula hybrida and Salvia sclarea, assessing their insecticidal and repellent properties, determining lethal concentrations (LC50 and LC90), and evaluating residual efficacy in vitro against Ctenocephalides felis felis. METHODS: Gas Chromatography with Flame Ionization Detector analyzed EO composition. In vitro tests involved preparing EO solutions at various concentrations. Ten specimens from each life stage (egg, larva, pupa, adult) were used for insecticidal activity assessment. Adulticidal activity was assessed using 10 cm2 filter paper strip, each treated with 0.200 mL of the test solution. Immature stages activities were evaluated using 23.76 cm2 discs of the same filter paper, each treated with 0.470 mL of the test solution. Mortality percentage was calculated using (number of dead insects × 100) / number of incubated insects. Probit analysis calculated LC50 values with a 95% confidence interval. RESULTS: Major EO constituents were ß-caryophyllene (EOCR), linalool (EOLH), linalyl acetate (EOSS), and limonene (EOCP). LC50 values were obtained for all stages except for the essential oil of C. paradisi. All oils showed repellent activity at 800 µg/cm2. OECR exhibited greater residual efficacy. CONCLUSION: Each EO demonstrated superior insecticidal activity against specific C. felis felis stages.

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Essential oils (EOs) are natural products currently used to control arthropods, and their interaction with insect odorant-binding proteins (OBPs) is fundamental for the discovery of new repellents. This in silico study aimed to predict the potential of EO components to interact with odorant proteins. A total of 684 EO components from PubChem were docked against 23 odorant binding proteins from Protein Data Bank using AutoDock Vina. The ligands and proteins were optimized using Gaussian 09 and Sybyl-X 2.0, respectively. The nature of the protein-ligand interactions was characterized using LigandScout 4.0, and visualization of the binding mode in selected complexes was carried out by Pymol. Additionally, complexes with the best binding energy in molecular docking were subjected to 500 ns molecular dynamics simulations using Gromacs. The best binding affinity values were obtained for the 1DQE-ferutidine (-11 kcal/mol) and 2WCH-kaurene (-11.2 kcal/mol) complexes. Both are natural ligands that dock onto those proteins at the same binding site as DEET, a well-known insect repellent. This study identifies kaurene and ferutidine as possible candidates for natural insect repellents, offering a potential alternative to synthetic chemicals like DEET.

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This study aimed to determine the repellent and insecticidal activity of four essential oils (EOs) from plants collected in the Chocó rain forest, Colombia, against T. castaneum . Conventional hydrodistillation was used to obtain the EOs. The repellent and insecticidal activities were evaluated by the preference area and gas dispersion methods, espectively. Statistical differences (p<0.05) were determined by applying a student's t-test. EOs of Siparuna guianensis, S. conica, Piper marginatum, and Nectandra acutifolia showed excellent repellent properties as the main findings, highlighting S. conicaEO with 84% repellency (1-hµL/cm2), while P. marginatum showed to be bioactive to the dose of 500 µL/mL (72 h), inducing mortality of 100% of the exposed population. In conclusion, the results evidenced the repellent properties of the EOs evaluated against T. castaneum , which allows us to conclude that these plant species are potential natural sources producing bio-repellents that contribute to the integrated control of T. castaneum.

Se evaluaron cuatro aceites esenciales (AEs) de plantas recolectadas en la selva pluvial del Chocó, Colombia, para determinar su actividad repelente e insecticida contra T. castaneum. Los AEs fueron obtenidos por hidrodestilación convencional. Las actividades repelentes e insecticidas se evaluaron por los métodos de área de preferencia y dispersión de gas, respectivamente. Las diferencias significativas (p<0,05) fueron determinadas aplicando una prueba t de student. Los AEs de Siparuna guianensis, S. conica, Piper marginatum y Nectandra acutifolia mostraron excelentes propiedades repelentes, destacando el AE de S. conicacon un 84% de repelencia (1µL/cm2), mientras que el AE de P. marginatummostró ser bioactivo a la dosis de 500 µL/mL (72 h) al inducir la mortalidad del 100% de la población expuesta. Se concluye que estas especies de plantas son fuentes naturales potencialmente viables para la producción de biorepelentes que contribuyan en el control integrado de T. castaneum.

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BACKGROUND: A simple treated fabric device for passively emanating the volatile pyrethroid transfluthrin was recently developed in Tanzania that protected against nocturnal Anopheles and Culex mosquitoes for several months. Here these transfluthrin emanators were assessed in Port-au-Prince, Haiti against outdoor-biting Aedes. METHODS: Transfluthrin emanators were distributed to participating households in poor-to-middle class urban neighbourhoods and evaluated once every two months in terms of their effects on human landing rates of wild Aedes populations. A series of three such entomological assessment experiments were conducted, to examine the influence of changing weather conditions, various transfluthrin formulations and emanator placement on protective efficacy measurements. Laboratory experiments assessed resistance of local Aedes aegypti to transfluthrin and deltamethrin, and the irritancy and repellency of the transfluthrin-treated fabric used in the field. RESULTS: Across all three entomological field assessments, little evidence of protection against wild Ae. aegypti was observed, regardless of weather conditions, transfluthrin formulation or emanator placement: A generalized linear mixed model fitted to the pooled data from all three assessment rounds (921 females caught over 5129 hours) estimated a relative landing rate [95% Confidence interval] of 0.87 [0.73, 1.04] for users of treated versus untreated emanators (P = 0.1241). Wild Ae. aegypti in this setting were clearly resistant to transfluthrin when compared to a fully susceptible colony. CONCLUSIONS: Transfluthrin emanators had little if any apparent effect upon Aedes landing rates by wild Ae. aegypti in urban Haiti, and similar results have been obtained by comparable studies in Tanzania, Brazil and Peru. In stark contrast, however, parallel sociological assessments of perspectives among these same end-users in urban Haitian communities indicate strong satisfaction in terms of perceived protection against mosquitoes. It remains unclear why the results obtained from these complementary entomological and sociological assessments in Haiti differ so much, as do those from a similar set of studies in Brazil. It is encouraging, however, that similar contrasts between the entomological and epidemiological results of a recent large-scale assessment of another transfluthrin emanator product in Peru, which indicate they provide useful protection against Aedes-borne arboviral infections, despite apparently providing only modest protection against Aedes mosquito bites.

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The yeast-encapsulated orange oil (YEOO) is a novel larvicide under development against vector mosquitoes. Despite its efficiency against Aedes aegypti (L.) in small scale experiments, its applicability in vector control can be influenced by other effects on mosquito behaviour or physiology. For this reason, the impact of YEOO particles in mosquito oviposition was evaluated in laboratory and semi-field conditions. Oviposition assays with one gravid Aedes aegypti female were carried under laboratory and semi-field conditions with natural light and temperature fluctuation. For all ovitraps, the number of eggs was manually counted in the wooden paddle and in the solution of each ovitrap. The proportion of eggs between substrates (wooden paddle and solution) varied between conditions, with females in laboratory presenting a lower preference to lay eggs in paddles when compared with studies in semi-field. This behaviour shifts in laboratory can create challenges to extrapolate results from laboratory to the field. Here, studies in both conditions indicate a similar impact of YEOO particles in Aedes aegypti oviposition. The potential treatment concentration of YEOO particles presents a strong repellent/deterrent effect (-0.559 > OAI > -0.760) within the initial 72h of application when compared with water, and weak repellent/deterrent signal (OAI = -0.220) when compared against inactivated yeast. Control ovitraps with water were more positive for egg presence than treated ovitraps, while ovitraps with YEOO particles and inactivated yeast present similar number of positive ovitraps. It is possible that the repellent/deterrent action is partially driven by the delivery system, since most times Citrus sinensis EO oviposition repellent/deterrent signal is weak, and it seem influenced by solvent/delivery used. However, it is unclear how the yeast wall that protect/surrounds the orange oil will negatively affect oviposition since live yeast are normally consider an attractant for mosquito oviposition.

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OBJECTIVE: To analyze the factors associated with the individual use of insect repellent by women of childbearing age living in area endemic for arboviruses in Fortaleza, Brazil. METHODS: This is a cohort study carried out between 2018 and 2019 with women aged between 15 and 39 years in Fortaleza, state of Ceará, Brazil. A total of 1,173 women users of one of the four selected primary health care units participated in the study. The outcome was divided into: continued use, discontinued use, and nonuse of insect repellent. Crude and adjusted multinominal logistic regression analysis was carried out guided by a hierarchical model, with presentation of the respective odds ratio (OR) and 95% confidence intervals (95%CI). The independent variables include: socioeconomic and demographic data, environmental and sanitary characteristics, knowledge of the insect repellent, and behavioral and pregnancy-related aspects. RESULTS: Only 28% of the participants reported using insect repellent during the two waves of the cohort. Women with higher education (OR=2.55; 95%CI 1.44-4.51); who are employed (OR=1.51; 95%CI 1.12-2.03); who received guidance from healthcare professionals (OR=1.74; 95%CI 1.28-2.36) and the media (OR=1.43; 95%CI 1.01-2.02); who intensified precautions against mosquitoes during the epidemic (OR=3.64; 95%CI 2.29-5.78); and who were pregnant between 2016 and 2019 (OR=2.80; 95%CI 1.83-4.30) had increased odds for continued use of insect repellent. CONCLUSION: The use of insect repellent among women of childbearing age was associated with a higher level of education, employment, guidance on insect repellent provided by healthcare professionals and the media, behavioral changes to protect against mosquitoes during the Zika virus epidemic, and pregnancy when occurring as of the beginning of the epidemic period.

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The repellent capacity against Sitophilus zeamais and the in vitro inhibition on AChE of 11 essential oils, isolated from six plants of the northern region of Colombia, were assessed using a modified tunnel-type device and the Ellman colorimetric method, respectively. The results were as follows: (i) the degree of repellency (DR) of the EOs against S. zeamais was 20-68% (2 h) and 28-74% (4 h); (ii) the IC50 values on AChE were 5-36 µg/mL; likewise, the %inh. on AChE (1 µg/cm3 per EO) did not show any effect in 91% of the EO tested; (iii) six EOs (Bursera graveolens-bark, B. graveolens-leaves, B. simaruba-bark, Peperomia pellucida-leaves, Piper holtonii (1b*)-leaves, and P. reticulatum-leaves) exhibited a DR (53-74%) ≥ C+ (chlorpyrifos-61%), while all EOs were less active (8-60-fold) on AChE compared to chlorpyrifos (IC50 of 0.59 µg/mL). Based on the ANOVA/linear regression and multivariate analysis of data, some differences/similarities could be established, as well as identifying the most active EOs (five: B. simaruba-bark, Pep. Pellucida-leaves, P. holtonii (1b*)-leaves, B. graveolens-bark, and B. graveolens-leaves). Finally, these EOs were constituted by spathulenol (24%)/ß-selinene (18%)/caryophyllene oxide (10%)-B. simaruba; carotol (44%)/dillapiole (21%)-Pep. pellucida; dillapiole (81% confirmed by 1H-/13C-NMR)-P. holtonii; mint furanone derivative (14%)/mint furanone (14%)-B. graveolens-bark; limonene (17%)/carvone (10%)-B. graveolens-leaves.

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The use of essential oils (EOs) in the development of alternative management methods for bruchid control under storage conditions aroused great interest because they have proven to be effective, less toxic, and less persistent in the ecosystem than synthetic pesticides. In this sense, leaves of Lippia turbinata (Griseb.) Moldenke EO were studied in the present work. The monoterpene limonene and the monoterpenoid eucalyptol were its main constituents. EO showed a potent insecticidal activity, both in contact and fumigant conditions, against Rhipibruchus picturatus (F.) which is one of the main pests of Prosopis alba pods in stored conditions. Moreover, the EO produces repellency in these insects. Additionally, the toxicity mechanism of action was studied. In this regard, the EO inhibits the acetylcholinesterase enzyme in in vitro assays, alters the activity of the antioxidant enzymes superoxide dismutase and catalase, and produces an increase in the lipid peroxidation reactions. This is the first report of the use of the L. turbinata EO against R. picturatus insect pest. The data obtained demonstrate its potential for developing more efficient and natural storage pest control strategies.

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The main way to avoid contact with ticks and consequently tick-borne disease is the use of synthetic repellents. The search of new repellent compounds to increase the possibilities of use in strategies controls are necessary. The present study evaluated the repellent activity of two natural terpenes carvacrol and thymol in each one two different formulation (encapsulated and nonencapsulated with yeast cell wall) against the ticks Amblyomma sculptum and Rhipicephalus sanguineus sensu lato nymphs. Nymphs of A. sculptum and R. sanguineus s.l. of a single generation were used. The vertical filter paper repellency assay were performed with different concentration of both terpenes encapsulated and nonencapsulated in yeast cell wall. The repellent concentration 50% (RC50) were calculated to each compound formulation. Both carvacrol and thymol (encapsulated and nonencapsulated), had a repellent activity against A. sculptum and R. sanguineus s.l nymphs. Amblyomma sculptum was more sensitive to nonencapsulated carvacrol (RC50 values: 0.0032 to 0.0082 mg/cm2 after 1 and 15 min) (P < 0.05), while R. sanguineus s.l. was more sensitive to encapsulated carvacrol (RC50 values: 0.00008 to 0.0035 mg/cm2 after 1 and 15 min) (P < 0.05). Among tick species, R. sanguineus s.l. was more sensitive for most compounds than A. sculptum (P < 0.05). Although with distinct repellent activities, carvacrol and thymol encapsulated can be a promising alternative to synthetic repellents against A. sculptum and R. sanguineus s.l.

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Lactones are cyclic esters of hydroxy carboxylic acids, present in several fruits and animals consumed by humans. There is evidence that some lactones modify insect behavior. The aim of the present study was to evaluate the repellent effect of four lactones (γ- and δ-nonalactone, and γ- and δ-dodecalactone) in first instar nymphs of the German cockroach, Blattella germanica (Linnaeus). To assess repellency, a nymph was placed on a circle of filter paper, half of which had been treated with lactone dissolved in acetone and the other half with acetone alone. The behavior of the nymph was recorded and the time the nymph spent in each half of the paper was quantified using Ethovision XT 10.1 software. Values of Distribution Coefficient (DC) were calculated: DC = (Tt - TA) / Tt, where Tt is the experimental time and TA is the time the nymph spent in the area treated with the repellent agent. DC can vary between 0 and 1. Values significantly higher than 0.5 indicate repellency. N,N-diethyl-meta-toluamide (DEET) was used as a positive control. DEET, δ- and γ-nonalactone caused repellency as from 77.9 µg/cm2, whereas γ- and δ-dodecalactone had a repellent effect starting at 779.0 µg/cm2. The values of DC for these concentrations were 0.89 (DEET), 0.86 (γ-nonalactone), 0.87 (δ-nonalactone), 0.83 (γ-dodecalactone), and 0.72 (δ-dodecalactone). To our knowledge, this is the first report of repellency produced by lactones in the German cockroach. This work allowed to identify two lactones that have a repellent effect similar to DEET.

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Amblyomma ticks pose a significant public health threat due to their potential to transmit pathogens associated with rickettsial diseases. (E)-2-octenal, a compound found in donkeys (Equus asinus), exhibits strong repellent properties against Amblyomma sculptum nymphs under laboratory conditions. This study assessed the effectiveness of the (E)-2-octenal in wearable slow-release devices for personal human protection against Amblyomma ticks under natural conditions. Slow-release devices treated with (E)-2-octenal and untreated controls were prepared and tested on two volunteers walking through a tick-infested area in Goiania, Brazil. The experiment was conducted twice daily for three series of 10 days, with each volunteer wearing two devices attached to each leg, one on the ankle and one just above the thigh. Volunteers with control and treated devices exchanged them between rounds. Also, the daily release rate of (E)-2-octenal from the slow-release devices was determined in the laboratory, increasing significantly from 0.77 ± 0.14 µg/day on the first day to 9.93 ± 1.92 µg/day on the 4th day and remaining constant until the 16th day. A total of 5409 ticks were collected from both volunteers. Treated devices resulted in recovering fewer ticks (n = 1,666; 31%) compared to untreated devices (control: n = 3,743; 69%). (E)-2-octenal effectively repelled Amblyomma spp. larvae, A. sculptum adults, and exhibited pronounced repellency against A. dubitatum nymphs and adults. These findings suggest the potential of (E)-2-octenal delivered by wearable slow-release devices as a green-based repellent. Further improvements, however, are necessary to provide better protection for humans against A. sculptum and A. dubitatum in field conditions.

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Triatomines are haematophagous insects, some species are vectors of Trypanosoma cruzi, the aetiological agent of Chagas disease. The main strategy for interrupting T. cruzi transmission is to avoid contact of the vector populations with humans. Volatiles from commercial essential oils are excellent candidates to serve as repellents of kissing bugs. We used an exposure device to assess the repellence effect of eight commercial essential oils on Triatoma pallidipennis. The most effective oils were blended and evaluated against T. infestans, T. pallidipennis and Rhodnius prolixus. The blend was also evaluated on parasitised T. pallidipennis. Data were compared with the commercial repellent NN-diethyl-3-methylbenzamide. We recorded the time the insects spent in the proximity of the host and determined if any of the evaluated oils served as kissing bug repellent. We found commercial essential oils and a blend that significantly reduced the time spent in the proximity of the host. The blend was effective for use by human males and females, repelling infected and non-infected insects. The study of essential oils as repellents of blood-sucking disease-vector insects could shed light on the development of new control strategies.

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The incidence of viruses such as Zika, Dengue, and Chikungunya affects human health worldwide, and insect repellents are recommended for individual protection. Formulations incorporating nanotechnology should be carefully assessed for toxicity, particularly regarding the security levels established for human health and the environment. This study evaluates the cytotoxicity of a repellent formulation containing zein nanoparticles (NP) loading geraniol (Ger) and icaridin (Ica) in three cell lines: NIH/3T3, HaCaT, and SIRC. To address formulation hazards, IC50 values were determined by MTT and Calcein-AM assays. In both NIH/3T3 and HaCaT, the IC50 values for NP + Ger + Ica formulation were around 0.2%. For risk assessment, cell viability was also determined after a single exposure and repeated exposure to the formulation. No evidence of cytotoxicity was observed for NP + Ger + Ica formulation-treated cells. The risk assessment for eye damage revealed cytotoxicity in SIRC cells when exposed to a 5% concentration, which may be attributed to ocular geraniol toxicity, because zein nanoparticles alone did not exhibit any signs of toxicity. Cell internalization indicated low uptake in NIH/3T3 and HaCaT cells. Phenotypic profiling resulted in similar phenotypes for untreated cells and cells exposed to NP + Ger + Ica formulation. The toxicological profile outlined by the multiparametric and orthogonal approach suggests that the NP + Ger + Ica formulation poses no significant risk to the topical application under the tested conditions. Adopting an orthogonal approach brings robustness to our findings.

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The mosquito Aedes aegypti is a major threat to public health because it spreads several arboviruses. Since this insect is an anthropophilic mosquito that has evolved to thrive in urban settings and is common in Brazil and other tropical nations, controlling its population growth is difficult. The two basic methods of control are eradicating its breeding grounds and applying pesticides. There have been reports of pesticide resistance emerging as well as DEET's potential danger for people, particularly youngsters. Therefore, research has been done to find novel insecticides and repellents. In this way, the goal of this research was to assess thymol's insecticidal and repellent activities in Ae. aegypti. Bioassays were performed with eggs, larvae and adults exposed to different concentrations of thymol. The findings demonstrated that thymol has insecticidal effect in both the immature and adult phases, eliminating the larvae in 24 hours. In addition, necrosis was observed in hemocytes, without alteration in the production of nitric oxide by the insects. When evaluating repellency, thymol showed 99.5% of landing inhibition. This leads to the conclusion that thymol can be employed as an active component in the formulation of insecticides and repellents for the Ae. aegypti mosquito.

O Aedes aegypti é um mosquito que causa grande impacto na saúde pública por ser o vetor de diversas arboviroses. Controlar a proliferação desse inseto é desafiador, já que é um mosquito antropofílico, altamente adaptado a ambientes urbanos e disseminado no Brasil e em outros países de clima tropical. A principal forma de combatê-lo é destruindo seus criadouros ou utilizando inseticidas. Há relatos do desenvolvimento de resistência aos inseticidas e da potencial toxicidade do DEET para os seres humanos, sobretudo crianças. Dessa forma, estudos vêm sendo realizados, a fim de buscar novas substâncias inseticidas e repelentes. Nesse sentido, o objetivo deste trabalho foi avaliar a atividade inseticida e repelente do timol em mosquitos Ae. aegypti. Foram realizados bioensaios com ovos, larvas e adultos expostos a diferentes concentrações de timol. Os resultados demonstraram que o timol possui ação inseticida tanto nas fases imaturas quanto no adulto, matando 100% das larvas em 24h. Além disso, observou-se necrose em hemócitos, sem alteração na produção de óxido nítrico pelos insetos. Ao avaliar a repelência, o timol apresentou 99,5% de inibição do pouso. Dessa forma, conclui-se que o timol pode ser utilizado como princípio ativo na composição de inseticidas e repelentes contra o mosquito Ae. aegypti.

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BACKGROUND: Herbicides are the most used class of pesticides worldwide, and insect repellents are widely used globally. Yet, there is a dearth of studies characterizing the associations between these chemical groups and human neurobehavior. Experimental studies suggest that glyphosate and 2,4-dichlorophenoxyacetic acid (2,4-D) herbicides can affect neurobehavior and the cholinergic and glutamatergic pathways in the brain. We aim to assess whether herbicides and insect repellents are associated with neurobehavioral performance in adolescents. METHODS: We assessed 519 participants (11-17 years of age) living in agricultural communities in Ecuador. We quantified urinary concentrations of glyphosate, 2,4-D, and two N,N-diethyl-meta-toluamide (DEET) insect repellent metabolites [3-(diethylcarbamoyl)benzoic acid (DCBA) and 3-(ethylcarbamoyl)benzoic acid (ECBA)] using isotope-dilution mass spectrometry. We assessed neurobehavioral performance using 9 subtests across 5 domains (attention/inhibitory control, memory/learning, language, visuospatial processing, and social perception). We characterized the associations using generalized estimating equations and multiple imputation for metabolites below detection limits. Models were adjusted for demographic and anthropometric characteristics, urinary creatinine, and sexual maturation. Mediation by salivary cortisol, dehydroepiandrosterone, 17ß-estradiol, and testosterone was assessed using structural equation modeling. RESULTS: The mean of each neurobehavioral domain score was between 7.0 and 8.7 [standard deviation (SD) range: 2.0-2.3]. Glyphosate was detected in 98.3% of participants, 2,4-D in 66.2%, DCBA in 63.3%, and ECBA in 33.4%. 2,4-D was negatively associated with all neurobehavioral domains, but statistically significant associations were observed with attention/inhibition [score difference per 50% higher metabolite concentration (ß)=-0.19 95% confidence interval (CI): -0.31, -0.07], language [ß=-0.12 (95% CI: -0.23, -0.01)], and memory/learning [ß=-0.11 (95% CI: -0.22, 0.01)]. Glyphosate had a statistically significant negative association only with social perception [ß=-0.08 (95% CI: -0.14, -0.01)]. DEET metabolites were not associated with neurobehavioral performance. Mediation by gender and adrenal hormones was not observed. CONCLUSION: This study describes worse neurobehavioral performance associated with herbicide exposures in adolescents, particularly with 2,4-D. Replication of these findings among other pediatric and adult populations is needed. https://doi.org/10.1289/EHP11383.

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Among the efforts to reduce mosquito-transmitted diseases, such as malaria and dengue fever, essential oils (EOs) have become increasingly popular as natural replacements for the repellant DEET. In this study, seven commercially available plant EOs against Aedes species mosquitoes were evaluated for their complete protection time (CPT, min) in vivo using human-hand in cage tests (GB2009/China and WHO2009). Among the EOs with the highest efficacy in repelling mosquitoes, Aedes albopictus (Skuse) were clove bud oil and patchouli oil. Both were further assessed according to the in vivo method recommended by the WHO, to determine their minimum effective dose and CPT. A comparison of the ED50 values (dose yielding a 50% repellent response) of these two EOs against Aedes aegypti(L.) showed that the ED50 (2.496 µg/cm2) of patchouli oil was 1248 times higher than that of clove bud oil (0.002 µg/cm2), thus demonstrating them greater efficacy of the latter in repelling Ae. aegypti mosquitoes. For the 2 EOs, eugenol was the major component with higher than 80% in relative amount of the clove bud oil. The patchouli oil had more than 30% of character chemical patchouli alcohol along with α-bulnesene (10.962%), α-guaiene (9.227%), and seychellene (7.566%). Clove bud oil was found to confer longer complete protection than patchouli oil against a common species of mosquito. These results suggest use of EOs as safe, highly potent repellents for use in daily life and against mosquito-transmitted diseases, such as malaria and dengue fever.

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Mosquito-borne diseases such as dengue, malaria, yellow fever, chikungunya and Zika virus affect millions of people worldwide each year. Vector control and personal protection are very important to minimize the spread of diseases, and the use of repellent is an economic practice to prevent them. The application of repellent, which acts on the skin to form a vapor layer with a repellent odor to mosquitos, is recommended as an economic prevention and practice. The natural botanical product Citronella is an effective mosquito repellent due to the high concentrations of active chemical constituents present, notably terpenic alcohols. However, citronella tends to evaporate quickly from the skin surface, resulting in a rapid loss of activity. Strategies to increase repellency time, while at the same time minimizing toxicity, are major focuses of research and development in natural repellent products. Here we highlight the role of extended-release systems (ERS) of citronella oil in this approach.