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Item Susceptibility among Dengue Vectors to Malathion and Deltamethrin Insecticides in Three Selected Medical Officer of Health (MOH) Areas in the District of Gampaha, Sri Lanka(International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Dalpadado, C.P.R.D.; Amarasinghe, L.D.; Gunathilaka, P.A.D.H.N.Dengue has become the most important public health problem in Sri Lanka at present. As there is no effective vaccine or drug up to now, vector control is the main arm of disease control. Of these approaches, insecticide based control is used widely. However, excess use of chemicals and inappropriate application without determining the discriminative doses has given rise to the insecticide resistance among vector mosquitoes. Entomological surveys (Ovitap) were conducted in Negombo, Attanagalla and Dompe Medical Officer of Health (MOH) areas representing Urban, Sub urban and rural conditions, respectively from December 2016 December to June 2019. A total of 100 ovitraps each was placed outdoor and indoor in randomly followed by the collection after 5 - 7days. Eggs collected from ovitraps were reared under laboratory condition the laboratory (Temperature; 27 ± 10C: Relative Humidity 70 - 80%). The reared larvae were identified using standard taxonomic keys. Identification was further confirmed by identification of adults emerged from larvae . Adult mosquitoes were reared under optimized insectary conditions provided with sugar feeding. Batch of 140 mosquitoes from Aedes aegypti (Linnaeus) and Ae. albopictus (Skuse) was taken separately from the colony 24 hour after a sugar feeding. Each batch of mosquito was exposed to malathion (0.8%) and Deltamethrin (0.03%) insecticide susceptibility following the World Health Organization (WHO) defined procedures. The experiment setup was repeated for 2 times. Mortality and corrected morality was calculated using Abbortt’s formula after 24 hours’ exposure period. The results indicate that both dengue vectors have evolved high level of insecticide resistance to malathion (0.8%) and deltamethrin (0.03%) in the District of Gampaha except Ae. albopictus mosquitoes in rural areas. Ae. albopictus mosquitoes were found fully susceptible for 0.03% deltamethrin in Dompe (rural) MOH area and emergence of resistance (95.9%) was observed in Attanagalla (suburban) area. It was found resistant in Negombo area (83.8%) which is highly populated. Ae. albopictus mosquitoes were found fully resistant for 0.8% malathion in both urban (71.5%) and Sub urban (85.3%) areas while emergence of resistance was observed in Dompe MOH area (90.8%). Ae. aegypti was found resistance to both 0.03% deltamethrin and 0.8% malathion in Negombo area (88.1%, 53.5% respectively) and resistance was suggested for 0.03% deltamethrin in Attanagalla MOH area (91.8%) while it was found resistant for 0.8% malathion (89.8%) in the same area. Ae. aegypti was not recorded in Dompe MOH area during the study period. Since both the dengue vectors have developed resistance to WHO diagnostic discriminative doses for Malathion and deltamethrin intensity bioassays (five times and ten times of discriminative dose) are needed to be done to confirm the level of resistance in these vectors. Therefore, results highlight the requirement of continuous insecticide resistance monitoring incorporated with the surveillance and control efforts. Hence, use of evidence based discriminative doses of insecticide for each area should be vital to delay the development of resistance among natural populationItem Antagonist Potential of Vorticella microstoma on the larval development of Culex gelidus and Aedes aegypti(19th Conference on Postgraduate Research, International Postgraduate Research Conference 2018, Faculty of Graduate Studies,University of Kelaniya, Sri Lanka, 2018) Ranasinghe, H.A.K.; Amarasinghe, L.D.Selection of effective biological agents which can suppress the growth of immature stages of mosquito vectors has drawn a wide attention in disease control programmes. Vorticella microstoma is a parasitic ciliate which has an ability to parsitize on larval stages of mosquitoes and inhibit their growth. However, the potential antagonist activity has not been evaluated in detail in Sri Lanka. Fifteen each of first, second, and third instar larvae of Cx. gelidus and Ae. aegypti were placed in separate V. microstoma culture bottles at room temperature (27± 2 ºC) and mortality rate of mosquito larvae was observed after 48 h. Bioassay was done in completely randomized design with controls. The first, second, and third instar larvae of Cx. gelidus were allowed to be infested with the trophont stage of V. microstoma. Heavily infested larvae with V. microstoma were identified by the presence of parasites attached all over the body surface. V. microstoma trophonts did not usually attach to siphon region of mosquito larvae when they are alive. None of the instar levels of Ae. aegypti showed susceptible to infection with V. microstoma. In the first instar larvae of Cx. gelidus, thorax and the abdominal segments had the attachment of 30–35 trophonts of V. microstoma, whereas 2–4 trophonts had attached to the anal papillae. Higher densities of V. microstoma were found in abdominal segments of second instar larvae of Cx. gelidus, whereas total of 45–50 trophonts had attached to thoracic region and abdominal segments. Fifty to fifty-five trophonts of V. microstoma had attached to third instar larvae of Cx. gelidus, with higher densities in the anal papillae followed by abdominal segments; in the anal papillae, 20–25 trophonts were found to be attached. V. microstoma infection was positively correlated with the body size of mosquito larvae. The percentage mortality of the first, second, and third instar larvae of Cx. gelidus did not significantly differ from each other (One-Way ANOVA: IBM SPSS Statistic Software, P<0.05). Therefore, the study results would be a new avenue to work on environmentally agreeable manner in reducing the Cx. gelidus vector mosquito populations.