Date of Award

2010

Thesis Type

PhD

Document Type

Thesis

Divisions

Faculty of Science

Department

Institute of Biological Sciences

Institution

Universiti Malaya

Abstract

In this study, selective pressure bioassay test against malathion, permethrin and temephos had been carried out at the larval stage of Cx. quinquefasciatus, Ae. aegypti and Ae. albopictus. Meanwhile, only selection pressure against malathion and permethrin was taken for the adults. The rate of resistance had reduce 52.68 and 13,130 fold in the malathion and permethrin strains of Cx. quinquefasciatus larvae while for the adults, a reduction of 6.14 and 10.37 fold had been observed. A reduction of 4.97, 64.16 dan 51.0 fold had been observed for the Ae. aegypti larvae while 2.74 and 4.48 fold in their adults. Treatment on the Ae. Albopictus larvae showed a reduction of 10.22, 21.1 and 4.49 fold while a reduction of 1.54 and 2.68 fold had been observed in the adults. All Aedes sp. dan Cx. quinquefasciatus were survived after 1-3 hours exposure to temephos. However, exposure of more than 24 hours had resulted into 70 - 80% mortality rate. The rate of resistance towards the insecticides was tested by using non-pressure selective bioassay tests on larval and adults mosquitoes. Bioassay tests at the Cx. quinquefasciatus larvae showed a reduction of 1.93 and 1.97 fold for the malathion and permethrin strains while 1.64 and 1.74 fold in the adults. A decrease of 2.49, 1.36 and 6.26 fold had been observed for the Ae. aegypti larvae while 1.11 and 1.49 fold for the adults. The resistance also decreased for the Ae. albopictus larvae with 1.17 fold in malathion strains and 1.47 fold in permethrin strains compared to 1.39 and 1.27 folds in the adults. Cross resistance tests towards the same and different groups of insecticides were carried out on bioassays of adult mosquito strains by using DDT (4.0%), permethrin (0.75%), malathion (5%), propoxur (0.1%), fenitrothion (1%), -cyhalothrin (0.05%) and cyfluthrin (0.15%). Adults Cx. quinquefasciatus and Ae. aegypti malathion and temephos strain showed a high rate of resistance towards DDT and fenitrothion. Universiti Malaya xvii Tolerance towards propoxur had been observed in malathion and temephos strains of Ae. aegypti but not in Ae. aegypti permethrin strains. A high resistance towards propoxur had been shown in all Cx. Quinquefasciatus strains. Results also showed that all strains tested were tolerant towards -cyhalothrin, cyfluthrin and permethrin. Microassays technique had been used to determine the non-specific esterase, AChE and MFO enzymes associated with the increase of the rate of resistance. An increase of esterase activities had been observed in Cx. quinquefasciatus larvae with 6.66 and 4.3 fold while in 6.89 and 4.08 fold showed by the adult’s strains. An increase of 4.27, 4.05 and 1.98 fold had been observed in Ae. Aegypti larvae while 3.64, 2.43 and 3.91 fold in the adults. As for the Ae. albopictus larvae, an increase of 4.37, 4.42 and 3.11 fold had been observed compared to 3.81, 3.78 and 3.48 for in their adults. The MFO enzyme activities had showed an increase of 5.54 and 6.1 fold in Cx. quinquefasciatus larvae while 2.69 and 2.7 fold in the adults. Ae. aegypti larvae showed an increase of 3.96, 4.03 and 4.31 fold while 1.79, 2.0 and 1.95 fold in their adults. The Ae. albopictus larvae showed an increase of 2.71, 2.5 and 2.45 fold compare to the adults with 2.39, 1.96 and 1.76 respectively. Results also showed that AChE enzyme activities do not contribute to the increase of the resistance in all species. Enzyme activities are inhibited by propoxur with the concentration of 25mg/L. The presence of E4 esterase in both larval and adults malathion and temephos strains indicates that E4 could be responsible for the resistance mechanism towards organophosphate insecticides.

Initial

khm

Additional Information

Thesis (PhD) - Faculty of Science, Universiti Malaya, 2010.

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