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RESUMEN Introducción: el temefos es el producto más utilizado para el tratamiento focal. Existe en diferentes formulaciones y se aplica para los depósitos de agua potable, en forma de gránulos de arena a una concentración del 1 %. Objetivo: determinar la duración de la efectividad del temefos, en su formulación costarricense Biolarv G1, en una población matancera de Culex quinquefasciatus. Materiales y métodos: se realizó un bioensayo de laboratorio, utilizando la F1 de una cepa matancera de Culex quinquefasciatus, la que se sometió a los efectos del Biolarv G1, lote 1180829. Se utilizaron tres variantes de recambio de agua potable. Resultados: la efectividad fue del 100 % de mortalidad larvaria hasta el 7º día en el recambio del 100 % de agua. Para el recambio del 50 % de agua, la mortalidad promedio del 1º al 17º día fue del 97,5 %. En el caso del recambio del 30 % de agua, la mortalidad fue del 100 % hasta el 27º día. Conclusiones: se demostró que el temefos, en su formulación Biolarv G1, puede tener mayor efectividad en recambios del 30 % de agua, con una durabilidad de alrededor de 30 días, lo que propicia la protección de los depósitos durante los ciclos de trabajo diseñados para la vigilancia y lucha antivectorial en Cuba.
ABSTRACT Introduction: temefos is the most widely used product for focal treatment. It exists in different formulations and is applied for drinking water tanks, in the form of sand-like granules at a concentration of 1 %. Objective: to determine the duration of temefos effectiveness, in its Costa Rican formulation Biolarv G1, in a Matanzas population of Culex quinquefasciatus. Materials and methods: a laboratory bioassay was performed, using the F1 of a Matanzas strain of Culex quinquefasciatus, which was subjected to the effects of Biolarv G1, lot 1180829. Three variants of drinking water replacement were used. Results: the effectiveness was 100% of larval mortality until the 7th day when 100 % of wáter was replaced. For the replacement of 50 % of water, average mortality was 97.5 % from the 1st to the 17th day. In the case of 30 % water replacement, mortality was 100 % up to the 27th day. Conclusions: it was shown that temefos, in its formulation Biolarv G1, can be more effective in replacements of 30 % of water, with a durability of about 30 days, which facilitates the protection of reservoirs during work cycles designed for surveillance and anti-vector control in Cuba.
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@# Larviciding is an effective control method in managing mosquito-borne diseases. However, most of the current larvicide formulations have raised environmental concerns due to the presence of non-biodegradable inert or carrier materials. Therefore, the utilisation of biodegradable natural cellulosic fibres has created much attention. This study aims to evaluate the application of biodegradable kenaf cellulose nanofibre (KCNF) in larvicide formulation where the larvicide, namely temephos, is impregnated onto the fibre matrix (KCNF+T). The bioefficacy of the formulation was evaluated against Aedes aegypti (A. aegypti) mosquito larvae. The presence of the temephos on the KCNF was evaluated through micromorphological analysis using a field emission scanning electron microscope (FESEM) and a transmission electron microscope (TEM), while the quantity of temephos impregnated, released, and retained on the fibres upon dispersion in water were determined using high performance liquid chromatography (HPLC). It was observed that 97% of the temephos (0.1 mg) were impregnated on the KCNF. Upon dispersion in water, 53% of the temephos were released from the KCNF+T and the retention of temephos on the KCNF+T gradually decreased to 30%, 17%, and 7% on the first, third, and fifth month, respectively. Exposure of the A. aegypti larvae to the KCNF+T at concentrations ranging between 0.006 to 0.01 mg/L was effective in killing A. aegypti larvae at 17–25 folds as compared to using the temephos without KCNF. Microscopic examination revealed the accumulation of the KCNF on the larval appendages. In conclusion, this study demonstrated that the utilisation of KCNF in pesticide formulation is an effective way of delivering the temephos to control A. aegypti mosquito larvae.
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BACKGROUND Aedes aegypti populations in Brazil have been subjected to insecticide selection pressures with variable levels and sources since 1967. Therefore, the Brazilian Ministry of Health (MoH) coordinated the activities of an Ae. aegypti insecticide resistance monitoring network (MoReNAa) from 1999 to 2012. OBJECTIVES The objective of this study was to consolidate all information available from between 1985 and 2017 regarding the resistance status and mechanisms of Brazilian Ae. aegypti populations against the main insecticide compounds used at the national level, including the larvicide temephos (an organophosphate) and the adulticide deltamethrin (a pyrethroid). METHODS Data were gathered from two sources: a bibliographic review of studies published from 1985 to 2017, and unpublished data produced by our team within the MoReNAa between 1998 and 2012. A total of 146 municipalities were included, many of which were evaluated several times, totalling 457 evaluations for temephos and 274 for deltamethrin. Insecticide resistance data from the five Brazilian regions were examined separately using annual records of both the MoH supply of insecticides to each state and the dengue incidence in each evaluated municipality. FINDINGS Ae. aegypti resistance to temephos and deltamethrin, the main larvicide and adulticide, respectively, employed against mosquitoes in Brazil for a long time, was found to be widespread in the country, although with some regional variations. Comparisons between metabolic and target-site resistance mechanisms showed that one or another of these was the main component of pesticide resistance in each studied population. MAIN CONCLUSIONS (i) A robust dataset on the assessments of the insecticide resistance of Brazilian Ae. aegypti populations performed since 1985 was made available through our study. (ii) Our findings call into question the efficacy of chemical control as the sole methodology of vector control. (iii) It is necessary to ensure that sustainable insecticide resistance monitoring is maintained as a key component of integrated vector management. (iv) Consideration of additional parameters, beyond the supply of insecticides distributed by the MoH or the diverse local dynamics of dengue incidence, is necessary to find consistent correlations with heterogeneous vector resistance profiles.
Subject(s)
Humans , Insecticide Resistance/immunology , Temefos/analysis , Aedes , Vector Control of Diseases , Brazil/epidemiologyABSTRACT
Abstract INTRODUCTION The organophosphate temephos was first used in Brazil in the 1960s for the control of Aedes aegypti. Because of its extensive and longstanding use worldwide, selection for mosquito populations resistant to the chemical has been observed not only in different regions of Brazil but also in several parts of the world. The objective of this study was to evaluate the susceptibility of Ae. aegypti to the organophosphate temephos, a larvicide used in vector control activities in Sergipe/Northeast Brazil. METHODS This study included mosquito populations from seven municipalities of Sergipe and was carried out from October 2010 to August 2011. Qualitative bioassays of diagnostic dose and dose responses were performed. The resistance ratio was calculated based on lethal concentrations for mosquitoes of the susceptible Rockefeller strain. RESULTS: All populations were classified as resistant to temephos. The resistance ratio ranged from 22.2 to 297.9, the lowest being seen in Aracaju, a coastal area of the state, and the highest in Pinhão, a semi-arid region, 96.6km from Aracaju. CONCLUSIONS: High levels of temephos resistance were observed in the Ae. aegypti populations of Sergipe. The variation between regions indicates that there have been different regimes of insecticide use and also points to the potential of small cities to generate and spread insecticide resistance.
Subject(s)
Animals , Biological Assay , Temefos , Insecticide Resistance , Aedes , Mosquito Vectors , Insecticides , BrazilABSTRACT
Abstract The effects of temephos resistance on the fitness cost of the wild populations of Aedes albopictus was evaluated. The larvae of two wild populations were exposed to the diagnostic dose of 0.02 mg and 0.012 mg/L. The larvae which survived after the 24 h exposure to diagnostic dose were considered as resistant and F1 generations were chosen for the comparisons of fitness parameters with the control strain, which includes larval developmental time, adult longevity, fecundity, wing length and hatchability. We found that temephos resistance had negative effects on larval developmental time which was longer for Gelugor strain among the populations with the median range of 10 days and a shorter longevity was observed with the median range of 13 days for males and 16 days for females. Whereas, an effective reduction of 29.8 and 38.6% was observed in fertility and fecundity of Gelugor strain as compared to control strain. In contrast, no clear differences were found in biological parameters of Balik Palau and USM strain, except fecundity and fertility with a reduction of 13.4 and 15.5%, respectively. Whereas, no significant differences were seen in the wing size between the populations with the mean length (mm) of 2.40 for Gelugor, 2.44 for Balik Palau and 2.46 for USM control (p > 0.05). Present results indicated that the temephos resistance is associated with the developmental and reproduction potential of resistant population of A. albopictus and the fitness has been compromised.
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Objective To evaluate the efficacy of a sustained releasing mosquito larvicide package against larval breeding and its impact on water and plant,in order to provide a scientific evidence for its application in control and prevention of Dengue.Methods Guangzhou Center for Disease Control and Prevention was chosen as the test place.Twenty test sites were set up,2 bags of sustained releasing larvicides package,1 bag of sustained releasing larvicides package,3 g 1％ temephos granules and nothing were put into 4 glass bottles for each test site from July to December in 2014,respectively.The 4 glass bottles were called high dose (H) group,low dose (L)group,positive control (P) group and blank control (B) group,respectively.The 4 groups were observed at intervals of 10 days for 19 times.Environmental air temperature,turbidity of water,number of larvae and damage of plant were recorded.And 5 test sites were selected to collect water specimen.The chemical oxygen demand,ammonia nitrogen concentration and temephos concentration of water specimen were detected.Results The larval breeding rates were 0 (0/380),1.1％ (4/380),0.8％ (3/380) and 63.4％ (241/380),damage rates of plant were 5.0％ (19/380),5.5％ (21/380),4.7％ (18/380),4.7％ (18/380) and turbidty rates of water were 24.5％ (93/380),19.7％ (75/380),33.4％ (127/380) and 20.3％ (77/380) in H,L,P and B groups,respectively.Statistically significant differences were seen in larval breeding rate and turbidity rate of water between different groups (x2 =823.565,24.715,all P ＜ 0.05),but they were not seen in damage rate of plant (x2 =0.332,P ＞ 0.05).The temephos concentrations were 1.24,0.78 and 2.33 mg/L in H,L and P groups,respectively.Statistically significant differences were seen in temephos concentration between different groups (H =35.426,P ＜ 0.01),but they were not seen in chemical oxygen demand and ammonia nitrogen concentration (H =0.239,0.013,all P ＞ 0.05).Conclusions The sustained releasing package of mosquito larvicide makes less pollution to water and has no impact on water turbidity.Moreover,it doesn't damage the aquatic plant.The efficacy of the sustained releasing package of mosquito larvicide could effectively prevent mosquito larval breeding in Dengue epidemic period.
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Introducción: el aumento de enfermedades transmitidas por mosquitos se ha asociado a cambios globales: el crecimiento de la población, la urbanización y el cambio climático. Dentro de las alternativas para evitar epidemias están el control químico y biológico. Objetivos: determinar las concentraciones efectivas de tres compuestos químicos para el control de larvas de Aedes aegypti en la región costa norte de Jalisco, México, y evaluar la capacidad predatoria de diversas especies acuáticas sobre larvas de mosquitos. Métodos: se evaluaron cinco concentraciones de temefos (1,5; 1; 0,1; 0,05 y 0,01 g/L), hipoclorito de sodio (5,5; 0,55; 0,05; 0,005 y 0,0005 g/L) y detergente (10; 5; 1; 0,5; 0,1 g/L). Se determinó la muerte de las larvas a 1, 3, 6 y 24 h y se calculó la CL50. Se evaluaron cuatro especies de peces, un crustáceo y una larva de díptero culícido. Se les suministraron diferentes cantidades de larvas (5, 10, 30, 50 y 80) por quintuplicado y se registró su consumo a diferentes tiempos (1, 3, 5, 9 y 24 h). Resultados: el temefos provocó el 100 por ciento de mortalidad en todas las concentraciones probadas. El NaClO provocó mortalidad del 100 por ciento en las dos concentraciones más altas. El detergente fue más eficiente a las tres concentraciones mayores. Los peces demostraron un consumo de casi el 100 por ciento en la mayoría de las densidades probadas. La larva de díptero culícido demostró un consumo cercano al 80 por ciento, el crustáceo solo consumió el 53 por ciento Conclusiones: el uso del temefos debe continuar siendo el larvicida químico de elección en Puerto Vallarta, México. La utilización de peces nativos se sugiere como adecuada para el control biológico(AU)
Introduction: the increase of diseases transmitted by mosquitoes has been associated to global changes such as the population growth, urbanization and climate change. Among the alternatives to avoid epidemics are the chemical and biological control. Objectives: to determine effective concentrations of three chemical compounds to control Aedes aegypti larvae in the northern coastal region of Jalisco and to evaluate the predatory ability of various aquatic species on mosquito larvae. Methods: five concentrations of temephos of (1.5, 1, 0.1; 0.05 and 0.01 g/L), sodium hypochlorite (5.5, 0.55, 0.05, 0,005 and 0.0005 g/L) and detergent (10, 5, 1, 0.5, 0.1 g/L) were evaluated. Larval death was estimated at different times (1, 3, 5, 9 and 24 h) and the LC50 was calculated. Four fish species, one crustacean and one dipteral culicid larva were evaluated. All were provided with different numbers of larvae (5, 10, 30, 50 and 80) five times and the larval consumption was recorded at different times (1, 3, 5, 9 and 24 h). Results: temephos caused 100 percent mortality of larvae in all tested concentrations. The NaClO caused 100 percent mortality at the two highest concentrations. The detergent was more efficient at the three higher concentrations. Fish proved to be efficient predators of larvae, as they consumed almost 100 percent of larvae in most of tested densities. The diptera culicid larva reached around 80 percent consumption whereas crustacean consumed only 53 percent. Conclusions: the use of temephos should remain the chemical larvicide of choice in Puerto Vallarta region. Native fish are suggested to be used as appropriate biological control agents(AU)
Subject(s)
Temefos , Pest Control, Biological/methods , Aedes , Larva , MexicoABSTRACT
Introducción: el programa de control de Aedes aegypti (Linnaeus) (Diptera: Culicidae) en Cuba utiliza temefos como larvicida y piretroides como adulticidas, aunque el organofosforado clorpirifos ha sido utilizado esporádicamente. Conocer el nivel de resistencia a estos insecticidas es esencial para lograr un control efectivo de esta especie. Objetivo: determinar el nivel de resistencia a insecticidas en su grado técnico y en sus formulaciones comerciales en Ae. aegypti de Pinar del Río. Métodos: una cepa de Ae. aegypti del Área de Salud Raúl Sánchez, Pinar del Río, fue evaluada a través de los bioensayos de la Organización Mundial de la Salud para determinar la susceptibilidad en larvas al organofosforado temefos en su formulación técnica. Se evaluaron además tres formulaciones granuladas de temefos (Abatex-G1, Biolarv G-1 y Temefar G-1). En el estado adulto se determinó el nivel de susceptibilidad a los insecticidas piretroides: cipermetrina, deltametrina, lambdacialotrina y al organofosforado clorpirifos, en su formulación técnica. Además se evaluaron algunos en su formulación comercial: Galgotrin 25 EC (cipermetrina), Aqua K-Otrina 2 EW (deltametrina) y Clorcide 44 EC (clorpirifos). Resultados: en larvas, se encontró alta resistencia a temefos, en su formulación técnica, y con los productos en su formulación comercial, se observó una efectividad del 100 por ciento, con recambio diario de agua, de hasta 20 días para Temefar G1, 18 días para Biolarv G1 y 12 días para Abatex G1. En los ensayos de adultos, la cepa resultó susceptible a cipermetrina, deltametrina y clorpirifos, y resistente a lambdacialotrina. Con respecto a las tres formulaciones comerciales evaluadas, solo se observó resistencia a Aqua K-Otrina 2 EW. Conclusiones: el uso de estrategias de control integrado de Ae. aegypti se hace necesario para disminuir la frecuencia de uso de temefos, y así recuperar la efectividad de este insecticida. Además, se evitaría la aparición de resistencia a productos adulticidas que aun mantienen su efectividad para el control efectivo de esta especie en la zona de estudio(AU)
Introduction: the control program of Aedes aegypti (Linnaeus) (Diptera: Culicidae) in Cuba uses temephos as larvicide and pyrethroids as adulticide although the organophosphorate chlorpyrifos has been barely used. The level of knowledge about resistance to insecticides is essential to effectively control this species. Objective: to determine the level of resistance to insecticides of Ae. aegypti from Pinar del Rio in its technical aspect and in commercial formulations. Methods: one Ae. aegypti strain from the health area Raul Sánchez in Pinar del Rio province was evaluated through the World Health Organization bioassays to determine susceptibility of larvae to temephos in its technical formulation. Additionally, three granulated formulations of temephos were evaluated (Abatex-G1, Biolarv G-1 and Temefar G-1). In the adult state, the level of susceptibility to pyrethroids called cypermethrin, deltamethrin, lambda cyhalothrine and to organophosphate chlorpyrifos in its technical formulation. Some of them were evaluated in its commercial formulation (Galgotrin 25 EC (cypermethrin), Aqua K-Otrina 2 EW (deltamethrin) and Clorcide 44 EC (chlorpyrifos). Results: it was found in larvae that the resistance to temephos was high in the technical formulation, but the commercial formulation showed an effectiveness rate of 100 percent., with daily change of water, up to 20 days for Temefar G1, 18 days for Biolarv G1 and 12 for Abatex G1. In the assays with adult vectors, the strain turned to be susceptible to cypermethrin, deltamethrin and chlorpyrifos and resistant to lambda cyhalothrin. Regarding the three evaluated commercial formulations, resistance to Aqua K-Otrina 2 EW was proved. Conclusions: the use of integrated control strategies for Ae. aegypti makes it necessary to reduce the frequency of use of temephos and to recover the effectiveness of this insecticide. Moreover, it will avoid the occurrence of resistance to adulticide products that are still effective for the control of this species in the study area(AU)
Subject(s)
Insecticide Resistance/physiology , Pest Control, Biological/methods , Aedes , Cuba , Insecticides, Organophosphate/methodsABSTRACT
En Paraguay, el control del mosquito Aedes aegypti involucrado en la transmisión de varias arbovirosis implica la utilización del Temefos, un organofosforado que ha sido utilizado por los programas nacionales para el control vectorial por más de dos décadas en busca de la reducción de los estadios larvarios. En vista de la necesidad de evaluar periódicamente la actividad larvicida del compuesto químico mencionado, este estudio tuvo como objetivo monitorear el perfil de susceptibilidad de larvas de Ae. aegypti al Temefos. Para ello se aplicó un estudio analítico experimental con ensayos biológicos tipo dosis - respuesta, utilizando larvas del tercer estadio de la primera generación procedentes de una colonia de mosquitos colectada en Ciudad del Este. Las larvas fueron expuestas a la acción del Temefos a diferentes concentraciones definidas por un pre- test. Se registraron valores correspondientes al número de larvas expuestas y mortalidad al término de cada ensayo. Los resultados fueron concentración letal CL50 = 0,00966 mg/L y CL90 = 0,03015mg/L, a partir de estos valores se obtuvieron los indicadores cuantitativos de resistencia, Razón de resistencia RR50 = 2,3734 y RR90 = 4,1643 respectivamente. Este último es un indicativo de resistencia baja en las poblaciones de Ae. aegypti evaluadas, acorde con rangos estandarizados (RR>3<5). Los resultados observados en las poblaciones silvestres de larvas revelan una situación de alerta, considerando que el presente estudio evidenció un proceso de resistencia incipiente al Temefos. Finalmente, basados en los resultados se recomienda plantear y ejecutar estrategias basadas en acciones que permitan preservar la actividad larvicida de este compuesto, evitando el aumento progresivo de resistencia en las poblaciones silvestres.
In Paraguay, the control of Aedes aegypti mosquitoes, involved in the transmission of several arboviruses, implies the use of temephos, an organophosphate that has been used by national vector control programs for more than two decades in search of reducing larval stages. In view of the need to evaluate periodically the larvicidal activity of this chemical compound, this study aimed to monitor the susceptibility profile to temephos of larval stages of Ae. aegypti. For this, an experimental analytical study with bioassays dose rate response was applied, using third instar larva e of the first generation from a mosquitoescolony collected in Ciudad del Este. The larvae were exposed to different concentrations ranges of themephos that were defined by a pre-test. The number of larva e exposed and mortality at the end of each trial were recorded. The results determined the LC50 =0.00966 mg/L and LC90 = 0.03015 mg/L, from which quantitative indicators of resistance were obtained, resistance ratio RR = 2.3734 and 4.1643 respectively. The latter valueindicates characteristics related to low resistance in populations of Ae. aegypti evaluateda ccording to standardized ranges (RR> 3 <5). The results observed in larval wild populations indicate an alert situation, considering that our study showed an incipient process of resistance to temephos. Finally, based on these results, proposing and implementing strategies based in actions that allow to preserve the larvicidal activity of this compound are recommended to avoiding the progressive increase of resistance in wild populations.
Subject(s)
Humans , Mosquito Control , Vector Control of Diseases , Temefos/radiation effects , Public HealthABSTRACT
Introducción: el programa de control de Aedes aegypti (L.) (Diptera: Culicidae) en Cuba utiliza fundamentalmente temefos (ABATE) como larvicida y piretroides como adulticidas, y se ha utilizado, esporádicamente, el organofosforado (OF) clorpirifos. El monitoreo de la resistencia a estos insecticidas es esencial para lograr un control efectivo de esta especie. Objetivo: determinar la resistencia a temefos en larvas y sus mecanismos, y evaluar el nivel de resistencia a los insecticidas más utilizados como adulticidasen cinco áreas de salud del municipio Boyeros, La Habana, colectadas indistintamente en los años 2010-2012. Métodos: se evaluó la resistencia a temefos y la eficacia del mismo, en su formulación comercial (ABATEX G1), en larvas, a través de los bioensayos recomendados por la Organización Mundial de la Salud. Los mecanismos de resistencia se realizaron a través de ensayos bioquímicos. La resistencia en el estado adulto se determinó a través del método de las botellas impregnadas. Resultados: la resistencia a temefos en larvas disminuyó del año 2010 al 2012. El producto comercial de temefos mostró 100 por ciento de mortalidad entre 5 y 12 días. Se demostró que las esterasas y monooxigenasas desempeñaron un papel importante en la resistencia a temefos en larvas. En el estado adulto, se observó resistencia a piretroides y a clorpirifos en algunas cepas. Conclusiones: estos resultados corroboran la necesidad de establecer estrategias de control integrado para preservar la vida útil de los insecticidas disponibles para el control de Ae. aegypti en el municipio Boyeros(AU)
Introduction: the program for control of Aedes aegypti (L.) (Diptera: Culicidae) in Cuba is mainly based on the use of temephos (Abate) as larvicide and pyrethroids as adulticides. Organophosphate (OP) insecticide Chlorpyrifos has also been used on occasion. Monitoring resistance to these insecticides is essential to achieve effective control of the species. Objective: determine temephos resistance in larvae and its mechanisms, and evaluate the level of resistance to the insecticides most commonly used as adulticides in five health areas from the municipality of Boyeros, Havana, surveyed in the years 2010 and 2012. Methods: an evaluation was conducted of resistance to and effectiveness of temephos in its commercial formulation (Abatex G1) in larvae, using tests recommended by the World Health Organization. Resistance mechanisms were assessed with biochemical assays. The impregnated bottle bioassay was used to determine resistance in the adult stage. Results: larval resistance to temephos decreased from 2010 to 2012. The commercial product temephos showed 100 percent mortality between 5 and 12 days. Esterases and monooxygenases were found to play an important role in larval resistance to temephos. Some strains showed resistance to pyrethroids and Chlorpyrifos in the adult stage. Conclusions: these results corroborate the need to set up integrated control strategies to preserve the useful life of the insecticides available to control Aedes aegypti in the municipality of Boyeros(AU)
Subject(s)
Animals , Insecticide Resistance , Aedes , Biological Assay/methods , Vector Control of DiseasesABSTRACT
ABSTRACT After a dengue outbreak, the knowledge on the extent, distribution and mechanisms of insecticide resistance is essential for successful insecticide-based dengue control interventions. Therefore, we evaluated the potential changes to insecticide resistance in natural Aedes aegypti populations to Organophosphates (OP) and Pyrethroids (PY) after chemical vector control interventions. After a Dengue outbreak in 2010, A. aegypti mosquitoes from the urban area of Jacarezinho (Paraná, Brazil) were collected in 2011 and 2012. Insecticide resistance to OP Temephos was assessed in 2011 and 2012 by dose–response bioassays adopting WHO-based protocols. Additionally, in both sampling, PY resistance was also investigated by the Val1016Ile mutation genotyping. In 2011, a random collection of mosquitoes was carried out; while in 2012, the urban area was divided into four regions where mosquitoes were sampled randomly. Bioassays conducted with larvae in 2011 (82 ± 10%; RR95 = 3.6) and 2012 (95 ± 3%; RR95 = 2.5) indicated an incipient altered susceptibility to Temephos. On the other hand, the Val1016IIe mutation analysis in 2011, presented frequencies of the 1016Ilekdr allele equal to 80%. Nevertheless, in 2012, when the urban area of Jacarezinho was analyzed as a single unit, the frequency of the mutant allele was 70%. Additionally, the distribution analysis of the Val1016Ile mutation in 2012 showed the mutant allele frequencies ≥60% in all regions. These outcomes indicated the necessity of developing alternative strategies such as insecticide rotations for delaying the evolution of resistance.
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Introducción. El uso continuo de insecticidas para el control de la transmisión del dengue puede generar una reducción en los niveles de sensibilidad de las poblaciones de los mosquitos vectores. La vigilancia oportuna es necesaria para detectar cualquier problema potencial de resistencia. Objetivo. Determinar el estado de la sensibilidad a insecticidas de uso en salud pública en poblaciones de Aedes aegypti del departamento de Caldas, Colombia, en el 2007 y el 2011. Materiales y métodos. Se realizaron pruebas de sensibilidad a los organofosforados temefós, malatión, fenitrotión y metil-pirimifós y al piretroide deltametrina, siguiendo las metodologías estandarizadas de la Organización Mundial de la Salud y de los Centers for Disease Control and Prevention de los Estados Unidos. Resultados. En el 2007 se encontró resistencia al temefós en dos barrios del municipio de La Dorada, con grados de resistencia de 11,5 y 13,3. Por ello, la Dirección Territorial de Salud de Caldas suspendió el uso de este larvicida en dichos barrios. Cuatro años después, en el 2011, se observó una reducción en los grados de resistencia al temefós, así como resistencia al metil-pirimifós. Todas las poblaciones evaluadas fueron sensibles a los insecticidas deltametrina, malatión y fenitrotión en los dos períodos. Conclusión. La cuantificación de los grados de resistencia en dos períodos permitió evidenciar la reducción de la resistencia al temefós después de suspender su uso. Se recomienda mantener la vigilancia de los niveles de sensibilidad de los insecticidas usados en los programas de control de dengue.
Introduction: Continuous use of insecticides for the control of dengue transmission may lead to decreased susceptibility levels in mosquito vector populations. Timely monitoring is necessary to ensure detection of any potential resistance problems. Objective: To determine the susceptibility status of Aedes aegypti to insecticides used in public health in Caldas, Colombia, during 2007 and 2011. Materials and methods: Susceptibility tests to the organophosphates temephos, malathion, fenitrothion and pirimiphos methyl, as well as to the pyrethroid deltamethrin, were carried out using standard World Health Organization and Centers for Disease Control and Prevention protocols. Results: In 2007, resistance to temephos was detected in Ae. aegypti populations from La Dorada with resistance ratios of 11.5 and 13.3, prompting the Caldas Health Department to suspend the use of this larvicide. A reduction in resistance ratios to temephos was observed in 2011, as well as an apparent resistance to pirimiphos methyl. All Ae. aegypti populations tested were susceptible to deltamethrin, malathion and fenitrothion in both years. Conclusion: Evaluating the resistance ratios during two distinct periods allowed a decrease in resistance to be detected after suspension of the use of temephos. Surveillance of mosquito populations for changes in susceptibility levels to the insecticides used in dengue control programs is therefore recommended.
Subject(s)
Animals , Aedes/drug effects , Insecticides/pharmacology , Colombia , Drug Resistance , Time FactorsABSTRACT
Objective:To investigate the susceptibility to temephos, permethrin and deltamethrin ofAedes aegypti(Ae. aegypti), collected from areas with high incidence of dengue hemorrhagic fever cases inPhitsanulokProvince,Thailand.Methods:TheF1 progenies ofAe. aegypti colony, originated from five sub-districts includingAranyik,HuaRo,NaiMuang,BanKrang andThaPho, were used in the bioassays following the procedures ofWorldHealthOrganization.For larval bioassay, the late third or early fourth-instar larvae were tested with different concentrations of temephos. For adult bioassay, the females were exposed to0.75% permethrin or0.05% deltamethrin.LC50 value and mortality rate were analyzed to compare the insecticide susceptibility of the larvae and the adults in each area, respectively. Results:TheLC50 value of temephos for the larvae from Aranyik,HuaRo,NaiMuang,BanKrang andThaPho sub-districts was0.017,0.017,0.026,0.061, and0.113 ppm, respectively.For permethrin, the highest mortality rate(86.84%) was found in the mosquitoes fromAranyik but the others were more resistant with the lower mortality rates(16.00-42.67%).The adult mortality rates after exposing to deltamethrin were higher(82.34-98.67%) in all areas.Conclusions:Ae. aegypti larvae were still susceptible to temephos.Conversely, most tested adults tended to resist the permethrin and deltamethrin.
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OBJECTIVE@#To investigate the susceptibility to temephos, permethrin and deltamethrin of Aedes aegypti (Ae. aegypti), collected from areas with high incidence of dengue hemorrhagic fever cases in Phitsanulok Province, Thailand.@*METHODS@#The F1 progenies of Ae. aegypti colony, originated from five sub-districts including Aranyik, Hua Ro, Nai Muang, Ban Krang and Tha Pho, were used in the bioassays following the procedures of World Health Organization. For larval bioassay, the late third or early fourth-instar larvae were tested with different concentrations of temephos. For adult bioassay, the females were exposed to 0.75 % permethrin or 0.05% deltamethrin. LC50 value and mortality rate were analyzed to compare the insecticide susceptibility of the larvae and the adults in each area, respectively.@*RESULTS@#The LC50 value of temephos for the larvae from Aranyik, Hua Ro, Nai Muang, Ban Krang and Tha Pho sub-districts was 0.017, 0.017, 0.026, 0.061, and 0.113 ppm, respectively. For permethrin, the highest mortality rate (86.84%) was found in the mosquitoes from Aranyik but the others were more resistant with the lower mortality rates (16.00-42.67%). The adult mortality rates after exposing to deltamethrin were higher (82.34-98.67%) in all areas.@*CONCLUSIONS@#Ae. aegypti larvae were still susceptible to temephos. Conversely, most tested adults tended to resist the permethrin and deltamethrin.
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Objective: To investigate the susceptibility to temephos, permethrin and deltamethrin of Aedes aegypti (. Ae. aegypti), collected from areas with high incidence of dengue hemorrhagic fever cases in Phitsanulok Province, Thailand. Methods: The F1 progenies of Ae. aegypti colony, originated from five sub-districts including Aranyik, Hua Ro, Nai Muang, Ban Krang and Tha Pho, were used in the bioassays following the procedures of World Health Organization. For larval bioassay, the late third or early fourth-instar larvae were tested with different concentrations of temephos. For adult bioassay, the females were exposed to 0.75 % permethrin or 0.05% deltamethrin. LC50 value and mortality rate were analyzed to compare the insecticide susceptibility of the larvae and the adults in each area, respectively. Results: The LC50 value of temephos for the larvae from Aranyik, Hua Ro, Nai Muang, Ban Krang and Tha Pho sub-districts was 0.017, 0.017, 0.026, 0.061, and 0.113 ppm, respectively. For permethrin, the highest mortality rate (86.84%) was found in the mosquitoes from Aranyik but the others were more resistant with the lower mortality rates (16.00-42.67%). The adult mortality rates after exposing to deltamethrin were higher (82.34-98.67%) in all areas. Conclusions: Ae. aegypti larvae were still susceptible to temephos. Conversely, most tested adults tended to resist the permethrin and deltamethrin.
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Introduction The effects of piperonyl butoxide (PBO) on the toxicity of the organophosphate temephos (TE) and the role of esterases in the resistance of Aedes aegypti to this insecticide were evaluated. Methods A. aegypti L4 larvae susceptible and resistant to TE were pre-treated with PBO solutions in acetone at concentrations of 0.125, 0.25, 0.5, 1, and 2% for 24h and subsequently exposed to a diagnostic concentration of 0.02mg/L aqueous TE solution. The esterase activity of the larvae extracts pre-treated with varying PBO concentrations and exposed to TE for three time periods was determined. Results At concentrations of 0.25, 0.5, 1, and 2%, PBO showed a significant synergistic effect with TE toxicity. High levels of esterase activity were associated with the survival of A. aegypti L4 larvae exposed to TE only. Conclusions The results of the biochemical assays suggest that PBO has a significant inhibitory effect on the total esterase activity in A. aegypti larvae. .
Subject(s)
Animals , Aedes/drug effects , Aedes/enzymology , Esterases/physiology , Insecticide Resistance , Pesticide Synergists/pharmacology , Piperonyl Butoxide/pharmacology , Temefos/toxicity , Larva/drug effects , OrganophosphatesABSTRACT
Introducción: el Ministerio de Salud Pública de la ciudad de Guayaquil, Ecuador, ha utilizado, hasta la fecha, temefos (abate) como principal medida química para el control larval de Aedes aegypti, principal vector del dengue en este país.Objetivos: determinar la resistencia a temefos y sus mecanismos bioquímicos en dos cepas Aedes aegypti de Ecuador, así como determinar la eficacia del regulador de crecimiento, pyriproxifeno, como posible alternativa para su control.Métodos: en larvas de Aedes aegypti provenientes de dos localidades (Pascuales y Guayacanes), de la ciudad de Guayaquil, Ecuador, se evaluó la resistencia al insecticida oganofosforado temefos y la eficacia del pyriproxifeno mediante metodologías recomendadas por la Organización Mundial de la Salud. Los mecanismos de resistencia metabólicos se determinaron a través de ensayos bioquímicos y electroforesis en gel de poliacrilamida.Resultados: las larvas de la cepa Pascuales resultaron con moderado nivel de resistencia a temefos y Guayacanes resultó susceptible. A través de ensayos bioquímicos y electroforesis se demostró que el mecanismo de resistencia de acción metabólica, basado en una incrementada actividad de la esterasa-A4, resultó ser responsable de la resistencia detectada a temefos. Las dosis de pyriproxifeno que causaron 50 por ciento de inhibición de la emergencia (IE50) y 95 por ciento (IE95), resultaron muy similares entre las cepas de Ecuador y la cepa de referencia susceptible a insecticidas, Rockefeller.Conclusiones: se demostró que el mecanismo de esterasas, responsable de la resistencia a temefos, está presente en Aedes aegypti de Guayaquil, Ecuador, de ahí la necesidad de monitorear este fenómeno en diferentes regiones del país. El regulador de crecimiento pyriproxifeno resultó muy eficaz, y esto lo convierte en una alternativa a evaluar para el control de poblaciones de Aedes aegypti en Ecuador.
Introduction: the Ministry of Public Health in the city of Guayaquil, Ecuador, has so far used temephos (abate) as the main chemical measure for larval control of Aedes aegypti, the fundamental dengue vector in the country. Objectives: determine temephos resistance and its biochemical mechanisms in two strains of Aedes aegypti in Ecuador, and determine the efficacy of the growth regulator pyriproxyfen as a possible control alternative. Methods: resistance to organophosphorus insecticide temephos and the efficacy of pyriproxyfen were evaluated in Aedes aegypti larvae from two areas (Pascuales and Guayacanes) in the city of Guayaquil, Ecuador, by means of methodologies recommended by the World Health Organization. Metabolic resistance mechanisms were determined by biochemical assays and polyacrylamide gel electrophoresis. Results: larvae from the Pascuales strain showed moderate resistance to temephos, whereas those from the Guayacanes strain were found to be susceptible. Biochemical assays and electrophoresis revealed that the resistance mechanism of metabolic action, based on increased esterase-A4 activity, was responsible for the temephos resistance observed. The doses of pyriproxyfen causing 50 percent emergence inhibition (EI50) and 95 percent (EI95) were very similar between strains from Ecuador and the reference insecticide susceptible strain Rockefeller. Conclusions: it was found that the esterase mechanism, responsible for temephos resistance, is present in Aedes aegypti from Guayaquil, Ecuador. Hence the need to monitor this phenomenon in different regions of the country. The growth regulator pyriproxyfen proved to be very effective, which turns it into an alternative to evaluate for the control of Aedes aegypti populations in Ecuador.
Subject(s)
Aedes/virology , Densovirinae/chemistry , Juvenile Hormones/therapeutic use , Insecticides, Organophosphate/prevention & control , Myiasis/prevention & control , TemefosABSTRACT
Introducción: el uso intensivo del larvicida químico temefos (abate) en Cuba, ha generado el desarrollo de mecanismos de resistencia en Aedes (Stegomyia) aegypti (Linnaeus, 1762). Por esta razón, apremia la necesidad de evaluar otras alternativas de control, como el pyriproxyfeno, inhibidor de crecimiento. Objetivos: determinar la eficacia de pyriproxyfeno como larvicida, pupicida y adulticida en cepas de referencia de Aedes aegypti y establecer su efecto sobre la reproducción. Métodos: para el estudio se utilizó una cepa de Aedes aegypti de referencia susceptible (Rockefeller) y otra resistente (SANtemF13) a temefos. La evaluación de pyriproxyfeno se realizó a través de bioensayos recomendados por la Organización Mundial de la Salud. Se determinó el efecto en la reproducción, midiendo la fecundidad y viabilidad de los huevos (fertilidad) en larvas de la cepa Rockefeller, sobrevivientes a dosis subletales de pyriproxyfeno. Resultados: en Rockefeller, pyriproxyfeno manifestó actividad larvicida en 32 por ciento, pupicida en 21 por ciento y adulticida solo 1 por ciento. En SANtem F13, resultó larvicida en 31 por ciento, pupicida 12 por ciento y adulticida 1 por ciento. El análisis de varianza entre rangos de dosis letales para larvas, pupas y adultos de las cepas referenciales, Rockefeller y SANtem F13, no mostró diferencias significativas (p= 0,000001). El pyriproxyfeno resultó ser un excelente inhibidor de la emergencia de adultos en las cepas de Aedes aegypti estudiadas a concentraciones bajas, inferiores a las recomendadas por la Organización Mundial de la Salud en mosquitos del género Aedes. También tuvo fuerte efecto subletal y afectó la fertilidad de los adultos, en condiciones de laboratorio. Conclusión: el inhibidor de crecimiento pyriproxyfeno representa una buena alternativa a incluir dentro de las estrategias de control integrado de Aedes aegypti en Cuba, sin afectarse su eficacia por la resistencia que esta especie ha...
Introduction: intensive use of chemical larvicide temephos (abate) in Cuba has resulted in the development of resistance mechanisms in Aedes (Stegomyia) aegypti (Linnaeus, 1762). Therefore, there is an urgent need to consider other control alternatives, such as pyriproxyfen, a growth inhibitor. Objectives: determine the efficacy of pyriproxyfen as larvicide, pupicide and adulticide in reference strains of Aedes aegypti and establish its effect on reproduction. Methods: the study was based on a strain of reference Aedes aegypti susceptible to temephos (Rockefeller) and a strain resistant to temephos (SANtemF13). Pyriproxyfen was evaluated with bioassays recommended by the World Health Organization. Determination was made of the effect of pyriproxyfen on reproduction by measuring fecundity and egg viability (fertility) in larvae of the Rockefeller strain surviving sublethal doses of pyriproxyfen. Results: in the Rockefeller strain, pyriproxyfen was larvicidal in 32 percent, pupicidal in 21 percent and adulticidal in a mere 1 percent. In the SANtem F13 strain, it was larvicidal in 31 percent, pupicidal in 12 percent and adulticidal in 1 percent. Analysis of variance between ranges of lethal doses for larvae, pupas and adults of the reference strains Rockefeller and SANtem F13 did not show any significant differences (p= 0.000001). Pyriproxyfen was found to be an excellent inhibitor of adult emergence in the strains of Aedes aegypti studied when used at low concentrations, below those recommended by the World Health Organization for mosquitoes of the genus Aedes. It also showed a strong sublethal effect and affected the fertility of adults in laboratory conditions. Conclusion: growth inhibitor pyriproxyfen is a good alternative to be included among integrated control strategies against Aedes aegypti in Cuba without affecting its efficacy, due to the resistance that this species has developed to larvicide temephos
Subject(s)
Mosquito Control/methods , Densovirinae , Insecticide Resistance/immunologyABSTRACT
Se realizó un estudio experimental en 4 viviendas de la colonia Villa Nueva de Tegucigalpa, en Honduras, a fin de evaluar la efectividad y residualidad del temefos a 1 % (Abate®) en el control de larvas de Aedes aegypti, desde octubre del 2007 hasta abril del 2008. Para ello se llevaron a cabo bioensayos en el campo y en el laboratorio; los de campo se efectuaron en 9 depósitos de agua de uso doméstico, como pilas y barriles, que fueron inspeccionados inicialmente para detectar la presencia de larvas; entonces se aplicó el temefos a los que fueron positivos --acorde con su capacidad en litros--, y se utilizaron como grupo de control los que resultaron negativos. Asimismo, se efectuaron observaciones a las 24 horas de aplicado el tratamiento, y luego semanalmente por más de 4 meses (anotadas en un registro diseñado a los efectos), a fin de comprobar la existencia de larvas y, además, medir los valores de cloro disuelto, el pH y la temperatura del agua. Por su parte, los bioensayos de laboratorio se realizaron con el agua de la pila abatizada, y se determinaron los porcentajes de mortalidad de las larvas a las 24 horas de tratar el líquido. Se evidenció la efectividad del Abate® y una residualidad de más de 100 días, a pesar de la influencia de los factores ambientales, sociales y antropogénicos.
An experimental study was carried out in 4 homes of Villa Nueva community of Tegucigalpa, in Honduras, to evaluate the effectiveness and residual 1% temephos (Abate®) in controlling Aedes aegypti larvae from October 2007 to April 2008. Field and laboratory bioassays were performed; those from the field were made in 9 water tanks for domestic use, such as "pila" and barrels, which were initially inspected for the presence of larvae, so that if they were positive, temephos was applied --according to its capacity in liters--, and if they were negative, then they were used as a control group. Furthermore, observations were made at 24 hours after applying the treatment, and then weekly for about 4 months (which were compiled in a register) in order to check the presence of larvae and measure the values of dissolved chlorine, pH and water temperature. On the other hand, the laboratory bioassays was made in the Abate-treated water from "pila", and the percentages of larvae mortality were determined at 24 hours of treating the liquid. Effectiveness of the Abate® and its residual level of more than 100 days were evidenced, in spite of the influence of environmental, social and anthropogenic factors.
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In Brazil, decades of dengue vector control using organophosphates and pyrethroids have led to dissemination of resistance. Although these insecticides have been employed for decades against Aedes aegypti in the country, knowledge of the impact of temephos resistance on vector viability is limited. We evaluated several fitness parameters in two Brazilian Ae. aegypti populations, both classified as deltamethrin resistant but with distinct resistant ratios (RR) for temephos. The insecticide-susceptible Rockefeller strain was used as an experimental control. The population presenting the higher temephos resistance level, Aparecida de Goiânia, state of Goiás (RR95 of 19.2), exhibited deficiency in the following four parameters: blood meal acceptance, amount of ingested blood, number of eggs and frequency of inseminated females. Mosquitoes from Boa Vista, state of Roraima, the population with lower temephos resistance level (RR95 of 7.4), presented impairment in only two parameters, blood meal acceptance and frequency of inseminated females. These results indicate that the overall fitness handicap was proportional to temephos resistance levels. However, it is unlikely that these disabilities can be attributed solely to temephos resistance, since both populations are also resistant to deltamethrin and harbour the kdr allele, which indicates resistance to pyrethroids. The effects of reduced fitness in resistant populations are discussed.