title: Pyrethroid resistance in Aedes aegypti larvae (Diptera: Culicidae) from Singapore.
abstract: We report the first comprehensive insecticide susceptibility status ofAedes aegypti (L.) larvae from Singapore. The study indicated that Ae. aegypti is susceptible to temephos, although resistance (RR50 = 1.29-4.43-fold) couldbe developing. Of high concern is the detection of moderate to high resistance to permethrin (RR50 = 29-47-fold) and etofenprox (RR50 = 14-34-fold). Biolarvicide Bacillus thuringiensis israelensis (Bti) remains effective. The insecticide susceptibility profile of Ae. aegypti larvae was found to be homogenous among the different sites studied across the island city. The addition of 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 resistance, and a possible involvement of target site resistance. Further biochemical investigation of specific metabolic enzyme activities suggested that detoxifying enzymes, mono-oxygenases, esterases, glutathione S-transferases, and altered acetylcholinesterases, generally did not contribute to the resistance observed. This study clearly demonstrated that pyrethroid resistance is widespread among Ae. aegypti population and lowered susceptibility to organophosphates is developing.
authors.affiliation: Environmental Health Institute, National Environment Agency, 11 Biopolis Way #06-05/08, Helios Block, Singapore 138667.
authors.forename: Sin-Ying
authors.initials: SY
authors.lastname: Koou
authors.affiliation: Environmental Health Institute, National Environment Agency, 11 Biopolis Way #06-05/08, Helios Block, Singapore 138667.
authors.forename: Chee-Seng
authors.initials: CS
authors.lastname: Chong
authors.affiliation: Parasitology Department, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Indra
authors.initials: I
authors.lastname: Vythilingam
authors.affiliation: Environmental Health Institute, National Environment Agency, 11 Biopolis Way #06-05/08, Helios Block, Singapore 138667.
authors.forename: Lee-Ching
authors.initials: LC
authors.lastname: Ng
authors.affiliation: Urban Entomology Laboratory, Vector Control Research Unit, School of Biological Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia.
authors.forename: Chow-Yang
authors.initials: CY
authors.lastname: Lee
mesh_terms: D000330:Aedes; D000818:Animals; D007305:Insecticide Resistance; D007306:Insecticides; D007814:Larva; D010574:Pesticide Synergists; D011722:Pyrethrins; D012846:Singapore; D018675:Toxicity Tests
chemical_list: D007306:Insecticides; D010574:Pesticide Synergists; D011722:Pyrethrins