Lethal and behavioural effects of three synthetic repellents (DEET, IR3535 and KBR 3023) on Aedes aegypti mosquitoes in laboratory assays.
The knock-down, mortality and 'irritancy' effects of three synthetic repellents (DEET, IR3535 and KBR 3023) on Aedes aegypti (L) (Diptera: Culicidae) were evaluated in the laboratory in the absence of animal bait. Filter paper tests were carried out to assess the knock-down effect (KDt(50) and KDt(95)) and mortality (LC(50) and LC(95)) induced by each repellent. 'Irritancy' tests were carried out to compare the flight response (time to first take-off, or FT) to increasing concentrations of repellents (2-7%) and at five distances from the treated surface (0-40 mm). DEET had an insecticidal effect (KDt(50) = 9.7 min at 7%; CL(50)= 1165 mg/m(2)), whereas IR3535 and KBR 3023 did not. Relative to an untreated control, IR3535 was an irritant (relative irritancy or RI > 1) at doses of 5% and 7% (RI = 17.7 and 9.9, respectively), whereas DEET was an irritant at lower concentrations (RI = 12.3 at 2% DEET). KBR 3023 was the weakest irritant over the same range of concentrations (RI(max) = 3.6 at 6%). DEET was more of an irritant (RI(20) = 9.4) than IR3535 (RI(20) = 2.9) over a range of distances (0-20 mm), and KBR 3023 was not an irritant unless mosquitoes made contact with the treated surface. All three repellents had a significant effect on mosquitoes, but DEET exhibited a more complex mode of action than the others due to its insecticidal properties. The repellents do not behave as a single class of compounds with a common mode of action, but most probably affect different physiological systems in insects. The physiological and molecular mechanisms of repellents, especially DEET, should be investigated to ensure a better use of these molecules for skin applications and/or for treating materials against mosquitoes.
Licciardi
S
S
Institut de Recherche pour le Développement, Montpellier, France.
Herve
J P
JP
Darriet
F
F
Hougard
J-M
JM
Corbel
V
V
D000330:Aedes / Q000187:drug effects*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D003671:DEET / Q000494:pharmacology*; D007302:Insect Repellents / Q000494:pharmacology; D007928:Lethal Dose 50; D010880:Piperidines / Q000494:pharmacology*; D011422:Propionates / Q000494:pharmacology*
D007302:Insect Repellents; D010880:Piperidines; D011422:Propionates; D003671:DEET; C462400:ethyl-3-(N-n-butyl-N-acetyl)aminopropionate; C483506:picaridin