Dwelling space repellents: their use on military tentage against mosquitoes in Kenya, East Africa.
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Normal and branched-chain aliphatic monoethers of triethylene glycol are effective topical mosquito repellents. In terms of duration of protection, they are generally superior to the corresponding diethylene glycol analogs and some are superior to diethyltoluamide. The n-heptyl monoether of triethylene glycol affords double the protection time of diethyltoluamide under controlled laboratory conditions and appears to be a useful new mosquito repellent.
Three topical repellents were evaluated against Phlebotomus perniciosus using dose-response techniques. A total of 1800 laboratory reared nulliparous females of P. perniciosus, 2 to 15 days old, and 21 human volunteers were used. The effective dose (ED50 and ED90) for Deet, Indalone and MGK 11 has been determined. Indalone and MGK 11 were more effective than standard Deet. The data obtained indicate that P. perniciosus is highly sensitive to the repellents compared with other blood-sucking arthropods.
Essential oils extracted from the seeds of anise (Pimpinella anisum), dried fruits of eucalyptus (Eucalyptus camaldulensis), dried foliage of mint (Mentha piperita) and basil (Ocimum basilicum) and fresh foliage of laurel (Laurus nobilis) were tested for their repellency against the adult females of Culex pipiens. All essential oils showed repellency in varying degrees, eucalyptus, basil and anise being the most active.
Essential oil extracts from Callicarpa americana and Callicarpa japonica were investigated. Bioassay-guided fractionation of C. americana extracts using the yellow fever mosquito, Aedes aegypti, led to the isolation of alpha-humulene, humulene epoxide II, and intermedeol and a newly isolated terpenoid (callicarpenal). Similar work involving C. japonica resulted in the isolation of an additional compound, spathulenol, as well as the four compounds isolated from C. americana. Structure elucidation was performed on all isolated compounds using a combination of gas chromatography-mass spectrometry-electron ionization, high-resolution liquid chromatography-MS-electrospray ionization, and one- and two-dimensional NMR experiments. Heretofore, 13,14,15,16-tetranorclerodane, callicarpenal, has never been identified from natural sources. Complete (1)H and (13)C NMR assignment data are provided for this compound. In bite deterrent studies, spathulenol, intermedeol, and callicarpenal showed significant repellent activity against A. aegypti and Anopheles stephensi.
A susceptible, laboratory strain of bed bug, Cimex lectularius L., was used to determine the efficacy of insecticide products labeled or possessing a site label for bed bug control. Field strain bed bugs also were used to evaluate one insecticide product. The lethal time (LT),, values calculated for the laboratory strain bed bugs indicated that all of the pyrethroid products killed significantly faster than chlorfenapyr (0.5% [AIl; Phantom: BASF; LT50 = 10 d and 9 h). lamda-Cyhalothrin (0.03%; Demand CS; Syngenta) was the fastest acting insecticide (LT50 = 20 min), followed by bifenthrin (0.02% [AI]; Talstar One, FMC; LT50 = 53 min), deltamethrin (0.06% [AI]; Suspend SC; Bayer; LT50 = 61 min), and permethrin (0.05%; Dragnet SFR; FMC; LT50 = 88 min). The field strain bed bugs exposed to deltamethrin had an LT50 value of 14 day 8 h, indicating that the field strain was significantly less susceptible to deltamethrin than the laboratory strain. Chlorfenapyr exposure did not prevent the laboratory strain bed bugs from mating and laying eggs, nor did it prevent the eggs from hatching during the 2-wk exposure period. Surprisingly, none of the insecticides tested, including the pyrethroids, were repellent to laboratory strain bed bugs. Bed bugs rested on pyrethroid-treated panels and remained in contact with the panels until they died (2 h). Chlorfenapyr was also not repellent to bed bugs, but it caused no mortality during the 2-h test period. This study suggests that although pyrethroids were effective for controlling laboratory strain bed bugs, there is the potential for significant resistance in field strains. This study also determined that pyrethroid products were not repellent to bed bugs and would not cause bed bug aggregations to scatter or avoid treated surfaces.
Four stereoisomers of p-menthane-3,8-diol, which make up the natural product obtained from Eucalyptus citriodora, were synthesized through stereoselective procedures. Repellency assays showed that all the four were equally active against Anopheles gambiae s.s. Racemic blends and the diastereoisomeric mixture of all the four isomers were also equally repellent. 1-alpha-terpeneol, with a single hydroxyl function at C-8 and unsaturation at C-8, and menthol, with a single hydroxyl function at C-3, were not repellent. The practical implication of these results is discussed.
Seventeen analogs of the repellent compounds N,N-diethyl-3-methylbenzamide (DEET) and N,N-diethylphenylacetamide (DEPA) were evaluated in vitro for repellency against laboratory-reared Aedes aegypti (L.) and Anopheles stephensi Liston mosquitoes by using a modified membrane blood feeding test system. The system was a valuable tool for comparing the effective concentrations of the repellent analogs. Additionally, this method used easily controlled test conditions, allowing completion of the many test replications necessary to evaluate all of the repellent analogs over a period of several years. One compound, N,N-diethyl-2-[3-(triflouromethyl)phenyl] acetamide, provided significantly better repellency than DEET against Ae. aegypti and slightly improved efficacy against An. stephensi. Eight of the analogs were as effective as or slightly more repellent than DEET against both species. Seven analogs were less effective than DEET and one compound, N,N-diethyl-3-hydroxybenzamide, was as a poor repellent. Overall, two DEPA analogs and a single DEET analog provided better repellency than DEET against both mosquito species and warrant future laboratory and field evaluation.
A clinical trial (n = 120, 60 males and 60 females) was conducted to assess the efficacy of an extended duration tropical insect/arthropod repellent (EDTIAR) topical formulation of N,N-diethyl-m-toluamide (DEET). The amount of EDTIAR (mean +/- confidence interval), applied by participants in accordance with label directions, was not significantly different between females (3.66 +/- 0.32 mg/cm2) and males (3.45 +/- 0.33 mg/cm2). There also was no significant difference in the number of Anopheles stephensi mosquitoes biting the control arm of females or males at 0, 3, 6, 9, and 12 hr. While gender had no effect on feeding, the time of day did effect mosquito feeding with fewer mosquitoes feeding in the afternoon than in the morning or evening. The percent protective efficacy at 0, 3, 6, 9, and 12 hr was 100.0, 99.3, 92.8, 79.7 and 66.3 for females, and 100.0, 100.0, 97.6, 91.9, and 77.5 for males. These data are inconsistent with the EDTIAR label claim that the repellent provides 95% or greater protection against mosquitoes for 12 hr or more under normal use conditions. The results of a multivariate regression analysis indicated that 1) protection decreased linearly as time after application of repellent increased (P < 0.001), 2) individuals who applied higher doses of repellent were better protected against mosquito bites (P < 0.001), 3) females experienced significantly less protection over time than did males (P = 0.005), and 4) the estradiol concentration in the blood had no effect on efficacy of the repellent (P = 0.110).
The repellent 1-(3-cyclohexen-1-yl-carbonyl)-2-methylpiperidine (AI3-37220) was compared with 2 formulations of diethylmethylbenzamide (deet) for its effectiveness in protecting 4 humans against the bites of Anopheles koliensis mosquitoes at a village in Central Province, Papua New Guinea. A mean of 77.2 +/- 10.5 bites/human/10 min of An. koliensis was collected on ethanol-treated (control) volunteers, a much higher density than most previous studies with Anopheles sp. mosquitoes. The protection provided by all repellents did not last long. Both 25% A13-37220 in ethanol and a formulation containing 35% deet in a gel provided >95% protection for only 2 h. A formulation of 25% deet in ethanol provided only 93% protection 1 h after repellent application and 39% protection 5 h after application.
Method of thin-layer chromatography was used to estimate threshold dosages of diethytoluamide, benzoylhexamethylene, dihexamethylenecarbamide, diethilamide of phenoxyacetic acid and dimethylphthalate for repelling of mosquitoes (Aedes hexodontus, Aedes vexans, Aedes caspius caspius), simuliids (Simulium venustrum), midges (Culicoides obsoletus) and sand-flies (Phlebotomus papatsi). Maximum sensitivity to all the preparations studied was shown by sand-flies (Phlebotomus papatasi, and most sensitive to repellents, out of all the studied species of mosquitoes, were Aedes caspius caspius. Giving recommendations on pellents one must take into consideration the level of sensitivity to repellents of dominating species of blood-sucking arthropods.
With the interruption of larva treatments done by OCP as part of onchocerciasis control in West Africa, Simulium came back in abundance in forest regions and savannah fertile valleys. In addition to the severe discomfort, nuisance by Simulium is in certain cases incompatible with land use. Since ground treatment of larval breading sites using insecticides is not always possible or efficient, it is therefore a necessity to develop other methods among which individual protection against Simulium bites. The general objective of our study was to evaluate different vegetable oil compound repellent formulas against Simulium bites. Activities were carried out in savannah zone (Niakaramandougou) and in forest zone (Soubré) in Côte d'Ivoire. The methodology consisted in catching blackflies on volunteers whose legs were rubbed with a repellent. Gobi raw oil and coconut, palm nut and gobi formulas (lotions and creams) were tested. During each session, which lasted from 07:00 am to 12:00 and from 03:00 pm to 06:00 pm, one person did not apply any repellent and was used as the control person. The results of our experimentations show that for a given zone (savannah, forest), a repellent (coconut, palm nut, gobi) and a compound (shea butter, vaseline), there is no significant difference between protection rates obtained with lotions (maximum: 21 bites/person/day) and those obtained with creams (maximum: 30 bites/person/day). In other respects, the lotion of a given repellent seems to be efficient in savannah as in the forest, in protecting against Simulium bites. It is the same situation with creams. So, repellents can be an efficient solution against Simulium nuisance. However, experimentations should continue to confirm the high repellency of tested formulas, proceed to the identification of principles and evaluate the toxicity and irritant effect of repellents to be applied on the skin.
Bioefficacy of commercially used synthetic insecticides/repellents and potential of selected essential oils and terpenoids were assessed against mosquitoes. Essential oils and terpenoids, were vapourised in commercially manufactured mosquito repellent electronic assemblies and effects of such vapours were tested on 6-7 days old adult female Aedes aegypti. Commercially available 'mats' (coir rectangles) impregnated with allethrin were used as standards for comparison of Kt50 and Kt90 values. Fastest knock-down was seen in case of allethrin, followed by terpeneol (anhydrous) and (-) carvone. Maximum knock-down time was observed for beta citronellol. All compounds exhibited a repellent effect also, terpeneol (anhydrous) being the best, followed by (-) carvone and citronellal. In repellent tests, no mortality was caused by terpenoids, but allethrin caused > 80 per cent knock-down.
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