Laboratory selection of Aedes aegypti field populations with the organophosphate malathion: Negative impacts on resistance to deltamethrin and to the organophosphate temephos

Abstract

BackgroundResistance 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 findingsWe 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/SignificanceOur 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.

Resistance to temephos and deltamethrin in Aedes aegypti from Brazil between 1985 and 2017

“…19 , 20 , 21 For academic purposes, this same criterion has also been used to classify the resistance status of vector populations to deltamethrin. 13 , 22 …”

Evaluation of resistance to pyrethroid and organophosphate adulticides and kdr genotyping in Aedes aegypti populations from Roraima, the Northernmost Brazilian State

“…Lineages of Ae. aegypti Brazilian populations that acquired resistance to malathion through selection pressure in the laboratory exhibited increased activity of GST, multi-function Oxidases (MFO P450) and Esterases, as determined by biochemical analyses [20]. Over expression of genes related to metabolic resistance was detected in Ae.…”

Survei Entomologi, Kerentanan Aedes aegypti terhadap Insektisida Organofosfat, dan Identifikasi Gen VGSC di Dusun Malangrejo, Sleman, Yogyakarta

“…9 Resistensi yang terjadi dapat dipengaruhi oleh beberapa faktor di antaranya adalah faktor lama penggunaan insektisida dan dosis yang tidak tepat serta penggunaan insektisida sejenis atau memiliki aktivitas yang sama secara terusmenerus. 25 Berdasarkan hal tersebut perlu dilakukannya rotasi terhadap penggunaan insektisida yang memiliki jenis serta cara kerja yang sama. 26 Insektisida piretroid merupakan salah satu insektisida yang paling banyak digunakan oleh masyarakat karena kemudahannya dalam aplikasi.…”

“…30 Resistensi terhadap insektisida piretroid dapat terjadi jika paparan terhadap insektisida dilakukan dalam jangka panjang lebih dari 5 generasi. 25,31 Hasil penelitian ini menunjukkan bahwa populasi nyamuk uji dari dusun endemik DBD Sleman telah menunjukkan adanya indikasi resistensi pada dua golongan isektisida, yaitu malation dan piretroid, sehingga penggunaan insektisida tersebut haruslah bijaksana. Upaya yang dapat dilakukan untuk mengendalikan resistensi adalah dengan rotasi insektisida organofosfat dengan insektisida jenis lain dan tentunya monitoring penggunaan insektisida.…”