Medicine
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This repository contains the published and unpublished research of the Faculty of Medicine by the staff members of the faculty
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Item Detection of dengue virus in Aedes albopictus mosquitoes by Reverse Transcription Polymerase-Chain Reaction-Liquid Hybridization (RT-PCR-LH) based assay.(Sri Lanka College of Microbiologists, 2003) Hapugoda, M.D.; Gunasekera, M.B.; de Silva, N.R.; Gunasena, S.; Prithimala, L.D.; Dayanath, M.Y.D.; Abeyewickreme, W.Dengue is an important public health problem. In this study an RT-PCR-LH assay was developed for the detection of dengue virus in Ae.albopictus, a vector of dengue. Laboratory bred Ae.albopictus (adults inoculated with dengue prototypes were tested by RT-PCR-LH assay. RT-PCR products of NS3 gene of 4 dengue prototypes were hybridized in liquid phase with 32P) labelled cocktail of dengue serotype-specific ologonucliotides. Semi-Nested-PCR agarose gel electrophoresis (Semi-Nested-PCR-AGE) assay with dengue type specific oligonucliotides was carried out for typing of RT-PCR products. Wild-caught Ae.albopictus (larvae (n=89 pools) and adults (n=69 pools) collected from dengue case reported stations during the period of 1999-2002 were also tested by RT-PCR-LH and typed by Nested-PCR-AGE assay). A DNA band (470bp) specific for dengue virus was observed in all pools of Ae.albopictus (inoculated with dengue prototypes in RT-PCR-LH assay. When RT-PCR products of dengue prototypes inoculated mosquitoes were typed by Semi-Nested-PCR-AGE assay, bands of 169,362, 265, 426 bp sizes corresponding to DEN1, DEN2, DEN3 and DEN4 respectively were observed. The DNA band specific for dengue virus (470bp) was also observed in 6 pools of wild-caught adults in RT-PCR-LH assay. They were found to be infected with DEN3 (265bp DEN3 specific DNA band was detected) by Semi-Nested-PCR-AGE assay. None of the wild-caught larvae showed dengue specific DNA band (470bp) in RT-PCR-LH assay). RT-PCR-LH with Semi-Nested-PCR-AGE assays are useful for the detection and typing of dengue virus in Ae.albopictus. Ae.albopictus (in Sri Lanka is competent in transmitting DEN3 and possibly other serotypes. Detection of dengue virus for the first time in Ae.albopictus in Sri Lanka confirms earlier observations that it may play an important role in transmitting dengue). Acknowledgements: Financial assistance by the International Atomic Energy Agency (Technical Co¬operation grant no SLR/ 06 / 024) and University of Kelaniya (Research grant no RP/03/04/06/01/00) is gratefully acknowledged.Item Silent transmission as a risk factor affecting transmission of dengue fever.(Faculty of Veterinary Medicine and Animal Science, University of Peradeniya, 2007) Hapangama, H.A.D.C.; Hapugoda, M.D.; Gunawardene, Y.I.N.S.; Premaratna, R.; Dayanath, M.Y.D.; Abeyewickreme, W.The global incidence of dengue fever has increased by more than four-folds over the last 30 years, making it the most threatening mosquito-borne viral disease at present. Objective of this study is to determine the role of silent transmission •on' incidence of dengue. A total of 40 households, living within a 300 m radius of seven selected ‘confirmed dengue cases at different dengue high risk localities in Gampaha District were recruited for this study. A minimum of three inhabitants were tested for anti-dengue antibodies using a commercial kit to determine the prevalence of silent transmission on dengue infection in each households. Entomological surveillance was carried out in all seven localities. Out of 40 households, 26 (65%) houses were positive for dengue viral infection. Total of 148 inhabitants (68 Males); mean age; 35.9 years were enrolled. Of the 148, 41 (27.7%) had evidence of exposure to dengue virus [positive for IgM: 28/41(68.4%), IgM'& IgG: 7/41(17%) and IgG: 6/41(14.6%)]. Out of 28 primary infections, 20(71.4%) were asymptomatic. Of the 7 secondary infections, 1(14.28%) was asymptomatic. Of the 6 previous exposures to dengue 4(66.67%) were asymptomatic. Of the 7 localities investigated, 1 had >50%, 4 had >25% and 2 had <25% clustering of cases. Ae. albopictus found in all seven localities and Ae. aegypti found only in two localities. This study suggests presence of silent transmission of dengue virus with a trend towards clustering around cases and also this shows that the presence of vectors increases the incidence of dengue.Item Effect of silent transmission and clustering of cases on transmission of dengue in Gampaha district(Sri Lanka Association for the Advancement of Science, 2007) Hapangama, H.A.D.C.; Gunawardene, Y.I.N.S.; Hapugoda, M.D.; Premaratna, R.; Dayanath, M.Y.D.; Abeyewickreme, W.Silent transmission of dengue virus and clustering of cases have been suggested as possible factors for the increasing incidence of dengue fever. Objective of this study was to determine the presence of silent transmission and clustering of cases of dengue fever in the Gampaha District. Study was carried out using cluster investigation method. A cluster consists of family members and immediate neighbours (minimum of 20) of a dengue index-case. Serum samples from volunteers were tested for anti-dengue antibodies using Dengue-Duo-IgM/IgG Rapid Cassette (Panbio diagnostics, Australia). Using 7 index cases, 148 volunteers (68 Males); mean age: 35.9 years were enrolled. Of the 148, 41 had evidence of exposure to dengue virus [positive for IgM: 68.4% (28/41), IgM & IgG: 17% (7/41) and IgG: 14.6% (6/41)]. Out of 28 primary infections, 71.4% (20/28) were asymptomatic. Of the 7 secondary infections, 14.28% (1/7) was asymptomatic. Of the 6 previous exposures to dengue, 4 (66.67%) were asymptomatic. There was no significant association between sex and exposure to infection [31% (21/68) males vs 25% (20/80) females, p>0.05] or between sex and occurrence of symptoms among exposed individuals [71% (15/21) males vs 50% (10/20) females, p>0.05]. Older individuals aged over 40 years, were most likely to be asymptomatic than younger persons (94% (14/15 exposed) vs 50% (13/26 exposed), P<0.01). Out of 7 clusters investigated, 1 had >50%, 4 had >25% and 2 had <25% clustering effects. A high proportion of asymptomatic infections were observed among adults over 40 years without gender difference. Study suggests persistence of silent transmission of dengue virus with a trend towards clustering around cases. Acknowledgement: World Health Organization (WHO/SEARO SN1144) and technical co-operation by International Atomic Energy Agency (TC/SRL 06/28)