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Repellent action of neem oil was evaluated against different mosquito species. 2% neem oil mixed in coconut oil provided 96-100% protection from anophelines, 85% from Aedes, 37.5% from Armigeres whereas it showed wide range of efficacy from 61-94% against Culex spp. Therefore, neem oil can be applied as a personal protection measure against mosquito bites.
The efficacy of fabrics impregnated with N,N-diethylphenylacetamide (DEPA), a new repellent, was studied in the laboratory and field against Aedes aegypti (L.) and Culex quinquefasciatus Say. DEPA-treated polyester cotton and cotton fabrics provided repellency for 30 and 36 d and had a half-life of 11 and 5 d, respectively. The repellent could not be applied at a rate of greater than 15% of fabric weight. DEPA-treated fabric patches were found to be a practical and novel approach and were effective for 90 d in the laboratory against Ae. aegypti and 77 d in the field against Cs. quinquefasciatus.
Studies were carried out to evaluate the repellent action of Cymbopogan martinii martinii Stapf var. sofia (F. Gramineae) against mosquitoes under field conditions. Results revealed that the oil has strong repellent action and provided absolute protection for 12 h against Anopheles culicifacies, a principal vector of malaria in the country. Similar degree of protection was evident against An. annularis and An. subpictus. The protection against Culex quinquefasciatus, a pest mosquito was 96.3% for 12 h. Results of evaluation in captivity revealed complete protection against this species for 5 h.
Animal experiments ascertained that the repellent N,N-diethylamide of phenoxyacetic acid (P-203) increases the frequency of chromosomal aberration in the bone marrow cells of mice following its intraperitoneal introduction and also in the cells of a regenerating liver of rats after its repeated skin application. Dimethylphthalate displayed a mutagenic action only with respect to the rats' hepatocytes when applied repeatedly to the skin.
A series of amide analogues of N,N-diethyl-m-toluamide (DEET) and N,N-diethylphenylacetamide (DEPA) were synthesized to study their mosquito repellency in relation to chemical structure and physical properties. None of these parameters (vapor pressure, lipophilicity, and molecular length) could be related to protection time. However, when the protection time of all five amides derived from the same carboxylic acid was expressed in terms of all three parameters together, excellent correlation was obtained.
The repellency of fennel (Foeniculum vulgare Miller)-containing products (5% aerosol and 8% cream) against mosquitoes was compared with those of citronella oil, geranium oil and deet, as well as three commercial repellents, Baby Keeper cream containing IR3535, MeiMei cream containing citronella and geranium oils, and Repellan S aerosol containing 19% N,N-diethyl-m-toluamide (deet) under laboratory and field conditions. In a laboratory study with female Aedes aegypti (L), fennel oil exhibited good repellency in a release-in-cage test and repellency in skin and patch tests of the oil was comparable with those of citronella and geranium oils. In paddy field tests with five human volunteers, 5% and 8% fennel oil-containing aerosol and cream produced 84% and 70% repellency, respectively, at 90 min after exposure, whereas Baby Keeper cream and MeiMei cream gave 71% and 57% repellency at 90 min after exposure, respectively, and Repellan S aerosol gave 89% repellency at 210 min. The species and ratio of mosquitoes collected were the genera Culex (44.1%), Anopheles (42.2%), Aedes (7.8%) and Armigeres (5.9%). Fennel oil-containing products could be useful for protection from humans and domestic animals from vector-borne diseases and nuisance caused by mosquitoes.
Four fractions of Kaempferia galanga (hexane fraction, dichloromethane fraction 1, dichloromethane fraction 2 and methanolic fraction) were tested for larvicidal activity toward fourth instar Culex quinquefasciatus. The hexane fraction was found to exhibit the highest larvicidal effect with the LC50 of 42.33 ppm. Testing for adulticidal activity, the hexane fraction did not show any promising adulticidal effect. However, it caused a knockdown effect which might be useful as a repellent. It was then tested for repellent activity in human volunteers both in laboratory and field studies. In a laboratory study, the hexane fraction possessed repellency against Aedes aegypti (ED50 value of 30.73 microg/cm2), and provided biting protection for 3 hours. In a field study, it could protect against certain mosquitos, ie, Armigeres subalbatus, Anopheles barbirostris, An. aconitus, Mansonia uniformis, Cx. quinquefasciatus, Cx. gelidus, Cx. tritaeniorhynchus and Ae. aegypti. The hexane fraction did not cause dermal irritation when applied on human skin.
A field study was carried out to evaluate the mosquito repellent action of neem (Azadirachta indica) oil in tribal forested villages of District Mandla. Various concentrations of neem oil mixed in coconut oil (1-4%) were applied to the exposed body parts of human volunteers. Results revealed 81-91% protection during 12 h period of observation from the bites of anopheline mosquitoes. Neem oil is an indigenous product and a practical solution to curtail mosquito nuisance.
Permethrin-impregnated clothing and three topical repellent formulations of deet (diethyltoluamide) were field tested against natural populations of tsetse flies, mostly Glossina morsitans centralis Machado, in central Zambia. Volunteers wore different combinations of clothing impregnated with permethrin 0.125 mg ai/cm2 and repellents while riding in a vehicle that was driven slowly (4-6 km/h), with the windows and rear door open, through fly-infested areas. The mean rate of tsetse bites was about twenty per 75 min for unprotected people. The treatment combination of permethrin-impregnated clothing (blue cotton coveralls) and either of two controlled-release deet formulations on exposed skin of face and arms provided 91% mean protection, but this was not significantly better (P greater than 0.05) than wearing deet repellent alone (76-87% protection). No significant differences of protection were observed between the three repellent treatments, although the two controlled-release formulations (intended to be more persistent) were applied at approximately half the dosage of the standard 75% deet. Wearing permethrin-impregnated coveralls alone provided relatively poor protection (34%) for the untreated and exposed skin of head and hands. However, olive drab mesh jackets treated with permethrin reduced the tsetse biting rate by 75%.
The essential oil of catnip, Nepeta cataria L., contains two isomers of nepetalactone, E,Z-and Z,E-nepetalactone, and was tested for repellent activity to adult male German cockroaches, Blattella germanica (L.), in a choice-test arena. The two isomers of nepetalactone were purified by using preparative thin-layer chromatography and tested for behavioral activity in the choice-test arena. Significant differences due to concentration were detected by analysis of variance, and the responses were compared by least-squared means analysis. The activities of the essential oil and purified isomers were compared with N,NA-diethyl-3-methylbenzamide (DEET) by a paired t-test. E,Z-Nepetalactone was the most active of the compounds tested, being significantly more active to this species than equivalent doses of DEET, the essential oil, or Z,E-nepetalactone. Antennectomized insects showed no response to concentrations that were active against intact insects.
Eight polymer and 9 microcapsule formulations of deet were tested on laboratory rabbits against Aedes aegypti and Anopheles albimanus. Several formulations were significantly more effective than simple (unformulated) deet at the same strength for periods up to 24 h. Best results were obtained with a polymer formulation containing a high molecular weight fatty acid and 3 microcapsule formulations containing lanolin, gum arabic, gelatin, tannic acid, stearic acid, polypropylene glycol, water, and a commercial lotion in the microcapsule and carrier fractions.
There is an interest in the development of repellents for personal protection of humans and animals against ticks. Evaluation of new substances or formulations needs adequate test procedures to show efficacy of the compounds. A variety of repellent assays for ticks are described in the literature. Available biotests can be grouped in three categories (i) use of live hosts, (ii) use of some kind of tick attractant associated with hosts, or (iii) no use of attractants at all. The latter are often better to standardize and are cheap, but suffer from a poor ability to filter out weak repellents. The former two are usually more predictive in terms of forecasting the efficacy of the product under practical conditions, although sometimes difficult to standardize, particularly in the field, but usually expensive and time consuming. Therefore, recent developments concentrated on laboratory assays like the Moving-object bioassay or the human volunteer test, allowing the tick to display its host-seeking behaviour as close as possible to that shown in nature, yet offering a standardized procedure.
Although malaria kills approximately 1 million children each year, preventive measures can be effective in limiting the mortality and morbidity associated with malaria. Mosquito bites can be avoided by use of appropriate environmental control and use of protective clothing, bed nets, repellents, and insecticide. Chemoprophylaxis is a mainstay of malaria prevention, and new, effective agents are increasingly available. Rapid, accurate diagnosis and effective medical treatment can help people who become ill with malaria despite their preventive efforts. With careful attention to preventive efforts, malaria should be extremely rare in travelers; similarly, broader implementation of preventive measures could decrease the burden of malaria on residents in areas where it is endemic.
Laboratory tests were conducted to compare the response of Eutrombicula hirsti (Sambon) larvae to the compounds dibutylphthalate (DBP), dimethylphthalate (DMP), diethyl methylbenzamide (Deet), benzyl benzoate (BB), and permethrin. The ED50 for E. hirsti of these compounds when applied to filter paper were 0.17 mg/cm2 for DMP, 0.24 mg/cm2 for permethrin, 0.26 mg/cm2 for Deet, 1.42 mg/cm2 for BB, and > 7.21 mg/cm2 for DBP. When impregnated in cloth, DMP, Deet, and BB were highly toxic to larvae at low concentrations, whereas permethrin and DBP were not as rapidly toxic, but were effective.
The phenomenon of herding is a very general feature of the collective behavior of many species in panic conditions, including humans. It has been predicted theoretically that panic-induced herding in individuals confined to a room can produce a nonsymmetrical use of two identical exit doors. Here we demonstrate the existence of that phenomenon in experiments, using ants as a model of pedestrians. We show that ants confined to a cell with two symmetrically located exits use both exits in approximately equal proportions to abandon it in normal conditions but prefer one of the exits if panic is created by adding a repellent fluid. In addition, we are able to reproduce the observed escape dynamics in detail using a modification of a previous theoretical model that includes herding associated with a panic parameter as a central ingredient. Our experimental results, combined with theoretical models, suggest that some features of the collective behavior of humans and ants can be quite similar when escaping under panic.
The repellence of the plant-derived bicyclic monoterpenoid isoborneol on subterranean termites was assessed in short-term laboratory bioassays. Depending on concentration, application of isoborneol to different soil types was efficient in creating repellent soil barriers, which were not penetrated by workers of Reticulitermes santonensis De Feytaud or R. flavipes Kollar within 2 wk after adding the substance to the substrate. Isoborneol-treated barriers did not affect termite survival. The bioavailability of the active ingredient decreased with increasing clay content of the soil. Evaporation of isoborneol from treated soil increased with increasing particle size of the substrate and could be reduced by covering the soil surface.
A field study was carried out to evaluate the mosquito repellent action of Cymbopogan martinii martinii Stapf var sofia oil in tribal village of Car Nicobar Island. Results revealed that application of 1 ml of the oil provided 98.7% protection in indoor and 96.52% in outdoor conditions during 12 h period of observation from the bites of An. sundaicus. Cymbopogan martinii martinii Stapf var sofia oil is an indigenous product, its application is safe and can be widely used for protection from malaria.
The repellent effect of Lantana camara flowers was evaluated against Aedes mosquitoes. Lantana flower extract in coconut oil provided 94.5% protection from Aedes albopictus and Ae. aegypti. The mean protection time was 1.9 h. One application of Lantana flower can provide more than 50% protection up to 4 h against the possible bites of Aedes mosquitoes. No adverse effects of the human volunteers were observed through 3 months after the application.