Susceptibility of Aedes aegypti populations to pyriproxyfen in the Federal District of Brazil

Abstract INTRODUCTION: In Brasilia, pyriproxyfen (PPF; 0.01 mg/L) has been used for the larval control of Aedes aegypti mosquitoes since 2016. Information on the susceptibility of Ae. aegypti to PPF, and the development of resistance in populations from the Federal District of Brazil (FD) is limited. It is essential to monitor the susceptibility of Ae. aegypti to insecticides in order to improve vector control strategies. This study aimed to evaluate the susceptibility of Ae. aegypti populations from five areas of Brasilia to PPF. METHODS: We performed dose-response tests to estimate the emergence inhibition and resistance ratio of each field population, including the Rockefeller reference population. We also analyzed egg positivity, and the density and mortality of larvae and pupae. RESULTS: Populations from Vila Planalto (RR50=1.7), Regiment Guards Cavalry (RR50=2.5), and Sub-secretary of Justice Complex (RR50=3.7) presented high susceptibility to PPF, while the RR values of populations from Lago Norte (RR50=7.7) and Varjão (RR50=5.9) were moderately high, suggesting the emergence of insipient resistance to PPF in Brasilia. At 30 ng/mL, the highest larvae mortality rate was 2.7% for the population from Lago Norte, while that of pupae was 92.1% for Varjão and Vila Planalto. CONCLUSIONS: The five populations of Ae. aegypti from the FD are susceptible to PPF and there is a need to monitor the susceptibility of Ae. aegypti in new areas of the FD.

Bloodsucking insects in rural áreas adjacent to the Corumbá IV hydroelectric dam reservoir, Santo Antônio do Descoberto, Goiás, Brazil

Eutrophic reservoirs of hydroelectric dams may favor the proliferation of macrophytes andbloodsucking insects. Currently, macrophyte overgrowth has been observed in some stretches ofthe Corumbá IV hydroelectric dam (CIV) reservoir. The occurrence of bloodsucking insects wasanalyzed in rural areas adjacent to the CIV reservoir. In two periods (March and July/August) tenhouses in the area with increased macrophyte proliferation (AG) and ten others in the area with lowmacrophyte proliferation (AP) were selected and sampled. Additionally, 100 macrophytes fromeach area were analyzed. A total of 35,788 insects were captured in light traps and 28 percent of thembelonged to families of bloodsucking insects, especially Culicidae. The occurrence of culicids wasdifferent between the AG and AP areas (p<0.05). Mosquitoes were more frequent and abundant inthe AG area. The larval survey showed that 100 percent of the houses visited had potential for mosquitobreeding. Overall, 302 mosquito larvae were collected among macrophytes, mainly in the AG area.It is concluded that there is a higher frequency of mosquitoes in areas with increased macrophyteproliferation, but the CIV reservoir is not the only breeding source of mosquitoes in the studied areas.

Reservatórios de usinas hidrelétricas, quando eutrofizados, podem favorecer a proliferação demacrófitas e insetos hematófagos. Nos últimos anos, tem sido observado um crescimento excessivode macrófitas em alguns trechos do reservatório da hidrelétrica Corumbá IV (CIV). O estudoobjetivou analisar a ocorrência de insetos hematófagos em áreas rurais adjacentes ao reservatório daCIV. Foram selecionadas dez casas em área com grande proliferação de macrófitas (AG) e outras dezem área com baixa proliferação de macrófitas (AP), que foram amostradas em dois períodos (marçoe julho/agosto). Adicionalmente, analisaram-se 100 macrófitas em cada área. Foram capturados35.788 insetos nas armadilhas luminosas e 28 por cento deles pertenciam a famílias de insetos hematófagos,especialmente Culicidae. A ocorrência de culicídeos foi diferente entre as áreas AG e AP (p<0,05),uma vez que estes foram mais frequentes e abundantes na área AG. A pesquisa larvária mostrou que100 por cento das casas visitadas apresentaram potenciais criadouros de mosquitos. No total, 302 larvas demosquitos foram coletadas nas macrófitas, sobretudo na área AG. Pode-se concluir que há maiorfrequência de culicídeos nas áreas com maior proliferação de macrófitas, porém o reservatório CIVnão é o único criadouro de mosquitos nas áreas estudadas.