Conference Papers

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This collection contains abstracts of conference papers, presented at local and international conferences by the staff of the Faculty of Medicine

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    Dengue vector surveillance in a dengue hot-spot in Sri Lanka
    (Faculty of Tropical Medicine, Mahidol University, 2007) Sumanadasa, S.D.M.; Hapugoda, M.D.; Perera, D.; Bandara, S.; Mansoor, M.A.; Peris, I.; Abeyewickreme, W.
    BACKGROUND: In South Asia, dengue has been declared as one of the most, fast-spreading vector-borne diseases. Therefore, mosquito surveillance is important for early detection of outbreaks along with implementation of prompt control activities. OBJECTIVES: To identify entomological risk factors with regard to transmission of dengue in a dengue hot-spot. Seventy five human dwellings in Vehara in the Kurunegala District of the Western Province were selected based on high disease incidence during 2000-2004, high Aedes as well as human population density and increased building activities. Entomological surveillance was done during May-August, 2007. RESULTS: The house Index ranged from 2.67% to 5.33% for Aedes aegypti while it for Aedes albopictus was 1.33% to 6.60%. The container index ranged from 23.67% to 29.33% for Ae. aegypti and from 1.33% to 18% for Ae. aibopictus. Man biting rates of 0.43-5.78 bites/man/hour were estimated for Ae, aegypti, while it ranged between 0.49 and 1.33 for Ae. aibopictus. The most common breeding place for Aedes species was plastic baskets (16%, n=12). DISCUSSIONS: Vector surveillance showed that the predominant vector species present in the study area was Ae. ageypti. Aedes mosquito larval densities and adult biting rates were sufficient to promote outbreaks of dengue in this study area. Community must be educated regarding effective measures to protect them from dengue. Their cooperation should be elicited in the early detection and elimination of vector species by source reduction, environmental management and personal protection measures.
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    Potential use of IGR Pyriproxifen for control of dengue vector Aedes albopictus
    (Sri Lanka College of Microbiologists, 1999) Gunawardene, Y.I.N.S.; de Silva, N.R.; Abeyewickreme, W.
    Dengue Fever (DF) Dengue Haernorrhagic Fever (DHF) is now a significant problem in Sri Lanka. The incidence of DHF has increased cyclically since the first recognized outbreak in 1989. Of the 203 suspected DHF cases recorded in 1989, 87 were confirmed and 26 deaths were reported. By 1997, 5882 clinical cases, 1558 serologically confirmed cases and over 300 deaths have been reported. Without an effective vaccine against dengue, and considering the clinical difficulty in managing DHF cases, vector control has become an important com¬ponent in the integrated attempts for dengue con¬trol. Aedes aegypti and Aedes albopictus not only transmit dengue but are also a nuisance and cause annoyance by their day biting behaviour. In this study an attempt was made to control Ae. albopictus by exploiting its oviposition behaviour, us¬ing an Insect Growth Regulator (IGR), Pyriproxifen. The IGR is known to interfere with the synthesis and deposition of chitin in insects and thereby prevent growth and development. Different concentrations of the IGR (0.01 g/1 -0.08g/1) were tested against Ae.albopictus, in laboratory experiments. The most effective larvisidal concentration of Pyriproxifen for Ae.albopictus was determined to be 0.03g/1. Field trials were also carried out to determine the feasi¬bility of employing used automobile tyres contain¬ing Pyriproxifen as ovitraps against Ae.albopictus. Tyres containing water were treated with Pyriproxifen (0.03g/1) and the emergence of adults was recorded. Pyriproxifen at a concentration of 0.03g/1 was found to inhibit the emergence of adult Aedes mosquitoes up to 6 weeks.
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    Ovi-trap based surveillance for Aedes in dengue endemic Gampaha District, Sri Lanka during rainy season
    (Faculty of Tropical Medicine, Mahidol University, 2008) Hapangama, H.A.D.C.; Wijegunawardana, N.D.A.D.; Gunawardene, Y.I.N.S.; Benjamin, S.; Abeyewickreme, W.
    Dengue is endemic in Gampaha District, Sri Lanka. Aedes aegypti and Aedes albopictus have been incriminated as vectors in urban and suburban environments. An ovitrap-based weekly surveillance was carried out to determine the distribution and abundance of Dengue vectors, in six dengue endemic areas; Galudupita, Gongitota, Wanawasala, Kerangapokuna, Mabole and Welikadamulla in the Gampaha District during May and June 2008 in both indoors and outdoors. Galudupita and Gongitota gave the highest ovitrap indices, both indoors and outdoors as 97% and 73% respectively. Of the total positive ovitraps(1320), positivity for Ae. albopictus, Ae. aegypti and both were 63.5%, 32.9% and 3.6% respectively. Highest mean number of Ae. aegypti and Ae. albopictus larvae per ovitrap in both indoor and outdoor ovitraps were observed Galudupita and Gongitota respectively. However, statistical analysis showed that ovitrap index of Ae. aegypti in six study was not significantly different from each other (P > 0.05). Outdoor mean number of Ae. aegypti larvae per ovitrap in Galudupita, was significantly higher than other sites (F=3.587, P=0.012). Indoor Ae. albopictus ovitrap index of Gongitota was significantly higher than of Welikadamula (F=2.59, P=0.046) while outdoor Ae. albopictus ovitrap index of Gongitota and Wanawasala was significantly higher than of Welikadamula F=3.19 P=.0.02). Results irnplicate that Ae. albopictus prefers more vegetation as observed in Gongitota and Wanawasala. In highly populated and urbanized Galudupita, area with less vegetation, Ae. albopictus population was less than Ae. aegypti even outdoors. Study implicates that Ae. albopictus is the predominant indoor and outdoor breeder during rainy season.
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    Surveillance for dengue vector mosquito in Kurunegala district, Sri Lanka
    (Elsevier, 2008) Sumanadasa, S.D.M.; Hapugoda, M.D.; Peiris, I.; Perera, D.; Bandara, S.; Mansoor, M.A.C.M.; Abeyewickreme, W.
    BACKGROUND: Dengue vector surveillance is an important tool to determine the time and area/s to initiate control action. Our objective was to identify entomological risk factors with regard to transmission of dengue in a dengue hot-spot. METHODS: In the study 75 human dwellings in a dengue hot-spot in the District of Kurunegala was selected based on high disease incidence during 2000—2004, high Aedes as well as human population density and increased building activities. House to house mosquito surveillance was carried out from 08.00 am to 12.00 noon during May—August, 2007. Larvae and adult Aedes mosquitoes were collected indoors and outdoors using normal larval surveillance and human landing diurnal collection techniques respectively. Environmental and sociological data were obtained from households by interviewer administered questionnaires and observations. RESULTS: The house index for Aedes aegypti and Aedes albopictus ranged from 1.33%—6.60% and 2.67%—5.33% respectively. The Breatu index ranged between 23.67%—29.33% for Ae. aegypti and 1.33%—18% for Aedes albopictus. Man biting rates of 0.43—5.78 bites/man/hour were estimated for Ae. aegypti, while it ranged from 0.49—1.33 for Ae. albopictus. The most common breeding place for Aedes species was plastic baskets (16%, n = 12). More than half of the households (61%, n = 45) stored water in large cement tanks for their daily activities. Majority of the group (99%, n = 74) had a basic knowledge on dengue mosquito breeding places (97%, n = 73), their life cycle (95%, n = 71) and mode of transmission (99%, n = 74). Domestic waste of majority of households was carried away daily by the local authorities (n = 69). CONCLUSION: These results suggest that a vector control program should be adopted to reduce Aedes population levels below dengue transmission thresholds. Discarded containers of various types were identified as potential mosquitoes breeding habitats. Therefore, community must be educated on effective vector control measures to contain the transmission levels. © 2008 Elsevier Inc.
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    Climatic factors affecting density of Anopheles vector mosquitoes in Ampara District, Sri Lanka
    (University of Kelaniya, 2014) Kannangara, D.N.; Ranathunge, R.M.T.B.; Abeyewickreme, W.; Hapugoda, M.D.; Subasinghe, S.M.C.U.P.
    Background: Apart of many vector-borne diseases malaria played a major role during past decades in Sri Lanka. Controlling strategies had effectively addressed this issue so that there were no malaria patients recently. However it has been observed that abundance of vector mosquitoes in districts like Ampara is high, which signifies a potential of spreading of malaria in the area in future. Identification of the relationship between the climatic factors and vector density could be a cost effective way in controlling the mosquito instead of costly strategies currently followed. This study attempts to identify the relationship exists between climatic factors and the vector density in Ampara District.