Novel repellents for the blood-sucking insects Rhodnius prolixus and Triatoma infestans, vectors of Chagas disease

Background: Studying the behavioral response of blood-sucking disease-vector insects to potentially repellent volatile compounds could shed light on the development of new control strategies. Volatiles released by human facial skin microbiota play diferent roles in the host-seeking behavior of triatomines. We assessed the repellency efect of such compounds of bacterial origin on Triatoma infestans and Rhodnius prolixus, two important vectors of Chagas disease in Latin America. Methods: Using an exposure device, insects were presented to human odor alone (control) and in the presence of three individual test compounds (2-mercaptoethanol, dimethyl sulfde and 2-phenylethanol, the latter only tested in R. prolixus) and the gold-standard repellent NN-diethyl-3-methylbenzamide (DEET). We quantifed the time the insects spent in the proximity of the host and determined if any of the compounds evaluated afected the behavior of the insects. Results: We found volatiles that signifcantly reduced the time spent in the proximity of the host. These were 2-phenylethanol and 2-mercaptoethanol for R. prolixus, and dimethyl sulfde and 2-mercaptoethanol for T. infestans. Such an efect was also observed in both species when DEET was presented, although only at the higher doses tested. Conclusions: The new repellents modulated the behavior of two Chagas disease vectors belonging to two diferent triatomine tribes, and this was achieved using a dose up to three orders of magnitude lower than that needed to evoke the same efect with DEET. Future eforts in understanding the mechanism of action of repellent compounds such as 2-mercaptoethanol, as well as an assessment of their temporal and spatial repellent properties, could lead to the development of novel control strategies for these insect vectors, refractory to DEET.

Degradação do repelente DEET pelas lacases do Pleurotus ostreatus / Degradation of repellent DEET by Pleurotus ostreatus laccases

Objetivo: Avaliar a capacidade de remediação do DEET em meio líquido, pelo fungo de decomposição branca Pleurotus ostreatus usando como indutor enzimático os resíduos sólidos do cacau e realizar bioensaios de toxicidade com as amostras pós-tratamento, para aplicações em tratamentos de águas. Método: Foi realizada a produção enzimática com resíduos do Cacau. A biorremediação com o caldo enzimático foi realizada em erlenmeyers de 250mL, contendo a solução do composto, tampão acetato de sódio pH 5 e o caldo batata, incubados à 28°C, com rotação de 120 rpm, por 48 horas. Já com o fungo ativo, o mesmo foi incubado a 28 ºC e teve em seu meio a adição do composto. As amostras foram quantificados em Cromatografia líquida de alta performance (CLAE). O teste de adsorção foi feito com o fungo autoclavado e analisado após 14 dias. Resultado: O composto se apresentou possivelmente tóxico e a remediação mostrou uma tendência linear de degradação com o fungo de 39%. Conclusão: Pleurotus ostreatus é um candidato promissor para o tratamento de contimanações geradas por DEET.

Objective: We evaluated the remediation capacity of DEET in liquid medium by the white decomposition fungus Pleurotus ostreatus using the solid residues of cocoa as an enzymatic inducer and performed toxicity bioassays with the post-treatment samples, for water treatment applications. Method: Enzymatic production with cocoa residues was performed. Bioremediation with the enzyme broth was performed in a 250mL erlenmeyer flasks, containing the solution of the compound, sodium acetate buffer pH 5 and the potato broth, incubated at 28 °C, with rotation of 120 rpm, for 48 hours. With the active fungus, the same was incubated at 28 ºC and had in its culture medium the addition of the compound. The samples were quantified in high performance liquid chromatography (HPLC). The adsorption test was performed with the autoclaved fungus and analyzed after 14 days. Results: The compound was possibly toxic and the remediation showed a linear tendency of degradation of 39% with the fungus. Conclusion: Pleurotus ostreatus is a promising candidate for the treatment of contaminants generated by DEET.

Pyrethroid Resistance Associated With a Decreased DEET Repellency in the Common Bed Bug (Hemiptera: Cimicidae)

The global resurgence of the bed bug (Cimex lectularius L.) and the widespread resistance of this insect to pyrethroid insecticides have created the need to find alternatives to chemical control. Thus, synthetic or natural repellents have been considered as a suitable choice to control bed bug infestations. Repellents not only keep insects away from their hosts, but also allow a decrease in insecticide selection pressure. The aim of this study was to evaluate the repellence effectivity of DEET against two bed bug colonies from Argentina (a susceptible one and a fieldcollected pyrethroid-resistant one), under two starving periods. We found different repellent effects of DEET on the two C. lectularius colonies and no differences between the two starving periods. In fact, DEET had a lower effect on the insecticide-resistant colony. The methodology used in this study proved to be useful to test the variation of the effect of DEET between pyrethroid-susceptible and -resistant bed bugs.

Efectividad de repelentes comerciales disponibles contra el mosquito Aedes aegypti (L ) en Yucatán, México / Effectiveness of commercial repellents against Aedes aegypti (L ) in Yucatan, México

Resumen: Objetivo: Determinar la eficacia de repelentes comerciales disponibles en Yucatán contra el mosquito Aedes aegypti, vector del dengue, Chikungunya y Zika. Material y métodos: Se determinó el tiempo de protección con base en el protocolo WHO/CTD/WHOPES/IC y la NOM-032-SSA2-2014. Resultados: Sólo el repelente con DEET (N, N-dietil-3-metilbenzamida) al 25% cumplió con la protección recomendada. La eficacia fue directamente proporcional a la concentración del DEET; aquéllos con componentes botánicos fueron poco o nada protectores. Conclusiones: Los resultados muestran que los repelentes con DEET proveen protección contra Ae. Aegypti; los repelentes botánicos, incluyendo las pulseras impregnadas, ofrecen nula protección.

Abstract: Objective: We assessed the efficacy of commercial repellents available in Yucatan against Aedes aegypti, vector of dengue, Chikungunya and Zika. Materials and methods: Protection time was determined based on WHO/CTD/ WHOPES/IC y la NOM-032-SSA2-20I4. Results: Products with DEET (N, N-diethyl-3-methylbenzamide) at 25% met the recommended protection. Efficacy was directly proportional to the concentration of DEET; botanicals repellents resulted no protective. Conclusions: Repellents with DEET provided more protection against Ae. aegypti and botanical repellents, including impregnated wristbands, provided no protection.

Efficacy of Advanced Odomos repellent cream (N, N-diethyl-benzamide) against mosquito vectors.

Background & objectives: Repellents are commonly used personal protection measures to avoid mosquito bites. In the present study, Advanced Odomos cream (12% N, N-diethyl-benzamide) was tested for its efficacy against mosquitoes in comparison to DEET (N,N-diethyl-3-methyl benzamide). Methods: Bioassays were conducted to assess the repellency of Advanced Odomos and DEET creams against Anopheles stephensi and Aedes aegypti. Their efficacy was tested on human volunteers applied with different concentrations of test creams ranging from 1 to 12 mg/cm2 and by exposing them to mosquitoes at hourly intervals. Field evaluation was also carried out to test the duration of protection of the test creams against Anopheles and Aedes mosquitoes during whole night and day time collections, respectively on human volunteers. Mosquito collections were done using torch light and aspirator. Results: Complete (100%) protection was achieved at 10 mg/cm2 cream formulation of Advanced Odomos (1.2 mg a.i/cm2) dose against An. stephensi and 12 mg/cm2 (1.44 mg a.i./cm2) against Ae. aegypti on human baits. There was no statistically significant differences in per cent protection against mosquito bites between Advanced o0 domos and DEET cream (P>0.05) in respective doses. Complete protection up to 11 h was observed against Anopheles mosquitoes during whole night collections and up to 6 h against Ae. aegypti in day time collections. No adverse reactions such as itching, irritation, vomiting, nausea, etc. were reported by the volunteers. Interpretation & conclusions: Advanced odomos cream applied at 10 mg/cm2 concentration provided 100% protection from Anopheles mosquitoes up to 11 h whereas about 6 h protection was recorded against Ae. aegypti. The laboratory and field trials indicate that for longer protection against Anopheles mosquitoes 10 mg/cm2 will be appropriate and in case of Ae. aegypti more than 10 mg/cm2 application is required for complete protection. In conclusion, the Advanced Odomos cream was comparable to the known repellent cream DEET for prolonged protection against malaria and dengue vectors.

Repellent activity of DEET against Amblyomma cajennense (Acari: Ixodidae) nymphs submitted to different laboratory bioassays / Atividade repelente do DEET contra ninfas de Amblyomma cajennense (Acari: Ixodidae) em bioensaio laboratorial

This study was developed to evaluate the repellent activity of N,N-diethyl-3-methylbenzamide (DEET) against Amblyomma cajennense nymphs. Two repellent bioassays were compared and the effective concentration and repellent time were calculated. The fingertip test was accomplished to evaluate in vivo four concentrations of the compound (0.200; 0.100; 0.050 and 0.025 mg.cm-2) and the filter-paper bioassay to evaluate in vitro the two highest concentrations. The compound provided repellence higher than 90 percent in all concentrations and at least 95 percent repellency in the highest concentration over 5 hours. The effective concentration against 50 percent of tested nymphs (EC50) was 0.006 mg.cm-2 and the EC99 was 0.036 mg.cm-2. Those concentrations were lower than the ones obtained against other tick species, denoting the effectiveness of DEET against A. cajennense. The repellency time against 50 percent of the ticks (RT50) was 4.8 hours and the RT90 was 2.7 hours. Both bioassays were adequate to evaluate A. cajennense repellency and provided similar results; however the in vivo test is more appropriate to estimate the effective concentration and repellency time.

Este estudo foi conduzido com o objetivo de avaliar a atividade repelente do N,N-diethyl-3-methylbenzamide (DEET) sobre ninfas de Amblyomma cajennense. Dois bioensaios para a avaliação de repelência foram comparados e cálculos da concentração eficaz e do tempo de repelência foram realizados. Foram empregados o bioensaio da ponta do dedo, para avaliação in vivo de quatro concentações do químico (0,200; 0,100; 0,050 e 0,025 mg.cm-2) e o bioensaio do papel filtro, para a avaliação in vitro das duas concentrações mais altas. O composto conferiu mais de 90 por cento de repelência em todas as concentrações utilizadas e 95 por cento de repelência por mais de cinco horas na maior concentração. A concentração do composto efetiva contra 50 por cento das ninfas testadas (CE50) foi de 0,006 mg.cm-2 e a CE99 foi de 0,036 mg.cm-2. Estas concentrações são mais baixas do que as observadas em outras espécies de carrapatos, denotando a efetividade do princípio contra A. cajennense. O tempo de repelência de 50 por cento dos carrapatos (TR50) foi de 4,8 horas e o TR90 de 2,7 horas. Os dois bioensaios avaliados permitiram a observação de percentuais de repelência igualmente altos e se mostraram adequados para tal avaliação, sendo que o teste in vivo é mais indicado para cálculo da concentração eficaz e da duração da repelência.

Avaliação do uso de repelentes contra picada de mosquitos em militares na Bacia Amazônica / Evaluation of the use of repellent against mosquito bite by military personnel in the Amazon Basin

FUNDAMENTOS: No Brasil, doenças provocadas por picadas de insetos são frequentes, o que torna extremamente importante a execução de medidas profiláticas de forma adequada, sobretudo, em áreas endêmicas como a Amazônia, que recebe um grande contingente de visitantes, a trabalho ou turismo. OBJETIVOS: Avaliar o uso dos repelentes de insetos disponíveis no mercado por militares que costumam realizar missões em ambiente de selva, na região amazônica. MÉTODOS: Foram selecionados cinquenta e um militares da região amazônica que responderam um questionário em junho/2008. RESULTADOS: 63,7 por cento dos militares usaram produtos contendo Deet na concentração máxima de apenas 15 por cento, que possui mínima ação de repelência; 36 por cento relataram usar protetor solar associado, o que levou a um risco maior de intoxicação; 36,4 por cento fizeram uso de um repelente natural em suas missões; dois militares usaram vitamina B e consideraram a sua ação de repelência ineficaz. CONCLUSÕES: Os repelentes à base de Deet utilizados pelo grupo estudado apresentam concentrações inferiores às consideradas seguras para uso em ambiente de selva. Foi frequente a associação do Deet com protetor solar, que é uma combinação potencialmente tóxica. Os repelentes naturais à base de andiroba e copaíba apresentaram o maior grau de percepção de proteção.

BACKGROUND: In Brazil, diseases caused by insect bites are frequent. Therefore, it is extremely important that prophylatic measures are adequately carried out, especially in endemic areas such as the Amazon which receives a great number of visitors, for both business and tourism purposes.. OBJECTIVES: To evaluate the use of insect repellents available in the market by military personnel who often go in missions in the middle of the jungle, in the Amazon region. METHODOLOGY: Fifty - one militaries in the Amazon region were selected and they answered a questionnaire in June/2008. RESULTS: 63,7 percent of the militaries used products that contained Deet in the maximun concentration of only 15 percent that has minimum repellent action; 36 percent reported to combine these products with sun protective products which increased the risk of intoxication; 36,4 percent used a natural repellent during their missions; two of the militaries participants used vitamin B and considered their repellent action ineffective. CONCLUSION: The repellents that contain Deet and which were used by the group present concentrations that are lower than the concentrations considered safe for using in the jungle. It was frequent the combination of Deet with sun protective products ,which is a potentially toxic association. Natural repellents that have "andiroba" and" copaíba" as components presented a higher perception of protection from the participants.

Evaluation of Larvicidal and Repellent Activity of Xanthium Strumarium (Asteraceae) Ethanol Extract agaist Mosquito Vectors.

Ethanol extract of leaf and seed of Xanthium strumarium was investigated for anti-mosquito potential, including larvicidal and repellent activities against Anopheles culicifacies, Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti. The ethanol-extracted Xanthium strumarium possessed larvicidal activity against fourth instar larvae of An. culicifacies, An. stephensi Cx. quinquefasciatus and Ae. aegypti. The LD 50 and LD values of ethanol-extracted of leaf were 0.19, 0.8, 0.27, 0.27% and 90 1.3, 1.3, 1.0, 1.8% and seed were 0.15, 0.9, 0.25, 0.23 and 1.5, 1.4, 1.7, 1.9% against An. culicifacies An. stephensi Cx. quinquefasciatus and Ae. aegypti respectively. It showed 100% repellency against An. culicifacies, An. stephensi and Culex quinquefasciatus in 0h 1h, 2h 4h and 1h 2h 6h, at 10% concentration respectively. It also provided biting protection time of 0h, 1h, 2h, 4h, and 6h when applied at a concentration of 2.5, 5, and 10 %. Against Deet- 2.5% An. culicifacies Giles species A 100% repellency in 1h, 2h, An. stephensi Liston 100% repellency in 2h, 4h, and Culex quinquefasciatus Say have shown 100% repellency in 4h. Xanthium strumarium, therefore, can be considered as a probable source of some biologically active compounds used in the development of mosquito control agents, particularly repellent and larvicidal products.

Repelentes de insetos: recomendações para uso em crianças: [revisão] / Insect repellents: recommendations for use in children: [revision]

OBJETIVO: Apresentar uma revisão bibliográfica sobre o uso de repelentes de insetos em crianças, com ênfase especial na proteção contra mosquitos. FONTES DE DADOS: Realizou-se uma pesquisa bibliográfica nas bases de dados Pubmed e Lilacs, cujos artigos incluíam produtos comercialmente disponíveis no Brasil. Foram selecionados artigos publicados nos últimos dez anos em língua inglesa ou portuguesa, referentes a crianças, obtidos com as seguintes palavras-chave: "insect repellents", "children", "mosquitoes", "N,N-dietil-metatoluamida (DEET)". SÍNTESE DOS DADOS: Entre os repelentes tópicos, DEET, icaridina e óleo natural de eucalipto-limão apresentam, em concentrações adequadas, perfil de segurança favorável e são eficazes na prevenção de picadas de mosquitos em crianças e adultos. Em geral, são indicados para crianças acima de dois anos de idade. Medidas físicas são fundamentais para proteger lactentes jovens, especialmente menores de seis meses, com destaque para o uso de telas com permetrina. CONCLUSÕES: Os mosquitos são vetores de doenças infectoparasitárias que acometem, anualmente, milhões de pessoas no mundo e causam milhares de mortes. O combate aos mosquitos inclui medidas ambientais e de proteção individual. O uso de repelentes tópicos para proteção individual da criança exige cuidados específicos e conhecimento quanto ao produto ideal para cada idade, especialmente quando consideradas sua eficácia e segurança.

OBJECTIVE: To present a literature review about the use of insect repellents on children, highlighting the protection against mosquitoes. DATA SOURCES: Pubmed and Lilacs databases were searched for articles in English and Portuguese published in the last ten years with the following key-words: "insect repellents", "children", "mosquitoes", "N,N-dietil-metatoluamida (DEET)". DATA SYNTHESIS: Concerning topical repellents, DEET, icaridine and natural oil of lemon eucalyptus are effective to prevent mosquito bites in children and adults and have favorable safety profile when used in appropriate concentration. They are generally recommended for children older than two years-old. Physical barriers are essential for infant protection, especially if they are six months old or less, with special interest in the permethrin-treated nets. CONCLUSIONS: Mosquitoes are vectors of a variety of infectious and parasitic diseases which annually affect millions of people and cause thousands of deaths worldwide. The combat to mosquitoes includes individual and environmental measures. Topic repellents for children's individual protection demand specific handling attention and knowledge about the ideal product for each age, especially regarding their efficacy and safety.

Evaluation of Tribulus terrestris Linn (Zygophyllaceae) Acetone extract for Larvicidal and Repellence Activity against Mosquito Vectors.

Acetone extracts of leaves and seeds from the Tribulus terrestris (Zygophyllaceae) were tested against mature and immature different mosquito vectors under laboratory condition. The extract showed strong larvicidal, properties 100 per cent mortality in the 3rd-instar larvae was observed in the bioassays with An. culicifacies Giles species A, An. stephensi Liston , Culex quinquefasciatus Say and Aedes aegypti Linn ,against 200ppm of the leaf acetone extract and 100 ppm seed acetone extract. The LC values 50 of leaf acetone extract estimated for 3rd-instars An. culicifacies species A, An. stephensi, Cx. quinquefasciatus and Ae. aegypti after 24 hour of exposure were 117, 124, 168 and 185 ppm respectively. The LC values of seed 50 acetone extract estimated for 3rd-instars An. culicifacies species A, An. stephensi, Cx. quinquefasciatus and Ae. aegypti after 24 hour of exposure were 100, 72, 91 and 91 ppm respectively. It is confirmed from the LC values 50 that the seed acetone extract of T. terrestris is more effective compared to leaf extracts. A significant (P<0.004) higher concentration of acetone extract leaf was required to kill equal number of larvae i.e. against acetone extract of seed. The seed acetone extract showed strong repellent activity against adults mosquitoes. Per cent protection obtained against Anopheles culicifacies species A 100% repellency in 1h, 6h; Anopheles stephensi 100% repellency in 0h, 4h, 6h; and Culex quinquefasciatus 100% repellency in 0h, 2h, 4h, at 10% concentration respectively. Against Deet- 2.5% An. culicifacies Giles species A has shown 100% repellency in 1h,2h,6h , An. stephensi Liston 99% repellency in 4h , and Culex quinquefasciatus Say has shown 100% repellency in 1h,2h.

Deet-a cheap but effective repellent cream for protection of people overnight in forest from mosquito bite

A product with 15% DEET gave an overall bite protection of 85%, without evidence for a diminishing effect through the night. When mosquitoes had a choice at one site between people using repellent or not, the repellent had most effect (88% protection with choice and 57% - 79% without choice). A product containing 27% DEET worked significantly better with 93% overall bite protection. The 15% product is locally available, cheap (0.8 US$ for a flacon of 75ml which lasted 30 person-nights) and in the opinion of the capturers well compatible

Preparation and evaluation of DEET-ethylcellulose microsphere / 第二军医大学学报

Objective:To prepare DEET-ethylcellulose microsphere(DEET-EC) and observe its properties to retard volatilization of DEET. Methods: DEET-EC was prepared with solvent evaporation method. DEET was dissolved in CH 2Cl 2 with EC served as dispersed phase and 1% PVA water solution as continuous phase. The dispersed phase was added into the continuous phase with stirring rate at 1 000 r/min. The stirring rate was changed into 600 r/min after 30 min, and was kept until CH 2Cl 2 was entirely volatilized. After being watered, precipitated and lyophilized for 12 h, DEET-EC was derived, and the shape was observed with electron microscope. The particle size distribution was detected in 500 microspheres with optical microscope. HPLC method was established to determine the embedding ratio and loaded ratio of DEET-EC microsphere. Chromatograph conditions: Diamonsil ODS column (150 mm?4.6 mm), CH 3OH∶H 2O=65∶35 as mobile phase at 1 ml/min, the detected wavelength 210 nm. Results: The DEET-EC was egg-white and had spherical shape. Almost 90% of the MS distributed in 30-70 ?m, while ( ar ) and ( v ) were 49.6 ?m and 51.2 ?m, respectively. The loading ratio was 18.7% and the embedding ratio was 56.1%(n=6). Conclusion: The solvent evaporation method is convenient and simple to prepare DEET-EC microsphere.

Comparison of effect of three DEET formulations preventing Schistosoma japonicum infection in mice / 中国血吸虫病防治杂志

Objective To compare the effica cy of three N,N-diethyl-m-toluamide (DEET) formulations against Schistosoma japonicum infection in mice. Methods Three 10% DEET formulations (DEET isopropanol solution,DEET cr eam and DEET vaseline ointment)were prepared and two experiments, no-dipping or dipping after applying DEET preparation ,were designed. In each experiment, mice were randomly divided into three experiment groups and three control groups . D ifferent DEET preparations were applied in the experiment groups and isopropanol solution, “yumeijing” cream , vaseline ointment were applied in the control g roups, respectively. At different time points after skin application (0.5, 1, 2 , 4 h and 8 h),the mice were infected with (50?5) Schistosoma j apon icum cercariae on the abdominal skin in no dipping experiment. I n dipping experiment,after mice skin were applied and were dipped for 10,30 min, 1 ,2 h and 4 h, respectively, the mice were infected with (50?5) cercariae. Af ter 6-7 weeks ,all the mice were sacrificed and the worms were collected by hea rt perfusion and counted.Worm reduction rates were calculated and rank sum tests w ere carried out. Results In no-dipping experim ent,three DEET formulations provided 100.0% protection in mice at least for 1 h .A t 2 ,4 h and 8 h ,the worm reduction rates were 94.8%,89.9% and 13.3% for DE ET isopropanol solution, 100.0%,97.8% and 50.7% for DEET cream and 100.0%,9 9.0% and 9 8.0% for DEET vaseline oinment, respectively. In dipping experi-ment, given 50.0% wor m reduction rate as efficient in preventing penetration by the cercariae, the e ffective times were 10 min for DEET isopropanol solution,30 min for DEET cream a nd 2 h for DEET vaseline oinment,respectively. Conclusion Three DEET formulations are effectiv e in preventing Schistosoma japonicum infection in mice.DEET vaseline oinment can provide better protection than the other two D EET formulations.