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Field evaluation of repellent formulations containing deet and picaridin against mosquitoes in Northern Territory, Australia.

Field efficacy of repellent formulations containing picaridin (1-methyl-propyl 2-(2-hydroxyethyl)-1-piperidinecarboxylate) or deet (N,N,-diethyl-3-methylbenzamide) against mosquitoes in Northern Territory, Australia, was evaluated. The following repellent treatments were evaluated: 19.2% picaridin (Autan Repel Army 20), a solution of 20% deet in ethanol, and 35% deet in a gel (Australian Defense Force [ADF]). The predominant mosquito species were Culex annulirostris Skuse (57.8%), Anopheles merankensis Venhuis (15.4%), and Anopheles bancroftii Giles (13.2%). The protection provided by repellents against Anopheles spp. was relatively poor, with 19.2% picaridin and ADF deet providing >95% protection for only 1 h, whereas 20% deet provided <95% protection at 1 h after repellent application. In contrast, the repellents provided good protection against Cx. annulirostris, with 19.2% picaridin providing >95% protection for 5 h and both deet formulations providing >95% protection for 7 h when collections ceased. This study provides additional field data showing tolerance of Anopheles spp. for repellents. The response of field populations of Cx. annulirostris, an important vector of arboviruses in Australia, to repellents containing deet and picaridin is reported for the first time.

Animals↗

Attraction, feeding, and repellency responses in mutant strains of Aedes aegypti.

In a laboratory olfactometer, 12% of female Aedes aegypti with a marker gene for red eye (re), 0.7% of females with a marker gene for white eye (we), and 54.1% of females with normal (norm) eye color were attracted to odor from a human hand. When a synthetic attractant blend was used in place of the hand, the attraction rate was 7%, 0.3%, and 35.4%, respectively. On average, re females required significantly less time (76.8 sec) than we (189.6 sec) or norm (176.7 sec) females to locate, land on, and probe human skin but no difference was found between mosquito strains in the time required for females to bloodfeed to repletion on a restrained guinea pig. Differences among mosquito strains in the repellency of 15% diethyltoluamide (deet), 6.65% deet, and 10% citronella were not significant.

Aedes↗

Effects of partial blood engorgement and pretest carbohydrate availability on the repellency of deet to Aedes albopictus.

The pretest availability of 10% sucrose solution and/or partial blood engorgement in Aedes albopictus Skuse significantly influenced mosquito attack rates and the time of repellent protection in laboratory bioassays. In 46 cm L x 38 cm W x 37 cm H cages used in USDA repellent tests, non-blood-fed and partially blood-fed mosquitoes attempted to bite at similar rates. In small cages (5 cm dia. x 4 cm H), holding individual females, mean mosquito attack rates were reduced when females were partially blood fed, compared with those not blood fed. The protection period from bites by Ae. albopictus using 25% ethanolic deet (N,N diethyl-3-methylbenzamide) increased significantly in small and USDA standard cages when females had pretest access to sucrose solution, compared with females starved for 12 h. Partial blood engorgement in mosquitoes affected repellent protection time in USDA standard test cages but not in small cages.

Aedes↗

Relative repellency of two formulations of N,N-diethyl-3-methylbenzamide (deet) and permethrin-treated clothing against Culex sitiens and Aedes vigilax in Thailand.

Field tests were conducted to compare the effectiveness of 2 repellent formulations of N,N-diethyl-3-methylbenzamide (deet) in combination with permethrin-impregnated military uniforms against Culex sitiens and Aedes vigilax in Thailand. Repellency was determined during a 2 h crepuscular period using volunteers who had been treated with repellents 6, 8, 10, and 12 h prior to the end of each test period. An extended-duration repellent formulation (EDRF) containing 35% deet repelled significantly more Ae. vigilax than 75% deet in ethanol. Although not statistically significant, the EDRF also resulted in fewer biting attempts by Cx. sitiens. Neither formulation provided complete protection against either species 4-12 h post-application, but both provided greater overall protection against Ae. vigilax. Volunteers who wore treated uniforms without repellents were attacked by significantly fewer mosquitoes than controls.

Adult↗

Mosquito repellents: monocarboxylic esters of aliphatic diols.

Selected monocarboxylic esters of aliphatic diols that contained an alicyclic group in the acyl portion of the molecule were effective repellents for Aedes aegypti, Anopheles quadrimaculatus and An. albimanus when tested on cloth. Although 25 of the esters provided greater than 21 days of protection against all 3 species, the repellent potency of the 143 hydroxyesters that were tested was found to vary with mosquito species. Anopheles quadrimaculatus was especially susceptible to this type of structure; 112 of the esters provided greater than 21 days of protection and 56 provided greater than 100 days of protection. Aedes aegypti was moderately susceptible to these repellents; 72 esters provided greater than 21 days of protection. Anopheles albimanus was the most difficult mosquito to repel. Only 29 of the esters provided greater than 21 days of protection.

Aedes↗

Repelling properties of some plant materials on the tick Ixodes ricinus L.

The repellent effects on nymphal stages of Ixodes ricinus L. of some plant materials have been studied in the laboratory. The plant material consisted of an ethanolic extract from Achillea millefolium L., and volatile oils of birch and/or pine tar, citronella, cloves, eucalyptus, geranium, lavender, lily of the valley and peppermint. The most pronounced effects were observed for the oils of citronella, cloves and lily of the valley. They possessed repelling activities of the same magnitude as the reference repellent DEET (N,N-diethyl-m-toluamide). Some major constituents of these oils, e.g. citronellol and geraniol (oil of citronella and lily of the valley) and eugenol (oil of cloves) showed pronounced repelling effects. This was also the case for phenethyl alcohol, a minor component in the oil from lily of the valley.

Achillea↗

Laboratory and field evaluation of deet, CIC-4, and AI3-37220 against Anopheles dirus (Diptera: Culicidae) in Thailand.

Laboratory and field tests of the repellents diethyl methylbenzamide (deet), 1-(3-Cyclohexen-1-yl-carbonyl)-2-methylpiperidine (AI3-37220), and (2-hydroxymethylcyclohexyl) acetic acid lactone (CIC-4) were conducted against Anopheles dirus Peyton & Harrison, the principal malaria vector in Thailand. In the laboratory, An. dirus was more sensitive to CIC-4 than either AI3-37220 or deet. The duration of protection provided by each repellent in laboratory tests increased with higher concentrations of repellents and when exposed in cages containing fewer mosquitoes. A field study in Chanthaburi Province, southeastern Thailand, during November 1993 tested 25% (wt:wt) ethanol solutions of each repellent against An. dirus. In contrast to the laboratory experiments, protection provided by AI3-37220 was significantly better than either deet or CIC-4 and there was no significant difference between deet and CIC-4. Protection provided by deet and CIC-4 fell to below 95% 2 h after repellent application, whereas AI3-37220 provided > 95% protection for 4 h. The protection provided by all repellents fell to < or = 65% 7 h after repellent application.

Aedes↗

Laboratory evaluation of 18 repellent compounds as oviposition deterrents of Aedes albopictus and as larvicides of Aedes aegypti, Anopheles quadrimaculatus, and Culex quinquefasciatus.

Among 18 experimental skin repellent compounds tested at five concentrations in the laboratory as oviposition deterrents against Aedes albopictus. 12 compounds showed significant activity, with median effective dose values ranging from 0.005 to 0.052%. The test compounds also were evaluated in the laboratory as larvicides against laboratory-reared 4th instars of Aedes aegypti, Anopheles quadrimaculatus, and Culex quinquefasciatus with the same concentrations employed for the oviposition deterrency tests against Ae. albopictus. Larval mortality data at 24 and 48 h after treatment indicated that 12 test repellents caused larval mortalities in the range of 67 to 100% against An. quadrimaculatus, 10 compounds induced 55-100% larval mortalities of Ae. aegypti, whereas larval mortality caused by 9 compounds ranged from 74 to 100% against Cx. quinquefasciatus. These mortality data did not fit the linear model of the statistical analysis. However, multiway analysis of variance of these data showed that the repellent compounds, concentrations used, species of mosquitoes, and exposure times affect the degree of larval mortalities.

Aedes↗

Field evaluation of spatial repellency of metofluthrin-impregnated latticework plastic strips against Aedes aegypti (L.) and analysis of environmental factors affecting its efficacy in My Tho City, Tien Giang, Vietnam.

Spatial repellency of metofluthrin-impregnated polyethylene latticework plastic strips against Aedes aegypti mosquitoes was evaluated. Analysis of environmental factors affecting the efficacy of these strips, such as room temperature, humidity, and house structure, was performed in a residential area in My Tho City, Tien Giang Province, Vietnam. Treatment with the strips at the rate of 1 strip per 2.6-5.52 m(2) (approximately 600 mg per 2.6-5.52 m(2)) reduced the collection of Ae. aegypti resting inside the houses for at least eight weeks. Multiple regression analysis indicated that both increase in the average room temperature and decrease in the area of openings in the rooms that were treated with the strips positively affected the spatial repellency of metofluthrin.

Aedes↗

[Tests for evaluating the effectiveness of pediculicides: importance and limitations].

The obligation to prove pediculicides efficacy is relatively recent. Two tests are required by the authorities to obtain registration. In vitro test (with Pediculus humanus humanus) is the first step to evaluate the efficacy of new molecules. It must be followed by bio-clinical tests (with infested children by Pediculus humanus capitis). For those tests the authors advise to respect the "three units rule": unit of time (no more than 2 days for the test), unit of place (same environment) and unit of action (only one team to apply and evaluate products). This type of tests is possible only in countries with high infestation (at least 60% of prevalence). A third test is consequently advised, the ex vivo test using Pediculus humanus capitis obtained from infested children in France. This test can be useful also to re-evaluate current products in the light of increased resistance or decreased sensitivity of the lice. Finally some other tests can be advised to prove some other activities like remanence or repellent properties or to estimated lice resistance.

Evaluation Studies as Topic↗

Repellent activity of constituents identified in Foeniculum vulgare fruit against Aedes aegypti (Diptera: Culicidae).

The repellent activity of materials derived from the methanol extract of fruits from Foeniculum vulgareagainst hungry Aedes aegypti females was examined using skin and patch tests and compared with that of the commercial N,N-diethyl-m-toluamide (deet) and (Z)-9-octadecenoic acid. The biologically active constituents of the Foeniculum fruits were characterized as (+)-fenchone and (E)-9-octadecenoic acid by spectroscopic analyses. Responses varied according to compound, dose, and exposure time. In a skin test with female mosquitoes, at a dose of 0.4 mg/cm(2), (+)-fenchone and (Z)-9-octadecenoic acid exhibited moderate repellent activity at 30 min after treatment, whereas deet provided >1 h of protection against adult mosquitoes at 0.2 mg/cm(2). (Z)-9-Octadecenoic acid was a more potent repellent agent than (E)-9-octadecenoic acid. (+)-Fenchone and (E)-9-octadecenoic acid merit further study as potential mosquito repellent agents or as lead compounds.

Aedes↗

Field evaluation of deet and a piperidine repellent (AI3-37220) against Amblyomma americanum (Acari: Ixodidae).

Repellent efficacy of deet (N,N-diethyl-3-methylbenzamide) and a piperidine, AI3-37220, was evaluated topically on human volunteers against lone star tick, Amblyomma americanum (L.), nymphs and adults in the field. AI3-37220, at 0.5 mg/cm2, provided > 90% repellency against adult and nymphal ticks over a 6-h test period and showed significantly better repellent efficacy than deet. Deet, at the same concentration, provided 85% repellency at 0 h and deteriorated to 55% repellency at 6 h.

Animals↗

Synthesis and repellent efficacy of a new chiral piperidine analog: comparison with Deet and Bayrepel activity in human-volunteer laboratory assays against Aedes aegypti and Anopheles stephensi.

Optically active (1S,2'S)-2-methylpiperidinyl-3-cyclohexen-1-carboxamide (SS220) is a new synthetic arthropod repellent. A three-step synthesis based on a chiral Diels-Alder reaction and diastereomeric resolution of 2-methylpiperidine was developed to prepare the compound. Quantitative laboratory assays using human volunteers compared the effectiveness of SS220 with the commonly used repellents Deet and Bayrepel against Aedes aegypti (Linnaeus) and Anopheles stephensi Liston mosquitoes. In two experiments using Aedes aegypti, one using a single identical dose and one with varying doses used to develop a dose-response curve, SS220 was as effective as Deet and both compounds were more effective than Bayrepel. The three compounds were equally effective against An. stephensi. Based on the ease of its synthetic preparation and its repellent efficacy, we surmise that SS220 is a candidate to serve as a new and effective alternate repellent for protection against arthropod disease vectors.

Aedes↗

Repellents: past, present, and future.

The use of repellents in protecting people against vector-borne diseases is predicated on the assertion that reducing human/vector contact will reduce the incidence of disease. The methods that have been used in developing countries have been simple to apply and relatively cheap. This article will discuss the use of repellents for protection against vector-borne disease in Southeast Asia and the Southwest Pacific region.

Animals↗

Monoterpenes from thyme (Thymus vulgaris) as potential mosquito repellents.

Five monoterpenes (carvacrol, p-cymene, linalool, alpha-terpinene, and thymol) derived from the essential oil of thyme (Thymus vulgaris) were examined for their repellency against the mosquito Culex pipiens pallens. All 5 monoterpenes effectively repelled mosquitoes based on a human forearm bioassay. Alpha-terpinene and carvacrol showed significantly greater repellency than a commercial formulation, N,N-diethyl-m-methylbenzamide (deet), whereas thymol showed similar repellency to that of deet. The duration of repellency after application for all these monoterpenes was equal to or higher than that of deet. These findings indicate that a spray-type solution containing 2% alpha-terpinene may serve as an alternative mosquito repellent.

Acyclic Monoterpenes↗