Comparison of esterases between life stages and sexes of resistant and susceptible strains of vector mosquitoes

Subramaniam, Selvi (2009) Comparison of esterases between life stages and sexes of resistant and susceptible strains of vector mosquitoes. Masters thesis, University of Malaya.

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2) TITLE PAGE.pdf

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3) LITERARY DECLARATION.pdf

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4) ABSTRACT.pdf

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6) ACKNOWLEDGEMENTS.pdf

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8) TABLE OF CONTENTS.pdf

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9) LIST OF TABLES.pdf

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14) CHAPTER 1.pdf

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21) CHAPTER 8.pdf

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12) LIST OF APPENDICES.pdf

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7) LIST OF PUBLICATIONS FROM THESIS.pdf

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10) LIST OF FIGURES.pdf

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Official URL: http://dspace.fsktm.um.edu.my/handle/1812/620

Abstract

Three strains of Culicine species, namely Culex quinquefasciatus, Aedes aegypti and Aedes albopictus were bioassayed to determine resistance development to malathion (OP), temephos(OP), permethrin (pyrethroid) and propoxur (CARB). Two methods were i.e., WHO procedures of larval bioassay to determine the susceptibility of lethal concentration (LC) and adult bioassay to determine the lethal time (LT). These mosquito strains were bred in the Insectarium, Division of Medical Entomology, IMR. Thousands of late fourth instar larvae which survived the selection pressure to yield 50% mortality of malathion, permethrin and temephos were reared and colonies were established from adultsthat emerged. Larvae from these colonies were then subjected to the subsequent 10 generations. Selection pressure at 50% - 70% mortality level was applied to the larvae of each successive generation. The resultsshowed that LC50 for both malathion (F61 – F70)and permethrin (F54 – F63) resistant Culex quinquefasciatus increased steadily to the subsequent 10 generations indicating a marked development of resistance. The adult female malathion resistant strain have developed high resistance level to malathion diagnostic dosage with resistance ratio 9.3 to 9.6 folds of resistance. Permethrin resistance ratio remained as 1.0 folds of resistance at every generation. It was obvious that malathion resistance developing at a higher rate in adult females compared to permethrin. Female adults exposed to 2 hours of exposure period for propoxur 0.1% showed presence of cross-resistance among the both strains of mosquitoes towards propoxur and it wasindicated by 70%- 100% mortality at 24 hours post-recovery period.Aedes aegypti shown degree of potency or effectiveness to larvae of when comparison made on its resistance ratio (RR) in ascending order permethrin > malathion > temephos. It is recommended that temephosis a promising chemical larvicidal agent for the control of Aedes aegypti larvae. In contrast, malathion and permethrin were the effective adulticide agent for the control of adult Aedes aegypti. There wassome degree of a crossresistance relationship against propoxur in these three strains.Interestingly, the LC50 for temephosselected Ae. albopictuslarvae fell well within the diagnostic concentration recommended by WHO 1992, i.e. 0.02 mg/L. Permethrin selected Ae. albopictus exhibited overall mean ± S.E. for LC 50 0.28 ± 0.01 and this indicated Ae. albopictus was more tolerant to permethrin 14 fold than temephos and 2.5 fold than malathion. Percentage mortality ofselected adults were lesser or can be defined as developed cross-resistance against propoxur for malathion and temephos strain and permethrin selected strain found to be moderately resistant to propoxur. In none of the strains did the LT50 approach the World Health Organization (1992) recommended diagnostic dosage. Adult bioassay results for Ae. albopictus exhibited permethrin as the most potent insecticide to produce high level of mortality rate in adults.Microplate assay was performed to measure levels of non-specific esterase enzyme in all the three species of selected strains. There is no correlation observed between the LC50 values of malathion and permethrin and non-specific esterasesin larval stage of Cx. quinquefasciatus. The present study also exhibited no correlation between the resistance ratios of LT50 and mean esterase activity in female permethrin strain.Malathion and permethrin selected Ae. aegypti and Ae. albopictus, the frequency population of female replicates distributed below the resistance threshold and defined non-specific esterase was not associated in malathion and permethrin resistance in adult female of Ae. albopictus. The polyacrylamide electrophoresis gel detected 4 distinct esterase bands in Cx. quinquefasciatus malathion and permethrin strain, Ae. aegypti selected strains revealed 6bands labeled as E1, E2, E3, E4, E5 and E6; and 5 regions of esterase bands were detected in Ae. albopictus named accordingly E1, E2, E3, E4 and E5. E3 esterase band in Cx. quinquefasciatus was very heavily stained when compared to susceptible strain indicating that E3 could be responsible in the resistance mechanism due to malathion (OP). There was also a noticeable increase of band intensity with regards to the esterase activity from one instarto another. It is concluded that non-specific esterase band patterns at different life stages demonstrated a direct relationship between levels of enzyme activity and resistance development in these strains. In Ae. aegypti and Ae. albopictus selected strains the esterase activity in relation to the band intensity found to be in low level in all the developmental stages, thus suggesting non-specific esterase not playing a role in resistance to malathion and permethrin in these strains. This comprehensive study has provided information and detailed knowledge about pattern of resistance development, identified potential resistance mechanisms and techniques for their detection; and these information can help to formulate potential strategiesfor resistance management.

Item Type: Thesis (Masters)
Subjects: Q Science > Q Science (General)
Depositing User: MS SITI NUR ATIKAH MOHAMAD RUSDI
Date Deposited: 31 Jul 2013 03:07
Last Modified: 31 Jul 2013 03:07
URI: http://repository.um.edu.my/id/eprint/1186

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