Browsing by Author "Dharshini, S."

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    Assessment of Dengue Risk by means of Larval Indices and Insecticide Susceptibility in two Localities of Batticaloa District, Sri Lanka
    (University of Kelaniya, 2012) Dharshini, S.; Vinobaba, M.
    Dengue is the most important vector borne disease in Sri Lanka and globally due to its increasing incidence over the years. Climate changes coupled with rapid urban development result in increasing the breeding and survival of Aedes mosquitoes, the vector for dengue, hence the success of dengue virus transmission. This study aims to identify the relationship between Aedeslaval indices (House Index [HI], Container Index [CI] and Breteau Index [BI]) and dengue risk, and study the insecticide susceptibility to strengthen future mosquito control strategies in the Batticaloa district. The two locations selected for collection of Aedes larvae were Batticaloa and Oddamavadi, in Batticaloa District. Larval collections were made fortnightly using conventional ovitraps for nine months covering the dry and wet seasons. 15 Ovitraps were placed in randomly selected houses on each locality based on the data obtained from Anti Malaria Campaign where dengue cases were available. WHO kit with insecticide impregnated papers with the following concentration recommended by WHO were used for the susceptibility test (Malathion – 0.8%, DDT – 4% and Permathrin – 0.25%). This study demonstrates that all larval indices HI, CI and BI were higher than WHO standard. This indicated a high risk of DF/DHF transmission in both localities. Present investigations revealed that, Ae.aegypti and Ae.albopictus from all study sites were completely resistant to 4% DDT, moderate to high level resistance to 0.8% Malathion but were susceptible to 0.25% Permathrin. This study suggests that regular and continuous monitoring of resistance should be conducted in all dengueendemic sites, to confirm the continued efficacy of insecticides, and to help choose the most effective insecticides for dengue control.
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    Preliminary study of the water quality and plankton abundance in Batticaloa lagoon, Sri Lanka
    (Faculty of Graduate Studies, University of Kelaniya, 2015) Dharshini, S.; Vinobaba, P.; Yatigammana, S.K.
    The present study investigated the prevailing condition of water quality and the abundance of phytoplankton and zooplankton assemblages across the Batticaloa lagoon. Physicochemical parameters including Salinity, Dissolved Oxygen, Turbidity, Nitrate, Phosphate, Temperature and pH were determined using the samples collected at fortnight intervals for six months from July 2013 to December 2013 from seven selected sites: Katthankudy, Kallady, Mandur, Eravur, Thiruperumthurai, Paalameenmadu and Kaluthavalai of the Batticaloa Lagoon, Sri Lanka. A distinct variation of the physico-chemical characteristics of the different regions of the Batticaloa lagoon was observed during the study. In total, 58 species of phytoplankton and 18 species of zooplankton were recorded from all seven sites. Among the 58 species of phytoplankton recorded, a diatom (Bacillariophycea) was the dominant group, which included 25 species comprising 43% of the total taxa. In addition 13 species of Cyanophycea (22%), 10 species (17%) of Chlorophycea, 8 species (14%) of Conjugatophycea, and 2 species (4%) Fragillariophycea were recorded during the study period. The zooplankton communities of the Batticaloa lagoon consisted of the members of the taxonomic groups of Rotifera, Cladocera, Copepoda, Decapoda, Podocopida, Ploima, Arcellinida and Sessilida. Members of the phylum Rotifera was the dominant group which consist 33% of the total zooplankton. The results of the multivariate statistical analysis show that pH, turbidity, dissolved oxygen and salinity were the most important measured environmental variables that explained the species variation of zooplankton, while pH, salinity and turbidity were the most important variables that helped to discriminate phytoplankton species in all sites during the study. Thus the variation of environmental conditions and the plankton communities in different regions of the lagoon demonstrate that both zooplankton and phytoplankton species respond to environmental conditions proving the use of plankton communities in environmental predictions.