Insecticide resistance in Aedes aegypti populations from Ceará, Brazil

Abstract

BackgroundOrganophosphates and pyrethroids are used widely in Brazil to control Aedes aegypti, the main vector of dengue viruses, under the auspices of the National Programme for Dengue Control. Resistance to these insecticides is widespread throughout Brazil. In Ceará the vector is present in 98% of districts and resistance to temephos has been reported previously. Here we measure resistance to temephos and the pyrethroid cypermethrin in three populations from Ceará and use biochemical and molecular assays to characterise resistance mechanisms.ResultsResistance to temephos varied widely across the three studied populations, with resistance ratios (RR95) of 7.2, 30 and 192.7 in Juazeiro do Norte, Barbalha and Crato respectively. The high levels of resistance detected in Barbalha and Crato (RR95 ≥ 30) imply a reduction of temephos efficacy, and indeed in simulated field tests reduced effectiveness was observed for the Barbalha population. Two populations (Crato and Barbalha) were also resistant to cypermethrin, whilst Juazeiro do Norte showed only an altered susceptibility. The Ile1011Met kdr mutation was detected in all three populations and Val1016Ile in Crato and Juazeiro do Norte. 1011Met was significantly associated with resistance to cypermethrin in the Crato population. Biochemical tests showed that only the activity of esterases and GSTs, among the tested detoxification enzymes, was altered in these populations when compared with the Rockefeller strain.ConclusionsOur results demonstrate that two A. aegypti populations from Ceará are under strong selection pressure by temephos, compromising the field effectiveness of this organophosphate. Our results also provide evidence that the process of reducing resistance to this larvicide in the field is difficult and slow and may require more than seven years for reversal. In addition, we show resistance to cypermethrin in two of the three populations studied, and for the first time the presence of the allele 1016Ile in mosquito populations from northeastern Brazil. A significant association between 1011Met and resistance was observed in one of the populations. Target-site mechanisms seem not to be implicated in temephos resistance, reinforcing the idea that for the studied populations, detoxification enzymes most likely play a major role in the resistance to this insecticide.

Insecticide resistance and genetic variability in natural populations of Aedes (Stegomyia) aegypti (Diptera: Culicidae) from Colombia

“…However, long-term use of this insecticide has caused the emergence of resistance in several Latin American countries (RODRÍGUEZ et al 2007, LIMA et al 2011, BISSET et al 2013). Colombia's participation in the continental vector control campaign led by OPS (SANTACOLOMA et al 2010), and several dengue outbreaks in 1970 and in 1980 in most Colombian regions (BOSHELL et al…”

Evaluación de la susceptibilidad a insecticidas en poblaciones de Aedes aegypti (Diptera: Culicidae) del departamento de Caldas, Colombia, en los años 2007 y 2011

“…aegypti y el insecticida temefós, Melo-Santos, et al, (40) obtuvieron en Brasil una reversión de la resistencia a este organofosforado en experimentos llevados a cabo en el laboratorio con una cepa de campo resistente para evaluar tres escenarios diferentes en cuanto a la intensidad de la presión con temefós y al ingreso de individuos sensibles, y en todos ellos encontraron reversión de la resistencia, lo que demuestra que es posible recuperar la sensibilidad al temefós. En una población de Brasil (Juazeiro do Norte) se observó una disminución de los grados de resistencia, que pasaron de 10,2 a 7,2 después de la suspensión del uso de este organofosforado y su sustitución por Bacillus thuringiensis israelensis (41). Tales observaciones, así como los resultados de este trabajo, indican que es posible recuperar la sensibilidad al temefós, por lo cual es muy importante continuar la vigilancia del estado de la sensibilidad de las poblaciones de mosquitos a lo largo del tiempo, no solo con la dosis diagnóstica, sino estimando los grados de resistencia, lo cual permite cuantificar los niveles de resistencia y vigilar los cambios generados ya sea por el incremento o la disminución de la presión ejercida por el uso de los insecticidas (35).…”

Development of Nematophagous Fungi on Dead Adults of Aedes aegypti (Diptera: Culicidae) and Molt Inhibition Experimental

“…However, there is a growing concern about the use of chemicals insecticides in relation to selection of Aedes spp. populations resistant to the same (Dusfour et al, 2011;Lima et al, 2011;Prophiro et al, 2011;Tikar, Kumar, Prasad & Prakash, 2009). Several studies have been performed encompassing the biological control with entomopathogenic fungi in an attempt to develop alternative methods to chemical control of A. aegypti (Kay & Vu, 2005;Leles et al, 2010;Leles & D`Alesandro, 2011;Luz et al, 2007Luz et al, , 2008Scholte, Takke & Knols, 2007;Silva et al, 2004).…”