Contrasting patterns of tolerance between chemical and biological insecticides in mosquitoes exposed to UV-A

• Published in: Aquatic toxicology Vol. 140-141; pp. 389 - 397
• Main Authors: Tetreau, Guillaume, Chandor-Proust, Alexia, Faucon, Frédéric, Stalinski, Renaud, Akhouayri, Idir, Prud’homme, Sophie M., Raveton, Muriel, Reynaud, Stéphane
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.09.2013; Elsevier
• Subjects: Aedes aegypti; Animals; Bacillus thuringiensis; Bacillus thuringiensis subsp. israelensis; Bioassays; Biochemistry, Molecular Biology; breeding; breeding sites; Candidate gene expression; control methods; Culicidae; Culicidae - drug effects; Culicidae - enzymology; Culicidae - genetics; Culicidae - radiation effects; cytochrome P-450; Cytochromes - genetics; Cytochromes - metabolism; DDT (pesticide); dengue; Environmental Sciences; Enzymatic activities; Enzyme Activation - radiation effects; enzyme activity; esterases; fever; Gene Expression Regulation - radiation effects; genes; Genomics; glutathione transferase; human diseases; imidacloprid; insect physiology; Insecticide Resistance - radiation effects; Insecticides - toxicity; Larva - enzymology; Larva - radiation effects; Life Sciences; malaria; mosquito control; permethrin; RT-qPCR; temephos; Ultraviolet; ultraviolet radiation; Ultraviolet Rays; vaccines; vegetation; Aedes aegypti; Ultraviolet; Candidate gene expression; RT-qPCR; Bioassays; Enzymatic activities
• ISSN: 0166-445X; 1879-1514
• DOI: 10.1016/j.aquatox.2013.07.004

•Mosquito tolerance to chemical insecticides is induced by UV-exposure.•Metabolic tolerance to chemicals is linked to susceptibility to a bioinsecticide.•CYP6Z7 and CYP6Z8 are over-expressed in UV-exposed mosquitoes.•Increased detoxification enzyme activities in mosquitoes is induced by UV-exposure. Mosquitoes are vectors of major human diseases, such as malaria, dengue or yellow fever. Because no efficient treatments or vaccines are available for most of these diseases, control measures rely mainly on reducing mosquito populations by the use of insecticides. Numerous biotic and abiotic factors are known to modulate the efficacy of insecticides used in mosquito control. Mosquito breeding sites vary from opened to high vegetation covered areas leading to a large ultraviolet gradient exposure. This ecological feature may affect the general physiology of the insect, including the resistance status against insecticides. In the context of their contrasted breeding sites, we assessed the impact of low-energetic ultraviolet exposure on mosquito sensitivity to biological and chemical insecticides. We show that several mosquito detoxification enzyme activities (cytochrome P450, glutathione S-transferases, esterases) were increased upon low-energy UV-A exposure. Additionally, five specific genes encoding detoxification enzymes (CYP6BB2, CYP6Z7, CYP6Z8, GSTD4, and GSTE2) previously shown to be involved in resistance to chemical insecticides were found over-transcribed in UV-A exposed mosquitoes, revealed by RT-qPCR experiments. More importantly, toxicological bioassays revealed that UV-exposed mosquitoes were more tolerant to four main chemical insecticide classes (DDT, imidacloprid, permethrin, temephos), whereas the bioinsecticide Bacillus thuringiensis subsp. israelensis (Bti) appeared more toxic. The present article provides the first experimental evidence of the capacity of low-energy UV-A to increase mosquito tolerance to major chemical insecticides. This is also the first time that a metabolic resistance to chemical insecticides is linked to a higher susceptibility to a bioinsecticide. These results support the use of Bti as an efficient alternative to chemical insecticides when a metabolic resistance to chemicals has been developed by mosquitoes.