Sequential Isolation of Essential Oils Repellent to the Red Palm Weevil Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae).

The push-pull approach using semiochemicals in pest control requires both an attractant and a repellent. Many previous studies have arbitrarily tested one or more known insect repellents or plant essential oils (EOs) hoping to find repellents of an insect pest. We used a comprehensive approach that synergistically tests in the field numerous natural volatiles from commercial EOs to identify repellents of the red palm weevil Rhynchophorus ferrugineus (Coleoptera: Curculionidae), a worldwide pest of palms and date palms. Volatiles from 79 EOs in slow-release devices were divided into five groups and tested in traps with attractive pheromone compared to traps with pheromone alone. EO-treatment groups exhibiting repellency due to significant trap shutdown, were further subdivided into subgroups of four EOs each and tested further. Two groups of four EOs (cypress, desert wormwood, elemi, and Eucalyptus citriodora) and (niaouli, nutmeg, oregano, and orange sweet), or their corresponding mixtures of major volatiles, caused pheromone trap reductions of up to 92%. Further tests showed that seven of the eight EOs are similarly repellent as the corresponding subgroup. This systematic approach of successively testing sub-fractions of EOs in the field for trap shutdown should be useful to identify repellents of other insect pests of crops.

The Effect of Long-lasting Permethrin Impregnated Socks on Tick Bite in Korea.

BACKGROUND: The risk of tick-borne diseases is decreased by increasing awareness and knowledge through prevention education. The aim of the present study was to evaluate the effect of long-lasting permethrin impregnated (LLPI) socks for tick bites. METHODS: A randomized open label study was conducted to determine the effectiveness of LLPI socks for prevention of tick bites among 367 adults living in a rural area. Participants completed questionnaires at the start of follow-up (July 2014) and at the end of follow-up (December 2014), and tick bites were reported. RESULTS: A total of 332 subjects completed the follow-up survey. The tick bite rate of the two groups was not significantly different (3.6% vs. 3.1%). But the tick bite rate of lower extremities of subjects wearing LLPI socks was significantly lower compared to that of subjects wearing general socks. CONCLUSION: The tick bite rate was not different between the two groups, but the tick bite rate of lower extremities of LLPI was significantly lower than general groups. Further study is needed to investigate the effect of LLPI clothes with larger populations.

Ethnobotanical knowledge on botanical repellents employed in the African region against mosquito vectors - A review.

Mosquitoes (Diptera: Culicidae) represent a huge threat for millions of humans and animals worldwide, since they act as vectors for important parasites and pathogens, including malaria, filariasis and important arboviruses, such as dengue, West Nile and Zika virus. No vaccines or other specific treatments are available against the arboviruses transmitted by mosquitoes, and avoidance of mosquito bites remains the best strategy. African regions are usually hit most whose inhabitants are poor, and the use of repellent plants is the only efficient protection against vectors they have. Ethnobotanical knowledge of such plants and their use is usually passed on orally from one generation to another. However, it is also important to preserve this information in a written form, as well. Ethnobotanical research projects carried out in the regions of today's Ethiopia, South Africa, Nigeria, Kenya, and Tanzania indicate that the native inhabitants of the African study regions traditionally use 64 plant species, belonging to 30 families. Aromatic plants (i.e., Citrus spp., Eucalyptus spp., Lantana camara, Ocimum spp. and Lippia javanica) the most commonly used in all the study regions. Native people know three major methods of using repellent plants: (i) production of repellent smoke from burning plants, (ii) hanging plants inside the house or sprinkling leaves on the floor, (iii) the use of plant oils, juices from crushed fresh parts of the plants, or various prepared extracts applied on uncovered body parts. Overall, this review covers studies conducted only in a limited part of the African continent, highlighting the importance to undertake further research efforts to preserve the unique knowledge and traditions of the native tribes.

Sigillin†A, a unique polychlorinated arthropod deterrent from the snow flea Ceratophysella sigillata.

The snow flea Ceratophysella sigillata, a winter-active species of springtail, produces unique polychlorinated octahydroisocoumarins to repel predators. The structure of the major compound, sigillin A, was elucidated through isolation, spectroscopic analysis, and X-ray crystallography. Sigillin A showed high repellent activity in a bioassay with predatory ants. A promising approach for the total synthesis of members of this new class of natural compounds was also developed.

Two Lactones Non-toxic to Humans Are Effective Repellents for the German Cockroach.

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.

Repellent and Attractant Activities of Organic Compounds on Female and Male Philonthus decorus (Coleoptera, Staphylinidae).

The use of organic compounds in different spheres of human activity is accompanied by their influx to and accumulation in the environment. The negative impact of those compounds can be one of the reasons for a decline in populations and biodiversity of aboveground invertebrates. Chemical compounds can potentially cause a variety of effects (attractant or repellent) on insects, including species of the Staphylinidae family. In a laboratory experiment, we identified repellent and attractant influence of 40 organic compounds and mixtures of compounds (acids, alcohols, ketones, phenols, aldehydes, aromatic carbohydrates solvents, and vehicle fuels) on Philonthus decorus Gravenhorst, 1802. The ambulatory responses of the males and females to the same chemical compounds most often varied. A strong repellent activity against both sexes of Ph. decorus was caused by oleic acid, while hexane repelled the males. Acetic acid, 1-butanol, and ammonia solution were found to be strongly repellent against females. A moderate (average) repellent activity towards male Ph. decorus was displayed by organic solvents and fuels, some alcohols (isopropanol, isoamyl alcohol, methanol, ethanol), acids (acetic, formic acid), aromatic carbohydrates (toluene, xylene), and formaldehyde. Female Ph. decorus in general were less sensitive to the odors. The list of repellents with moderate activity against the females was much shorter: solvent 646, white spirit, toluene, isopropanol, isoamyl alcohol, citric and oxalic acids, and glycerol. Moderate attractant activity for Ph. decorus was exhibited by some amino acids, alcohols, and fuel mixes: glycine and L-cysteine (for the males), and phenylalanine, methanol, and diesel fuel (for the females). The rest of the 40 chemical compounds we studied caused no ambulatory responses in Ph. decorus. The difficulties we encountered in the interpretation of the results suggest a need for further experimental studies that would expand the knowledge of the chemoecology of insects.

Dengue havoc: overview and eco-friendly strategies to forestall the current epidemic.

Dengue fever is a mosquito-borne viral illness that affects over 100 nations around the world, including Africa, America, the Eastern Mediterranean, Southeast Asia, and the Western Pacific. Those who get infected by virus for the second time are at greater risk of having persistent dengue symptoms. Dengue fever has yet to be treated with a long-lasting vaccination or medication. Because of their ease of use, mosquito repellents have become popular as a dengue prevention technique. However, this has resulted in environmental degradation and harm, as well as bioaccumulation and biomagnification of hazardous residues in the ecosystem. Synthetic pesticides have caused a plethora of serious problems that were not foreseen when they were originally introduced. The harm caused by the allopathic medications/synthetic pesticides/chemical mosquito repellents has paved the door to employment of eco-friendly/green approaches in order to reduce dengue cases while protecting the integrity of the nearby environment too. Since the cases of dengue have become rampant these days, hence, starting the medication obtained from green approaches as soon as the disease is detected is advisable. In the present paper, we recommend environmentally friendly dengue management strategies, which, when combined with a reasonable number of vector control approaches, may help to avoid the dengue havoc as well as help in maintaining the integrity of the ecosystem.

Essential Oils: Useful Tools in Storage-Pest Management.

This study aimed to verify the level of repellent and mortality effect of two chemical substances (DEET and 2-undecanone) and seven essential oils (EOs), Allium sativum, Artemisia annua, Ocimum basilicum, Lavandula angustifolia, Eucalyptus globulus, Pinus sylvestris, and Curcuma longa. The storage pests Tribolium confusum, Tenebrio molitor, and Acanthoscelides obtectus were exposed to various concentrations in an olfactometer-and-mortality test. The effects were recorded 24-48-72 h after the treatments were applied. A. sativum, E. globulus, and L. augustifolia were found to have significant repellence effects. A substantial lethal effect was observed for A. sativum, E. globulus, and O. basilicum. We also found that even if the most efficient EOs were diluted to low concentrations, they still produced repellent and mortality effects. The presented results indicate that A. sativum and O. basilicum were the most effective against T. confusum and T. molitor; simultaneously, L. angustifolia and C. longa showed high activity against A. obtectus. All of these efficient EOs could be applied as effective bio-control agents in various stored conditions.

Drosophila melanogaster Chemosensory Pathways as Potential Targets to Curb the Insect Menace.

From a unicellular bacterium to a more complex human, smell and taste form an integral part of the basic sensory system. In fruit flies Drosophila melanogaster, the behavioral responses to odorants and tastants are simple, though quite sensitive, and robust. They explain the organization and elementary functioning of the chemosensory system. Molecular and functional analyses of the receptors and other critical molecules involved in olfaction and gustation are not yet completely understood. Hence, a better understanding of chemosensory cue-dependent fruit flies, playing a major role in deciphering the host-seeking behavior of pathogen transmitting insect vectors (mosquitoes, sandflies, ticks) and crop pests (Drosophila suzukii, Queensland fruit fly), is needed. Using D. melanogaster as a model organism, the knowledge gained may be implemented to design new means of controlling insects as well as in analyzing current batches of insect and pest repellents. In this review, the complete mechanisms of olfactory and gustatory perception, along with their implementation in controlling the global threat of disease-transmitting insect vectors and crop-damaging pests, are explained in fruit flies.

A Combined Computational Methodology for the Discovery of Hit Compounds with Putative Insect Repellency Properties.

Mosquitoes and other hematophagous arthropods, the primary vectors of multiple parasites and viruses, are responsible for the transmission of serious diseases to humans. Nowadays, the interest is focused on the development of novel repellents to the existing ones with advanced properties. The present study attempts the discovery of novel hit compounds which may evolve as insect repellents using a combined computational methodology targeting the Odorant Binding Protein 1 (OBP1). The in silico results indicated two compounds, namely coniferyl alcohol and 1,2-diphenyl-2-propanol, which were further evaluated (a) in vitro for their binding affinity to AgamOBP1 and (b) in vivo using dose-dependent repellence tests against the aggressive-day biting Aedes albopictus. The combination of in vitro and in vivo results pointed that coniferyl alcohol and 1,2-diphenyl-2-propanol exhibited high binding affinity over OBP1 with 69.4 and 84.7 nM, respectively as well as efficient repellent activity. Compounds were also tested for their dose-dependent repellency activity in vivo against Aedes albopictus. Overall, the selected compounds can serve as scaffolds for the development of novel repellents.

Efficacy and safety of repellents marketed in Brazil against bites from Aedes aegypti and Aedes albopictus: A systematic review.

BACKGROUND: Dengue, Zika and Chikungunya viruses represent a serious public health problem. No evidence is available on the efficacy of repellents commercially available in Brazil. This systematic review assessed the efficacy and safety of products containing repellents commercially available in Brazil for protection against bites from Aedes aegypti and Aedes albopictus. METHODS: We performed a systematic review using the CENTRAL, MEDLINE, EMBASE, CINAHL, Web of Science, AMED, LILACS and Scopus databases. Randomized clinical trials and non-randomized clinical trials comparing topical repellent products registered with the Brazilian Health Surveillance Agency were included. Main outcomes of interest investigated were adverse effects, percentage repellency and protection time against bites. Pairs of reviewers selected the studies, extracted the data and evaluated the risk of bias. RESULTS: Sixteen studies were included. No adverse effects were reported by the studies. Against Ae. aegypti: protection time using DEET (10% and 20%-spray) was similar to IR3535 (10% and 20%-spray) and longer than citronella (5%-spray). DEET (25%-solution) had longer protection time than eucalyptus (25%-solution), while DEET (20%-lotion) had longer protection time than citronella (10%-lotion). There was no difference in protection time between herbal repellents. DEET (7% and 15%- spray) had higher percentage repellency compared to both icaridin (7%-spray) and IR3535 (20%-spray). Against Ae. albopictus: DEET (15%-spray) had a similar protection time to icaridin (20%-spray), but longer than citronella (10%-spray). CONCLUSION: DEET proved more effective than the other synthetic and natural repellents marketed in Brazil for protecting against bites from the mosquito species investigated. All repellents studied exhibited satisfactory safety profile.

Use of insect repellent as personal protection among women of childbearing age in an arbovirus endemic area in Northeastern Brazil / Uso de repelente como medida de proteção pessoal por mulheres em idade fértil residentes em áreas endêmicas para arboviroses no Nordeste do Brasil

ABSTRACT 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.

RESUMO Objetivo: Analisar os fatores associados ao uso de repelente individual por mulheres em idade fértil residentes em área endêmicas para arboviroses em Fortaleza, Brasil. Métodos: Coorte realizada entre 2018 e 2019, com mulheres entre 15 e 39 anos, moradoras em Fortaleza, Ceará, Brasil. Participaram 1.173 mulheres, usuárias de quatro unidades primárias de saúde do município. O desfecho foi categorizado em: uso continuado, uso descontinuado e não uso de repelente. Realizada análise de regressão logística multinominal norteada por modelo hierárquico, com apresentação dos respectivos odds ratio (OR) e intervalos de confiança de 95% (IC95%). As variáveis independentes incluem: dados socioeconômicos e demográficos, características ambientais e sanitárias, conhecimento sobre o repelente e aspectos comportamentais e relacionados à gravidez. Resultados: Somente 28% das participantes referiram o uso de repelente durante as duas ondas da coorte. Mulheres com escolaridade superior (OR=2,55; IC95% 1,44-4,51); com emprego (OR=1,51; IC95% 1,12-2,03); que receberam orientações por profissionais da saúde (OR=1,74; IC95% 1,28-2,36) e pela mídia (OR=1,43; IC95% 1,01-2,02); que intensificaram os cuidados contra o mosquito na epidemia (OR=3,64; IC95% 2,29-5,78); estavam grávidas entre 2016 e 2019 (OR=2,80; IC95% 1,83-4,30) tiveram as chances aumentadas para uso continuado de repelente. Conclusões: O uso de repelente entre mulheres em idade fértil mostrou-se associado a um maior nível de escolaridade, ao emprego, às orientações sobre repelente fornecidas por profissionais de saúde e pela mídia, às mudanças comportamentais de cuidado contra o mosquito durante a epidemia da Zika e à gravidez quando ocorrida a partir do início do período epidêmico.

The insect repellents: A silent environmental chemical toxicant to the health.

In recent years, a large number of insect repellents have been developed with the idea of consumer benefits. In addition to already known advantageous application of insect repellents, there is increasing concern about the potential toxicity in environment leading to health caused by random use of these compounds. An increasing number of evidence suggests that insect repellents may trigger undesirable hazardous interactions with biological systems with a potential to generate harmful effects including intermediate metabolites. Biotransformation followed by bioaccumulation (vice e versa) may be an important phenomenon for toxic response of this chemicals. In this review, we have summarized the current state of knowledge on the insect repellent toxicity, including biochemical pathway alteration under in vitro and in vivo conditions considering different classes of organisms, from lower to higher vertebrate. Furthermore, we have tried to incorporate the effects of insect repellent in light of some clinical reports. We hope this review would provide useful information on potential side effects of uncontrolled use of insect repellents.

Mosquito repellents: An insight into the chronological perspectives and novel discoveries.

Mosquito being the major medically important arthropod vector; requires utmost attention to reduce the sufferings and economic consequences of those living in the endemic regions. This is only possible by minimising the human-mosquito contact by an absolute preventing measure. However, unfortunately, such absolute measures are yet to be developed despite enormous efforts and huge investments worldwide. In the absence of vaccines for number of mosquito-borne diseases, repellents could be an attractive option for both military personal and civilians to minimise the risk of contacting different mosquito-borne diseases. However, to achieve this golden goal, the detailed knowledge of a particular repellent is must, including its mode of repellency and other relevant informations. Here, in the present article, an effort has been made to convey the best and latest information on repellents in order to enhance the knowledge of scientific community. The review offers an overview on mosquito repellents, the novel discoveries, and areas in need of attention such as novel repellent formulations and their future prospective.

The risk of incomplete personal protection coverage in vector-borne disease.

Personal protection (PP) techniques, such as insecticide-treated nets, repellents and medications, include some of the most important and commonest ways used today to protect individuals from vector-borne infectious diseases. In this study, we explore the possibility that a PP intervention with partial coverage may have the counterintuitive effect of increasing disease burden at the population level, by increasing the biting intensity on the unprotected portion of the population. To this end, we have developed a dynamic model which incorporates parameters that describe the potential effects of PP on vector searching and biting behaviour and calculated its basic reproductive rate, R0. R0 is a well-established threshold of disease risk; the higher R0 is above unity, the stronger the disease onset intensity. When R0 is below unity, the disease is typically unable to persist. The model analysis revealed that partial coverage with popular PP techniques can realistically lead to a substantial increase in the reproductive number. An increase in R0 implies an increase in disease burden and difficulties in eradication efforts within certain parameter regimes. Our findings therefore stress the importance of studying vector behavioural patterns in response to PP interventions for future mitigation of vector-borne diseases.

Preparation and characterization of physicochemical properties of N, N-diethyl-meta-toluamide niosomes.

INTRODUCTION: The insect repellent compounds are used to protect humans, animals and plants against insect bites. Aromatic amides have insect repellent effects. N,N-diethyl-meta-toluamide (DEET) (C12 H17 NO) is one of the best insect repellents has been used for many years. DEET is a colorless, odorless liquid that is approximately insoluble in water and soluble in glycerin, ethanol, and isopropyl alcohol. Due to the solubility problem of DEET, its topical formulations usually have alcoholic bases, but these kind of formulations increase skin permeation and also systemic absorption of DEET, which leads to some toxic effects. The main goal of this study was to prepare the formulation of DEET niosomes in a topical dosage form with suitable stability properties. MATERIALS AND METHODS: Three different methods were used to prepare niosome formulations: Dehydration rehydration vesicle method, direct mixing method, homogenizer method. Sorbitan surfactants, cholesterol, polyoxyethylenecetyl, phosphate buffer (pH 7.4), and charge inductive compounds like cetyltrimethylammonium bromide were used to provide a net negative charge to the final membrane structure. A high-performance liquid chromatography method was then used for the determination of the loaded DEET. RESULTS: A large number of niosomes were multi-layered and have a spherical shape. In comparison, syringe method against direct mixing is more appropriate because of creation MLV and uniform niosomes but the best method is homogenizer method. Drug entrapment was between 14% and 21% in selected formulation. CONCLUSION: According to this study, homogenizing method can be used for formulation of DEET in niosome form in topical formulations.