Repellency and Contact Irritancy Responses of Aedes aegypti (Diptera: Culicidae) Against Deltamethrin and Permethrin: A Cross-Regional Comparison

Abstract

Control strategies exploiting the innate response of mosquitoes to chemicals are urgently required to complement existing traditional approaches. We therefore examined the behavioral responses of 16 field strains of Aedes aegypti (L.) from two countries, to deltamethrin and permethrin by using an excito-repellency (ER) test system. The result demonstrated that the escape percentage of Ae. aegypti exposed to pyrethroids did not vary significantly between the two countries in both contact and noncontact treatment despite the differing epidemiological patterns. Deltamethrin (contact: 3.57 ± 2.06% to 31.20 ± 10.71%; noncontact: 1.67 ± 1.67% to 17.31 ± 14.85%) elicited relatively lower responses to field mosquitoes when compared with permethrin (contact: 16.15 ± 4.07% to 74.19 ± 4.69%; noncontact: 3.45 ± 2.00% to 41.59 ± 6.98%) in contact and noncontact treatments. Compared with field strains, the mean percentage of escaping laboratory susceptible strain individuals were significantly high after treatments (deltamethrin contact: 72.26 ± 6.95%, noncontact: 61.10 ± 12.31%; permethrin contact: 78.67 ± 9.67%, noncontact: 67.07 ± 7.02%) and the escaped individuals spent significantly shorter time escaping from the contact and noncontact chamber. The results indicated a significant effect of resistance ratio on mean escape percentage, but some strains varied idiosyncratically compared to the increase in insecticide resistance. The results also illustrated that the resistance ratio had a significant effect on the mortality in treatments. However, the mortality in field mosquitoes that prematurely escaped from the treated contact chamber or in mosquitoes that stayed up to the 30-min experimental period showed no significant difference.

Effects of piperonyl butoxide synergism and cuticular thickening on the contact irritancy response of field Aedes aegypti (Diptera: Culicidae) to deltamethrin

“…[9][10][11] Because pyrethroid insecticide is widely used in space spraying, a rapid increase in A. aegypti mosquito resistance to pyrethroids is a considerable concern and may compromise the utility of IRS and LLINs. This paper is a continuation of our previous study, 12 which revealed that permethrin and deltamethrin exhibited low repellent and irritant effects on field mosquitoes with increased insecticide tolerance in Taiwan and Thailand. The underlying factors of these delayed responses are associated with the sensory impairment of neurons due to the pleiotropic effect following target-site gene mutation in insecticide-resistant mosquitoes.…”

“…Eggs were collected with ovitraps from December 2017 to March 2018. The mosquito rearing method followed the protocol of Yu et al 12 The eggs were hatched in dechlorinated water containing two to three drops (1 mL) of vitamin C for 24 h, and then 200-250 larvae were transferred to a plastic container (29.5 × 23.0 × 5.0 cm 3 , length × width × height) containing 1 L of dechlorinated water. The larvae were given ad libitum access to pig liver powder mixed with dry yeast (1:1).…”

“…All testing mosquitoes that had either escaped from or remained in the chambers were transferred to clean paper cups and provided with a 10% sugar solution to determine the mortality rate at 24 h. The test was replicated four times. A similar procedure without exposing mosquitoes to PBO for nonsynergistic treatment purposes was conducted as described in Yu et al 12 The data was used for comparison in the present study. All tests were performed between 6:00 a.m. and 4:00 p.m. in a laboratory at a temperature of 25.0 ± 1.0 °C and relative humidity of 70.0 ± 2.0% over a photoperiod of 12:12 h (light:dark).…”

“…[30][31][32][33] In the present study, we were primarily interested in determining the relative importance of cuticular thickness in the irritant response of field mosquitoes. The pyrethroid resistance profiles have been described in Yu et al 12 Because most field mosquitoes have some degree of tolerance to deltamethrin, we investigated whether the irritant response of field mosquitoes is also affected due to elevated cytochrome monooxygenase P450s. To test this, field mosquitoes were pretreated with PBO before behavioral observation.…”

The impact of sublethal permethrin exposure on susceptible and resistant genotypes of the urban disease vector Aedes aegypti

“…22 Sublethal doses of pyrethroids are also noted to have irritant effects on resting mosquitoes. [23][24][25] Life-history traits such as longevity and fecundity, and mosquito behaviours including mating, host-seeking and locomotion are critical factors governing the dynamics of mosquito populations in the field. 26 If sublethal doses of insecticide affect these traits differentially in susceptible and resistant mosquito populations, this will define the relative fitness of insecticide-resistant genotypes and determine the extent of resistance introgression into a population.…”