Revealing the rise of resistance: spatial and seasonal resistance to commonly used insecticides in Aedes aegypti among four cities in southern Ecuador

Authors: Sadie Ryan*, University of Florida, Stephanie Jane Mundis, University of Florida, Alex Aguirre, Center for Research on Health in Latin America (CISeAL), Pontificia Universidad Católica del Ecuador, Quito, Catherine Anne Lippi, University of Florida, Efrain Beltran, Universidad Tecnica de Machala, Froilan Heras, Universidad Tecnica de Machala, Anna Maria Stewart-Ibarra, Institute for Global Health and Translational Science, SUNY Upstate Medical University, Marco Neira, Center for Research on Health in Latin America (CISeAL), Pontificia Universidad Católica del Ecuador, Quito
Topics: Medical and Health Geography, Latin America, Quantitative Methods
Keywords: Ecuador, vector-borne disease, mesoscale, insecticide resistance
Session Type: Paper
Day: 4/5/2019
Start / End Time: 9:55 AM / 11:35 AM
Room: Marshall South, Marriott, Mezzanine Level
Presentation File: No File Uploaded

El Oro province, Ecuador on the Peruvian border, contains the port city of Machala, a binational hospital in the border city of Huaquillas, and is an essential location for monitoring emergence and persistence of arboviruses. Aedes aegypti is the main vector of resurging diseases across the Americas such as yellow fever and dengue, and recently emerging chikungunya and Zika viruses, which caused unprecedented epidemics in the region. Vector control remains the primary public health intervention for Aedes transmitted diseases, so insecticide resistance (IR) can undermine these efforts. Yet in many high-risk regions like southern Ecuador, we have limited information on IR in Ae. aegypti. We measured IR status in Ae. aegypti across four cities in El Oro, using phenotypic assays and genetic screening. We found significant inter-seasonal variation in resistance to deltamethrin and alpha-cypermethrin, pyrethroid insecticides used by the Ministry of Health, and differences in deltamethrin resistance between cities. Phenotypic responses to the organophosphate Malathion also differed between two cities. Genotyping showed moderate to high frequencies of resistance alleles in all four cites, which varied between cities in the first sampling season, not in the later seasons, suggesting a selective response to vector control. IR levels were highest in Machala, where dengue is hyperendemic and insecticide use has historically been highest. This is an initial examination of the genotypic and phenotypic indicators of IR in this region. It revealed meso-scale spatiotemporal variability in IR in southern Ecuador, which has complex implications for vector control interventions by the public health sector.

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