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PubMed1995

Influence of body size and age of Aedes albopictus on human host attack rates and the repellency of deet.

Human host attack rates and the repellency of deet (25% in ethanol) to nulliparous Aedes albopictus in the laboratory were significantly influenced (P = 0.05) by mosquito age and body size and by the interaction of age and body size. Host attack rates were higher for 20-day- (24.5%) and 15-day-old females (22.9%) than for 10- (15.1%) and 5-day-old females (11.0%), regardless of body size, and for large females (22.2%) compared with small females (16.6%), regardless of mosquito age. Deet on human skin repelled small-bodied females longer (3.87 h) than large females (2.31 h); 15-day-old females were repelled longer (3.75 h) than 5- (2.33 h), 10- (3.08 h), or 20-day-old females (3.07 h), regardless of body size. Host attack rates and deet repellency among 15-day-old parous and 15-day-old nulliparous large- and small-bodied female Ae. albopictus were similar but deet repellency was less (by approximately 2 h) against large females compared with small-bodied females.

Aedes↗
PubMed1995

Impact of deltamethrin-impregnated bednets on biting rates of mosquitoes in Zaire.

In a rural area of Zaire, the whole population of a village was protected by deltamethrin-impregnated mosquitoes bednets. A similar village was observed as a control. Biting rates for mosquitoes were recorded in both villages. The principal man-biting species were Mansonia africana, Mansonia uniformis, and Aedes aegypti. In the village protected by the impregnated mosquito bednets, the number of Mansonia bites was reduced 96% indoors and at a lesser rate outdoors. Biting rates of Ae. aegypti dropped to 0 indoors, but the outdoor biting rate remained unchanged. It is concluded that the reduction in mosquito bites is not only caused by the repellent action of the deltamethrin but also by a reduction in mosquito numbers.

Animals↗
PubMed2005

[Effect of pyrethoid and organophosphate bi-treated nets on the behaviour of Kdr+ Anopheles gambiae mosquitoes].

The efficacy of mosquito nets treated with bifenthrin (pyrethroid) and chlorpyrifos-methyl (organophosphate), alone and in mixture, was evaluated against the pyrethroid-resistant strain (VKPR) of Anopheles gambiae using the tunnel test technique. Results first showed that bifenthrin and chlorpyrifos-methyl kept a good excito-repellency effect against resistant mosquitoes despite the low doses applied on nets. With the mixture, irritancy significantly increased, which consequently limited the duration of exposure of females to impregnated surface. This phenomenon most probably explained the absence of synergism between bifenthrin and chlorpyrifos-methyl concerning the insecticidal activity of this mixture. This study demonstrated the importance of the mosquito behaviour in the global effectiveness of insecticide treated materials and in the development of alternative strategies for vector control. Concerning the prospective insecticide mixtures, not only will we have to consider the insecticidal properties of each insecticide selected, but also their excito-repellency which affects the time of duration of mosquitoes on the treated surface.

Animals↗
PubMed1999

A new tactic for Triatoma infestans control: fabrics impregnated with beta-cypermethrin.

Triatoma infestans is the most important vector of Chagas' disease in Argentina. Experiences from Argentine national campaigns have shown indoor spraying to control triatomine bugs is both expensive and difficult. An alternative control method may be the use of pyrethroid-impregnated fabrics (PIFs), which could be both a practical and cheap complement to conventional control measures. In this study, a formulation of emulsifiable concentrate of beta-cypermethrin [alpha-cyano-3-phenoxybenzyl-3-(2,2-dichlorovinyl)-2,2- dimethylcyclopropanecarboxilate] pyrethroid was used to impregnate different fabrics. The fabrics were then tested for their efficacy and persistence in killing Triatoma infestans. Insects attempting to penetrate or grasp the fabric in search of blood meals were poisoned by the exposure to the absorbed pyrethroid. Laboratory bioassays showed that the insecticidal effect of the PIFs with a dosage of 0.2 g/m2 lasted longer on wool than on cotton or rayon. Eight months after impregnation, a residual efficacy of 100% was found for wool, 80% for rayon-cotton fabrics, and 50% for rayon-polyester fabrics. In addition, beta-cypermethrin-impregnated fabrics showed a better repellency effect than did fabrics impregnated with either deltamethrin or cypermethrin. For field trials, fabrics were impregnated either in the laboratory or "in situ" at a dosage of 1 g beta-cypermethrin/m2 and then dried. The PIFs were placed inside homes, either under the roof or under the bed mattress. The field trials showed the PIF approach to be very effective in keeping dwellings free of triatomine bugs for at least one year and found a high degree of acceptability among the houses' residents.

Animals↗
PubMed2007

Metabolomic profiling of natural volatiles: headspace trapping: GC-MS.

Plants are a fabulously rich source of naturally volatile metabolites, which are derived from a range of contrasting biochemical pathways (e.g., mono-, di-, and sesquiterpenoids, benzoates, alcohols, esters). Such volatiles may immediately be released from the plant or they may be stored, e.g., in glycosylated form for release later "on demand." Certain roles for these molecules have already been determined in that they can function as attractants (e.g., to pollinators, seed dispersers, and others) or as protectants (repellants, pathogen inhibitors, and so on). The flavor and fragrance of plant materials to humans and other animals are also, to a great extent, determined by natural volatiles. Other more sophisticated roles have also been elucidated where plant volatiles have been shown to be involved either as signal molecules to attract the predators of damaging herbivorous insects or potentially even as signal molecules warning other plants of imminent danger. As such, detailed knowledge of these components can be valuable in relation to breeding crop varieties for enhanced product quality or for achieving improved resistance to pathogens and insects. Furthermore, knowledge of the metabolites can result in a corresponding knowledge of the genes responsible for their synthesis and this can lead to dedicated strategies for their in vitro production through, e.g., reverse genetics in heterologous microbial expression systems in fermentors for the production of high-value fine chemicals. Various analytical techniques based on gas chromatography-mass spectrometry have been devised for the analysis of this complex group of metabolites. Two of these key methods are detailed in this chapter.

Arabidopsis↗
PubMed2005

Hydroquinone is not a phagostimulant for the Formosan subterranean termite.

It has been suggested that hydroquinone found in the labial glands of a number of termite species acts as a primary phagostimulating factor. We tested hydroquinone as a phagostimulant using workers from three colonies of the Formosan subterranean termite, Coptotermes formosanus, under both laboratory and field conditions. Hydroquinone at concentrations ranging from ca. 0.002-20.0 ng/cm2 did not increase visitation by C. formosanus workers to treated over control filter papers, and was actually repellent at a 20 ng/cm2 dose. No phagostimulant response to hydroquinone was observed in two colonies. In the third, there was a significant increase in feeding on filter paper treated with a 2 ng/cm2 dose, but was significantly lower at a 20 ng/cm2 dose. Furthermore, sand treated with a gradient of hydroquinone, did not evoke increased tunneling activity compared with controls. GC-MS analysis of C. formosanus workers indicated that hydroquinone was present at an average of 41 pg/worker. It was also determined that within one week about 11% hydroquinone in aqueous solution oxidized to 1,4-benzoquinone. Our findings indicate that hydroquinone alone does not act as a phagostimulant but instead may act as a repellent at higher concentrations. The attractant/arrestant of the Formosan termite may have multiple components of which hydroquinone, at low doses, could be one.

Animals↗
PubMed2005

Effects of post-ingestion and physical conditions on PCR amplification of host blood meal DNA in mosquitoes.

The effects of post-ingestion and physical conditions under which killed mosquitoes are stored on the success of detecting blood meal DNA of Anopheles stephensi and Culex quinquefasiatus were investigated by polymerase chain reaction (PCR) amplification at the human mitochondrial DNA cytochrome b (cytB) gene. Host DNA extracted from the blood meal up to 33 h post-ingestion in both species acts as an efficient template for PCR amplification. However, more DNA concentration is needed for meals digested for a longer time, and successful PCR amplification from meals digested for 36 h,dropped to a faint band. There were no differences between PCR success rate for samples stored at +4 or -20 degrees C, but less successful products were observed in samples kept at 4 degrees C for the periods longer than 30 h digestion. The results of this study are important for conducting malaria epidemiological studies that provide information about the degree of contact between human hosts and mosquito vectors, impact of vector controls such as bed nets and repellents, and the transmission dynamics of human malaria and other vector-borne diseases.

Animals↗
PubMed2003

Reassessment of the role and utility of wind in suppression of mosquito (Diptera: Culicidae) host finding: stimulus dilution supported over flight limitation.

In a Central Michigan wetland setting, with abundant Aedes vexans (Meigen), Anopheles walkeri (Theobald), and Coquillettidea perturbans (Walker), electric fan-generated wind strongly reduced mosquito catches in Centers for Disease Control and Prevention light traps releasing carbon dioxide at 650 or 1,950 ml/min. This relationship was negatively logarithmic over the range of velocities tested (0 m/s to 3.7 m/s; 0-8.3 mph) and closely matched the theoretical dilution function predicted to occur with increasing wind flows over a constantly releasing point source of volatile chemical. Tripling the carbon dioxide release rate consistently doubled the number of mosquitoes caught across the range of wind velocities tested. Neither applied wind velocity nor carbon dioxide release rate was correlated with mosquito body mass across the range of wind velocities tested. Collectively, these data support the conceptual model that applied wind diminishes mosquito catches primarily by diluting attractants rather than by exceeding mosquito flight capability. Previously published estimates of maximum air speeds of which mosquitoes are capable may now need to be reassessed if they were based upon shut-down of catches in traps baited with chemical attractants. Addition of DEET vapor significantly reduced the number of mosquitoes caught relative to equivalently moving air without repellent. We recommend that fan-generated wind should be pursued as a practical means of protecting humans or pets from mosquitoes in the backyard setting.

Aedes↗
PubMed2004

Excito-repellency of deltamethrin on the malaria vectors, Anopheles minimus, Anopheles dirus, Anopheles swadiwongporni, and Anopheles maculatus, in Thailand.

This study compared the behavioral avoidance responses of 4 mosquito malaria vectors, Anopheles minimus, Anopheles dirus, Anopheles maculatus form B, and Anopheles swadiwongporni, to deltamethrin, the primary insecticide used for indoor residual spraying for malaria vector control in Thailand. Six test populations. representing 4 laboratory colonies and 2 wild-caught populations, were observed during and after exposure to deltamethrin at the operational dose (0.02 g active ingredient/m2) in excito-repellency escape chambers. The laboratory colonies included a deltamethrin-susceptible colony and a deltamethrin-resistant colony of An. minimus species A, 1 colony of An. dirus species B, and 1 colony of An. maculatus form B. The 2 wild-caught populations included An. swadiwongporni and members of the An. dirus complex. Times to escape by female mosquitoes during 30 min of exposure to deltamethrin-treated papers were observed in all populations and compared to nontreated paired controls in contact and noncontact test configurations. Strong behavioral avoidance was observed in the deltamethrin-resistant colony of An. minimus, followed by An. swadiwongporni and An. maculatus. The slowest escape response was observed in the colony of An. dirus species B. All 6 populations of Anopheles showed marked contact irritancy to deltamethrin compared to paired controls and noncontact repellency trials, in both controlled laboratory colonies and field-caught populations. The degree of repellency was less profound than irritancy but, in most cases, produced a significant escape response compared to paired controls. Avoidance behavior appears to be an innate behavior of mosquitoes, as indicated by the general avoidance response detected in all 4 species, regardless of deltamethrin susceptibility status, age, or nutritional and physiological status. Excito-repellency assays of the type described in this study should become an integral part of the overall assessment of an insecticide's ability to control disease transmission in any given area.

Animals↗
PubMed1997

Pesticide avoidance behavior in Anopheles albimanus, a malaria vector in the Americas.

The behavioral responses of 4 populations of Anopheles albimanus females to DDT, permethrin, and deltamethrin were characterized in excito-repellency tests. One test population (ST) from El Salvador has been maintained as a colony for 20 years. A second population (ES) from Guatemala was colonized in 1992. Third and fourth populations consisted of field-caught specimens from Toledo District (TO) of southern Belize in 1994 and Corozal District (CO) of northern Belize, respectively. Females of ES, TO, and CO populations rapidly escaped from direct contact with treated surfaces for each of the 3 insecticides. Similarities in escape responses of insecticide-resistant (ES) versus insecticide-susceptible populations (TO, CO) suggest that there is no relationship between physiological and behavioral responses of An. albimanus populations to DDT, permethrin, and deltamethrin. Females from all but the ST colony escaped in greater numbers from chambers without direct contact with treated surfaces than from control chambers (P < 0.05). Few females from the ST colony escaped from test chambers, regardless of which insecticide was used or whether contact was allowed, indicating that the ST colony has lost its capability to respond to insecticides. Repellent responses were significant; but they were not pronounced in 30-min exposures, and they were very pronounced in 4-h exposures. We conclude that irritant and repellent responses of malaria vectors to insecticides are important components of malaria control operations.

Americas↗
PubMed1990

Malaria in a peri-urban area of The Gambia.

A clinical and entomological survey of malaria was carried out in Bakau, a peri-urban coastal settlement in The Gambia, from June 1988-May 1989. Only 41 of a cohort of 560 children, aged from three months to nine-years-old, experienced a clinical episode of malaria during the observation period. The majority of cases were identified at clinics and not by regular community surveillance. In Bakau Old Town episodes of malaria were more common on the periphery of the settlement, adjacent to typical anopheline breeding sites, than in the centre. Overall malaria cases were not significantly clustered in space and time, although three pairs of cases among children sleeping in the same room at the same time were identified. A cross-sectional survey in November, at the end of the rainy season, revealed a point prevalence parasitaemia of 2.0% and a spleen rate of 0.3%. All malariometric parameters measured were much lower than any found in comparable studies undertaken in rural areas of the country, reflecting the low number of malaria vectors, Anopheles gambiae complex mosquitoes, found in Bakau. Chloroquine consumption, sleeping under bednets, houses with ceilings, the use of insecticide aerosols and burning traditional mosquito repellents may all have contributed to the low prevalence of malaria in the study area.

Animals↗
PubMed1994

Culicoides responses to 1-octen-3-ol and carbon dioxide in salt marshes near Sea Island, Georgia, U.S.A.

The semiochemicals carbon dioxide (CO2) and 1-octen-3-ol (octenol) were evaluated as attractants at several release rates, alone and in combination, for the major coastal species of biting midges in Georgia: Culicoides furens, C. hollensis and C. melleus (Diptera: Ceratopogonidae). The data show that CO2 is an effective attractant for the females of all three species, but each has a different response pattern. In contrast, octenol was an effective attractant only for C.furens, either alone or in combination with CO2; octenol had a repellent effect on the other two species. The combination of octenol and CO2 had a synergistic effect on the collections of C.furens.

Analysis of Variance↗
PubMed2002

Behavioral responses of the parsnip webworm to host plant volatiles.

Sixth instars of the parsnip webworm, Depressaria pastinacella, orient by olfaction to bud, male flowers, and female flowers of their primary host plant, Pastinaca sativa. Because octyl acetate and octyl butyrate are characteristic of tissues consumed by the sixth instar, we investigated the influence of these esters on webworm feeding behavior and chemo-orientation. Although octyl acetate and octyl butyrate are feeding deterrents, and octyl butyrate is an olfactory repellent, octyl acetate serves as an olfactory attractant. In olfactometers, webworms do not show a preference when given a choice between octyl acetate and host plant tissues. These findings suggest that octyl acetate is a sufficient cue for olfactory orientation. Such behavior may explain differences in the relative abundance of these esters observed among populations of wild parsnip under differential selection pressure from these insects.

Animals↗
PubMed2005

Malaria in Indonesia: a summary of recent research into its environmental relationships.

A review of the literature was carried out to evaluate malaria and its environmental relationships. Research, in 6 parts of Indonesia, addressed the relationship between malaria incidence and physical and socioeconomic environmental factors, using longitudinal and cross-sectional approaches. Physical factors, which are generally important for malaria, included rainfall, mosquito breeding and resting sites, their distance from human habitation, and elevation, though the latter was not statistically significant. Housing conditions were occasionally important. Social and economic factors of importance were income, education, use of bednets and pattern of outdoor activities, especially at night. Use of repellents, mosquito coils and sleeping arrangements were significant in some of the studies.

Adolescent↗
PubMed2000

An aphid repellent glycoside from Solanum laxum.

A spirostanic saponin was isolated from the ethanolic extract of the aerial parts of Solanum laxum Steud. The compound, named luciamin, was characterised by NMR spectroscopy, mass spectrometry and chemical methods, as (22R, 25S)-spirost-5-en-3 beta, 15 alpha-diol 3-O-|beta-D-glucopyranosyl (1 --> 2)-beta-D-glucopyranosyl-( 1 --> 4)-[alpha-L-rhamnopyranosyl-( 1 --> 2)]-beta-D-galactopyranoside|. The compound was tested against the aphid Schizaphis graminum by incorporation in artificial diets. It showed a deterrent (toxic) activity against the insect and is the first spirostane glycoside reported to have this activity.

Journal Article↗
PubMed2003

Studies on effects of Pelargonium citrosa leaf extracts on malarial vector, Anopheles stephensi Liston.

Methanol extracts of Pelargonium citrosa leaf were tested for their biological, larvicidal, pupicidal, adulticidal, antiovipositional activity, repellency and biting deterrency against Anopheles stephensi. Larval mortality was dose dependent with the highest dose of 4% plant extract evoking 98% mortality. The extracts affected pupicidal and adulticidal activity and significantly decreased fecundity and longevity of A. stephensi. The larval, pupal and adult development were completely inhibited by the treatment. At 4% the extracts evoked strong repellent action. They also interfered with oviposition, egg hatchability, and exhibited a growth inhibiting effect against larvae and good repellency against adults of A. stephensi. The leaf extract treatment significantly enhanced biting deterrency. As naturally occurring insecticides, these plant derived materials could be useful as an alternative for synthetic insecticides controlling field populations of mosquitoes.

Animals↗
PubMed1976

Ploy and counterploy in predator-prey interactions: Orb-weaving spiders versus bombardier beetles.

Bombardier beetles (Brachinus spp.) offered to orb-weaving spiders are either captured or lost, depending on the attack strategy of the spider. Nephila clavipes grasps a beetle directly and attempts to bite it outright, but is repelled by the beetle's defensive spray. As the spider recovers from the spray, the beetle makes its escape from the web. Argiope first imprisons the beetle by wrapping it delicately in silk, without causing it to spray. When the spider then proceeds to bite, the wrapping protects it against the full effects of the spray. The wrapping strategy may be generally effective against chemically protected insects, and it is suggested that this may be one of its principal adaptive justifications.

Journal Article↗
PubMed2003

Economics versus alleles: balancing integrated pest management and insect resistance management for rotation-resistant western corn rootworm (Coleoptera: Chrysomelidae).

Western corn rootworm, Diabrotica virgifera virgifera LeConte, has overcome crop rotation in several areas of the central United States. We expanded a simple model of adult behavior and population genetics to explain how rotation resistance may have developed and to study ways to manage the western corn rootworm in a landscape of corn, soybean, and winter wheat where evolution of resistance may occur. We modeled six alternative management strategies over a 15-yr time horizon, as well as a strategy involving a 2-yr rotation of corn and soybean in 85% of the landscape, to investigate their effectiveness from both a biological and economic perspective. Generally, resistance to crop rotation evolves in fewer than 15 yr, and the rate of evolution increases as the level of rotated landscape (selection pressure) increases. When resistance is recessive, all six alternative strategies were effective at preventing evolution of rotation resistance. The two most successful strategies were the use of transgenic rotated corn in a 2-yr rotation and a 3-yr rotation of corn, soybean, and wheat with unattractive wheat (for oviposition) preceding corn. Results were most sensitive to increases in the initial allele frequency and modifications of the density-dependent survival function. Economically, three alternative strategies were robust solutions to the problem, if technology fees were not too high. Repellant soybean, attractive rotated corn, and transgenic rotated corn, all in 2-yr rotations, were economically valuable approaches. However, even the currently common 2-yr rotation was economical when resistance was recessive and the actual costs of resistance would not be paid until far in the future.

Agriculture↗