Lethal and behavioural effects of three synthetic repellents (DEET, IR3535 and KBR 3023) on Aedes aegypti mosquitoes in laboratory assays

Abstract

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.

Insecticidal, acaricidal and repellent effects of DEET- and IR3535-impregnated bed nets using a novel long-lasting polymer-coating technique

“…These findings correspond with the results reported by Licciardi et al (2006) demonstrating that DEET and IR3535 both had significant effects against A. aegypti but DEET exhibited a higher knockdown effect and mortality than IR3535. This study also demonstrated that another synthetic skin repellent, KBR3023, also known as Icaridin, caused no obvious toxicological effects, and a lack of mosquito take-off behaviour was detected suggesting that this substance does not "repel" insects as defined by negative chemotaxis, thus making DEET and IR3535 the best candidates for future fabric impregnation aiming at arthropod bite protection which were, therefore, further tested in our study.…”

“…The latter resulted in 100% repellency for 8 h, partially preserved even after exposure to air for 48 h (Fei and Xin 2007). Lethal and behavioural effects of the skin repellents DEET, IR3535 and KBR 3023 have been documented against Aedes aegypti mosquitoes by using filter paper tests freely releasing their natural vapour characteristics (Licciardi et al 2006;Pridgeon et al 2009). Obviously, these skin repellents toxicologically do not behave like a single class of compounds with a common mode of action; DEET exhibits a more complex mode of action than the other compounds.…”

“…Obviously, these skin repellents toxicologically do not behave like a single class of compounds with a common mode of action; DEET exhibits a more complex mode of action than the other compounds. Their physiological and molecular mechanisms of action remain unknown, but differ from pyrethroids and may potentially overcome protective shortages basing on pyrethroid resistance mechanisms (Licciardi et al 2006). In addition, Pennetier et al (2005) demonstrated a high level of synergy between DEET and propoxur (a carbamate insecticide) in terms of knockdown effect and mortality against susceptible and pyrethroid-resistant A. aegypti mosquitoes.…”

Repellent activity of DEET against Amblyomma cajennense (Acari: Ixodidae) nymphs submitted to different laboratory bioassays

“…The neurotoxic effects such as locomotor alterations and death after exposure to DEET were described for other arthropods (LICCIARDI et al, 2006), but as far as we know, they are reported for ticks for the first time. Salafsky et al (2000) observed high mortality of A. americanum and D. variabilis when exposed to LIPODEET, a long-lasting action formulation of DEET, but it was not proved for DEET.…”

Evolution, Current Status and Prospects of Phyto-Repellents against Mosquitoes

“…Activation of TRPA1 gene has been reported as eliciting aversive response [98]. Attenuation or masking of the perception to host odorants by the antennal sensors is an alternative mechanism reported for the repellent activity of picaridin in different vector mosquitoes like Aedes spp., C. quinquefasciatus, and A. minimus [99,100]. …”