Nava Yugavathy, Selvaraja (2016) Genotypic variation of Aedes aegypti and its relation to dengue transmission / Nava Yugavathy Selvaraja. Masters thesis, University of Malaya.
Abstract
Dengue has now become a global public health problem and in Malaysia cases of dengue has increased about 30 folds compared to decades ago. Aedes aegypti is the primary vector of dengue and its vectorial capacity differs from one strain to another. In this study, the genetic diversity of Ae. aegypti collected from 19 localities in peninsular Malaysia based on two mitochondrial DNA genes; CO1 and ND5 was determined. The total number of haplotypes obtained for CO1 and ND5 gene were 14 (C1-C14) and five (N1-N5), respectively. Haplotype genealogical network constructed using concatenated CO1-ND5 gene sequences revealed 18 haplotypes (H1-H18) that were separated into two distinct lineages. Phylogenetic analysis showed that the first lineage (C11 and C3) was more closely related to those from Brazil and France. Vector competency can be categorized into infection rate and dissemination rate. The presence of haplotypically varied Ae. aegypti strains in Klang Valley and its surrounding areas in the state of Selangor where dengue is hyperendemic, suggests the importance to study the degree of its contribution to dengue transmission. Mentari Court, located in Klang Valley, reported high number of dengue cases and was an endemic area in recent years. However, Ae. aegypti from Pasir Puteh, located in state of Perak had a unique and specific haplotype. Dengue cases were rare in that location. In the phylogenetic analysis, the mtDNA sequence of Mentari Court and Pasir Puteh sample happens to fall into two different clades, further suggesting the presence of two different lineages of Ae. aegypti population. The overall result of this study showed both the population to be susceptible towards DENV type 1 and was able to disseminate the infection by day seven post infection. The percentage of positive organs was higher in Pasir Puteh’s Ae. aegypti on all three days except on day 10 salivary gland of Mentari Court exhibited a higher rate. However Mentari Court proved to have a better dissemination rate although not significant. This is the first study in Malaysia which serves as an initial preliminary iii phase for a much larger study throughout the country. The understanding of the population diversity of Ae. aegypti and its impact on dengue transmission will be essential for planning of effective control programmes to reduce the burden of dengue.
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