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1.
Nat Commun ; 12(1): 2553, 2021 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-33953207

RESUMO

Pyrethrum extracts from flower heads of Chrysanthemum spp. have been used worldwide in insecticides and repellents. While the molecular mechanisms of its insecticidal action are known, the molecular basis of pyrethrum repellency remains a mystery. In this study, we find that the principal components of pyrethrum, pyrethrins, and a minor component, (E)-ß-farnesene (EBF), each activate a specific type of olfactory receptor neurons in Aedes aegypti mosquitoes. We identify Ae. aegypti odorant receptor 31 (AaOr31) as a cognate Or for EBF and find that Or31-mediated repellency is significantly synergized by pyrethrin-induced activation of voltage-gated sodium channels. Thus, pyrethrum exerts spatial repellency through a novel, dual-target mechanism. Elucidation of this two-target mechanism may have potential implications in the design and development of a new generation of synthetic repellents against major mosquito vectors of infectious diseases.


Assuntos
Chrysanthemum cinerariifolium/metabolismo , Culicidae/efeitos dos fármacos , Repelentes de Insetos/farmacologia , Inseticidas/farmacologia , Piretrinas/farmacologia , Aedes/efeitos dos fármacos , Animais , Chrysanthemum cinerariifolium/genética , Técnicas de Inativação de Genes , Controle de Mosquitos , Mosquitos Vetores , Neurônios , Receptores Odorantes/genética , Canais de Sódio Disparados por Voltagem
2.
Pest Manag Sci ; 77(7): 3500-3507, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33837642

RESUMO

BACKGROUND: The rice weevil, Sitophilus oryzae (L., 1763) (Coleoptera: Curculionidae), is a stored grain/seed pest of several crops. Botanicals represent an option to manage this pest, especially those with high toxicity determined by its structure and physicochemical properties and low residue left behind on treated grains/seeds. Enantiomers are bioactive molecules in organic processes. The aim of this study was to evaluate the insecticidal activity of two enantiomeric forms of the monoterpenes citronellal, limonene, linalool, menthone and α-pinene against S. oryzae adults through contact, fumigant and repellent assays. RESULTS: All results were compared with absolute acetone as the negative control and those from contact assays also with malathion as the positive control. (S)-(-)-linalool was the most toxic by contact to S. oryzae and (S)-(-)-menthone through fumigation, while the two enantiomeric forms of menthone and α-pinene were the best repellents. CONCLUSIONS: The high toxicity of only one of the two monoterpene enantiomers showed the importance of form and percentage of enantiomer in the commercial product, which affect the success of the product to controlling S. oryzae. © 2021 Society of Chemical Industry.


Assuntos
Repelentes de Insetos , Inseticidas , Óleos Voláteis , Gorgulhos , Animais , Fumigação , Repelentes de Insetos/farmacologia , Inseticidas/farmacologia , Monoterpenos/farmacologia
3.
SAR QSAR Environ Res ; 32(5): 395-410, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33870800

RESUMO

The fumigant and topical activities exhibited by 27 plant-derived essentials oils (EOs) on adult M. domestica housefly are predicted through the Quantitative Structure-Activity Relationship (QSAR) theory. These molecular structure based calculations are performed on 253 structurally diverse compounds from the EOs, where the number of constituents in each essential oil mixture varies between 2 to 24. A large number of 86,048 non-conformational mixture descriptors are derived as linear combinations of the molecular descriptors of the EO components. Two strategies are compared for the mixture descriptor formulation, which consider or avoid the use of the chemical composition. The multivariable linear regression QSAR models of the present work are useful for fumigant and topical applications, describing predictive parallelisms for the insecticidal activity of the analysed complex mixtures.


Assuntos
Moscas Domésticas/efeitos dos fármacos , Inseticidas/farmacologia , Óleos Voláteis/farmacologia , Animais , Fumigação , Repelentes de Insetos/química , Repelentes de Insetos/farmacologia , Inseticidas/química , Óleos Voláteis/química , Relação Quantitativa Estrutura-Atividade
4.
J Environ Sci Health B ; 56(4): 423-430, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33678144

RESUMO

In this work, we investigated the bioactivities of the essential oil (EO) extracted from the Rhododendron thymifolium and its principal germacrone against Lasioderma serricorne and Tribolium castaneum. The EO was obtained by steam distillation. Germacrone was obtained by cryogenic crystallization. The bioactivity of EO and germacrone was tested via contact and repellent activity assays. The results showed that EO and germacrone possessed contact and repellent activities against two species of insects. EO exhibited obvious contact activity against the L. serricorn adults, larvae and T. castaneum larvae with LD50 values of 29.15 µg/adult, 42.73 µg/larva, 19.65 µg/larva respectively. Germacrone exhibited excellent contact activity against the L. serricorne adults, larvae and the T. castaneum larvae with LD50 values of 17.18 µg/adult, 20.94 µg/larva, 20.93 µg/larva respectively. And at the highest testing concentrations (78.63 and 15.73 nL/cm2), the repellent activity of EO and germacrone on two target insects was comparable to that of the positive control (DEET) after 30 h exposure. In especially, in the treatment of the 120 h after the repellent activity of EO and germacrone against T.castaneum adults and larvae were still very significant and showed the same level percentage repellency as DEET. Meanwhile, germacrone exhibited inhibition of acetylcholinesterase activity with IC50 values of 3%. The results indicated that the EO of R. thymifolium and germacrone had the potential to be developed as natural insecticides and repellents for the control of T. castaneum and L. serricorne.


Assuntos
Inibidores da Colinesterase/farmacologia , Besouros/efeitos dos fármacos , Inseticidas/farmacologia , Óleos Voláteis/farmacologia , Rhododendron/química , Animais , Inibidores da Colinesterase/química , Proteínas de Insetos/antagonistas & inibidores , Proteínas de Insetos/metabolismo , Repelentes de Insetos/química , Repelentes de Insetos/farmacologia , Inseticidas/química , Dose Letal Mediana , Óleos Voláteis/química , Sesquiterpenos de Germacrano/farmacologia , Tribolium/química , Tribolium/efeitos dos fármacos
5.
Molecules ; 26(4)2021 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-33557353

RESUMO

Haematobia irritans is an obligate bloodsucking ectoparasite of cattle and is the global major pest of livestock production. Currently, H. irritans management is largely dependent upon broad-spectrum pesticides, which lately has led to the development of insecticide resistance. Thus, alternative control methods are necessary. Endophyte-infected grasses have been studied as an alternative due to their capability to biosynthesize alkaloids associated with anti-insect activities. Thus, the main aim of this study was to evaluate the antifeedant and repellent activity of lolines obtained from endophyte-infected tall fescue against H. irritans adults in laboratory conditions. The alkaloid extract (ALKE) was obtained by acid-base extraction. N-formyl loline (NFL) and N-acetyl loline (NAL) were isolated by preparative thin layer chromatography (pTLC) and column chromatography (CC), and the loline was prepared by acid hydrolysis of a NFL/NAL mixture. Loline identification was performed by gas chromatography coupled to mass spectrometry (GC/MS). Feeding behavior was evaluated by a non-choice test, and olfactory response was evaluated using a Y-tube olfactometer. Accordingly, all samples showed antifeedant activities. NFL was the most antifeedant compound at 0.5 µg/µL and 1.0 µg/µL, and it was statistically equal to NAL but different to loline; however, NAL was not statistically different to loline. NFL and NAL at 0.25 µg/µL were more active than loline. All samples except loline exhibited spatial repellency in the olfactometer. Thus, the little or non-adverse effects for cattle and beneficial activities of those lolines make them suitable candidates for horn fly management.


Assuntos
Alcaloides/farmacologia , Endófitos/fisiologia , Festuca/química , Festuca/microbiologia , Repelentes de Insetos/farmacologia , Muscidae/efeitos dos fármacos , Alcaloides/química , Alcaloides/isolamento & purificação , Animais , Repelentes de Insetos/química , Repelentes de Insetos/isolamento & purificação
6.
Pest Manag Sci ; 77(4): 1971-1980, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33314506

RESUMO

BACKGROUND: An over-the-counter medicine product of China known as essential balm effectively repelled red imported fire ants, Solenopsis invicta Buren. However, it was not clear which chemical component(s) accounted for the repellency, and whether they would effectively repel S. invicta in the field. RESULTS: Five components, eucalyptol, camphor, menthol, methyl salicylate, and eugenol, were identified in essential balm using gas chromatography-mass spectrometry (GC-MS). Each component elicited concentration-dependent electroantennography (EAG) response. Under field conditions, all components showed repellency against foraging ants. Interestingly, foraging ants managed to access the food items placed on a surface smeared with eucalyptol, camphor, menthol, or methyl salicylate by depositing soil particles on the surface and then walking on soil particles. However, they failed to do so when the surface was smeared with eugenol. Repellency of eugenol lasted for > 24 h, which was much longer than that of the other four components of essential balm and is comparable to that of N,N-diethyl-m-toluamide (DEET), the standard for insect repellants. CONCLUSION: Olfactory response of S. invicta to all five components of the essential balm was confirmed. Each component showed repellency against S. invicta workers in the field. However, only eugenol significantly suppressed both foraging and particle-covering behavior within 24 h. The repellent effect of eugenol lasted much longer than the other four components. Particle-covering behavior has been largely ignored in studying fire ant repellants. Our study demonstrated that it is necessary to consider such behaviors in ant repellent bioassays in the future. © 2020 Society of Chemical Industry.


Assuntos
Formigas , Repelentes de Insetos , Animais , Cânfora , China , Eucaliptol , Humanos , Repelentes de Insetos/farmacologia
7.
PLoS One ; 15(12): e0244447, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33373422

RESUMO

Rapidly increasing pyrethroid insecticide resistance and changes in vector biting and resting behavior pose serious challenges in malaria control. Mosquito repellents, especially spatial repellents, have received much attention from industry. We attempted to simulate interactions between mosquitoes and repellents using a machine learning method, the Self-Propelled Particle (SPP) model, which we modified to include attractiveness/repellency effects. We simulated a random walk scenario and scenarios with insecticide susceptible/resistant mosquitoes against repellent alone and against repellent plus attractant (to mimic a human host). Simulation results indicated that without attractant/repellent, mosquitoes would fly anywhere in the cage at random. With attractant, all mosquitoes were attracted to the source of the odor by the end. With repellent, all insecticide-susceptible mosquitoes eventually moved to the corner of the cage farthest from the repellent release point, whereas, a high proportion of highly resistant mosquitoes might reach the attractant release point (the human) earlier in the simulation. At fixed concentration, a high proportion of mosquitoes could be able to reach the host when the relative repellency efficacy (compare to attractant efficacy) was <1, whereas, no mosquitoes reached the host when the relative repellency efficacy was > 1. This result implies that repellent may not be sufficient against highly physiologically insecticide resistant mosquitoes, since very high concentrations of repellent are neither practically feasible nor cost-effective.


Assuntos
Anopheles/fisiologia , Comportamento de Busca por Hospedeiro/efeitos dos fármacos , Repelentes de Insetos/farmacologia , Malária/prevenção & controle , Mosquitos Vetores/fisiologia , Animais , Anopheles/efeitos dos fármacos , Simulação por Computador , Voo Animal/efeitos dos fármacos , Voo Animal/fisiologia , Comportamento de Busca por Hospedeiro/fisiologia , Humanos , Resistência a Inseticidas/fisiologia , Inseticidas/farmacologia , Aprendizado de Máquina , Modelos Biológicos , Controle de Mosquitos/métodos , Mosquitos Vetores/efeitos dos fármacos , Odorantes , Piretrinas/farmacologia
8.
PLoS One ; 15(8): e0237353, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32785255

RESUMO

Airborne spatial repellency (SR) is characterized and distinguished from other chemical actions including contact locomotor excitation and toxicity. The use of volatile spatial repellents is a potential new intervention class for combatting mosquito-borne pathogen transmission; therefore, continuing investigations on the actions of these chemicals that modify mosquito host-seeking behavior (i.e., bite prevention) is needed. The objective of this study is to characterize the key behavioral avoidance actions of transfluthrin (TFT) to advance spatial repellent development into practical products. Behavioral avoidance responses were observed for adult laboratory strains of Aedes aegypti, Anopheles minimus and An. dirus, and two field populations of An. harrisoni and Ae. aegypti, respectively. Established TFT sublethal (LC50 and LC75), lethal concentrations (LC99) and discriminating concentrations (DCs) were selected corresponding to each mosquito test species. Spatial repellency and contact excitation ('irritancy') responses on adult mosquitoes to TFT were assessed using an excito-repellency assay system. At LC50, TFT exhibited strong avoidance with An. minimus (60.1% escape) and An. dirus (80% escape) laboratory strains, showing between 12 and 16x greater escape response than Ae. aegypti (5% escape). Repellency responses for field collected Ae. aegypti and An. harrisoni were 54.9 and 47.1% escape, respectively. After adjusting the initial contact escape response (a measure of combined irritancy and repellency) to estimate only escape due to contact, the LC50 and LC99 showed moderate escape irritancy with laboratory Ae. aegypti (41.4% escape) and no contact activity against the field population. Adjustment showed only weak contact activity (16.1% escape) in laboratory An. minimus at LC50. Spatial repellency is the predominant mode of action of TFT among colonized and field mosquitoes used in this study. Established baseline (susceptible) dose-response curves assist in optimizing SR products for mosquito control and pathogen transmission prevention.


Assuntos
Comportamento Animal/efeitos dos fármacos , Ciclopropanos/farmacologia , Fluorbenzenos/farmacologia , Repelentes de Insetos/farmacologia , Mosquitos Vetores/efeitos dos fármacos , Compostos Orgânicos Voláteis/farmacologia , Aedes/efeitos dos fármacos , Aedes/fisiologia , Animais , Anopheles/efeitos dos fármacos , Anopheles/fisiologia , Aprendizagem da Esquiva , Relação Dose-Resposta a Droga , Feminino , Controle de Mosquitos/métodos , Mosquitos Vetores/fisiologia , Doenças Transmitidas por Vetores/prevenção & controle
10.
Aquat Toxicol ; 222: 105474, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32259658

RESUMO

Larval toxicity of ethanolic extract of C. parvula (Ex-Cp) was prominent in the second and the third instars at the maximum lethal dosage of 100 ppm with 98 and 97 % mortality rate respectively. The LC50 and LC90 was displayed at 43 ppm and 88 ppm dosage respectively. Correspondingly, the sub-lethal dosage (65 ppm) of Ex-Cp significantly alters the carboxylesterase (α and ß), GST and CYP450 enzyme level in both III and IV instar larvae in dose-dependent manner. Similarly, the Ex-Cp displayed significant repellent activity (97 %) with a maximum level of protection time (210 min). Photomicrography assay of Ex-Cp (65 ppm) were toxic to dengue larvae as compared to control. The non-target toxicity of Ex-Cp against the beneficial mosquito predators displayed less toxicity at the maximum dosage of 600 ppm as compared to Temephos. Thus the present research delivers the target and non-target toxicity of red algae C. parvula against the dengue mosquito vector.


Assuntos
Aedes/efeitos dos fármacos , Dengue , Repelentes de Insetos/farmacologia , Mosquitos Vetores/efeitos dos fármacos , Extratos Vegetais/farmacologia , Rodófitas/química , Aedes/virologia , Animais , Organismos Aquáticos/efeitos dos fármacos , Carboxilesterase/metabolismo , Dengue/virologia , Relação Dose-Resposta a Droga , Repelentes de Insetos/isolamento & purificação , Repelentes de Insetos/toxicidade , Larva/efeitos dos fármacos , Larva/enzimologia , Dose Letal Mediana , Extratos Vegetais/isolamento & purificação , Extratos Vegetais/toxicidade , Poluentes Químicos da Água/toxicidade
11.
Malar J ; 19(1): 127, 2020 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-32228701

RESUMO

BACKGROUND: The 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. METHODS: A 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. RESULTS: Anopheles 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. CONCLUSIONS: The 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.


Assuntos
Aedes/efeitos dos fármacos , Anopheles/efeitos dos fármacos , Culex/efeitos dos fármacos , Repelentes de Insetos/farmacologia , Percepção Olfatória , Aedes/fisiologia , Animais , Anopheles/fisiologia , Aprendizagem da Esquiva , Benzaldeídos , Culex/fisiologia , DEET/farmacologia , Relação Dose-Resposta a Droga , Eugenol/farmacologia , Feminino , Octanóis , Odorantes , Óleos Vegetais/farmacologia , Especificidade da Espécie , Terpenos/farmacologia
12.
Food Chem Toxicol ; 138: 111184, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32061727

RESUMO

Marsh rosemary (Ledum palustre, Ericaceae) has been widely used in the traditional medicine of various regions worldwide, and as insect repellent. Little is known on its essential oil insecticidal potential. This study explored the insecticidal effects of the essential oil obtained from L. palustre growing in Poland on selected insect pests and vectors. GC-MS analysis evidenced an uncommon chemotype characterized by ascaridole (35.3% as sum of cis-ascaridole and isoascaridole) and p-cymene (25.5%). The essential oil was effective against Culex quinquefasciatus, Spodoptera littoralis and Musca domestica, showing LC50/LD50 of 66.6 mg L-1, 117.2 µg larva-1 and 61.4 µg adult-1, respectively. It was not toxic to non-target Eisenia fetida earthworms and moderately toxic to Daphnia magna microcrustaceans, over the positive control α-cypermethrin. The essential oil cytotoxicity on human keratinocytes and fibroblasts showed high IC50 values (71.3 and 84.4 µg mL-1, respectively). Comet assay data highlighted no DNA damages. Based on our findings, this essential oil, characterized by the ascaridole/p-cymene chemotype, could be a candidate for the formulation of botanical insecticides; large-scale production of green insecticides by this rare species may be assured by ex situ cultivation and biotechnological techniques.


Assuntos
Monoterpenos Cicloexânicos/farmacologia , Inseticidas/farmacologia , Óleos Voláteis/farmacologia , Peróxidos/farmacologia , Rosmarinus/química , Animais , Linhagem Celular , Ensaio Cometa , Culex/efeitos dos fármacos , Culicidae/efeitos dos fármacos , Monoterpenos Cicloexânicos/análise , Cimenos/análise , Cimenos/farmacologia , Daphnia/efeitos dos fármacos , Moscas Domésticas/efeitos dos fármacos , Humanos , Repelentes de Insetos/análise , Repelentes de Insetos/farmacologia , Inseticidas/análise , Queratinócitos/citologia , Queratinócitos/efeitos dos fármacos , Larva/efeitos dos fármacos , Mosquitos Vetores/efeitos dos fármacos , Mariposas/efeitos dos fármacos , Óleos Voláteis/análise , Oligoquetos/efeitos dos fármacos , Peróxidos/análise , Polônia , Piretrinas/análise , Piretrinas/farmacologia , Spodoptera/efeitos dos fármacos
13.
Sci Rep ; 10(1): 2670, 2020 02 14.
Artigo em Inglês | MEDLINE | ID: mdl-32060382

RESUMO

Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae and Platypodinae) bore into tree xylem to complete their life cycle, feeding on symbiotic fungi. Ambrosia beetles are a threat to avocado where they have been found to vector a symbiotic fungus, Raffaelea lauricola, the causal agent of the laurel wilt disease. We assessed the repellency of methyl salicylate and verbenone to two putative laurel wilt vectors in avocado, Xyleborus volvulus (Fabricius) and Xyleborus bispinatus (Eichhoff), under laboratory conditions. Then, we tested the same two chemicals released from SPLAT flowable matrix with and without low-dose ethanol dispensers for manipulation of ambrosia beetle populations occurring in commercial avocado. The potential active space of repellents was assessed by quantifying beetle catch on traps placed 'close' (~5-10 cm) and 'far' (~1-1.5 m) away from repellent dispensers. Ambrosia beetles collected on traps associated with all in-field treatments were identified to species to assess beetle diversity and community variation. Xyleborus volvulus was not repelled by methyl salicylate (MeSA) or verbenone in laboratory assays, while X. bispinatus was repelled by MeSA but not verbenone. Ambrosia beetle trap catches were reduced in the field more when plots were treated with verbenone dispensers (SPLAT) co-deployed with low-dose ethanol dispensers than when treated with verbenone alone. Beetle diversity was highest on traps deployed with low-dose ethanol lures. The repellent treatments and ethanol lures significantly altered the species composition of beetles captured in experiment plots. Our results indicate that verbenone co-deployed with ethanol lures holds potential for manipulating ambrosia beetle vectors via push-pull management in avocado. This tactic could discourage immigration and/or population establishment of ambrosia beetles in commercial avocado and function as an additional tool for management programs of laurel wilt.


Assuntos
Ophiostomatales/efeitos dos fármacos , Persea/microbiologia , Doenças das Plantas/microbiologia , Simbiose/efeitos da radiação , Animais , Monoterpenos Bicíclicos/farmacologia , Besouros/microbiologia , Besouros/patogenicidade , Repelentes de Insetos/farmacologia , Insetos Vetores/microbiologia , Insetos Vetores/patogenicidade , Ophiostomatales/patogenicidade , Persea/crescimento & desenvolvimento , Persea/parasitologia , Doenças das Plantas/parasitologia , Doenças das Plantas/prevenção & controle , Salicilatos/farmacologia , Simbiose/efeitos dos fármacos
14.
Am J Trop Med Hyg ; 102(4): 758-767, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32043439

RESUMO

Kala azar occurs among seasonal and migrant agricultural workers in northwest Ethiopia and accounts for almost 60% of the disease burden in the country. We conducted a quantitative study on the level of knowledge and practice of this vulnerable group in relation to kala azar transmission and acceptability of its vector control tools. A total of 403 workers were randomly selected from eight farms using a purposive sampling technique. Knowledge and practice scores were calculated based on 12 and 9 core questions, respectively. Binary logistic regression was used to identify factors associated with knowledge and practice. A large gap in knowledge of the disease and the vector was evident with 61.8%, 24.6%, and 13.6% of the workers having poor, moderate, and good levels of knowledge scores, respectively. Similarly, 95% of the seasonal workers reported poor level of use of protective measures against the bite of the sand fly vector. Good level of knowledge about kala azar and its sand fly vector was statistically associated with formal education (adjusted odds ratio [AOR] = 2.11; 95% CI = 1.17, 3.80; P < 0.05) and previous exposure to health education (AOR = 4.72; 95% CI = 1.99, 11.16; P < 0.001). Despite poor current knowledge and practice, a large proportion of the study participants showed interest in using vector control tools if made available, with 78% of the seasonal and migrant workers expressing some willingness to pay for different measures that can protect against sand fly bites. Therefore, we strongly recommend that comprehensive health education and vector control programs should be provided to these workers.


Assuntos
Agricultura , Leishmaniose Visceral/prevenção & controle , Estações do Ano , Migrantes , Adulto , Animais , Etiópia/epidemiologia , Feminino , Conhecimentos, Atitudes e Prática em Saúde , Humanos , Mordeduras e Picadas de Insetos/prevenção & controle , Repelentes de Insetos/economia , Repelentes de Insetos/farmacologia , Mosquiteiros Tratados com Inseticida , Masculino , Pessoa de Meia-Idade , Roupa de Proteção/economia , Psychodidae , Adulto Jovem
15.
Vet Parasitol ; 278: 109036, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32004852

RESUMO

Amblyomma sculptum is a tick of medical-veterinary importance. Areas with high infestations need to be monitored, and parasitized hosts treated accordingly. Carbon dioxide (CO2) traps and acaricides are commonly deployed as control measures, although with some disadvantages such as high costs, challenging logistics and vertebrate intoxication. Semiochemicals have the potential to improve tick attraction to traps and monitoring devices and alleviate the burden of A. sculptum infestations. Four concentrations (10, 5, 2.5 and 1.25 %) of 13 semiochemical candidates (CO2 only at 5 % as the standard, benzaldehyde, benzoic acid, salicylic acid, 2,6 diclorophenol, R-limonene, S-limonene, methyl salicylate, 1-octen-3-ol, acetone, ammonium hydroxide, isobutyric acid and lactic acid) were tested on unfed A. sculptum nymphs and adults using a Y-tube olfactometer to evaluated repellence and attraction behaviors. All stages tested were attracted to CO2, whereas nymphs were repelled by benzaldehyde and R-limonene, both at 10 %, and isobutyric acid at 5 and 10 %. Nymphs were attracted by methyl salicylate, benzoic acid and salicylic acid, all at 1.25 %, and by ammonium hydroxide at 2.5 %. Males were attracted by benzoic acid at 2.5 %, while females were repelled by benzaldehyde at 5 %. Mixtures with the attractive compounds achieved no attraction response. The compounds that caused attractiveness in the olfactometer assay (CO2, methyl salicylate, benzoic acid, salicylic acid and ammonium hydroxide) were placed randomly in traps in a grassland plot naturally infested with A. sculptum in triplicate. Notably, dry ice (CO2) remained the best at luring ticks in the field (P < 0.001). Benzoic acid should be further investigated since attractant activity was strongly confirmed in both laboratory and field tests. On the other hand, isobutyric acid and R-limonene could be better exploited due to their repellent role revealed by the lab assay, which makes them worthwhile molecules as natural repellents for the management of this tick.


Assuntos
Repelentes de Insetos/farmacologia , Ixodidae/efeitos dos fármacos , Feromônios/farmacologia , Infestações por Carrapato/prevenção & controle , Animais
16.
Biol Pharm Bull ; 43(2): 284-288, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32009117

RESUMO

Thiamine hydrochloride has been suggested as a natural, safe yet effective alternative for chemical insect repellents. However, there is a demand for a reassessment of the minimum required dose that is sufficient to perform a topical repellency on the human skin. Therefore, the purpose of the current work is to establish a dose-response curve from which the effective dose (ED) is calculated. A series of increasing concentrations of thiamine hydrochloride were applied to the forearm of adult volunteers, the number of bites was counted and the percent repellency calculated accordingly. Data of percent repellency were converted to probit values which were plotted against log doses. A linear relation was obtained from the dose-response curve with an r2 = 0.958. Statistical validation of the equation was tested through linear regression analysis, where the slope and intercept were found significant from zero. No significant difference was shown between observed and expected responses (p > 0.05). ED 50 and 99.9% were computed from the linear equation and found to be 4.57 and 344 mg, respectively. This finding can be supported by future works in which a proper formulation of thiamine hydrochloride in the respective doses would be presented. One can get prolonged safe protection against insect bites.


Assuntos
Culicidae , Mordeduras e Picadas de Insetos/prevenção & controle , Repelentes de Insetos/farmacologia , Tiamina/farmacologia , Adulto , Animais , Humanos , Pele
17.
Chem Biodivers ; 17(2): e1900580, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31913571

RESUMO

Developing effective and eco-friendly antimicrobials and pesticides has become a highly important issue. The repellent, insecticidal and antimicrobial activity of essential oils (EOs) isolated by hydrodistillation from dried leaves of the three Eucalyptus species (E. cloeziana, E. umbellata and E. benthamii) were investigated. During GC/MS analysis, α-pinene (47.36 %), 1,8-cineol (38.53 %) and α-pinene (35.31 %) were identified as major components of E. cloeziana, E. umbellata and E. benthamii, respectively. The EOs from E. cloeziana exhibited the longest effective protection time (465 min, at 50.0 % w/w) for humans among the EOs studied. The effective protection time was 30 min and 300 min at concentrations of 12.5 % (w/w) and 25.0 % (w/w), respectively. Fumigating insecticidal activity of EOs from three Eucalyptus species was tested by airtight fumigation in conical flask, which indicated that essential oils had a highly and rapidly insecticidal activity on Culex pipiens quinquefasciatus. The antimicrobial activity of EOs was evaluated by using disc diffusion and agar dilution methods. There was no significant difference in the antibacterial activity of EOs from E. cloeziana and E. umbellate and they had the same MICs (20 mL/L) on Staphylococcus aureus, Salmonella typhi, Bacillus subtilis and Escherichia coli. E. benthamii had the worst microbial inhibitory effect among the three Eucalyptus essential oils and the MIC value for the test species is 40 mL/L except for Rhodotorula Harrison (10 mL/L).


Assuntos
Anti-Infecciosos/química , Eucalyptus/química , Repelentes de Insetos/química , Inseticidas/química , Óleos Voláteis/química , Folhas de Planta/metabolismo , Animais , Anti-Infecciosos/farmacologia , Aspergillus/efeitos dos fármacos , Candida/efeitos dos fármacos , Culex/efeitos dos fármacos , Eucalyptus/metabolismo , Cromatografia Gasosa-Espectrometria de Massas , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Repelentes de Insetos/farmacologia , Testes de Sensibilidade Microbiana , Óleos Voláteis/análise , Óleos Voláteis/farmacologia , Folhas de Planta/química
18.
PLoS Negl Trop Dis ; 14(1): e0007970, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31961867

RESUMO

BACKGROUND: Arboviruses transmitted by day-biting Aedes mosquitoes are a major public health concern. With the challenges inherent in arbovirus vaccine and therapeutics development, vector control and bite prevention strategies are among the limited options available for immediate intervention. Bite prevention through personal protective technologies (PPT), such as topical mosquito repellents or repellent-impregnated clothing, may help to decrease biting rates and, therefore, the risk of disease in groups most susceptible to adverse outcomes from Zika virus. However, achieving high uptake and compliance with PPT can be challenging. METHODOLOGY/PRINCIPAL FINDINGS: To gain an insight into the knowledge and concerns of pregnant women surrounding Zika and their opinions regarding PPT, particularly repellent clothing, a focus group study was carried out with pregnant women, women of reproductive age, and semi-structured interviews with their male partners in two cities in Colombia. The discussions revealed shortfalls in basic knowledge of Zika virus, with several pregnant participants reporting being unaware of the potential for Zika-related congenital malformations. Although participants generally considered Zika to be a significant personal threat, most rated it as less of a concern than dengue or diarrheal diseases. Overall, repellent clothing and other forms of PPT were viewed as effective, although some participants expressed concerns over the high costs of repellents, and safety fears of regular contact with repellent chemicals, which they perceived as potentially harmful. Plant-derived repellents were considered to be safer than synthetic chemical repellents. Discussions also highlighted that health centers were the preferred source of information on bite-reduction. CONCLUSIONS/SIGNIFICANCE: Achieving high uptake and compliance with PPT in populations most at risk of adverse outcomes from Zika infection requires engaging key users in open dialogue to identify and address any practical issues regarding PPT use, and concerns over safety. The findings presented here suggest that educational campaigns should strongly emphasize the risks associated with Zika during pregnancy, and discuss safety profiles of approved synthetic repellents and the availability of EPA-approved plant-based repellents. In addition, the economic and political context should be a major consideration when evaluating personal mosquito-repellent strategies.


Assuntos
Infecção por Zika virus/prevenção & controle , Infecção por Zika virus/psicologia , Zika virus/fisiologia , Adolescente , Adulto , Aedes/efeitos dos fármacos , Aedes/virologia , Animais , Colômbia , Estudos de Avaliação como Assunto , Feminino , Humanos , Repelentes de Insetos/farmacologia , Conhecimento , Masculino , Pessoa de Meia-Idade , Percepção , Equipamento de Proteção Individual/economia , Gravidez , Adulto Jovem , Infecção por Zika virus/economia , Infecção por Zika virus/virologia
19.
Ecotoxicol Environ Saf ; 189: 109988, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31767459

RESUMO

Tribolium casteneum is a major stored grains pest causing huge loss by secreting toxic quinones' which make the grains unfit for human consumption. Increasing concern about the fast-growing resistance in T. casteneum against fumigants has evoked more intense research worldwide. Therefore, finding an eco-friendly alternative for the management of the pest is of great importance. In this study, the insecticidal activity of the essential oils (EOs) of Artemisia annua is evaluated. Chemical composition of the EOs eluted with methanol and petroleum ether was analysed through Gas chromatography-mass spectrometry (GC-MS). The result has reported a total of 13 & 16 compounds in the methanol and petroleum ether EOs respectively. In contact toxicity studies, adults were found more susceptible to the petroleum ether EOs (LD50 = 0.43 mg adult-1) than the methanolic EOs (LD50 = 1.87 mg adult-1). Petroleum ether EOs was also superior in fumigant assays against both the adults (0.81 mg L air-1) and larvae (0.65 mg L air-1). Moreover, the same was also recorded as a strong repellent. The bio-molecular studies conducted to gain an insight into the extent of metabolic disturbances inflicted in the treatment sets has shown a significant increase in Lipid peroxidase and decrease (p˂0.01) in protein, Acetylcholinesterase, Glutathione S Transferees, Reduced Glutathione level. This indicates the major signs of oxidative stress in the treatment sets. The Results ascertain the knowledge to develop natural insecticides from Artemisia annua using a potential solvent to be used in the future as an efficient management tool against T. casteneum.


Assuntos
Artemisia annua/química , Controle de Insetos/métodos , Inseticidas/farmacologia , Óleos Voláteis/farmacologia , Tribolium/fisiologia , Animais , Repelentes de Insetos/química , Repelentes de Insetos/isolamento & purificação , Repelentes de Insetos/farmacologia , Inseticidas/química , Inseticidas/isolamento & purificação , Larva/metabolismo , Larva/fisiologia , Dose Letal Mediana , Óleos Voláteis/química , Óleos Voláteis/isolamento & purificação , Estresse Oxidativo/efeitos dos fármacos , Tribolium/metabolismo
20.
J Sci Food Agric ; 100(4): 1541-1546, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31769025

RESUMO

BACKGROUND: Citrus sinensis, Allium sativum, Ocimum basilicum, Mentha spicata, Curcuma longa, Carica papaya, Andrographis paniculata, Azadirachta indica, Cymbopogon citratus and Acorus calamus were compared in the form of extracts of chloroform, hexane and aqueous media for their effectiveness in repelling Tribolium castaneum. Filter paper of 9 cm in diameter was cut into halves. Using a micro-pipette, each extract was applied to one half of the filter paper. The volume applied was kept constant at 0.6 mL per 30 cm2 . The filter paper was dried and reattached leaving a 0.5 cm gap between, in a Petri-plate. Ten adults of T. castaneum were introduced and the repellency was observed after 30, 60 and 180 min. RESULTS: The aqueous extract of C. papaya exhibited the highest repellency (82-97%) followed by that of garlic bulbs (aqueous extract) with 86.67% repellency. Further, gunny bags were sprayed separately using bottle sprayers with the two most effective extracts at a constant volume of 42 mL per 575 cm2 . These treated gunny bags were compared with malathion-treated gunny bags in the insect management unit. The observations were taken after 2, 8 and 24 h. Papaya leaf extract-treated gunny bags showed relative repellent activity similar to that of malathion-treated gunny bags after 24 h of treatment. Thus, gas chromatography-mass spectrometry analysis of aqueous extract of papaya leaves was performed. CONCLUSIONS: It can be concluded that extract of papaya leaves containing 2-methoxy-4-vinylphenol (8.47% peak area) can be used as a repellent biopesticide. © 2019 Society of Chemical Industry.


Assuntos
Repelentes de Insetos/farmacologia , Extratos Vegetais/farmacologia , Tribolium/efeitos dos fármacos , Andrographis/química , Animais , Azadirachta/química , Carica/química , Curcuma/química , Cymbopogon/química , Alho/química , Repelentes de Insetos/química , Repelentes de Insetos/isolamento & purificação , Mentha spicata/química , Extratos Vegetais/química , Extratos Vegetais/isolamento & purificação , Tribolium/fisiologia
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