Browsing by Author "Peris, I."

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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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    Detection of dengue viruses in vector mosquitoes collected from localities with reported dengue cases in the Gampaha District, 2008-2009
    (Sri Lanka Association for the Advancement of Science, 2010) Hapugoda, M.D.; Abeyewickreme, W.; Peris, I.; Warakagoda, S.; Perera, V.; Weerasinghe, I.
    Dengue is an important mosquito-borne flaviviral infection in Sri Lanka. Aedes aegypti is considered as the predominant vector of dengue and Ae. albopictus is considered as a subsidiary vector of dengue in Sri Lanka. Detection of dengue virus in these two vector species is important for control activities. Objective of this study was to examine transmission of dengue viruses by Ae. aegypti and Ae. albopictus mosquitoes in the field. Hundred dengue patients confirmed by both clinically and serologically were selected. Mosquito surveillance was conducted by visiting patient's premise within one week of notification of a case. A buffer zone covering 500 m radius in each confirmed patient's premise was surveyed. Larvae and adults were collected using standard larval surveillance techniques and a back-pack aspirator respectively. Adult and larvae were pooled (1-50 larvae/adult per pool). Single step single tube R -PCR assay followed by Semi-Nested-PCR agarose gel electrophoresis was performed. Ethical permission for this study was obtained from the Ethical Review Committee of the Faculty of Medicine, University of Kelaniya. Informed written consent was obtained from each patient for conducting mosquito surveillance at his/her premise. From 100 confirmed dengue case reported stations, 10% (10/100) and 60% (60/100) pools of Ae. aegypti and Ae. albopictus larvae were collected respectively. Adult mosquito collection showed 8% (8/100) and 30% (30/100) of Ae. aegypti andAe.albopictus respectively. These results showed high density of Ae. albopictus mosquitoes. Dengue 3 viral infection was detected in 1 and 7 pools of Ae. aegypti and Ae. albopictus respectively. Transmission of dengue serotype 3 virus by Ae. albopictus and high density of this species in selected areas were observed. Although Ae. aegypti is still the main vector initiating outbreaks and transmitting the disease in city centers, the possibility of Ae. albopictus playing a major role in this region should not be ignored.Theseadultmosquitoes may acquire dengue viruses through horizontal or vertical transmission. Alargenumber of mosquito pools needed to test for confirmation.Acknowledgements: Financial assistance from the WHO/SEARO (WHO/SEARO SN1167)and technical assistance from the IAEA (IAEA TC SRL TC 5/042) are gratefullyacknowledged.