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Item Assessment of Possible Risk Factors Affecting Transmission of Dengue in the District of Gampaha Based on Reported Dengue Cases(International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Perera, E.H.L.; Viswakula, S.; Gunawardene, Y.I.N.S.; Subasinghe, U.; Hapugoda, M.D.Dengue is a fast spreading arboviral infection transmitted by the bite of infected females of Aedes aegypti (Linnaeus) and Ae. albopictus (Skuse). According to the Epidemiology Unit, the second highest number of dengue cases is reported in the District of Gampaha, Sri Lanka over past ten years. Objective of this study was to investigate the entomological and socio-economic risk factors affecting transmission of dengue in laboratory-confirmed dengue case reported stations in the District of Gampaha. Laboratory confirmed positive dengue patients (n=100) by dengue NS1 antigen test during the period of June, 2018-August, 2019 were selected. Entomological surveillance was conducted by visiting to each patient within one week of notification of a positive case. For the collection of socio-economic data, an interviewer-administrated questionnaire was used. Adult Aedes mosquito samples collected using a back-pack aspirator showed, 98.64% (73/74) of Ae. albopictus and 1.35% (1/74) of Ae. aegypti mosquitoes. Larval collection using standard larval surveillance techniques showed 92.96% (185/199) and 7.04% (14/199) of Ae. albopictus and Ae.aegypti larvae respectively. The highest House Index (55.17%-16/29), Container Index (28.89%-13/45) and Breteau Index (44.83%-13/29) were reported in the month of June, 2019. The major Aedes breeding place was identified as plastic buckets/barrels (48.6%-84/173) that being used to discard waste. Piped borne water (88%-88/100) was the major water source of the house-holds. Water source of tube well (9%-9/100) was the next popular water source and 66.67%(6/9) of tube wells were positive breeding places for Aedes larvae. Average homestead of the premises of dengue patients was 16.14 perches. From the 100 dengue cases, 67 cases were from middle of town areas, while 2 were from rural areas. Vegetation coverage of the 78% (78/100) house-holds were grass, bushes and small trees and 3% (3/100) house-holds didn’t have any vegetation coverage. The major mosquito prevention method was usage of mosquito nets (54%-54/100) and among dengue patients 7% (7/100) of dengue patients weren’t using any mosquito prevention method. High density of Ae. albopictus mosquitoes, was reported although Ae. aegypti is the major vector of dengue. Therefore, it is required to draw more attention about the Ae. albopictus breeding sites in dengue control programmes. Participants from the study sites were well aware about the disease but still there is a lack of knowledge on breeding sites and vector control methods. Drawbacks in the waste disposal methods, lack of cleanliness in gardens, unplanned water sources and neglecting preventive actions could be considered as the possible risk factors.Item Role of Aedes albopictus in transmitting dengue virus in some endemic areas in Kurunegala District(University of Kelaniya, Sri Lanka, 2003) Hapugoda, M.D.; de Silva, N.R.; Abesundara, S.; Bandara, K.B.A.T.; Dayanath, M.Y.D.; Abeyewickreme, W.Abstract AvailableItem IGamma- ray irradiation as a method for sterilization of males of Aedes albopictus (skuse) for its control through Sterile Insect Technique (SIT)(Faculty of Graduate Studies, University of Kelaniya, 2015) Harishchandra, J.; Abeyewickreme, W.; Hapugoda, M.D.; Premaratne, R.G.; Gilles, J.R.L.Sterile Insect Technique (SIT) can be integrated with other conventional control methods to suppress population of Aedes albopictus, a vector of dengue in Sri Lanka. A study was conducted to determine the effective dose of gamma radiation for producing sterile males of Ae. albopictus mosquitoes. A batch of male pupae (n=32) aged 24-48 hours in F1 was irradiated using Gamma 220, (Co60) irradiator with 25, 30, 40, 50, 60 and 70Gy in duplicates. Adult emergence rate and male longevity were recorded. Virgin females from the same cohort (F1) were introduced into each cage for mating and fed blood starting 5 days after emergence. Then, females were isolated in individual tubes and hatching rate of individual egg batches was calculated after two weeks of egg maturation in hatching solution. Spermacheca of female mosquitoes were dissected and insemination rates were calculated after egg laying. Male mosquito pupae in F1 showed low mortality (0-3.12%) immediately after exposing to radiation (0-48 hours). After 14 days of the irradiation, survival rate of male mosquitoes in F1 were 82.7%, 79.7%, 56.3%, 73.4%, 76.6%, 76.1% and 56.3% when irradiated at 0Gy, 25Gy, 30Gy, 40Gy, 50Gy, 60Gy and 70Gy respectively. No significant difference was observed among survival of males in different doses except in 30 Gy and 70 Gy (Kaplan-Meier survival analysis, Log Rank test). Low survival rate at 30 Gy could be due to mosquito handling errors and need to be retested. Based on the hatching rate of the F2 progeny, males (F1) showed 89%, 93%, 97%, 99%, 99% and 100% sterility when irradiated at 25Gy, 30Gy, 40Gy, 50Gy, 60Gy and 70Gy respectively. Insemination rate of the irradiated males among different doses and controls were above 90% in F1 based on spermatheca dissection of bloodfed females (F1). 50 Gy is recommended as the most suitable radiation dose to produce 99% sterility in Ae. albopictus males which has 76% survival after 14 days of irradiation. This dose can be used to produce sterile males of Ae. albopictus for a SIT programme.Item Assessment of possible social and entomological risk factors affecting transmission of dengue in the District of Gampaha(Faculty of Graduate Studies, University of Kelaniya, 2015) Withanage, G.P.W.K.; Abeyewickreme, W.; Hapugoda, M.D.Dengue is the most important mosquito-borne viral infection transmitted to humans in Sri Lanka causing more than 30,000 cases annually. The objective of the study was to identify possible social and entomological risk factors affecting transmission of dengue in Gampaha district where the second highest number of dengue cases recorded during last ten years. Four Medical Officer of Health (MOH) areas were selected based on annual number of dengue cases greater than 250 for last ten years. One GramaNiladhari (GN) division was selected from each MOH area as a study area where the highest number of dengue incidents reported. In each study area, a cluster of 150 households was selected and household and entomological surveys were conducted. The selected areas were Eriyawatiya (Kelaniya MOH), Welikadamulla (Wattala MOH), Akbar town (Mahara MOH), and 3-Kurana (Negombo MOH) GN divisions. There were 2577 population in 600 households in the study areas and 53.5% were females. Average size of a homestead was 17 perches and most of the households (98%-588/600) were individual house. Main vegetations in the homesteads were grass and bushes (97%-583/600) and potential breeding places of dengue vector mosquitoes were observed in 96.1% (577/600) households. Main dengue vector mosquito present in the captured Aedes adult mosquitoes was Aedes albopictusis (92.9%-183/197). Most prominent breeding places were discarded bottles and tins (4.0%-15/371), plant axils (9.7%-36/371), plastic containers (26.4%-98/371), and roof gutters (4.3%-16/371) in the observed premises and 9.2% (34/371) were Aedes larvae positive. Most frequent mosquito preventive measure was bed-nets (30.3%-182/600), but mosquito coils (30.8%-185/600) and vaporizers (17.6%- 106/600) were frequently used. Participants have adequate knowledge about the disease, but they neglect preventive measures and highly depend on government vector control programs. Unplanned households, crowded conditions, poor waste management systems, and negligence to pursue preventive measures may be possible risk factors and therefore, frequent encouragement is needed to control dengue transmission.