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Insecticide resistance and its underlying mechanisms in field populations of Aedes aegypti adults (Diptera: Culicidae) in Singapore.

Koou SY, Chong CS, Vythilingam I, Lee CY, Ng LC - Parasit Vectors (2014)

Bottom Line: The insecticide susceptibility profile of Ae. aegypti adults was homogenous among the different study sites.Further biochemical investigation of specific metabolic enzyme activities provided further evidence that detoxifying enzymes such as mono-oxygenases, esterases, glutathione S-transferases and altered acethylcholinesterases generally did not contribute to the resistance observed.This study confirmed the presence of pyrethroid resistance among Ae. aegypti adults in Singapore and documented the early onset of organophosphate resistance.

View Article: PubMed Central - PubMed

Affiliation: Environmental Health Institute, National Environment Agency, 11 Biopolis Way #06-05/08, Helios Block, S (138667), Singapore, ᅟ. koou_sin_ying@nea.gov.sg.

ABSTRACT

Background: In Singapore, dose-response bioassays of Aedes aegypti (L.) adults have been conducted, but the mechanisms underlying resistance to insecticides remain unclear. In this study, we evaluated insecticide resistance and its underlying mechanism in field populations of Ae. aegypti adults.

Methods: Seven populations of Ae. aegypti were collected from public residential areas and assays were conducted according to WHO guidelines to determine their susceptibility to several commonly used insecticides.

Results: Various levels of pyrethroid resistance (RR50 = 3.76 to 142.06-fold) and low levels of pirimiphos-methyl resistance (RR50 = 1.01 to 1.51-fold) were detected. The insecticide susceptibility profile of Ae. aegypti adults was homogenous among the different study sites. Addition of the synergists piperonyl butoxide, S,S,S,-tributyl phosphorotrithioate, and triphenyl phosphate generally failed to enhance the toxicity of the insecticides investigated, suggesting an insignificant role of metabolic-based insecticide resistance and possible involvement of target site resistance. Further biochemical investigation of specific metabolic enzyme activities provided further evidence that detoxifying enzymes such as mono-oxygenases, esterases, glutathione S-transferases and altered acethylcholinesterases generally did not contribute to the resistance observed.

Conclusions: This study confirmed the presence of pyrethroid resistance among Ae. aegypti adults in Singapore and documented the early onset of organophosphate resistance.

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Related in: MedlinePlus

Esterase activities with α-naphthyl acetate inAe. aegyptiadult populations from Singapore.
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Fig3: Esterase activities with α-naphthyl acetate inAe. aegyptiadult populations from Singapore.

Mentions: There was no evidence of elevated EST activity in any of the populations tested (Table 5, Figures 3 and 4). The population from Clementi was the only one with elevated GST level (Figure 5). The populations from Yishun, Woodlands and Jurong East exhibited significant increase in mean MFO levels (P < 0.05) (Table 5), but the increase in MFO activity was only detected at low frequency at the individual level in Jurong East population (Figure 6).Figure 3


Insecticide resistance and its underlying mechanisms in field populations of Aedes aegypti adults (Diptera: Culicidae) in Singapore.

Koou SY, Chong CS, Vythilingam I, Lee CY, Ng LC - Parasit Vectors (2014)

Esterase activities with α-naphthyl acetate inAe. aegyptiadult populations from Singapore.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4201922&req=5

Fig3: Esterase activities with α-naphthyl acetate inAe. aegyptiadult populations from Singapore.
Mentions: There was no evidence of elevated EST activity in any of the populations tested (Table 5, Figures 3 and 4). The population from Clementi was the only one with elevated GST level (Figure 5). The populations from Yishun, Woodlands and Jurong East exhibited significant increase in mean MFO levels (P < 0.05) (Table 5), but the increase in MFO activity was only detected at low frequency at the individual level in Jurong East population (Figure 6).Figure 3

Bottom Line: The insecticide susceptibility profile of Ae. aegypti adults was homogenous among the different study sites.Further biochemical investigation of specific metabolic enzyme activities provided further evidence that detoxifying enzymes such as mono-oxygenases, esterases, glutathione S-transferases and altered acethylcholinesterases generally did not contribute to the resistance observed.This study confirmed the presence of pyrethroid resistance among Ae. aegypti adults in Singapore and documented the early onset of organophosphate resistance.

View Article: PubMed Central - PubMed

Affiliation: Environmental Health Institute, National Environment Agency, 11 Biopolis Way #06-05/08, Helios Block, S (138667), Singapore, ᅟ. koou_sin_ying@nea.gov.sg.

ABSTRACT

Background: In Singapore, dose-response bioassays of Aedes aegypti (L.) adults have been conducted, but the mechanisms underlying resistance to insecticides remain unclear. In this study, we evaluated insecticide resistance and its underlying mechanism in field populations of Ae. aegypti adults.

Methods: Seven populations of Ae. aegypti were collected from public residential areas and assays were conducted according to WHO guidelines to determine their susceptibility to several commonly used insecticides.

Results: Various levels of pyrethroid resistance (RR50 = 3.76 to 142.06-fold) and low levels of pirimiphos-methyl resistance (RR50 = 1.01 to 1.51-fold) were detected. The insecticide susceptibility profile of Ae. aegypti adults was homogenous among the different study sites. Addition of the synergists piperonyl butoxide, S,S,S,-tributyl phosphorotrithioate, and triphenyl phosphate generally failed to enhance the toxicity of the insecticides investigated, suggesting an insignificant role of metabolic-based insecticide resistance and possible involvement of target site resistance. Further biochemical investigation of specific metabolic enzyme activities provided further evidence that detoxifying enzymes such as mono-oxygenases, esterases, glutathione S-transferases and altered acethylcholinesterases generally did not contribute to the resistance observed.

Conclusions: This study confirmed the presence of pyrethroid resistance among Ae. aegypti adults in Singapore and documented the early onset of organophosphate resistance.

Show MeSH
Related in: MedlinePlus