Oil Of Lemon Eucalyptus Research Articles

Commercial products are not effective at repelling European deer keds, Lipoptena cervi (Diptera: Hippoboscidae) but may increase mortality after exposure.

European deer keds, Lipoptena cervi (Linnaeus, 1758), are hematophagous ectoparasitic flies known to bite cervids and noncervids, including humans. To prevent deer keds from landing and biting hosts, 5 commercially available insect repellents (DEET, IR3535, oil of lemon eucalyptus (OLE), picaridin, and permethrin) and water control were evaluated to determine repellency efficacy and postexposure mortality of deer keds. While there was a significant difference between the groups tested, a post hoc analysis revealed that no treatment was significantly different from the water control. Deer ked survival was different amongst the treatments, with deer keds exposed to permethrin dying much sooner than those exposed to other treatments or control (median survival for permethrin = 0.58h). Post-hoc pairwise comparisons revealed that deer keds exposed to DEET or IR3535 had similar survival rates (4.82 and 5.15h, respectively). Still, there were significantly lower survival times for DEET compared to OLE (6.33h) and picaridin (15.00h). Deer keds exposed to the water control survived the longest (23.12h). Overall, deer ked repellency was not significantly different from the control, but permethrin-treated clothes can effectively kill deer keds in a short amount of time, thereby protecting those who recreate outdoors or encounter animals carrying deer keds.

A Study on Synthesis of para-menthane-3,8-diol (PMD) - A Safe Mosquito Repellent Active Ingredient

Active ingredient para-menthane-3,8-diol (PMD) is evaluated as effective in repelling insects in general and is recommended by the Centers for Disease Control and Prevention as an insect repellent, especially against mosquitoes worldwide. The present study attempted to evaluate the suitable conditions for the synthesis of PMD from two sources of materials that are pure (±)-citronellal (∼ 96%) and lemon eucalyptus (Eucalyptus citriodora) essential oil (∼ 60% citronellal) by treatment of sulfuric acid in a biphasic medium (H2O/essential oil). The one-factor-at-a-time method was used to determine the optimal conditions for the synthesis of PMD from pure (±)-citronellal. The effect of various factors such as oil-to-water ratio (citronellal to sulfuric acid aqueous solution), acid concentration (sulfuric acid), reaction temperature, and reaction time on the PMD yield and conversion of citronellal was investigated. The highest PMD yield (95.6%) with excellent conversion of citronellal (98.5%) was obtained at optimal conditions such as, oil to water ratio of 1:2, acid concentration of 0.75% (w/w), reaction temperature of 60°C, and reaction time of 6 h. These optimal conditions were applied to synthesize PMD from Eucalyptus citriodora essential oil. From 200 grams of essential oil and applied optimal conditions, PMD was obtained with a yield of 91.5%.

Preparation and evaluation of ecofriendly nanocreams containing some plant essential oils and monoterpenes against adults of Culex pipiens L. with some biochemical and histological studies on albino rat

Plant essential oils (EOs) are considered a vital tool of novel natural mosquito repellents and botanical adulticides. Five plant EOs (cinnamon, cypress, lavender, lemon eucalyptus and tea tree) and their major constituents (cinnamaldehyde, citronellal, β-cymene, (R)-linalool, and α-terpinyl acetate) were investigated against adults of Culex pipiens. The efficacy of the tested compounds was manipulated as mortality and knockdown using a fumigation technique. After that, the most active compounds against adults (lemon eucalyptus oil and linalool) were investigated once more as repellents after incorporating them on a cream base against C. pipiens adults compared to their nano-cream using arm-in-cage technique. In addition, the biochemical and histological effects of dermal treatment of linalool, lemon eucalyptus,, and their nanoemulsions (NEs) were studied on male albino rats. Total protein assay, acetylcholinesterase (AChE), adenosine triphosphatase (ATPase), and liver and kidney functions were determined in blood serum. Complete blood count (CBC) was determined in whole blood. The results showed that lemon eucalyptus oil and (R)-linalool caused the highest knockdown activity against C. pipiens adults with Kt50 40.29 s and 12.73 s, respectively. The repellent effect (RC50) of nanocream formulations of lemon eucalyptus oil (10.03 mg/L) and (R)-linalool (68.11 mg/L) were higher than the original effects of these compounds with RC50 values = 100.82 mg/L and 998.54 mg/L, respectively. There are no obvious harmful side effects of the dermal topical treatments of (R)-linalool and lemon eucalyptus oil on the tested biochemical parameters of treated albino rats compared with the control. Furthermore, there are no obvious effects of the dermal topical treatments of (R)-linalool and lemon eucalyptus oil on the histological status of the treated skin of albino rats compared with untreated treatment. The tested oils and monoterpenes could be considered promising candidates for botanical adulticides against C. pipiens. Also, nano-cream of lemon eucalyptus oil and (R)-linalool could be considered promising ecofriendly repellents for C. pipiens adults.

Ovicidal Aroma Shields for Prevention of Blow Fly Strikes Caused by Lucilia sericata (Meigen), Diptera: Calliphoridae.

The blow fly, Lucilia sericata (Meigen) (Diptera: Culicidae) is a primary facultative ectoparasite controlled by insecticides that have environmental and safety concerns; therefore, its natural and safe control is crucial. L. sericata eggs were subjected to 400 μL of 5% of 24 materials of plant-borne origin. The number of hatched and unhatched eggs were counted 24 h postexposure. Stopmyasis® expressed the highest ovicidal effect, followed by cedarwood, orange, and tea tree oils. The mean ovicidal results were 46.09-95.24% grouped as Class A, which provided the lowest hatchability rates. Even though benzoin, vanillin, citronella, and camphor oils grouped as Class B provided moderate ovicidal effects (33.69-43.92%), their efficacy differed significantly from those of the treatments in Classes A and C containing the control group and vetiver, eucalyptus, Olbas®, neem, sunflower, oil blends, patchouli, frankincense, p-menthane-3,8 diol (PMD), lavender, peppermint, cinnamon, calry sag, myrtle, and silicone oil. According to our knowledge, most (19 out of 24) applied materials were used as ovicides against L. serricata for the first time, except orange, eucalyptus, patchouli, cinnamon oils, and six of them were applied as ovicides against pests for the first time. Stopmyasis containing Géraniol and PMD is the drug of choice as an ecofriendly product to prevent blow fly strikes through correct diagnosis and prompt treatment preventing a disastrous and destructive course of the disease and improving quality of life.

EVALUATION OF POTENTIAL SPATIAL REPELLENCY OF CONTACT REPELLENTS AGAINST AEDES AEGYPTI (L.) IN A WIND TUNNEL

The use of arthropod repellents is an important personal protective measure against vector-borne diseases. For contact repellents, the recommendation to apply repellents to all exposed skin could be relaxed if the repellent exhibits spatial repellency. In 2019, we evaluated four contact repellents containing a mixture of geraniol and soybean natural oils, N,N-diethyl- 3-methyl-benzamide (DEET), 2-(2hydroxyethyl)-1-piperidine carboxylic acid 1-methylpropyl ester (Picaridin), and p-Menthane-3,8-diol (PMD) for their potential as spatial repellents against cohorts of irradiated and non-irradiated laboratory reared Aedes aegypti (L.) and irradiated Ae. aegypti females exposed to a radiation dose sufficient to sterilize (50 Gy). Evaluations were conducted in a modular wind tunnel, which provided mosquitoes the option to move within 15 minutes to the repellent side containing a repellent or to an attractant side containing BG lure. Mosquitoes on each side were counted and percent calculated based on the number of mosquitoes released for each test. The repellent containing PMD had significantly more non-irradiated mosquitoes on the attractant side than on the repellent side, indicating that it repelled non-irradiated mosquitoes. Picaridin had significantly more irradiated mosquitoes on the attractant side than on the repellent side indicating that it repelled irradiated mosquitoes. A minor change in behavior of irradiated and non-irradiated mosquitoes by these repellents can only create a false sense of protection. These results emphasize to strongly follow available guidance that the contact repellents tested in this study should be applied to all exposed skin.

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OPINION Reactions ShareShare onFacebookTwitterWechatLinked InRedditEmail C&EN, 2021, 99 (40), p 3November 1, 2021Cite this:C&EN 99, 40, 3Mosquito repellentI’m in the process of reading through this week’s C&EN and was looking forward to the article “A Better Natural Mosquito Repellent’’ (Oct. 4, 2021, page 8). Since I work in a forestry organization, our field crews are exposed to mosquitoes and, more worrisome these days, ticks.While my career vastly differs from what I researched during my PhD, working with insect attractants and such over the past decade has opened my eyes to how badly the cause-and-effect way of thinking adds blinders to peripheral vision, aka thinking outside the box. This is a great example: put out a citronella candle, see fewer mosquitoes. We accept the outcome, but are we missing steps with the mechanism? In the end, does this knowledge even matter? Perhaps yes, perhaps no.Given that p-menthane-3,8-diol (PMD) can be made at elevated temperatures, who’s to say the citronella candles are not producing PMD as the flame burns wax and generates the activation energy to convert citronellal. There would be ambient moisture in the air, and the proton could come from a number of sources. I have not taken the time yet to peruse the literature to see if any publications are out there that link PMD with a burning citronella candle, but it should be an easy connection to make with real-time mass spectrometry such as selected ion flow tube.I’ve always wondered about insect lures. Once we deploy them, they are at the mercy of the elements, and what we believe is the attractant could merely be an intermediate where a decomposition or rearrangement product is the true active compound, since the same could be happening with the insect that naturally produces these compounds. We know they work only because we catch specimens, but if we found out the attractant was a smaller degradation product, it would possibly save us time and effort at the bench level with fewer synthetic steps.Gaetan LeClairFredericton, New Brunswick CorrectionsOct. 11, 2021, page 35: The ACS Comment incorrectly says the Loconti Scholarship awarded by the Project SEED Committee was $20,000. It was $5,000.Oct. 18, 2021, page 21: The feature story on the conference of the National Organization for the Professional Advancement of Black Chemists and Chemical Engineers has the incorrect year for the 50th anniversary celebration. It is tentatively scheduled for 2023, not 2022.Oct. 25, 2021, page 7: The news article on jellyfish’s diets incorrectly describes the food in the experiment. The brine shrimp were live, not frozen. The krill were frozen, not live. And the moon jellies rejected the krill, not the brine shrimp.

A better natural mosquito repellent

Found in lemon eucalyptus, p -menthane-3,8-diol (PMD) is the only natural chemical on the US Centers for Disease Control and Prevention’s list of recommended mosquito repellents. Scientists have now discovered that one form of PMD may repel certain types of mosquitoes nearly as well as the benchmark synthetic mosquito repellent, DEET, while being significantly less toxic to people ( J. Agric. Food Chem. 2021, DOI: 10.1021/acs.jafc.1c03897 ). DEET is commonly used to fend off mosquitoes, but it can irritate the skin and be neurotoxic . Many natural alternatives are less toxic but evaporate quickly, limiting their effectiveness. In contrast, PMD lasts longer. In nature, PMD can be found as a mix of four diastereomers, so organic chemist Marc Lemaire of Claude Bernard University Lyon and colleagues in France and Madagascar tested how well each of the diastereomers repelled the Aedes albopictus mosquito . On human skin, one diastereomer, (1 R

Effect of the Stereoselectivity of para-Menthane-3,8-diol Isomers on Repulsion toward Aedes albopictus.

Vector-borne diseases cause around 700,000 deaths every year. Insect repellents are one of the strategies to limit them. Para-menthane-3,8-diol (PMD), a natural compound, is one of the most promising alternatives to conventional synthetic repellents. This work describes a diastereodivergent method to synthesize each diastereoisomer of PMD from enantiopure citronellal and studies their repellence activity against Aedes albopictus. We found that cis-PMD is the kinetic control product of the cyclization of citronellal, while trans-PMD is the thermodynamic control product. X-ray diffraction analysis of crystals highlighted some differences in hydrogen-bond patterns between cis or trans isomers. The present paper demonstrates that (1R)-(+)-cis-PMD has the highest repellency index using a new evaluation system for 24 h. (1S)-(-)-cis-PMD has somewhat lower and (1S)-(+)-trans-PMD and (1R)-(-)-trans-PMD have a slight effect. Volunteer tests show that (1R)-(+)-cis-PMD is the most efficient. This effect could be ascribed to the interaction of PMD/insect odorant receptors and their physical properties, that is, the evaporation rate.

A novel Tick Carousel Assay for testing efficacy of repellents on Amblyomma americanum L.

Ticks are important vectors of human and veterinary diseases. A primary way ticks gain access to human hosts is by engaging to clothing. Repellents or acaricides sprayed onto fabric are used to deter ticks’ access to human hosts. However, there are a limited amount of standardized laboratory assays that can determine the potency and efficacy of repellents. We present a novel fabric-engagement assay referred to as the ‘Tick Carousel Assay’. This assay utilizes fabric brushing past ticks located on an artificial grass patch and measures tick engagements to fabric over time. After screening a variety of tick species, we used the lone star tick (Amblyomma americanum) to test the efficacy of four commonly used active ingredients in repellents: DEET, Picaridin, IR3535, and Oil of Lemon Eucalyptus. Repellency was tested immediately, after three hours, and six hours post application to fabric. Our data show that each repellent we tested significantly reduced the number of tick engagements to fabric for at least 6 hours. We did not find significant differences in repellent efficacy between the four active ingredients tested directly and three hours after application. After six hours, Oil of Lemon Eucalyptus repelled ticks more than the other active ingredients. We show that our Tick Carousel Assay provides an affordable, repeatable, and standardized way to compare and test repellent efficacy on treated fabrics. Our results confirm that commonly used repellents applied to fabric are an effective way to reduce tick engagement.

A Novel Polymer Insect Repellent Conjugate for Extended Release and Decreased Skin Permeation of Para-Menthane-3,8-Diol.

Background: We developed a novel polymer insect repellent conjugate for extended release and decreased skin permeation of the volatile insect repellent p-menthane-3,8-diol (PMD). Methods: PMD was conjugated with acryloyl chloride via an ester bond to form acryloyl–PMD, which was subsequently copolymerised with acrylic acid at varying molar ratios. Copolymer structures were characterised by 1H NMR and FT-IR, analysed by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), molecular weights and reactivity ratios determined, and repellent loading assessed. Results: Using porcine liver esterases, ~45% of the insect repellent was released over five days. Penetration and permeation studies of the copolymer and free repellent using excised, full-thickness porcine ear skin showed no detectable permeation of the copolymer through skin compared to the PMD. Moreover, tape stripping revealed that over 90% of the copolymer remained on the outer surface of the skin, whereas free PMD was within all skin layers. A planarian toxicity fluorescence assay indicated that that the copolymer is unlikely to be a significant irritant when applied topically. Conclusions: this study demonstrates the feasibility of the copolymer approach to develop extended-release insect repellents while reducing skin uptake and transdermal permeation of the small-molecular-weight active ingredient, in order to minimise any adverse effects.

Characterisation of actions of p-menthane-3,8-diol repellent formulations against Aedes aegypti mosquitoes.

Characterisation of mosquito repellents using arm-in-cage tests are performed by assessing the 95% effective dose (ED95), half-life and complete protection time (CPT). This study fully characterizes these properties for p-menthane-3,8-diol (PMD), which has not been widely studied, and a long-acting formulation containing a PMD-vanillin composite. A series of arm-in-cage tests against Aedes aegypti (Diptera: Culicidae) mosquitoes were devised using 6 volunteers to estimate CPT or 10 to estimate the ED95 and half-lives for three repellents: 20% N,N-diethyl-3-methylbenzamide (DEET), 30% PMD and a novel 30% PMD-vanillin formulation. Non-linear regression analysis was used to characterize the relationship between applied dose and CPT. PMD and DEET showed a very similar log dose relationship to CPT; however, the PMD-vanillin formulation exhibited a sigmoidal 'S-shaped' relationship. This resulted in a 1.5-fold higher CPT for PMD-vanillin compared with that of 20% DEET when applied at a dose of 1.6mg/cm2, but little difference was observed at lower doses of 0.8-1mg/cm2. The ED95 value for the 30% PMD and PMD-vanillin formulations were 0.25 and 0.24mg/cm2, respectively, these being higher than that for 20% DEET (0.09mg/cm2). The half-lives for 30% PMD and 20% DEET were similar (2.23vs. 2.74h), but longer for the PMD-vanillin formulations (3.8h). A full characterisation for other repellent formulations, particularly those claiming extended longevity, should be conducted in order to identify differences at various applied doses.

The Effect of Essential Oil Formula and Para Menthane Diol on Mortality and Oviposition Deterrent of Brown Planthopper

<p><em>Essential oils such as clove, lemongrass, and citronella are known as botanical insecticides. Mixed-essential oils and a single compound of the oil itself may increase its efficacy. The experiment aimed to examine the effect of the essential oil mixture and para-menthane-3,8-diol (PMD) formulas in inhibiting of the egg-laying and mortality of brown planthopper. The study conducted at the greenhouse of Indonesian Spices and Medicinal Crops Research Institute, Bogor. The formula tested were clove+citronella oils (1:1), clove+lemongrass oils (1:1), the single essential oil, solvent materials (a mixture of tween 80, Turpentine, and surfactant), PMD-solvent substances (emulsifier, alcohol 96%, and surfactant). A contact application was applied to the insect. Observation parameters were egg numbers laid and brown planthopper adult and nymph mortalities. The result of the insect contact application method showed that adult mortality was not significantly different compare with control and synthetic insecticide. Based on the plant residue test, nymph mortality due to clove oil + citronella oils were not significantly <em>different from control and insecticide. Meanwhile, based on the insect and plant spray test, adult mortality on clove oil + citronella was not differently significant from the synthetic insecticide. However, the effectiveness of clove+lemongrass oils was slower. The efficacy of the oil formula to the egg laid was significantly different from the synthetic insecticide treatment, i.e., fewer eggs laid. PMD was less effective than the essential oil formula on the nymphs and adult mortalities </em>of <em>brown planthopper</em><em>. Further field evaluations of the clove oil + citronella formulas are required.</em></em></p>

Insect repellents mediate species-specific olfactory behaviours in mosquitoes

BackgroundThe species-specific mode of action for DEET and many other mosquito repellents is often unclear. Confusion may arise for many reasons. First, the response of a single mosquito species is often used to represent all mosquito species. Second, behavioural studies usually test the effect of repellents on mosquito attraction towards human odorants, rather than their direct repulsive effect on mosquitoes. Third, the mosquito sensory neuron responses towards repellents are often not directly examined.MethodsA close proximity response assay was used to test the direct repulsive effect of six mosquito repellents on Anopheles coluzzii, Aedes aegypti and Culex quinquefasciatus mosquitoes. Additionally, the behavioural assay and calcium imaging recordings of antennae were used to test the response of An. coluzzii mosquitoes towards two human odorants (1-octen-3-ol and benzaldehyde) at different concentrations, and mixtures of the repellents lemongrass oil and p-menthane-3,8-diol (PMD) with DEET.ResultsAnopheles coluzzii mosquitoes were repelled by lemongrass oil and PMD, while Ae. aegypti and Cx. quinquefasciatus mosquitoes were repelled by lemongrass oil, PMD, eugenol, and DEET. In addition, high concentrations of 1-octen-3-ol and benzaldehyde were repellent, and activated more olfactory receptor neurons on the An. coluzzii antennae than lower concentrations. Finally, changes in olfactory responses to repellent mixtures reflected changes in repulsive behaviours.ConclusionsThe findings described here suggest that different species of mosquitoes have different behavioural responses to repellents. The data further suggest that high-odour concentrations may recruit repellent-sensing neurons, or generally excite many olfactory neurons, yielding repellent behavioural responses. Finally, DEET can decrease the neuronal and behavioural response of An. coluzzii mosquitoes towards PMD but not towards lemongrass oil. Overall, these studies can help inform mosquito repellent choice by species, guide decisions on effective repellent blends, and could ultimately identify the olfactory neurons and receptors in mosquitoes that mediate repellency.

Efficacy and repellency of some essential oils and their blends against larval and adult house flies, Musca domestica L. (Diptera: Muscidae).

House flies are global pests and notoriously difficult to control. Essential oils of vetiver, cinnamon, and lavender and their blends were tested for toxic and repellent effects against larval and adult flies. All of the oils had moderate toxicity for eggs. Mortality of 2nd instar larvae was 57-78% in dipping assays, 38-100% in contact assays, and 94-100% in treated media. Lavender was less effective (38% mortality) than the others (91-100%) in contact bioassays. Oil blends were not more effective against larvae than individual oils. Vetiver and cinnamon oils were strongly repellent (84 and 78%, respectively) for larvae in treated media. None of the oils were repellent for adult house flies in olfactometer assays, but testing of additional products demonstrated significant repellency for neem oil, p-menthane-3,8-diol (PMD), and vanillin. Contact/fumigant toxicity of vetiver, cinnamon, and lavender oils was 100%, significantly higher than mortality from sunflower oil (67%). Blends of oils were not more effective against adults than the individual oils, but blends diluted with sunflower oil were as effective as the individual oils. Essentials oils of vetiver and cinnamon may have potential for fly management in situations where conventional insecticides cannot be used.

A Milestone In Botanical Mosquito Repellents: Novel PMD-Based Formulation Protects More Than Twice As Long As High-Concentration Deet and Other Leading Products.

The use of skin-applied repellents is the primary method recommended by the Centers for Disease Control and Prevention for personal protection against biting mosquitoes. Historically, the majority of long-efficacy mosquito repellents have been N,N diethyl-3-methylbenzamide (deet)-based. Recently, a variety of new botanical formulations have been marketed, but their protection times generally continue to fall well short of high-concentration deet products. We present a laboratory arm-in-cage study of a Neo-Innova® repellent that has a prolonged action "NEO-PART®" (Prolonged Action Release Technology) formulation with 40% Citriodiol®. This formulation provides the botanical molecule para-menthane 3,8-diol (PMD) at 25% w/v of the total formulation. Against Aedes aegypti, Neo-Innova's mean complete protection time (CPT; 14.2 h) was approximately 2 to 3 times longer than that of 5 leading high-performance repellents marketed in the USA, including 25% deet and a 20% PMD ethanolic formulation. When testing Neo-Innova, 5 of the 6 subjects had no landings after 15 h. The 6th had single landings at 10 and 11 h (individual CPT of 10 h), but received no additional landings in further exposures made at 13 and 15 h. Neo-Innova repellency against Culex quinquefasciatus was similarly prolonged. The tremendous increment in repellency duration observed for the Neo-Innova product, when compared with both current standard and botanical repellent options, represents a milestone in repellent development and supports "once-a-day" applications as a practical strategy for personal protection against mosquitoes.

Field evaluation of personal protection methods against outdoor-biting mosquitoes in Lao PDR

BackgroundProtecting people outdoors against mosquito-borne diseases is a major challenge. Here we compared commercially available personal protection methods to identify the most effective method for outdoor use in northern Lao PDR.MethodsFrom June to August 2016 the protective efficacy of treatments were compared in a secondary forest during the afternoon and a village during the evening. Comparisons were made using a replicated Latin square design between: (i) short permethrin-treated overalls; (ii) long permethrin-treated overalls; (iii) short untreated overalls with para-menthane-3,8-diol (PMD) applied topically; (iv) short permethrin-treated overalls plus PMD applied topically; (v) short untreated overalls with metofluthrin coils in a metal casing worn on a belt; and (vi) long untreated overalls. Short untreated overalls served as the control. Cone tests were conducted on the treated and untreated fabric before and after field experiments. A questionnaire survey was used to measure social acceptability.ResultsMosquito coils in a metal casing worn on a belt resulted in 92.3% (95% confidence interval, CI: 88.9–94.6%). landing protection from female mosquitoes in the afternoon and 68.8% (95% CI: 41.7–83.3%) protection in the evening compared to short untreated clothing. PMD was protective both when combined with short permethrin-treated overalls (afternoon, 68.2%, 95% CI: 52.6–78.7%; evening, 52.3%, 95% CI: 33.8–65.7%) and when used in combination with short untreated overalls (afternoon, 55.0%, 95% CI: 41.7–65.2%; evening, 25.2%, 95% CI: 9.4–38.2%). Whilst long permethrin-treated overalls were protective (afternoon, 61.1%, 95% CI: 51.4–68.8%; evening, 43.0%, 95% CI: 25.5–56.4%), short permethrin-treated overalls and long untreated overalls were not. Exposure to new permethrin-treated fabric in cone tests resulted in 25.0% (95% CI, 17.8–32.2%) and 26.2% (95% CI 16.7–35.8%) mortality for susceptible Ae. albopictus and susceptible Ae. aegypti, respectively. There was a loss of efficacy of permethrin-treated clothing after use in the field, with 3 min knockdown rates of Ae. albopictus and 1 h knockdown of Ae. aegypti decreasing over time. Participants considered all treatments acceptable.ConclusionsThe portable mosquito coils were highly protective against outdoor biting mosquitoes, although there are safety concerns related to its use. The combination of permethrin-treated clothing and PMD repellent represent an alternative treatment for protection against outdoor-biting mosquitoes.

Evaluation of standard field and laboratory methods to compare protection times of the topical repellents PMD and DEET

Mosquitoes are important vectors of pathogens, and travellers to disease endemic countries are advised to avoid bites by applying topical repellents. Topical repellents are typically tested either in the arm-in-cage (AIC) test under laboratory conditions or in the field, but not often under both conditions. We, therefore, investigated how two topical repellents, 15% para-menthane-3,8-diol (PMD) and 15% N,N-diethyl-3-methylbenzamide (DEET) compare against each other both in the AIC test against three species recommended by the World Health Organization (i.e. Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus) and at two field sites in Switzerland, while using the same study participants in all experiments. In the field, the median complete protection time (CPT) was at least 6 hours for both PMD and DEET, while in the AIC test DEET slightly outperformed PMD. CPTs for DEET in the AIC test were 0.5, 2 and 2 hours against Ae. aegypti, An. stephensi and Cx. quinquefasciatus, respectively, and the corresponding median CPTs for PMD were 0.5, 1 and 0.5 hours. In conclusion, DEET slightly outperformed PMD in the AIC test, while the observed landing rates suggest the AIC test to underestimate efficacy of topical repellents in areas with lower landing pressure.

Effect of the Topical Repellent para-Menthane-3,8-diol on Blood Feeding Behavior and Fecundity of the Dengue Virus Vector Aedes aegypti.

Dengue fever is an acute disease caused by the dengue virus and transmitted primarily by the mosquito Aedes aegypti. The current strategy for dengue prevention is vector control including the use of topical repellents to reduce mosquito biting. Although N,N-diethyl-m-methylbenzamide (DEET) is the most common active ingredient in topical repellent products, para-menthane-3,8-diol (PMD) is also used commercially. Studies have indicated PMD reduced biting by 90–95% for up to 6–8 h, similar to the efficacy of DEET, depending on the testing environment. The purpose of this study was to evaluate the behavioral effects of PMD on Ae. aegypti blood feeding and fecundity to explore the potential impact of PMD on downstream mosquito life-history traits. Two experiments were performed. In both experiments, cohorts of female Ae. aegypti (Belize strain) were exposed to 20% PMD or ethanol for 10 min in a closed system and introduced to an artificial membrane feeding system. Following a 30min feed time, mosquitoes of Experiment 1 were killed and weighed as a proxy measure of blood meal, whereas mosquitoes of Experiment 2 were monitored for oviposition, a measure of fecundity. Results showed a statistically significant reduction (p < 0.001) in the percentage of Ae. aegypti that blood-fed when exposed to PMD (38%) compared to those non-exposed (49%). No significant difference in fecundity between test populations was indicated. These findings suggest that exposure of Ae. aegypti to 20% PMD may influence the probability of subsequent blood feeding but of those mosquitoes that do blood feed, egg-lay density is not affected. Further studies are warranted to investigate the full range of effects of PMD exposure on other Ae. aegypti life-history traits such as mating, to continue characterizing the potential effects of PMD to impact overall vector population dynamics.

A review of recommendations on the safe and effective use of topical mosquito repellents.

Mosquito-borne disease is an annual problem in Australia, with endemic pathogens such as Ross River virus infecting thousands of people each year. The recent emergence of Zika virus in South America and the Pacific, together with ongoing outbreaks of dengue viruses in Southeast Asia, generated great community interest in the most effective strategies to avoid mosquito bites. Large-scale mosquito control programs are not common in Australia and are limited in New South Wales (NSW). The use of topical insect repellents is a key recommendation by health authorities to prevent mosquito-borne disease. All products sold in Australia purporting to repel mosquitoes must be registered with the Australian Pesticides and Veterinary Medicines Authority. Despite around 100 commercial products registered as repelling mosquitoes, there are relatively few active ingredients used across these formulations. The most common are diethyltoluamide (DEET), picaridin, p-menthane-3,8-diol (PMD) and a range of plant-derived products (e.g. melaleuca, eucalyptus, citronella oils). Research has shown that each of these active ingredients varies in the duration of protection provided against biting mosquitoes. Recommendations by health authorities are informed by this research, but inconsistencies between recommendations and available repellent formulations and their concentration of active ingredients can cause confusion in the community. There are conflicts between the data resulting from scholarly research, marketing promotion by manufacturers and recommendations provided by overseas health authorities. A review was undertaken of NSW Health's current recommendations on choosing and using insect repellents, taking into consideration recent research and currently registered topical repellents.

EPA-Registered Repellents for Mosquitoes Transmitting Emerging Viral Disease.

In many parts of the United States, mosquitoes were previously nuisance pests. However, they now represent a potential threat in the spread of viral diseases. The Aedes aegypti, Aedes albopictus, and Culex species mosquitoes are endemic to the United States and together may transmit a variety of viral diseases of growing concern, including West Nile virus, chikungunya, dengue fever, and Zika virus. The Centers for Disease Control and Prevention and the Environmental Protection Agency (EPA) recommend N,N-diethyl-meta-toluamide (DEET) as a first-line mosquito repellent, but for patients refusing to use DEET or other conventional repellents, guidance is limited to any EPA-registered product. Therefore, we conducted a systematic review of the literature to identify which EPA-registered personal mosquito repellent provides the best protection from A. aegypti, A. albopictus, and Culex spp. mosquitoes. We abstracted data from 62 published reports of EPA-registered mosquito repellents. The conventional repellent picaridin has the strongest data to support its use as a second-line agent, while IR3535 and oil of lemon eucalyptus are reasonably effective natural products. Citronella, catnip, and 2-undecanone offer limited protection or have limited data. These results can be used by pharmacists and other health care professionals to advise patients on the selection of an EPA-registered mosquito repellent. Regardless of the repellent chosen, it is vital for patients to follow all instructions/precautions in the product labeling to ensure safe and effective use.