IPRC - 2015
Permanent URI for this collectionhttp://repository.kln.ac.lk/handle/123456789/156
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Item 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 Emerging Spatio-Temporal Trends in Dengue Incidence in Poojapitiya Medical Officer of Health (MOH), Central province, Sri Lanka(Faculty of Graduate Studies, University of Kelaniya, 2015) Udayanga, N.W.B.A.L.; Gunathilaka, P.A.D.H.N.; Iqbal, M.C.M.; Kusumawathie, P.H.D.; Abeyewickreme, W.Dengue has emerged as one of the major threats to the health sector of many countries including Sri Lanka, due to the increasing number of reported dengue cases over time. Therefore, a statistical and geo-informatics based analysis of the spatio-temporal trends in dengue distribution was carried out to identify recent spatial and temporal trends in dengue distribution patterns, while assessing the susceptibility of the population to dengue infection in the Poojapitiya Medical Officer of Health (MOH) area. Monthly records of reported dengue cases from 2009 to 2013 of the Poojapitiya MOH area were acquired and spatial maps of the recorded dengue case distribution in each Grama Niladhari Division (GND) were developed by using Arc GIS (version 10.2). Normal Chi square test coupled with Paired-Chi square test in MINITAB (version 14.12.0) were used to investigate the impact of gender and age on the infection. Galhinna GND indicated the highest susceptibility to dengue throughout the study period, while the rest of the GNDs indicate less (37 GNDs) or null (29 GNDs) susceptibilities. As suggested by the results of the Paired-Chi square test [>Χ 2 (66, 0.95) = 85.951], the emergence of dengue outbreaks indicated a significantly declining trend in recorded dengue cases in all of the GNDs (regardless of the outbreak in 2012) during recent years. The Percentage Infected Male : Female Ratio (PIMFR) suggested that the, males had a relatively high susceptibility for dengue infection than females with 63.9 : 36.1 of average PIMFER (p=0.00<0.05 at 95% of significance). According to the Paired-Chi square test, the vulnerability of the age groups shifts significantly throughout the study period [>Χ 2 (7, 0.95) = 14.067], where the age groups of 11 - 20 and 21 – 30 indicated high vulnerability to dengue, while >61 age group remained as the least vulnerable group for dengue infection. The identification of the potential high risk GNDs with high susceptibility to the infection of dengue along with the vulnerable age groups in the community would assist the relevant vector controlling agencies to concentrate their efforts, ensuring the effective controlling of dengue outbreak occurrence within the of Poojapitiya MOH.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.