RESISTANCE OF AEDES AEGYPTI TO ORGANOPHOSPHATES IN SEVERAL MUNICIPALITIES IN THE STATE OF RIO DE JANEIRO AND ESPíRITO SANTO, BRAZIL
01 Mar 2003-American Journal of Tropical Medicine and Hygiene (American Society of Tropical Medicine and Hygiene)-Vol. 68, Iss: 3, pp 329-333
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.
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TL;DR: Two A. aegypti populations from Ceará are under strong selection pressure by temephos, compromising the field effectiveness of this organophosphate, and resistance to cypermethrin is shown in two of the three populations studied.
Abstract: Organophosphates and pyrethroids are used widely in Brazil to control Aedes aegypti, the main vector of dengue viruses, under the auspices of the National Programme for Dengue Control. Resistance to these insecticides is widespread throughout Brazil. In Ceara the vector is present in 98% of districts and resistance to temephos has been reported previously. Here we measure resistance to temephos and the pyrethroid cypermethrin in three populations from Ceara and use biochemical and molecular assays to characterise resistance mechanisms. Resistance to temephos varied widely across the three studied populations, with resistance ratios (RR95) of 7.2, 30 and 192.7 in Juazeiro do Norte, Barbalha and Crato respectively. The high levels of resistance detected in Barbalha and Crato (RR95 ≥ 30) imply a reduction of temephos efficacy, and indeed in simulated field tests reduced effectiveness was observed for the Barbalha population. Two populations (Crato and Barbalha) were also resistant to cypermethrin, whilst Juazeiro do Norte showed only an altered susceptibility. The Ile1011Met kdr mutation was detected in all three populations and Val1016Ile in Crato and Juazeiro do Norte. 1011Met was significantly associated with resistance to cypermethrin in the Crato population. Biochemical tests showed that only the activity of esterases and GSTs, among the tested detoxification enzymes, was altered in these populations when compared with the Rockefeller strain. Our results demonstrate that two A. aegypti populations from Ceara are under strong selection pressure by temephos, compromising the field effectiveness of this organophosphate. Our results also provide evidence that the process of reducing resistance to this larvicide in the field is difficult and slow and may require more than seven years for reversal. In addition, we show resistance to cypermethrin in two of the three populations studied, and for the first time the presence of the allele 1016Ile in mosquito populations from northeastern Brazil. A significant association between 1011M et and resistance was observed in one of the populations. Target-site mechanisms seem not to be implicated in temephos resistance, reinforcing the idea that for the studied populations, detoxification enzymes most likely play a major role in the resistance to this insecticide.
204 citations
Cites background or methods from "RESISTANCE OF AEDES AEGYPTI TO ORGA..."
...Over the last 10 years, resistance to organophosphate and pyrethroid insecticides employed for control of the dengue vector Aedes aegypti has been detected in all Brazilian regions, including Rio de Janeiro [4,12], Espírito Santo [35] and São Paulo [7,9-12] representing the Southeast, in all states from the Northeast region, in Distrito Federal and Goiás representing the Midwest region, and in Pará and Amazonas representing the North [8]....
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...Mosquito samples were collected in the field in November and December 2009 with the use of 100 oviposition traps (ovitraps), adapted from [34], distributed homogeneously in each area, based on the recommendations of the MoReNAa network [12,35]....
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...Lima JB, Da-Cunha MP, Da Silva RC, Galardo AK, Soares SS, Braga IA, Ramos RP, Valle D: Resistance of Aedes aegypti to organophosphates in several municipalities in the State of Rio de Janeiro and Espirito Santo, Brazil....
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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
Cites background or methods or result from "RESISTANCE OF AEDES AEGYPTI TO ORGA..."
...In the state of RJ, the comparison with 1999 data (Lima et al. 2003) indicated mortality rates equivalent to the present ones in Campos dos Goytacazes (74% in 1999 and 61.9% in 2001) and Niterói (34.6% in 1999 and 44% in 2001)....
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...At that time, calibrations performed by our group confirmed the concentration of 0.006 mg/l as the temephos LC99 (Lima et al. 2003)....
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...The number of ovitraps placed in the field was based on the number of buildings in each locality, as described previously (Lima et al. 2003)....
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...Bioassays were done with the recommended World Health Organization (WHO) protocol, described elsewhere (WHO 1981a, Lima et al. 2003), using 0.006 mg/l temephos as the diagnostic dose (twice the concentration of the dose that kills 99% of a susceptible strain – LC99 –, as defined by WHO (1981a, b)....
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...During the 1999 monitoring, the RR90 of three municipalities of RJ (Duque de Caxias, São Gonçalo, and São João de Meriti) was calculated (Lima et al. 2003)....
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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
Cites methods from "RESISTANCE OF AEDES AEGYPTI TO ORGA..."
...Ovitraps were adopted to collect mosquitoes complying with MoReNAa network recommendations.(7,8,14) In almost all cases, F1 (preferably) or F2 specimens were used....
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TL;DR: Evidence based community mobilization can add effectiveness to dengue vector control as each site implementing the intervention in its own way has the advantage of local customization and strong community engagement.
Abstract: Objective To test whether community mobilization adds effectiveness to conventional dengue control. Design Pragmatic open label parallel group cluster randomized controlled trial. Those assessing the outcomes and analyzing the data were blinded to group assignment. Centralized computerized randomization after the baseline study allocated half the sites to intervention, stratified by country, evidence of recent dengue virus infection in children aged 3-9, and vector indices. Setting Random sample of communities in Managua, capital of Nicaragua, and three coastal regions in Guerrero State in the south of Mexico. Participants Residents in a random sample of census enumeration areas across both countries: 75 intervention and 75 control clusters (about 140 households each) were randomized and analyzed (60 clusters in Nicaragua and 90 in Mexico), including 85 182 residents in 18 838 households. Interventions A community mobilization protocol began with community discussion of baseline results. Each intervention cluster adapted the basic intervention—chemical-free prevention of mosquito reproduction—to its own circumstances. All clusters continued the government run dengue control program. Main outcome measures Primary outcomes per protocol were self reported cases of dengue, serological evidence of recent dengue virus infection, and conventional entomological indices (house index: households with larvae or pupae/households examined; container index: containers with larvae or pupae/containers examined; Breteau index: containers with larvae or pupae/households examined; and pupae per person: pupae found/number of residents). Per protocol secondary analysis examined the effect of Camino Verde in the context of temephos use. Results With cluster as the unit of analysis, serological evidence from intervention sites showed a lower risk of infection with dengue virus in children (relative risk reduction 29.5%, 95% confidence interval 3.8% to 55.3%), fewer reports of dengue illness (24.7%, 1.8% to 51.2%), fewer houses with larvae or pupae among houses visited (house index) (44.1%, 13.6% to 74.7%), fewer containers with larvae or pupae among containers examined (container index) (36.7%, 24.5% to 44.8%), fewer containers with larvae or pupae among houses visited (Breteau index) (35.1%, 16.7% to 55.5%), and fewer pupae per person (51.7%, 36.2% to 76.1%). The numbers needed to treat were 30 (95% confidence interval 20 to 59) for a lower risk of infection in children, 71 (48 to 143) for fewer reports of dengue illness, 17 (14 to 20) for the house index, 37 (35 to 67) for the container index, 10 (6 to 29) for the Breteau index, and 12 (7 to 31) for fewer pupae per person. Secondary per protocol analysis showed no serological evidence of a protective effect of temephos. Conclusions Evidence based community mobilization can add effectiveness to dengue vector control. Each site implementing the intervention in its own way has the advantage of local customization and strong community engagement. Trial registration ISRCTN27581154
174 citations
TL;DR: The results strongly suggest that the Ae.
Abstract: Pyrethroids are the most used insecticide class worldwide. They target the voltage gated sodium channel (NaV), inducing the knockdown effect. In Aedes aegypti, the main dengue vector, the AaNaV substitutions Val1016Ile and Phe1534Cys are the most important knockdown resistance (kdr) mutations. We evaluated the fitness cost of these kdr mutations related to distinct aspects of development and reproduction, in the absence of any other major resistance mechanism. To accomplish this, we initially set up 68 crosses with mosquitoes from a natural population. Allele-specific PCR revealed that one couple, the one originating the CIT-32 strain, had both parents homozygous for both kdr mutations. However, this pyrethroid resistant strain also presented high levels of detoxifying enzymes, which synergistically account for resistance, as revealed by biological and biochemical assays. Therefore, we carried out backcrosses between CIT-32 and Rockefeller (an insecticide susceptible strain) for eight generations in order to bring the kdr mutation into a susceptible genetic background. This new strain, named Rock-kdr, was highly resistant to pyrethroid and presented reduced alteration of detoxifying activity. Fitness of the Rock-kdr was then evaluated in comparison with Rockefeller. In this strain, larval development took longer, adults had an increased locomotor activity, fewer females laid eggs, and produced a lower number of eggs. Under an inter-strain competition scenario, the Rock-kdr larvae developed even slower. Moreover, when Rockefeller and Rock-kdr were reared together in population cage experiments during 15 generations in absence of insecticide, the mutant allele decreased in frequency. These results strongly suggest that the Ae. aegypti kdr mutations have a high fitness cost. Therefore, enhanced surveillance for resistance should be priority in localities where the kdr mutation is found before new adaptive alleles can be selected for diminishing the kdr deleterious effects.
172 citations
Cites background or methods from "RESISTANCE OF AEDES AEGYPTI TO ORGA..."
...To assure virgin females would be used in the initial crosses, F1 specimens from Cachoeiro do Itapemirim, collected as described elsewhere [51], were reared until pupae, which were transferred to individual chambers....
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...Larvae and adult mosquitoes were reared according to standard conditions previously described [51]....
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References
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Book•
01 Jan 1996
TL;DR: This title focuses on the molecular and populational aspects of the insects and acarines that serve as transmitters (vectors) of disease agents and is designed to stimulate further studies worldwide.
Abstract: This title focuses on the molecular and populational aspects of the insects (mosquitoes, midges, black flies, etc.) and acarines (ticks and mites) that serve as transmitters (vectors) of disease agents and is designed to stimulate further studies worldwide. Vector-borne diseases continue to be among the most intractable infectious diseases for both humans and livestock, despite a hundred years of research and control efforts. Of the six diseases considered by the World Health Organisation to be the greatest threat to human health, only one is not vector-borne. Progress in alleviating their harmful effects is likely to come through fundamental studies utilising molecular techniques and epidemiological methods that have been developed over the past fifteen years. These methods are discussed in the book. The forty contributors to this volume are leading, active investigators in vectors and the disease agents they transmit.
430 citations
348 citations
"RESISTANCE OF AEDES AEGYPTI TO ORGA..." refers background in this paper
...Chemical insecticides have been used in Brazil since the Anopheles gambiae eradication campaign began in 1939.(19)...
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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
"RESISTANCE OF AEDES AEGYPTI TO ORGA..." refers methods in this paper
...Malathion, temephos, and fenitrothion resistance bioassays for adults were performed with F1 or F2 mosquitoes and followed the CDC methodology, based on the use of 250-mL glass bottles impregnated with insecticides.(10) Our previous assays indicated that 400 g of malathion per bottle, 900 g of temephos per bottle, and 800 g of fenithrotion per bottle were sufficient to induce 100% mortality in the susceptible Rockefeller strain....
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Journal Article•
TL;DR: An ovitrap containing hay infusion and a second Ovitrap adjacent to it containing a 10% dilution of the infusion in tap water together yielded 8 times more Aedes aegypti eggs than single CDC ovitraps containing tap water.
Abstract: An ovitrap containing hay infusion and a second ovitrap adjacent to it containing a 10% dilution of the infusion in tap water together yielded 8 times more Aedes aegypti eggs than single CDC ovitraps containing tap water. These "enhanced pairs" were significantly more attractive than pairs with other combinations of infusion, water or methyl propionate, and have proven useful for daily monitoring of Ae. aegypti populations. Our results shed light on the oviposition behavior of Ae. aegypti in the field.
249 citations
"RESISTANCE OF AEDES AEGYPTI TO ORGA..." refers methods in this paper
...Ovitraps were prepared according to the procedure of Fay and Eliason,(11) using black plastic jars filled with hay infusion.(12,13) The number of ovitraps installed followed a norm...
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