Effects of Physiological Conditioning on Behavioral Avoidance by Using a Single Age Group of Aedes aegypti Exposed to Deltamethrin and DDT

Abstract

The behavioral and physiological responses of 6-d-old Aedes aegypti (L.) adult females exposed to deltamethrin and DDT were characterized using a free-choice excito-repellency test system. Excluding varying pretest age and carbohydrate availability as possible confounders, insecticide contact (measuring irritancy) and noncontact (measuring repellency) behavioral assays were conducted on two nonbloodfed groups, either unmated or mated (nulliparous), and two blood-fed groups, either parous or newly full-engorged mosquitoes. The degree of escape response to deltamethrin and DDT varied according to the physiological conditioning. Escape rates from contact and noncontact chambers with deltamethrin were more conspicuous in nonbloodfed groups compared with mosquitoes previously bloodfed. There were no significant differences in escape responses between unmated and nulliparous test populations. With DDT, a more pronounced escape response was observed in unmated compared with other physiological conditions. More moderate escape response was seen in nulliparous mosquitoes, and the least was observed in full bloodfed test individuals, regardless of test compound. Ae. aegypti, regardless of pretest conditioning, was completely susceptible to deltamethrin, whereas showing high resistance to DDT. Despite profound differences in resistance, there was no significant difference in avoidance response between chemicals and mosquito conditioning. Moreover, pre- and postbloodmeals were found to influence assay outcome and thus to have relevance on the interpretation of susceptibility and excito-repellency assays.

Characterization of Spatial Repellent, Contact Irritant, and Toxicant Chemical Actions of Standard Vector Control Compounds1

“…A balance between one and more of these actions might help reduce selective pressure for resistance to a toxic mode of action. Although the toxicity results with DDT presented here were not unexpected considering predetermined resistance levels of the KAN population using the discriminating dose of 4.0% (,550 nmole/cm2) in the bottle assay (I. Dusfour unpublished data), results of our assay (Grieco et al 2005) and work of others (Chareonviriphap et al 1997, Potikasikorn et al 2005, Polsomboon et al 2008 show pyrethroid and DDT chemicals can induce contact irritancy and spatial repellency and reduce man-vector contact despite presence of insecticide resistance within test populations.…”

“…aegypti Thai strain do not necessarily translate directly to other vector species, or even different strains of Ae. aeygpti, because of behavioral variations that can occur between and among species populations (Potikasikorn et al 2005, Polsomboon et al 2008); however, experiments using Anopheles albimanus and Anopheles gambiae against alphacypermethrin, DDT, and permethrin have indicated similar trends (unpublished data). Further studies using several strains and vector species are warranted to identify the optimal chemical and dose for context-specific interventions.…”

Effects of Irritant Chemicals on Aedes aegypti Resting Behavior: Is There a Simple Shift to Untreated “Safe Sites”?

“…Also, as the THAI Ae. aegypti strain has been characterized as pyrethroid tolerant and DDT resistant [50], [51], it was expected that KD/mortality would be low in these test populations. More importantly, the THAI strain still exhibited a contact irritant response (indicated by increased flying) when exposed to both alphacypermethrin and DDT.…”

Behavioral Responses of Two Dengue Virus Vectors,Aedes aegyptiandAedes albopictus(Diptera: Culicidae), to DUET and its Components

“…Asterisks indicate signiÞcant differences between unfed and bloodfed mosquitoes for a particular treatment (paired t-test; P Ͻ 0.05). et al 2011), between sexes (Davidson 1958, Doyle et al 2009), and among blood-feeding status (Davidson 1958, Rawlings et al 1981, Polsomboon et al 2008. Within homes or their immediate surroundings, the common physiological states of Ae.…”