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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TL;DR: The CDC bottle bioassay is an effective tool to assess insecticide resistance in field populations of Ae.
Abstract: The objective of this study was to determine diagnostic doses (DDs) of 5 insecticides for the Rockefeller susceptible strain of Aedes aegypti , using the Centers for Disease Control and Prevention (CDC) bottle bioassay as a tool for monitoring insecticide resistance in the Cuban vector control program. The 30-min DD values determined in this study were 13.5 μg/ml, 6.5 μg/ml, 6 μg/ml, 90.0 μg/ml, and 15.0 μg/ml for cypermethrin, deltamethrin, lambda-cyhalothrin, chlorpyrifos, and propoxur, respectively. To compare the reliability of CDC bottle bioassay with the World Health Organization susceptible test, 3 insecticide-resistant strains were evaluated for deltamethrin and lambda-cyhalothrin. Results showed that the bottles can be used effectively from 21 to 25 days after treatment and reused up to 4 times, depending on the storage time. The CDC bottle bioassay is an effective tool to assess insecticide resistance in field populations of Ae. aegypti in Cuba and can be incorporated into vector management programs using the diagnostic doses determined in this study.
7 citations
Journal Article•
TL;DR: The aim is to evaluate the insecticidal potential of the LCC, fresh and after chilling for six months at 4 oC, on larvae of A. aegypti, as well as to determine their chemical constitution.
Abstract: To control the Dengue Fever epidemic it is necessary to eliminate the breeding of the mosquito Aedes aegypti, which transmits the virus, and to spray insecticides. The research seeks to evaluate new substances from native plants which are capable of controlling disease vectors, with less toxicity to humans and the environmental. The Net of Cashew Nut (LCC) of Anacardium occidentale L. (Anacardiaceae) is mostly composed of anacardic acid in varying concentrations. This product has shown promise in laboratory experiments demonstrating it contains biocidal active substances. The aim is to evaluate the insecticidal potential of the LCC, fresh (kept in environmental conditions) and after chilling for six months at 4 oC, on larvae of A. aegypti, as well as to determine their chemical constitution. The anacardic acid fresh or chilled shows the same toxicity profile while maintaining its strength and use in 0.013% to cause larval mortality. The LCC has tested 69% of Anacardic acid.
7 citations
Cites background from "Monitoring of resistance to the pyr..."
...Porém, o uso constante e em grande escala dos produtos químicos tem contribuído para o surgimento de problemas significativos, como o aumento de frequência de populações resistentes (Lima et al. 2006, Pereira da Cunha et al. 2005, Rodrigues Couto et al. 2000)....
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...Pereira da Cunha et al. (2005) constataram uma diminuição na susceptibilidade do A. aegypti da atividade do piretroides no Rio de Janeiro O potencial dos inseticidas a base de princípios ativos vegetais proporciona a utilização de moléculas que, pela complexidade de composição, diminuem os riscos…...
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TL;DR: It can be concluded that there has been Val1016Ile point mutation in the voltage gated sodium channel gene of Ae.aegypti as the marker of synthetic pyrethroid insecticides resistance in Palembang.
Abstract: Aedes aegypti merupakan vektor dari berbagai patogen, termasuk diantaranya virus dengue fever. Sebanyak 500 ribu kasus baru demam berdarah dengue (DBD) terjadi tiap tahunnya di seluruh dunia. Pengendalian nyamuk vektor merupakan cara efektif memutus rantai penularan DBD. Namun penggunaan satu jenis insektisida secara intensif dalam waktu lama terbukti menyebabkan resistensi. Resistensi Ae.aegypti terhadap insektisida awalnya terjadi pada dichloro diphenyl trichloroetane (DDT), lalu terhadap temefos kemudian sintetik piretroid. Tiga cara mendeteksi resistensi sintetik piretroid menurut WHO yaitu bioassay, biokimia dan molekuler. Deteksi biokimia yang pernah dilakukan di Palembang menunjukkan hasil negatif, tetapi kenyataan incidence rate DBD belum turun. Penelitian lebih lanjut menggunakan deteksi molekuler diperlukan untuk mengetahui mekanisme resistensi insektisida. Deteksi molekuler dapat mendeteksi mutasi pada gen enzim metabolisme dan gen target site insektisida, semisal pada voltage gated sodium channel (VGSC). Penelitian ini dilakukan untuk mengidentifikasi mutasi titik gen VGSC Val1016Ile dan Val1016Gly Aedes aegypti. Desain penelitian ini adalah berupa deskriptif laboratoris dengan uji molekuler. Populasi adalah seluruh larva instar III-IV Ae. aegypti yang berasal dari pembiakan telur yang diperoleh dari kelurahan-kelurahan di Kecamatan Bukit Kecil, Sukarami dan Ilir Timur I kota Palembang. Identifikasi larva dilakukan di Balai Besar Laboratorium Kesehatan (BBLK) Palembang dan uji molekuler dilakukan di Departemen Mikrobiologi Klinik Rumah Sakit Muhammad Hoesin Palembang dan BBLK Palembang. Hasil penelitian menunjukkan terjadi mutasi titik Val1016Ile serta tidak terjadi mutasi titik Val1016Gly gen VGSC. Disimpulkan terjadi mutasi titik Val1016Ile gen VGSC Ae.aegypti sebagai penanda resistensi yang bersifat target site atas sintetik piretroid di Palembang.
7 citations
TL;DR: The results suggested that the L932F+I936V mutations confer the Brazilian strain of Cx.
Abstract: Highly residual pyrethroids such as permethrin have been used for controlling mosquitoes that transmit infectious diseases. However, the selective pressure from such insecticides may result in cross-resistance against other pyrethroids used for household insecticides. In this study, we investigated the susceptibility of Culex quinquefasciatus Say collected from Brazil and Myanmar to permethrin in addition to four types of household pyrethroids. Both strains exhibited high resistance against all pyrethroids tested, indicating cross-resistance. Furthermore, we detected the knockdown resistance (kdr) mutations L932F+I936V in the voltage-gated sodium channel gene (VGSC) in the Brazilian strain. Notably, the L932F+I936V haplotype has previously been observed in in silico data, but it should be detected not directly from living insects. In comparison, a common kdr mutation, L1014F, was detected from the Myanmar strain. Although L1014F was also detected from the Brazilian strain, the allele frequency was too low to affect resistance. Both strains harbored the resistance-associated haplotypes of the cytochrome P450 gene, CYP9M10. The Brazilian strain demonstrated comparable resistance against pyrethroids as that of the Myanmar strain even when a cytochrome P450 inhibitor, piperonyl butoxide was added to the bioassay. Our results suggested that the L932F+I936V mutations confer the Brazilian strain of Cx. Quiquefasciatus with resistance at a comparable level to that conferred by the well-recognized kdr mutation L1014F in the Myanmar strain. The identification of unexplored mutations may improve the diagnosis and understanding of resistance of this medically important species.
7 citations
01 Jan 2009
TL;DR: In this paper, a SDIR (Susceptible, Displayed, Infectious and Removed)-type mathematical model was simulated which included a population of human hosts, dengue vectors, and control strategies for Aedes aegypti.
Abstract: A SDIR (Susceptible, Displayed, Infectious and Removed)-type mathematical model was simulated which included a population of human hosts, dengue vectors, and control strategies for Aedes aegypti. The simulations indicated that applications of insecticides should be combined in both the larval and adult stages of the vector in order to quickly reduce the epidemic. In order to avoid compromising control of the mosquito, it is also necessary to use highly efficient insecticides, ensure that applications have highly effective coverage, and that they are always accompanied by constant removal of breeding sites. It is concluded that densities of the vector must be kept close to zero throughout the year to avoid the coexistence of virus and vector.
7 citations
References
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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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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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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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