Complete Protection Time Research Articles

Preliminary Study of the Mosquito Repellent and Adulticidal Effects of Volatile Oils of Lemon grass (Cymbopogon winterianus) in Imo State, Southeast Nigeria

Lemon grass (Cymbopogon winteriatus) has been widely acclaimed to possess therapeutic, cosmetic and insecticidal activities. This study was conducted using a field controlled trial by human volunteers to confirm the effectiveness and applicability of locally-produced Lemon grass oil as a mosquito repellent and adulticidal agent for the prevention of mosquito-borne diseases in Nigeria. Volatile oil was extracted using petroleum ether as solvent while olive oil was used as oil base. The study was conducted between September and October 2017 and made use of 12 volunteers across three locations. The lotions were applied on exposed body parts of the volunteers and they worked three shifts daily. The biting rate, percentage repellence complete protection time and whole night protection were measured and recorded. Topical application of each lotion reduced the biting rate of mosquitoes across the three locations, with the 60% (v/v) exhibiting higher impact of 341 vs 32; 438 vs 44 and 388 vs 33. The 60% (v/v) formulation also had the highest percentage repellence of 91.92% at Location I, offered a whole night protection against mosquito in location I and O and offered a Complete Protection Time (CPT) of 21.6, 18.93 and 20.8 respectively across all three locations. There was a significant statistical association r=0.95 (p<0.05) between concentrations of the Lemon grass oil formulations and mean duration protection time against mosquitoes. All formulation exhibited adulticidal activities, with the 60% (v/v) formulation having higher impact, causing fast immobilization or paralyzing effect on some mosquitoes that were at close range to treated volunteer’s body. The study concludes that volatile oils of Lemon grass possess mosquito (A. gambiae and An. funestus) repellent and adulticidal effects, especially at higher concentrations and can be used to reduce human-mosquito contacts and hence mosquito-borne diseases and irritation caused by their bites.

Artemisia vulgaris efficacies against various stages of Aedes aegypti.

Background and Aim:Aedes aegypti is the vector of dengue fever, dengue hemorrhagic fever, chikungunya, and, most recently, Zika. Dengue fever is one of Indonesia’s endemic diseases. The principal tool for preventing dengue is controlling Ae. aegypti by chemical insecticides since vaccine against dengue is still under research. However, Ae. aegypti developed resistance to various chemical insecticides worldwide. Therefore, research on alternate compounds as mosquito insecticides is urgently needed. This study demonstrated the efficacy of Artemisia vulgaris extract as larvicidal, ovicidal, adulticidal, repellency, and oviposition deterrent activity against Ae. aegypti.Materials and Methods:A. vulgaris was obtained from Temanggung, Indonesia, while the eggs of Ae. aegypti were collected from Yogyakarta, Indonesia, and were hatched in Laboratory of Parasitology, Faculty of Veterinary Medicine, Universitas Gadjah Mada. Larvicidal activity was evaluated according to the WHO protocol; adulticidal activity was performed using the Centers for Disease Control protocol. Oviposition activity was evaluated using ovitraps added with A. vulgaris extract, complete protection time in the repellent assay was defined as the number of minutes elapsed between compound application and the landing of the first mosquito.Results:A test of the larvicidal activity of A. vulgaris extract returned an LC50 of 65.8 ppm (r2=0.9014) in 1 h and 18.6 ppm (r2=0.575) in 24 h. A. vulgaris was effective as an adulticidal, demonstrating LC50 values of 11.35 mg (r2=0.875) in 90 min, 9.63 mg (r2=0.924) in 105 min, and 6.46 mg (r2=0.925) in 120 min. A. vulgaris at a concentration of 1000 ppm was able to reach 96% of oviposition deterrent effect. The ovicidal assay, a concentration of 1000 ppm resulted in 82.67% of eggs remaining unhatched. An extract concentration of 80 mg/ml achieved 63.3±3.5% biting repellency in adults.Conclusion:This study gives a clear indication that A. vulgaris extract acts on Ae. aegypti at various developmental stages and is a potential alternative bioinsecticide for controlling this disease vector.

A Milestone In Botanical Mosquito Repellents: Novel PMD-Based Formulation Protects More Than Twice As Long As High-Concentration Deet and Other Leading Products.

The use of skin-applied repellents is the primary method recommended by the Centers for Disease Control and Prevention for personal protection against biting mosquitoes. Historically, the majority of long-efficacy mosquito repellents have been N,N diethyl-3-methylbenzamide (deet)-based. Recently, a variety of new botanical formulations have been marketed, but their protection times generally continue to fall well short of high-concentration deet products. We present a laboratory arm-in-cage study of a Neo-Innova® repellent that has a prolonged action "NEO-PART®" (Prolonged Action Release Technology) formulation with 40% Citriodiol®. This formulation provides the botanical molecule para-menthane 3,8-diol (PMD) at 25% w/v of the total formulation. Against Aedes aegypti, Neo-Innova's mean complete protection time (CPT; 14.2 h) was approximately 2 to 3 times longer than that of 5 leading high-performance repellents marketed in the USA, including 25% deet and a 20% PMD ethanolic formulation. When testing Neo-Innova, 5 of the 6 subjects had no landings after 15 h. The 6th had single landings at 10 and 11 h (individual CPT of 10 h), but received no additional landings in further exposures made at 13 and 15 h. Neo-Innova repellency against Culex quinquefasciatus was similarly prolonged. The tremendous increment in repellency duration observed for the Neo-Innova product, when compared with both current standard and botanical repellent options, represents a milestone in repellent development and supports "once-a-day" applications as a practical strategy for personal protection against mosquitoes.

Evaluation of standard field and laboratory methods to compare protection times of the topical repellents PMD and DEET

Mosquitoes are important vectors of pathogens, and travellers to disease endemic countries are advised to avoid bites by applying topical repellents. Topical repellents are typically tested either in the arm-in-cage (AIC) test under laboratory conditions or in the field, but not often under both conditions. We, therefore, investigated how two topical repellents, 15% para-menthane-3,8-diol (PMD) and 15% N,N-diethyl-3-methylbenzamide (DEET) compare against each other both in the AIC test against three species recommended by the World Health Organization (i.e. Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus) and at two field sites in Switzerland, while using the same study participants in all experiments. In the field, the median complete protection time (CPT) was at least 6 hours for both PMD and DEET, while in the AIC test DEET slightly outperformed PMD. CPTs for DEET in the AIC test were 0.5, 2 and 2 hours against Ae. aegypti, An. stephensi and Cx. quinquefasciatus, respectively, and the corresponding median CPTs for PMD were 0.5, 1 and 0.5 hours. In conclusion, DEET slightly outperformed PMD in the AIC test, while the observed landing rates suggest the AIC test to underestimate efficacy of topical repellents in areas with lower landing pressure.

Repellent activity of essential oil of the stem of <i>Kleinia squarrosa</i> against mosquitoes

Most commercially available repellents of mosquitoes and other biting arthropods are synthetic and have a severe toxic effect to human. Moreover, these chemicals cause an irreversible damage to the ecosystem as some of them are non-degradable in nature. Therefore, there is a need to develop safe and effective alternatives to the currently available chemicals used to control vectors. In southern Ethiopia, the smoke obtained from burning the stem of Kleinia squarrosa Cufod. is used as a fumigant to ward off mosquitoes. In the present study hydrodistillation of the powdered stem of K. squarrosa gave a pale yellow oil (0.04%; w/w) with a characteristic pungent odor. A total of twenty-seven compounds have been identified by GC-MS analysis, accounting 48.71% of the total oil. The main constituents of the oil were ( E )-iso-γ-bisabolene (9%), α-pinene (5.74%), caryophyllene (5.36%) and sabinene (5.55%). The powdered stem of K. squarrosa was also burned, and the smoke extracted to yield a trace amount brownish oil. Analysis of the oil by GC-MS afforded 36 compounds comprising 94.56% of the total peak area. Terpene-4-ol (18.09%), ( E )-iso-γ-bisabolene (14.07%), 5-epi-7-epi-α-eudesmol (12.45%), and caryophyllene (8.35%) figured as major compounds. Mosquito repellent activity of the essential oil was tested on guinea pigs against Anopheles gambiae by a modified Kunming mice technique under laboratory testing conditions. The essential oil exhibited a dose-dependent repellent action in the dose range tested (0.03 - 5%; v/v) with ED 50 and ED 99.9 values of 1.49% and 4.74% (v/v), respectively. The study further revealed that that the essential oil possesses a 3 h complete protection time. The similarity in the chemical profiles of the essential oil and the oil extracted from the smoke obtained by burning K. squarrosa stem supports the traditional use of the plant as a fumigant to kill mosquitoes. Keywords: Kleinia squarrosa ; fumigant; essential oil; mosquito repellent; Anopheles gambiae

Repellent Activity of TRIG (N-N Diethyl Benzamide) against Man-Biting Mosquitoes.

A study was conducted to assess efficacy of a new repellent brand TRIG (15% N-N Diethyl Benzamide) when compared to DEET (20% N-N Methyl Toluamide). The repellents were tested in laboratory and field. In the laboratory, the repellence was tested on human volunteers, by exposing their repellent-treated arms on starved mosquitoes in cages for 3 minutes at hourly intervals, while counting the landing and probing attempts. Anopheles gambiae and Aedes aegypti mosquitoes were used. Field evaluation was conducted by Human Landing Catch technique. During the night, the repellents were applied on arms and legs and mosquitoes landing on these areas were collected. In laboratory tests, TRIG provided complete protection (100%) against Anopheles gambiae when applied at 1.25 g, while DEET provided this at 0.75 g. When tested on Aedes aegypti, TRIG provided complete protection when applied at 1 g, compared to 0.5 g for DEET. In the field, when applied at a recommended dose, both TRIG and DEET achieved above 90% protection against both An. arabiensis and Culex quinquefasciatus and a Complete Protection Time of about 6 hrs against both species of mosquitoes. The performances of the two products were found to be comparable and TRIG was recommended for use as repellent against mosquito bites.

Protection against mosquito vectors Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus using a novel insect repellent, ethyl anthranilate

Growing concern on the application of synthetic mosquito repellents in the recent years has instigated the identification and development of better alternatives to control different mosquito-borne diseases. In view of above, present investigation evaluates the repellent activity of ethyl anthranilate (EA), a non-toxic, FDA approved volatile food additive against three known mosquito vectors namely, Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus under laboratory conditions following standard protocols. Three concentration levels (2%, 5% and 10% w/v) of EA were tested against all the three selected mosquito species employing K & D module and arm-in-cage method to determine the effective dose (ED50) and complete protection time (CPT), respectively. The repellent activity of EA was further investigated by modified arm-in-cage method to determine the protection over extended spatial ranges against all mosquito species. All behavioural situations were compared with the well-documented repellent N,N-diethylphenyl acetamide (DEPA) as a positive control. The findings demonstrated that EA exhibited significant repellent activity against all the three mosquitoes species. The ED50 values of EA, against Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus were found to be 0.96%, 5.4% and 3.6% w/v, respectively. At the concentration of 10% w/v, it provided CPTs of 60, 60 and 30min, respectively, against Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus mosquitoes. Again in spatial repellency evaluation, EA was found to be extremely effective in repelling all the three tested species of mosquitoes. Ethyl anthranilate provided comparable results to standard repellent DEPA during the study. Results have concluded that the currently evaluated chemical, EA has potential repellent activity against some well established mosquito vectors. The study emphasizes that repellent activity of EA could be exploited for developing effective, eco-friendly, acceptable and safer alternative to the existing harmful repellents for personal protection against different hematophagous mosquito species.

Repellent efficacy of DEET, MyggA, neem (Azedirachta indica) oil and chinaberry (Melia azedarach) oil against Anopheles arabiensis, the principal malaria vector in Ethiopia.

BackgroundIn Ethiopia, Anopheles arabiensis is the main vector responsible for the transmission of malaria in the country and its control mainly involves application of indoor residual spraying (IRS) and use of insecticide-treated bed nets (ITNs).ObjectiveAlthough the role of repellents for reducing man-vector contact is documented in the literature, the response of An. arabiensis to repellents was not previously evaluated under field conditions in Ethiopia.MethodThe trial was conducted in Sodere village assessing the repellent activities of four repellents, of which, two of them were commercially available DEET (N, N-diethyl-1,3-methylbenzamide) and MyggA (p-methane diol) and the other two were laboratory- produced, 20% neem oil and 20% chinaberry oil. A 6 by 6 Latin square design was employed by involving six volunteers who received rotated treatments of repellents and the Ethiopian Niger seed, noog abyssinia (Guizotia abyssinia), and locally called as noog oil (diluents to the two plant oils). Each volunteer also served as control. Volunteers were positioned at a distance of 20–40 m from each other and each was treated with one of the repellents, Niger seed/noog/ oil or untreated. Landing mosquitoes were collected from dusk to down using tests tubes. The tests were done in three replicates.ResultsBoth DEET and MyggA provided more than 96% protection. The mean protection time for DEET was 8 hrs while the time for MyggA was 6 hrs. Protection obtained from neem oil and chinaberry oil was almost similar (more than 70%), however, the complete protection time for neem was 3 hrs, while that of chinaberry oil was one hour.ConclusionThe commercial products and laboratory-produced repellents can be utilized by individuals to avoid contact with An. arabiensis in Ethiopia.

Angelica sinensis (Umbelliferae) with proven repellent properties against Aedes aegypti, the primary dengue fever vector in Thailand

Botanical resources with great diversity in medicinal and aromatic plants are a rich and reliable source for finding insect repellents of plant origin, which are widely popular among today's consumers. Although some herbal-based repellents have been proven comparable to or even better than synthetics, commercially available natural repellents generally tend to be expensive, with short-lived effectiveness. This critical flaw leads to ongoing research for new and effective repellents, which provide longer protection against vector and nuisance-biting insects, while remaining safe, user friendly, and reasonably priced. This study aimed to evaluate the repellent activity of plant-derived products against the primary dengue vector, Aedes aegypti, by following the human bait technique of World Health Organization guidelines. Preliminary laboratory screening tests for repellency of 33 plant species clearly demonstrated Angelica sinensis as the most effective repellent from each kind of extracted product, with its essential oil and ethanolic extract having median complete protection times of 7.0 h (6.0-7.5) and 2.5 h (2.0-2.5), respectively. Due to its low yield (0.02 %), pungent smell, and little cause of irritation, A. sinensis essential oil did not qualify as a candidate for further repellent assessment. However, subsequent extractions of A. sinensis with different organic solvents of increasing polarity provided four extractants with varying degrees of repellency against A. aegypti. The hexane extract of A. sinensis provided excellent repellency, with a median complete protection time of 7.5 h (6.5-8.5), which was longer than that of ethanol (2.5, 2.0-2.5 h), acetone (1.75, 0.5-2.5 h), and methanol extracts (0.5, 0-1.0 h). By being the most effective product, A. sinensis hexane extract gave significant protection comparable to that of its essential oil and the standard synthetic repellent, N,N-diethyl-3-methylbenzamide (DEET: 6.25, 5.0-6.5 h). Qualitative gas chromatography/mass spectrometry analysis demonstrated the presence of phthalides and phthalates, including 3-N-butylphthalide, butylidenephthalide, ligustilide, and di-iso-octyl phthalate, as the principal constituents in A. sinensis products. The success of A. sinensis products, particularly that of hexane extract, has proved their potential as bioactive candidates in the next step for developing and producing alternative natural repellents with commercial aspirations.

Laboratory evaluation of Indian medicinal plants as repellents against malaria, dengue, and filariasis vector mosquitoes.

Mosquito-borne diseases have an economic impact, including loss in commercial and labor outputs, particularly in countries with tropical and subtropical climates; however, no part of the world is free from vector-borne diseases. Mosquitoes are the carriers of severe and well-known illnesses such as malaria, arboviral encephalitis, dengue fever, chikungunya fever, West Nile virus, and yellow fever. These diseases produce significant morbidity and mortality in humans and livestock around the world. In view of the recently increased interest in developing plant origin insecticides as an alternative to chemical insecticides, in the present study, the repellent activity of crude hexane, ethyl acetate, benzene, chloroform, and methanol extracts of leaf of Erythrina indica and root of Asparagus racemosus were assayed for their repellency against three important vector mosquitoes, viz., Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus. The crude extract was applied on a membrane used for membrane feeding of unfed mosquitoes in a 1-ft cage. About 50 unfed 3-4-day-old laboratory-reared pathogen-free strains of A. stephensi, A. aegypti, and C. quinquefasciatus were introduced in a 1-ft cage fitted with a membrane with blood for feeding with temperature maintained at 37 °C through circulating water bath maintained at 40-45 °C. Three concentrations (1.0, 2.0, and 5.0 mg/cm(2)) of the crude extracts were evaluated. Repellents in E. indica afforded longer protection time against A. stephensi, A. aegypti, and C. quinquefasciatus than those in A. racemosus at 5.0 mg/cm(2) concentration, and the mean complete protection time ranged from 120 to 210 min with the different extracts tested. In this observation, these two plant crude extracts gave protection against mosquito bites; also, the repellent activity is dependent on the strength of the plant extracts. These results suggest that the leaf extract of E. indica and root extract of A. racemosus have the potential to be used as an ideal eco-friendly approach for the control of mosquitoes. This is the first report on the mosquito repellent activity of the reported A. racemosus and E. indica plants.

Mosquito repellent activity of essential oil of Ethiopian ethnomedicinal plant against Afro-tropical malarial vector Anopheles arabiensis

In Ethiopia, malaria remains to be one of the major public health issues that causes significant impediment to socio-economic development too. A laboratory-based study has been conducted to evaluate the repellency of Ethiopian ethnomedicinal plant Tedh [vernacular name (local native language, Amharic); Juniperus procera (Cupressaceae)], against Afro-tropical malarial vector, Anopheles arabiensis Patton at four different concentrations viz., 1.0, 1.5, 2.5, and 5.0mg/cm2. Experimentation on the percentage of protection in relation to the dosage has been performed. The tested concentrations of the essential oil of J. procera exhibited various degrees of repellency in terms of percentage of repellency and complete protection time against female An. arabiensis viz., 1.0, 1.5, 2.5 and 5.0mg/cm2 [64.10% (92min)], [68.10% (125min)], [72.20% (190min)], and [80.60% (311min)], respectively. Student’s t-test results show statistically significant (P<0.001) [0.1mg/cm2 (t=82.7; df=4); 0.15mg/cm2 (t=124.8; df=4); 2.5mg/cm2 (t=25.3; df=4); 5.0mg/cm2 (t=175.3; df=4)] difference between treated and control groups. The examined essential oil exhibited significant repellent properties and it has been identified that it could serve as a potent repellent against insect vectors of disease. In Africa, Tedh is well-known as a therapeutic agent to treat various illness and insects’ repellent plant to drive-away insect vector of diseases. As the essential oil of Tedh is exceptionally safe and economical it could serve as a potent personal protective tool to minimize the burden of insect-transmitted diseases particularly malaria in the future.

The efficacy of repellents against Aedes, Anopheles, Culex and Ixodes spp. – A literature review

Travellers are confronted with a variety of vector-borne threats. Is one type of repellent effective against all biting vectors? The aim of this review is to examine the literature, up to December 31st, 2012, regarding repellent efficacy. We searched PubMed for relevant papers. Repellents of interest were DEET, Icaridin as well as other piperidine-derived products (SS220), Insect Repellent (IR) 3535 (ethyl-butylacetyl-amino-propionat, EBAAP) and plant-derived products, including Citriodora (para-menthane-3,8-diol). As vectors, we considered the mosquito species Anopheles, Aedes and Culex as well as the tick species Ixodes. We selected only studies evaluating the protective efficacy of repellents on human skin. We reviewed a total of 102 publications. Repellents were evaluated regarding complete protection time or as percentage efficacy [%] in a time interval. We found no standardized study for tick bite prevention. Regarding Aedes, DEET at concentration of 20% or more, showed the best efficacy providing up to 10hprotection. Citriodora repellency against this mosquito genus was lower compared to the other products. Also between subspecies a difference could be observed: Ae. aegypti proved more difficult to repel than Ae. Albopictus. Fewer studies have been conducted on mosquito species Anopheles and Culex. The repellency profile against Anopheles species was similar for the four principal repellents of interest, providing on average 4-10hof protection. Culex mosquitoes are easier to repel and all four repellents provided good protection. Few studies have been conducted on the tick species Ixodes. According to our results, the longest protection against Ixodes scapularis was provided by repellents containing IR3535, while DEET and commercial products containing Icaridin or PMD showed a better response than IR3535 against Ixodes ricinus. Many plant-based repellents provide only short duration protection. Adding vanillin 5% to plant-based repellents and to DEET repellents increased the protection by about 2h.

Repellent activity of essential oils isolated from the leaves of Eupatorium odoratum against malaria, filaria and dengue vectors

Light green essential oils extracted from the leaves of Eupatorium odoratum (Asterace) from Himalaya region (India) were screened for repellent activity against Anopheles stephensi, Aedes aegypti and Culex quinquifaciatus mosquitoes. The repellent activity was evaluated in door condition. Four concentrations 2.5%, 5%, 7.5% and 10% (v/v) in ethanol were considered in this study. When the test oil was applied at 10% concentration were found most effective and provided more than 2hr of complete protection against all three mosquito species. The complete protection time (Mean ± S.D) were recorded as 160.2 ± 2.77min, 139.4 ± 1.14min and 125.6 ± 3.13min against Anopheles stephensi, Aedes aegypti and Culex quinquifaciatus respectively. There was no bite within 125min and 160min confirm due to action of essential oil and thus 100% protection from the bite of mosquitoes achieved. No adverse effects of the human volunteers were observed during the exposure and through three months after the application.Therefore, the essential oil of Eupatorium odoratum (Asterace) may prove useful in the development of mosquito natural repellents as an effective personal protection measure against mosquito bites.

Larvicidal, pupicidal, repellent and adulticidal activity of Citrus sinensis orange peel extract against Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae)

Mosquitoes are the carriers of severe and well-known illnesses such as malaria, arboviral encephalitis, dengue fever, chikunguniya fever, West Nile virus and yellow fever. These diseases produce significant morbidity and mortality in humans and livestock around the world. The present study explored the effects of orange peel ethanol extract of Citrus sinensis on larvicidal, pupicidal, repellent and adulticidal activity against Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus. The orange peel material was shade dried at room temperature and powdered coarsely. From orange peel, 300 g powdered was macerated with 1 L of ethanol sequentially for a period of 72 h each and filtered. The yields of the orange peel ethanol crude extract of C. sinensis 13.86 g, respectively. The extracts were concentrated at reduced temperature on a rotary vacuum evaporator and stored at a temperature of 4 °C. The larvicidal, pupicidal and adult mortality was observed after 24 h of exposure; no mortality was observed in the control group. For C. sinensis, the median lethal concentration values (LC(50)) observed for the larvicidal and pupicidal activities against mosquito vector species A. stephensi first to fourth larval instars and pupae were 182.24, 227.93, 291.69, 398.00 and 490.84 ppm; A. aegypti values were 92.27, 106.60, 204.87, 264.26, 342.45, 436.93 and 497.41 ppm; and C. quinquefasciatus values were 244.70, 324.04, 385.32, 452.78 and 530.97 ppm, respectively. The results of maximum repellent activity were observed at 450 ppm in ethanol extracts of C. sinensis and the mean complete protection time ranged from 150 to 180 min was tested. The ethanol extract of C. sinensis showed 100% repellency in 150 min and showed complete protection in 90 min at 350 ppm against A. stephensi, A. aegypti and C. quinquefasciatus, respectively. The adult mortality was found in ethanol extract of C. sinensis with the LC(50) and LC(90) values of 272.19 and 457.14 ppm, A. stephensi; 289.62 and 494.88 ppm, A. aegypti; and 320.38 and 524.57 ppm, respectively. These results suggest that the orange peel extracts of C. sinensis have the potential to be used as an ideal eco-friendly approach for the control of the vector control programmes.

Toxicity and Synergic Repellency of Plant Essential Oil Mixtures With Vanillin AgainstAedes aegypti(Diptera: Culicidae)

In all triplicate tests of six plant essential oils and of vanillin mixtures, we corroborated strong insecticidal and repellent activities against adult Aedes aegypti (L.). Essential oils with potent toxic fumigant activities also exhibited repellency. Compared with N, N-diethyl-3-methylbenzamide, 5% of the essential oil concentrations of cassia, lemongrass, lemon eucalyptus, and xanthoxylum oils did not show repellent effects. However, a composition oflemongrass oil, xanthoxylum oil, and vanillin (1:3:1, vol:vol:wt) provided 270 min of complete protection time (CPT) compared with 247.5 min CPT with 15% N, N-diethyl-3-methylbenzamide. The CPT depended on concentration, presence ofvanillin, or on both factors. When we applied a mixture of lemongrass oil: xanthoxylum oil: vanillin (1:1:1, vol:vol:wt) to the Viscopearl formulation, or porous cellulose beads, it provided gradual release of volatile compounds, thus showing >90% of repellency for 2 h. The behavioral and electrophysiological approaches we drew upon in our current study demonstrated that plant essential oil mixtures combined with vanillin showed strong and durable repellency to the mosquito. We claim that such combinations of plant essential oils and vanillin found in current study propose a viable commercial product suitable for future application in protecting a person from mosquito bites.

Mating Status and Body Size inAedes albopictus(Diptera: Culicidae) Affect Host Finding and Deet Repellency

ABSTRACT Variations in the conditions accompanying mosquito development and mating can result in females of variable size that have not been inseminated. In this study, we compared the host finding activity of mated and unmated large and small Aedes albopictus (Skuse) and the repellency to these mosquitoes of 25% DEET. The percentage of females seeking the source of human odor in an olfactometer was significantly influenced by body size (P = 0.007) but not mating status (P = 0.07). Most respondents were large (71%) but 40% of all host seeking females were not inseminated. Landing rates by Ae. albopictus on human skin were influenced in screened cage tests by mating status (P < 0.0001) and body size (P = 0.004). Mated females exhibited the highest landing rates (17.3% [large] and 12.7% [small]) followed by unmated large females (7.3%) and unmated small females (6.4%). The Complete Protection Time (CPT) from mosquito landing provided by 25% DEET was significantly influenced by mating status (P = 0.002) and ...

Larvicidal and repellent activity of medicinal plant extracts from Eastern Ghats of South India against malaria and filariasis vectors

Objective To evaluate the larvicidal and repellent activities of ethyl acetate and methanol extracts of Acacia concinna ( A. concinna), Cassia siamea ( C. siamea), Coriandrum sativum ( C. sativum), Cuminum cyminum ( C. cyminum), Lantana camara ( L. camara), Nelumbo nucifera ( N. nucifera) Phyllanthus amarus ( P. amarus), Piper nigrum ( P. nigrum) and Trachyspermum ammi ( T. ammi) against Anopheles stephensi ( An. stephensi) and Culex quinquefasciatus ( Cx. quinquefasciatus). Methods The larvicidal activity of medicinal plant extracts were tested against early fourth-instar larvae of malaria and filariasis vectors. The mortality was observed 24 h and 48 h after treatment, data were subjected to probit analysis to determine the lethal concentrations (LC 50 and LC 90) to kill 50 and 90 per cent of the treated larvae of the tested species. The repellent efficacy was determined against two mosquito species at five concentrations (31.25, 62.50, 125.00, 250.00, and 500.00 ppm) under the laboratory conditions. Results All plant extracts showed moderate effects after 24 h and 48 h of exposure; however, the highest activity was observed after 24 h in the leaf methanol extract of N. nucifera, seed ethyl acetate and methanol extract of P. nigrum against the larvae of An. stephensi (LC 50 = 34.76, 24.54 and 30.20 ppm) and against Cx. quinquefasciatus (LC 50 = 37.49, 43.94 and 57.39 ppm), respectively. The toxic effect of leaf methanol extract of C. siamea, seed methanol extract of C. cyminum, leaf ethyl acetate extract of N. nucifera, leaf ethyl acetate and methanol extract of P. amarus and seed methanol extract of T. ammi were showed 100% mortality against An. stephensi and Cx. quinquefasciatus after 48 h exposer. The maximum repellent activity was observed at 500 ppm in methanol extracts of N. nucifera, ethyl acetate and methanol extract of P. nigrum and methanol extract of T. ammi and the mean complete protection time ranged from 30 to 150 min with the different extracts tested. Conclusions These results suggest that the leaf and seed extracts of C. siamea, N. nucifera, P. amarus, P. nigrum and T. ammi have the potential to be used as an ideal ecofriendly approach for the control of the An. stephensi and Cx. quinquefasciatus.

Temperature and pH Stability Profiles of ortho and para DEET

ABSTRACT − DEET, N,N’-diethyl-m-toluamide, is the most commonly used mosquito repellent. However, it can easilypermeate through skin leading to toxic effects. A recent study showed that the ortho analogue of DEET showed enhancedrepellency with reduced permeation compared to the commercially used meta analogue. Thus, in order to understand thedifferences in properties and effectiveness among the m-, o- and p-analogues of DEET, an HPLC-UV method was developedfor separately analyzing the three analogues. Moreover, stability profiles at temperatures ranging from 30 o C to 70C as wellas pH ranging from pH 3 to pH 9 have been determined. All three analogues were stable with no degradation observed dur-ing the 5 day period. o-DEET therefore could be further developed into a safer and more effective mosquito repellent.Key words − DEET, Temperature stability, pH stability, Mosquito repellency m-DEET is known as the golden standard of mosquito repel-lents for being highly effective, stable and relatively safe (Katzet al., 2008). In most cases it is directly applied to the humanskin protecting against tick-borne diseases (Jensennius et al.,2005) and mosquito-mediated diseases including dengue fever,West Nile virus and Eastern Equine Encephalitis (Gubler,2001). However, information about the mechanism of action ofDEET is still controversial. Studies report that DEET mayblock behavior of mosquitoes by inhibiting chemo-receptorson the mosquito antennae that are stimulated by lactic acid(Dogan et al., 1999) whereas other studies refute this phe-nomenon (Syed and Leal, 2008). Nevertheless, m-DEETexhibits mosquito repellency as shown in the complete pro-tection time (CPT) ranging from 203 to 756 minutes, varyingwith factors including climatic effects, mosquito species andphysical activities (Barnard and Xue, 2004; Bidlingmayer,1994; Bernier et al., 2000).The search for safer and more effective repellents continuesto progress, however, due to the toxicities reported of DEET(Schofield et al., 2007). Possible substitutes to DEET that havebeen reported so far include synthetically prepared Picaridin,IR3535 and Permethrin or lemon eucalyptus or citronellawhich are natural products (Katz et al., 2008). Unfortunately,none of these alternatives seem to exhibit properties that couldbe more advantageous to the current DEET products.Current research for developing repellents make use of sys-tematic bioassays or computer based tools which include aQSAR study of N-acyl-piperidines (Katritzky et al., 2008) anda genetic trial of odorant-binding protein manipulation (Li etal., 2008). One of the shortcomings of the mosquito repellentinvestigation is the use of human subjects or living vertebratesin the bioassays (Dogan et al., 1999). However, recently, anefficient in vitro bioassay system has been established whereblood substitute and collagen membrane were used instead ofhuman blood and skin (Jahn et. al., 2010). The artificial bloodsubstitute was a slight modification of that used by Kogan foran in vitro feeding assay for maintenance of mosquito colonies(Corazza et al., 2005). Unlike Kogan who utilized stretchedparafilm as a skin substitute, Jahn made use of a collagen typemembrane (Ditzen et al., 2008) since the parafilm alone couldnot mimic the physiological skin sufficiently. Moreover, inJahn’s study, skin permeation profiles of DEET and its ana-logues were examined in correlation to the mosquito repel-lency, expressed as CPT. Among the DEET analogues tested,compared to the commercially used meta DEET analogue,ortho DEET revealed enhanced repellency with reduced skinpermeation rate, implying that toxicity due to skin penetrationwould be lessened (Jahn et al., 2010).To estimate the applicability of the ortho DEET analogue, aseparation method for the three DEET isomers needed to beestablished. Because of the similar physicochemical charac-teristics of the three isomers as revealed in the capacity factors

Insecticidal and Repellent Activities of Essential Oil from Leaves of &lt;i&gt;Eucalyptus grandis&lt;/i&gt; Against &lt;i&gt;Culex pipiens quinquefasciatus&lt;/i&gt;

The insecticidal and repellent activities of essential oil from leaves ofEucalyptus grandisagainstCulex pipiens quinquefasciatuswere investigated. The essential oil was obtained by hydro-distillation and analyzed by gas chromatography-mass spectrometry (GC-MS). The principal constituents in the essential oil werep-cymene (26.794%),α-pinene (15.864%), eucalyptol (6.281%),α-terpineol (4.100%), limonene (3.614%) and borneol (2.519%). The results indicated that the essential oil ofEucalyptus grandisleaves hold insecticidal and repellent activities againstCulex pipiens quinquefasciatus. The complete protection time for people againstCulex pipiens quinquefasciatuswas correlative with its concentration. It could protect people for 7h when its concentration was 50%. Fumigating insecticidal activity was evaluated by airtight fumigation in conical flask. The LC50values of the essential oil for adults ofCulex pipiens quinquefasciatuswere 4.5%(0.5h), 3.6%(1h), 2.6%(2h), 2.1%(4h), 0.56%(8h) and 0.56%(24h). The LT50value of the essential oil was 19.1 min when its concentration was 6.4%.

Novel Carboxamides as Potential Mosquito Repellents

A model was developed using 167 carboxamide derivatives, from the United States Department of Agriculture archival database, that were tested as arthropod repellents over the past 60 yr. An artificial neural network employing CODESSA PRO descriptors was used to construct a quantitative structure-activity relationship model for prediction of novel mosquito repellents. By correlating the structure of these carboxamides with complete protection time, a measure of repellency based on duration, 34 carboxamides were predicted as candidate mosquito repellents. There were four additional compounds selected on the basis of their structural similarity to those predicted. The compounds were synthesized either by reaction of 1-acylbenzotriazoles with secondary amines or by reaction of acid chlorides with secondary amines in the presence of sodium hydride. The biological efficacy was assessed by duration of repellency on cloth at two dosages (25 and 2.5 micromol/cm2) and by the minimum effective dosage to prevent Aedes aegypti (L.) (Diptera: Culicidae) bites. One compound, (E)-N-cyclohexyl-N-ethyl-2-hexenamide, was superior to N,N-diethyl-3-methylbenzamide (deet) at both the high dosage (22 d versus 7 d for deet) and low dosage (5 d versus 2.5 d for deet). Only one of the carboxamides, hexahydro-1-(l-oxohexyl)-1H-azepine, had a minimum effective dosage that was equivalent or slightly better than that of deet (0.033 micromol/cm2 versus 0.047 micromol/cm2).