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Journal ArticleDOI

Monitoring of resistance to the pyrethroid cypermethrin in Brazilian Aedes aegypti (Diptera: Culicidae) populations collected between 2001 and 2003

TL;DR: Although this pyrethroid was recently started to be used in the country to control the dengue vector, a decrease in susceptibility was noted between both periods analyzed, particularly in the city of Rio de Janeiro, indicating that resistance is due at least in part to a target site alteration.
Abstract: Resistance to cypermethrin of different Aedes aegypti Brazilian populations, collected at two successive periods (2001 and 2002/2003), was monitored using the insecticide-coated bottles bioassay. Slight modifications were included in the method to discriminate between mortality and the knock down effect. Although this pyrethroid was recently started to be used in the country to control the dengue vector, a decrease in susceptibility was noted between both periods analyzed, particularly in the city of Rio de Janeiro. The results indicate that resistance is due at least in part to a target site alteration.

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Citations
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Journal ArticleDOI
TL;DR: In Brazil, Aedes aegypti resistance to temephos, used since 1967, was detected in several municipalities in 2000, and Gluthathione-S-transferase alteration was encountered only in the northeast region in 2001, spreading the entire country thereafter.
Abstract: In Brazil, Aedes aegypti resistance to temephos, used since 1967, was detected in several municipalities in 2000. Organophosphates were substituted by pyrethroids against adults and, in some localities, by Bti against larvae. However, high temephos resistance ratios were still detected between 2001 and 2004. Field-simulated assays confirmed a low temephos residual effect. Acethylcholinesterase and Mixed Function Oxidase profiles were not altered. In contrast, higher Esterase activity, studied with three substrates, was found in all examined populations collected in 2001. From 2001 to 2004, a slight reduction in α-Esterase (EST) and β-EST activity together with a gradual increase of p-nitrophenyl acetate (PNPA)-EST was noted. Gluthathione-S-transferase alteration was encountered only in the northeast region in 2001, spreading the entire country thereafter. In general, except for α-EST and β-EST, only one enzyme class was altered in each mosquito specimen. Data are discussed in the context of historic application of insecticides in Brazil.

190 citations

Journal ArticleDOI
TL;DR: Results suggest intense risk of dengue epidemic, particularly in the urban area, and suggest two alternative models: exponential and nonlinear models with correction for the removal of individuals are used.
Abstract: Daily survival rates, life expectancy, dispersal, and parity are important components of vectorial capacity of Aedes aegypti. These parameters were estimated for mosquito populations from a slum and a suburban district in Rio de Janeiro, during the wet and dry seasons in 2005. In each mark-release-recapture experiment, three cohorts of dust-marked Ae. aegypti females were released. Recaptures were carried out daily in randomly selected houses, using backpack aspirators, adult traps, and sticky ovitraps. Recapture varied between 6.81% and 14.26%. Daily survival was estimated by fitting two alternative models: exponential and nonlinear models with correction for the removal of individuals. Slum area presented higher survival and parity rates (68.5%). Dispersal rates were higher in the suburban area, where a maximum dispersal of 363 m was observed. Results suggest intense risk of dengue epidemic, particularly in the urban area.

164 citations

Journal ArticleDOI
TL;DR: Results suggest that α-pinene in E. grandis and α- and β- pinene in turpentine serve as the principal larvicidal components of both oils.
Abstract: In the search for new alternatives for the control of Aedes aegypti the larvicidal activity of Eucalyptus grandis essential oil and pine resin essential oil (turpentine) and their major components (α- and β-pinene and 1,8-cineole) was determined. Gas chromatography–mass spectroscopy analysis of E. grandis essential oil revealed that its major components are α-pinene and 1,8-cineole. Similar analysis of turpentine obtained by distillation of the resin pitch of conifers showed that α- and β-pinene are the only major components. Third and early 4th instars of the CIPEIN-susceptible strain of Ae. aegypti were exposed to acetonic solutions of E. grandis essential oil, turpentine, and their major components for 24 h. Turpentine, with an LC50 of 14.7 ppm, was more active than the essential oil of E. grandis (LC50: 32.4 ppm). Larvicidal activity of the essential oil components showed that α- and β-pinene present low LC50 values (15.4 and 12.1 ppm, respectively), whereas pure 1,8-cineole showed an LC50 of...

160 citations

Journal ArticleDOI
TL;DR: The establishment of an A. aegypti colony resistant to temephos is extremely valuable for a deeper understanding of resistance mechanisms and thus for further improvements in control strategies against this vector.

158 citations

Journal ArticleDOI
TL;DR: Seasonal variation in container productivity and infestation levels by Aedes aegypti were evaluated in two areas with distinct levels of urbanization degrees in Rio de Janeiro, a slum and a suburban neighborhood, giving potential support to a more focused and cost-effective Ae.
Abstract: Seasonal variation in container productivity and infestation levels by Aedes aegypti were evaluated in two areas with distinct levels of urbanization degrees in Rio de Janeiro, a slum and a suburban neighborhood. The four most productive containers can generate up to 90% of total pupae. Large and open-mouthed containers, such as water tanks and metal drums, located outdoors were the most productive in both areas, with up to 47.49% of total Ae. aegypti pupae collected in the shaded sites in the suburban area. Water-tanks were identified as key containers in both areas during both the dry and rainy seasons. Container productivity varied according to seasons and urbanization degree. However, the mean number of pupae per house was higher in the suburban area, but not varied between seasons within each area (P > 0.05). High infestation indexes were observed for both localities, with a house index of 20.5-21.14 in the suburban and of 9.56-11.22 in the urban area. This report gives potential support to a more focused and cost-effective Ae. aegypti control in Rio de Janeiro.

148 citations


Cites background from "Monitoring of resistance to the pyr..."

  • ...…entrance of control teams because they are afraid of urban violence; (c) the insecticide resistance of Ae. aegypti populations (Braga et al. 2005, Da-Cunha et al. 2005); and (d) the high genetic differentiation between Ae. aegypti populations within Rio de Janeiro city, what could lead to…...

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References
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Journal ArticleDOI
TL;DR: At field-use rates, a neurotoxic effect of the ecdysteroid agonist RH-5849 is observed that involves blockage of both muscle and neuronal potassium channels, and the future use of ion channels as targets for chemical and genetically engineered insecticides is discussed.
Abstract: Ion channels are the primary target sites for several classes of natural and synthetic insecticidal compounds. The voltage-sensitive sodium channel is the major target site for DDT and pyrethroids, the veratrum alkaloids, andN-alkylamides. Recently, neurotoxic proteins from arthropod venoms, some of which specifically attack insect sodium channels, have been engineered into baculoviruses to act as biopesticides. The synthetic pyrazolines also primarily affect the sodium channel, although some members of this group target neuronal calcium channels as well. The ryanoids have also found use as insecticides, and these materials induce muscle contracture by irreversible activation of the calcium-release channel of the sarcoplasmic reticulum. The arylheterocycles (e.g. endosulfan and fipronil) are potent convulsants and insecticides that block the GABA-gated chloride channel. In contrast, the avermectins activate both ligand and voltage-gated chloride channels, which leads to paralysis. At field-use rates, a ne...

418 citations

Journal Article
TL;DR: A simple method is described for treating 250-ml glass Wheaton bottles with insecticide, and using them as test chambers for detecting insecticide resistance in mosquito and sandfly populations.
Abstract: A simple method is described for treating 250-ml glass Wheaton bottles with insecticide, and using them as test chambers for detecting insecticide resistance in mosquito and sandfly populations. The methods for treating bottles, obtaining baseline data, and applying this technique to insects from the field are described. Sample data are presented from tests run on different vector species using a variety of insecticides. Time-mortality data from the bottle bioassay are presented alongside results from biochemical detection methods applied to the same mosquito population. The potential role, advantages, and limitations of the time-mortality bottle method are discussed.

265 citations


"Monitoring of resistance to the pyr..." refers background or methods in this paper

  • ...According to the original methodology (Brogdon & McAllister 1998), the criterion for mortality was that mosquitoes were not able to fly or to right themselves when the bottle is gently rotated....

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  • ...According to Brogdon and McAllister (1998) these would be dead mosquitoes....

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  • ...Bioassays were performed with insecticide-coated bottles, as described by Brogdon and McAllister (1998)....

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  • ...This was attained after 30 min exposure, a period considered as the resistance threshold (Brogdon & McAllister 1998)....

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Journal ArticleDOI
TL;DR: Exposure of larvae to a diagnostic dose of temephos showed in alterations in susceptibility in all populations, and adults from only one municipality remained susceptible to both fenitrothion and malathion.
Abstract: Chemical insecticides have been widely used in Brazil for several years. This exposes mosquito populations to an intense selection pressure for resistance to insecticides. In 1999, the Brazilian National Health Foundation started the first program designed to monitor the resistance of Aedes aegypti to insecticides. We analyzed populations from 10 municipalities (from 84 selected in Brazil) in the states of Rio de Janeiro and Espirito Santo. Exposure of larvae to a diagnostic dose of temephos showed in alterations in susceptibility in all populations. Mosquitoes from eight municipalities exhibited resistance, with mortality levels ranging from 74% (Campos dos Goytacazes, Rio de Janeiro) to 23.5% (Sao Goncalo, Rio de Janeiro). The resistance ratios of mosquitoes from three municipalities ranged from 3.59 to 12.41. Adults from only one municipality (Nova Iguacu, Rio de Janeiro) remained susceptible to both fenitrothion and malathion. These results are being used to define new local vector control strategies.

234 citations


"Monitoring of resistance to the pyr..." refers background in this paper

  • ...The use of organophosphates, employed since 1967 throughout the country against Ae. aegypti larvae and adults, was intensified after the 1986 epidemics, that started at Rio de Janeiro and spread over several other regions (Lima et al. 2003, Braga et al. 2004)....

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Journal Article
TL;DR: The method with which the percentage of sodium channel population that needs to be modified to cause repetitive after-discharges can be measured accurately is developed and is applicable to other neuroactive drugs that act through the threshold phenomenon.
Abstract: Most insecticides are neurotoxicants causing various forms of hyperexcitation and paralysis in animals. A variety of neuroreceptors and ion channels have been identified as the major target sites of these neurotoxic insecticides. This paper gives the highlights of some of the recent development in this area. Pyrethroids keep the sodium channel open for unusually long times causing a prolonged flow of sodium current. The prolonged sodium current elevates and prolongs the depolarizing after-potential which reaches the threshold membrane potential to initiate repetitive after-discharges. We have developed the method with which the percentage of sodium channel population that needs to be modified to cause repetitive after-discharges can be measured accurately. In rat cerebellar Purkinje neurons, only 0.6% of sodium channels needs to be modified for hyperexcitation resulting in a large toxicity amplification. This concept is applicable to other neuroactive drugs that act through the threshold phenomenon. 'The mechanisms of selective toxicity of pyrethroids in mammals and insects have been quantitatively determined to be due mainly to the different sensitivity of the sodium channels to pyrethroids and the negative temperature dependence of pyrethroid action on the sodium channels. The degradation of pyrethroids play only a minor role. The negative temperature dependence of pyrethroid action is due to the increased sodium current flow at low temperature. The major site of action of dieldrin and hexachlorocyclohexane is the GABA A receptor chloride channel complex. Dieldrin exerts a dual action, initial stimulation and subsequent suppression, and the latter is responsible for hyperexcitation of animals. Dieldrin stimulation requires the γ2s subunit in the GABA receptor, whereas dieldrin suppression occurs in the presence or absence of the γ2s subunit.

202 citations


"Monitoring of resistance to the pyr..." refers background or methods in this paper

  • ...After linkage to pyrethroids, the sodium channels in the neurons are maintained for a longer length of time in their opened conformation, which results in a continuous nervous impulse that causes bursts of contractions, culminating with paralysis (Bloomquist 1996). Depending on the insecticide’s dosage, this effect, known as the “knock down” mechanism, is reversible if contact with the insecticide is interrupted. Resistant individuals that have a kdr mutation exhibit the knock down effect but can recover from pyrethroid dosages that are lethal to susceptible insects (Milani 1954, Pauron et al. 1989). Sodium channels are also the target site for organochlorines, an insecticide class that has not been used in the Public Health at Brazil since the reintroduction of Ae. aegypti in 1967 (Franco 1976). We report on the monitoring of Ae. aegypti resistance to cypermethrin in municipalities of three Brazilian states: Sergipe (SE) and Alagoas (AL), located at Northeast Brazil and Rio de Janeiro (RJ), at the Southeast (Figure). Bioassays were performed with insecticide-coated bottles, as described by Brogdon and McAllister (1998). We first calibrated the bottles with different dosages of cypermethrin, by testing mosquitoes from the Rockefeller strain....

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  • ...After linkage to pyrethroids, the sodium channels in the neurons are maintained for a longer length of time in their opened conformation, which results in a continuous nervous impulse that causes bursts of contractions, culminating with paralysis (Bloomquist 1996)....

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Journal ArticleDOI
TL;DR: Exposure of larvae to the diagnostic dose of temephos revealed resistance in all localities examined, with mortality levels ranging from 4% (Pilares district, Rio de Janeiro, RJ) to 61.9% (Campos dos Goytacazes, RJ).
Abstract: For more than 30 years temephos, an organophosphate insecticide, has been the sole larvicide used in Brazil in the control of Aedes aegypti. Organophosphates were also used for adult control, being replaced by pyrethroids since l999. In this same year, the Brazilian Health Foundation started the coordination of the Ae. aegypti Insecticide Resistance Monitoring Program. In the context of this program, our group was responsible for the detection of temephos resistance in a total of 12 municipalities in the states of Rio de Janeiro (RJ), Alagoas (AL), and Sergipe (SE) during 2001. In each municipality, a pool of mosquitoes collected from different districts was used, with the exception of Rio de Janeiro city, where eight districts have been separately evaluated. Exposure of larvae to the diagnostic dose of temephos revealed resistance in all localities examined, with mortality levels ranging from 4% (Pilares district, Rio de Janeiro, RJ) to 61.9% (Campos dos Goytacazes, RJ). Quantification of mortality showed resistance ratios from 6.1 (Aracaju, SE) to 16.8 (Sao Goncalo, RJ and Penha district, Rio de Janeiro, RJ). The national dengue control program is presently using these data to subside insecticide resistance management.

194 citations


"Monitoring of resistance to the pyr..." refers background in this paper

  • ...The use of organophosphates, employed since 1967 throughout the country against Ae. aegypti larvae and adults, was intensified after the 1986 epidemics, that started at Rio de Janeiro and spread over several other regions (Lima et al. 2003, Braga et al. 2004)....

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