ABSTRACT
BACKGROUND The longstanding application of insecticides for vector control without periodic monitoring of the population response to these chemicals can directly drive the selection of resistant populations of vector mosquitoes. Tocantins is the newest state of the Brazilian Federation. Despite a historically high number of dengue cases, studies and monitoring data concerning insecticide resistance in the state are lacking. OBJECTIVES To verify the resistance status of Aedes aegypti from 10 populations distributed throughout the state connected by rivers and roads. METHODS Between 50 and 150 ovitraps were installed in house gardens within each municipality. Collection points were established based on the importance of the towns and on geographic aspects. Dose response bioassays were performed in accordance with World Health Organization guidelines. Molecular assays were conducted to detect kdr mutations, which are related to pyrethroid resistance. FINDINGS Of the 3,200 ovitrap paddles analysed, 25.8% contained eggs, with a total of 55,687 eggs collected. With the exception of Caseara, all evaluated populations were considered to be resistant to temephos. The data showed different levels of resistance to deltamethrin among the samples. Caseara and Guaraí showed the lowest RR95 values. On average, the NaVR1 kdr allele was most frequent (40.3%), followed by NaVS (38.1%), and NaVR2 (21.6%). Palmas, the capital of the state, had the highest frequency of kdr alleles (87.5%). MAIN CONCLUSIONS With the exception of Palmas, the towns with the highest indexes (ovitrap positivity, number and density of eggs), as well with high levels of resistance and kdr alleles were located along the BR-153 road, indicating that the flow of people and cargo can contribute to the dispersion of the vector and potentially resistance. This study contributes substantially to knowledge regarding the insecticide resistance profile of Tocantins mosquito populations; the data generated via the study could facilitate the judicious use of insecticides by vector control programs.
Subject(s)
Humans , Arboviruses , Drug Resistance, Multiple , Amazonian EcosystemABSTRACT
No Brasil, diversas populações de Aedes aegypti são resistentes aos inseticidas mais utilizados, como o organofosforado temephos e o piretróide deltametrina. [...] O objetivo deste trabalho foi de avaliar a eficácia despinosad em laboratório e em simulado de campo, bem como o efeito deste inseticida sobrepopulações brasileiras de Ae. aegypti após pressão de seleção. Em laboratório, após padronização de ensaio tipo dose-resposta, foram avaliados: (i) a eficácia do spinosad sobre sete populações brasileiras de Ae. aegypti com diferentes níveis de resistência aos inseticidas temephos e deltametrina através de ensaio tipo dose resposta; (ii) efeito da pressão de seleção com CL80 de spinosad por seis gerações sobre parâmentros biológicos(longevidade, repasto sanguíneo, proporção entre machos e fêmeas, cópula e oviposição),de populações de campo e da linhagem Rockefeller...
In Brazil, several populations of Aedes aegypti are resistant to commonly used insecticidessuch as the pyrethroid deltamethrin and the organophosphate temephos. [...] The objectives of this study were to evaluate the efficacy of spinosad in laboratory and simulatedfield and the effect of this insecticide on Brazilian populations of Ae. aegypti after selectionpressure. In the laboratory, after standardization of dose-response assay, we evaluated (i)the efficacy of spinosad on seven populations with different levels of resistance to temephosand deltamethrin insecticides, and (ii) the effect of selection pressure with CL80 of spinosadon biological parameter settings (longevity, blood ingestion, ratio of males and females,copulation and oviposition) after six generations for two field populations and Rockefellerstrain...