Larvae of Aedes albopictus obtained from
dengue endemic areas in Selangor, Malaysia were evaluated for their susceptibility to operational dosage of
temephos (1 mg/L). Larval bioassays were carried out in accordance to modified WHO standard methods. Biochemical microassay of
enzymes in Ae. albopictus was conducted to detect the emergence of insecticide resistance and to define the mechanisms involved in
temephos resistance. The 50% mortality lethal time (LT50) for Ae. albopictus tested against
temephos ranged between 58.65 to 112.50 minutes, with resistance ratio ranging from 0.75 - 1.45. This study addressed the fluctuation of time-related susceptibility status of Ae. albopictus towards
insecticide. Significant difference on the weekly
enzyme levels of non-specific
esterases,
mixed function oxidases and
glutathione S-
transferases was detected (p ≤ 0.05). No significant correlation was found between
temephos resistance and
enzyme activity (p > 0.05). Only
glutathione S-
transferases displayed high level of activity, indicating that Ae. albopictus may be resistant to other groups of
insecticide. The insensitive
acetylcholinesterase was detected in some field collected Ae. albopictus populations, indicating the possibility of emergence of
carbamate or other
organophosphate resistance in the field populations. Continuous resistance monitoring should be conducted regularly to confirm the efficacy of
insecticides for
dengue control.