To tackle the problem of insecticide resistance, all resistance mechanisms need to be studied. This study investigated the involvement of the cuticle in pyrethroid resistance in a strain of Anopheles gambiae, MRS, free of kdr mutations. Bioassays revealed MRS to be resistant to pyrethroids and DDT, indicated by increasing knockdown times and resistance ratios. Moreover, biochemical analysis indicated that metabolic resistance based on enhanced CYP450 activity may also play a role. Insecticide penetration assays showed that there were significantly lower amounts of insecticide in the MRS strain than in the susceptible control. Analysis of the levels of the selected transcripts by qPCR showed that CYP6M2, a major pyrethroid metaboliser, CYP4G16, a gene implicated in resistance via its contribution to the biosynthesis of elevated epicuticular hydrocarbons that delay insecticide uptake, and the cuticle genes CPAP3-E and CPLCX1 were upregulated after insecticide exposure. Other metabolic (CYP6P3, GSTe2) and cuticle (CPLCG3, CPRs) genes were also constitutively upregulated. Microscopic analysis showed that the cuticle layers of the MRS strain were significantly thicker than those of the susceptible strain. This study allowed us to assess the contribution made by the cuticle and metabolic mechanisms to pyrethroid resistance in Anopheles gambiae without target-site mutations.

Urban Aedes mosquitoes are vectors of many viruses affecting human health such as dengue, chikungunya and Zika viruses. Insecticide resistance and environmental toxicity risks hamper the effectiveness of chemical control against these mosquito vectors. Alternative control methods, such as the use of mosquito-specific entomopathogenic viruses should be explored. Numerous studies have focused on evaluating the potential of different densoviruses species as biological control agents. However, knowledge on the extent of inter- and intra-specific variations in the susceptibility of Aedes mosquitoes to infection by different densoviruses remains insufficient. In this study, we compared infection and mortality rates induced by the Aedes albopictus densovirus 2 in different strains of Aedes albopictus and Aedes aegypti mosquitoes. The two Aedes species were different in terms of susceptibility to viral infection. Under laboratory conditions, Aedes albopictus densovirus 2 appeared more virulent for the different strains of Aedes aegypti tested than for those of Aedes albopictus. In addition, we also found significant intra-specific variation in infection and mortality rates. Thus, although even if Aedes albopictus densoviruses could be powerful biocontrol agents used in the management of urban Aedes populations, our results also call into question the use of single viral isolate as biocontrol agents.

Based on their resistance against excessive proteolysis, Cry2Aa δ-endotoxins, produced in the presence of P20, could be considered as a successful control agent for E. kuehniella and an effective alternative for mosquito control, implying its possible exploitation in pest management programmes. © 2016 Society of Chemical Industry.

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Bacillus thuringiensis (Bt) is a Gram-positive soil bacterium that has been recognized as an effective bioinsecticide active against plant, animal and human pathogenic and disease vector insects. During its sporulation phase, Bt produces crystals consisting of δ-endotoxins, which upon ingestion kill specifically insect larvae. Bt subsp. israelensis (Bti) is very active against dipteran insects. Bti based bioinsecticides are considered as a sustainable solution to control the Dipteran insects responsible of plant, animal and human diseases. In this study, Bti strains isolated from Qatar soil were analyzed for their insecticidal activities against the dipteran insect Aedes aegypti Bora Bora (Culicidae, Diptera) and for their δ-endotoxins yields per cell. Among the local Bti strains, four exceptional strains producing spherical crystals, were found to be more insecticidal than the reference strain Bti H14. When tested for their δ-endotoxin yield, the Bti QBT217 strain, producing typical spherical crystals and having the best insecticidal activity, was recognized as the best candidate strain for potential bioinsecticide production and biological control of dipteran insects, particularly the disease vector insect A. aegypti.

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17Urban Aedes mosquitoes are vectors of many viruses affecting human health such as Dengue, 18 Chikungunya and Zika viruses. Insecticide resistance and environmental toxicity risks hamper 19 the effectiveness of chemical control against these mosquito vectors. Alternative control 20 methods, such as the use of mosquito-specific entomopathogenic viruses should be explored. 21 Numerous studies have focused on evaluating the potential of different densoviruses species 22 as biological control agent. However, knowledge on the extent of inter-and intra-specific 23 variations in the susceptibility of Aedes mosquitoes to infection by different densoviruses 24 2 remains insufficient. In this study, we compared infection and mortality rates induced by the 25 Aedes albopictus densovirus 2 in different strains of Aedes albopictus and Aedes aegypti 26 mosquitoes. The two Aedes species were different in terms of susceptibility to viral infection. 27Under laboratory conditions, Aedes albopictus densovirus 2 appeared more virulent for the 28 different strains of Aedes aegypti tested than for those of Aedes albopictus. In addition, we 29 also found significant intra-specific variation in infection and mortality rates. Thus, although 30 even if Aedes albopictus densoviruses could be powerful biocontrol agents used in the 31 management of urban Aedes populations, our results also call into question the use of single 32 viral isolate as biocontrol agents. 33 34 42 through spatial treatments using pyrethroid-based chemical insecticides and by controlling 43 larvae through physical suppression of breeding sites or larvicides. The application of 44 insecticides can be problematic because of their high environmental and human health 45 toxicity 3-6 , their general toxicity to non-target insects 7 , and the insecticide resistance of target 46 mosquitoes 8,9 . Pyrethroids are the most widely used chemical insecticides in the world but 47 their intensive use has led to the selection of pyrethroid resistant mosquitoes worldwide 10-12 . 48 Many innovative approaches are being developed to control Aedes sp. mosquitoes such as 49 3 adult traps, lethal ovitraps, autodissemination stations, Release of insects with dominant 50 lethality (Ridl), Sterile Insect Technique, Incompatible Insect Technique 13 but larval control 51 remains essential and is systematically includes in any integrated control strategy. The control 52 of urban Aedes larvae is extremely complex to implement because of the diversity and 53 multitude of larval habitats, which are made up of small, and usually cryptic, water 54 containers 14 . Apart from chemical larvicides (e.g. temephos, pyriproxyfen, diflubenzuron), the 55 biological larvicide recommended against urban Aedes larvae is derived from Bacillus 56 thuringiensis subsp. israelensis (Bti), a natural soil bacteria selected for its exclusive 57 pathogenic action on some species of Diptera 15 . However, its effectiveness is limited by many 58 biological and environmental factors: sunlight, amount of organic ...