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.
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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- "Fenitrothion (O, O-dimethyl O-(3-methyl-4- nitrophenyl)-phosphorothioate), a broad spectrum organophosphorus compound has been used throughout the world, including Malaysia. In Malaysia, fenitrothion (FNT) is either used alone or in combination with other pesticides to enhance the quality of agriculture products and to control the spread of vector-borne disease (Knet and Seng, 2003; Nazni et al., 2005). "
ABSTRACT: Indiscriminate application of organophosphate (OP) pesticides has led to environmental pollution and severe health problems. The aim of the present study was to evaluate the effect of palm oil tocotrienol-rich fraction (TRF) on biochemical and morphological changes of the liver in rats treated with fenitrothion (FNT), a type of OP pesticide. A total of 28 male Sprague-Dawley rats were divided into four groups; control group, TRF-supplemented group, FNT-treated group and TRF+FNT group. TRF (200 mg/kg) was supplemented 30 minutes prior to FNT (20 mg/kg) administration, both orally for 28 consecutive days. Following 28 days of treatment, plasma biochemical changes and liver morphology were evaluated. The body and absolute liver weights were significantly elevated in TRF+FNT group compared to FNT group. TRF administration significantly decreased the total protein level and restored the activity of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in TRF + FNT group. In contrast, total bilirubin level, γ-glutamyltranferase (GGT) and cholinesterase activity in TRF + FNT group did not significantly differ from FNT group. Administration of TRF also prevented FNT-induced morphological changes of liver as observed by electron microscope. In conclusion, TRF supplementation showed potential protective effect towards biochemical and ultrastructural changes in liver induced by FNT.
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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). "
ABSTRACT: The resistance status towards permethrin among the laboratory strain, the permethrin-selected strain and four field strains of Culex quinquefasciatus collected in Kuala Lumpur, Malaysia was determined using three standard laboratory methods: WHO larval bioassay, WHO adult bioassay and biochemical microplate assay. Cx. quinquefasciatus permethrin-selected strain larvae were the least susceptible to permethrin with a resistance ratio of 47.28-folds, whereas all field strain larvae of the same species were tolerant to permethrin with resistance ratios of more than 3-folds. In contrast, in adult stage, the permethrin exposed permethrin-selected strain (resistance ratio = 1.27) was found to be more susceptible to permethrin than all permethrin-exposed field strains (resistance ratios = 2.23-2.48). Complete mortalities for all strains of Cx. quinquefasciatus adults proved the effectiveness of the synergist; piperonyl butoxide (PBO). For the biochemical microplate assay, the reduction of the mean optical density of elevated oxidase activity of three field strains upon exposure to PBO confirmed the association between oxidase activity and permethrin tolerance. On the other hand, irregular patterns of the mean optical density of elevated oxidase activity in the laboratory strain, permethrin-selected strain and Jalan Fletcher strain illustrated the gene variation within these mosquito colonies as well as the involvement of other enzyme activities in the permethrin resistance occurred.