RESUMEN
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 METHODS: Data were gathered from two sources: a bibliographic review of studies published from 1985 to 2017, and unpublished data produced by our team within the MoReNAa between 1998 and 2012.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.
Asunto(s)
Aedes/efectos de los fármacos , Dengue/prevención & control , Resistencia a los Insecticidas/efectos de los fármacos , Insecticidas/farmacología , Mosquitos Vectores/efectos de los fármacos , Nitrilos/farmacología , Piretrinas/farmacología , Temefós/farmacología , Animales , Bioensayo , Brasil/epidemiología , Dengue/epidemiología , Dengue/transmisión , Incidencia , Insecticidas/administración & dosificación , Nitrilos/administración & dosificación , Piretrinas/administración & dosificación , Temefós/administración & dosificaciónRESUMEN
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.
Asunto(s)
Humanos , Resistencia a los Insecticidas/inmunología , Temefós/análisis , Aedes , Control de Vectores de las Enfermedades , Brasil/epidemiologíaRESUMEN
BACKGROUND: Resistance to pyrethroids and to the organophosphate temephos is widespread in Brazilian populations of the dengue vector, Aedes aegypti. Thereof, since 2009 Insect Growth Regulators are employed as larvicides, and malathion is used against adults. METHODOLOGY/PRINCIPAL FINDINGS: We performed laboratory selection with malathion of two A. aegypti field populations initially susceptible to this organophosphate but resistant to temephos and deltamethrin. A fixed malathion dose inducing at least 80% mortality in the first generation, was used throughout the selection process, interrupted after five generations, when the threshold of 20% mortality was reached. For each population, three experimental and two control groups, not exposed to insecticides, were kept independently. For both populations, quantitative bioassays revealed, in the selected groups, acquisition of resistance to malathion and negative impact of malathion selection on deltamethrin and temephos resistance levels. In the control groups resistance to all evaluated insecticides decreased except, unexpectedly, to deltamethrin. Analysis of the main resistance mechanisms employed routine methodologies: biochemical and molecular assays for, respectively, metabolic resistance and quantification of the NaV pyrethroid target main kdr mutations at positions 1016 and 1534. No diagnostic alteration could be specifically correlated with malathion selection, neither with the unusual deltamethrin increase in resistance levels observed in the control groups. CONCLUSIONS/SIGNIFICANCE: Our results confirm the multifactorial character of insecticide resistance and point to the need of high throughput methodologies and to the study of additional field vector populations in order to unravel resistance mechanisms.
Asunto(s)
Aedes/efectos de los fármacos , Resistencia a los Insecticidas , Malatión/farmacología , Nitrilos/farmacología , Piretrinas/farmacología , Temefós/farmacología , Animales , Bioensayo , Insecticidas/farmacologíaRESUMEN
Insecticides are still largely applied in public health to control disease vectors. In Brazil, organophosphates (OP) and pyrethroids (PY) are used against Aedes aegypti for years. Since 2009 Insect Growth Regulators (IGR) are also employed in the control of larvae. We quantified resistance to temephos (OP), deltamethrin (PY), and diflubenzuron (IGR) of A. aegypti samples from 12 municipalities distributed throughout the country, collected between 2010 and 2012. High levels of resistance to neurotoxic insecticides were detected in almost all populations: RR95 to temephos varied between 4.0 and 27.1; the lowest RR95 to deltamethrin was 13.1, and values higher than 70.0 were found. In contrast, all samples were susceptible to diflubenzuron (RR95 < 2.3). Biochemical tests performed with larvae and adults discarded the participation of acetylcholinesterase, the OP target, and confirmed involvement of the detoxifying enzymes esterases, mixed function oxidases, and glutathione-S-transferases. The results obtained were discussed taking into account the public chemical control component and the increase in the domestic use of insecticides during dengue epidemic seasons in the evaluated municipalities.
Asunto(s)
Aedes/efectos de los fármacos , Aedes/fisiología , Diflubenzurón/farmacología , Resistencia a los Insecticidas/fisiología , Insecticidas/farmacología , Nitrilos/farmacología , Piretrinas/farmacología , Acetilcolinesterasa/metabolismo , Aedes/metabolismo , Animales , Brasil , Vectores de Enfermedades , Femenino , Glutatión Transferasa/metabolismo , Larva/efectos de los fármacos , Larva/fisiología , Masculino , Oxidorreductasas/metabolismo , Salud Pública , Temefós/farmacologíaRESUMEN
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 alpha-Esterase (EST) and beta-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 alpha-EST and beta-EST, only one enzyme class was altered in each mosquito specimen. Data are discussed in the context of historic application of insecticides in Brazil.