Adult and larval insecticide susceptibility status of Culex quinquefasciatus (Say) mosquitoes in Kuala Lumpur Malaysia

Medical Entomology Unit, Infectious Disease Research Centre, Institute For Medical Research, Jalan Pahang 50588, Kuala Lumpur, Malaysia.
Tropical biomedicine (Impact Factor: 0.85). 07/2005; 22(1):63-8.
Source: PubMed


The susceptibility of Culex quinquefasciatus to chemical insecticides in two field sites in Kuala Lumpur was evaluated using the WHO standard susceptibility test. Less then 7 days old female mosquitos, reared from wild caught females were exposed to discriminating dosages of insecticides at recommended exposure periods. The larval bioassay were conducted using the multiple concentrations and the LC50 value was determined. The results indicated that cyfluthrin is the most effective among all the insecticides tested with LT50 value of 29.95 min and 28.59 min, for the strain from Ampang Hill and Pantai Dalam, respectively. It was surprisingly to note that both these field strains showed 0% mortality when tested against malathion and DDT. The LC50 value indicated that both strains were highly resistant to malathion with resistance ratio of 17,988 folds and 14,053 folds, respectively. This concludes that resistance at larval stages is extremely high compared to adult stages.

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    • "In Malaysia, numerous studies on insecticide resistance mainly focused on Ae. aegypti (L.), Ae. albopictus, and Cx. quinquefasciatus (Lee et al. 1997, Chen et al. 2005, Nazni et al. 2005, Hidayati et al. 2011, Low et al. 2013b). However, report on the susceptibility status of Cx. vishnui against various insecticides has not been elucidated in this region. "
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    • "This trend is similar to a study done by Nazni et al. (1998) where the field collected Cx. quinquefasciatus larvae , which were already resistant to malathion and permethrin, showed a resistance ratio of 96.2-folds and 9.4-folds, respectively in comparison to a susceptible laboratory strain, developed higher resistance to permethrin compared to malathion after been subjected to selection pressure with malathion (eight generations) and permethrin (nine generations). Another study done by Nazni et al. (2005) also showed that Cx. quinquefasciatus has developed a high level of resistance to permethrin in the Ampang Hill and Pantai Dalam with a resistance ratio value of 12.20 and 10.95, respectively. Pyrethroids are frequently used in combination with synergists , including piperonyl butoxide (PBO). "
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