Browsing by Author "Hapangama, H.A.D.C."

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Dengue as-a public health problem in Sri Lanka
(La Fondation pour l’Université de Lyon, 2009) Hapangama, H.A.D.C.; Gunawardene, Y.I.N.S.; Hapugoda, M.D.; Premaratna, R.; Manamperi, A.; Gunasena, S.; Abeyewickreme, W.
Dengue infection is an important global public health problem and an increasing number of persons from the South Asian region have been directly or indirectly affected by the disease. In Sri Lanka, dengue has become a major threat to public health in many urban and sub-urban' areas during past three decades. Rapid unplanned urbanization and increasing human population has increase the rate of infection and the frequency. The study area, Gampaha District is the second most populous district in the country having a population density of 1 539 persons per km2 and was the district reporting the second highest incidence of dengue in 2008. Therefore, current research efforts are focused on dengue transmission, examining the presence of sub-clinical infections, role of vector mosquitoes and Knowledge, Attitude and Practices (KAP) of the community on dengue infection in an effort to contain the disease. In the present study, dengue antibodies were detected in samples collected from clinically suspected patients and as well as in samples collected from volunteers. Volunteer sera collected around the confirmed cases had a 23.6% sero-positive rate for dengue IgM antibodies. The rate of asymptomatic recent infections was calculated to be 16.9%. In present study we have serologically confirmed the presence of subclinical infections and according to the published data this is the first confirmation of asymptomatic dengue infections in Sri Lanka. According to the entomological investigations carried out, the common breeding places for Aedes vectors were found to be discarded small containers. Even though Ae. Aegypti has been considered as the principal vector transmitting dengue fever, current studies highlighted the predominant ro!e of Ae. albopictus in the disease transmission. A previous study in Sri Lanka also suggested that prevalence and .presence of high-density of Ae. albopictus should be considered as a risk factor for endemic/epidemic dengue. In view of the above, the spread of dengue by Ae. albopictus should be a matter of great concern. Findings of KAP survey revealed that the community possessed substantially higher knowledge on the spread of dengue, vectors, vector breeding and also seriousness of the infection. However it was observed that good knowledge does not necessarily lead to good practices. Since the attitudes of the respondents were found to be good and most of them were supportive of control measures; next effort of the present study is to see how a novel community mobilized solid waste management system will be effective in dengue vector control.
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)
Efficacy and potential use of VectoBac WGr for the control of Culex quinquifaciatus mosquitoes in three different localities of Gampaha district, Sri Lanka
(Sri Lanka Association for the Advancement of Science, 2009) Wijegunawardana, N.D.A.D.; Hapangama, H.A.D.C.; Gunawardene, Y.I.N.S.; Manamperi, A.; Abeyewickreme, W.
Some methods of mosquito population control, especially the application of pesticides for adult mosquitoes, can have an impact on the environment and individuals with a heightened sensitivity to pesticides. Of the available control tools, biological controls are considered to be generally host-specific and environmental friendly. Although biological controls are not feasible on a large scale, they are often very effective in localized areas. Therefore, efficacy and potential use of water dispersible granular (WDG) formulations of bacterial larvicide, Vectobac- WGr (Bacillus thuringiensis israelensis [Bti]) (Valent BioSciences Cooperation in USA) was tested against Culex quinquefasciatus in three selected localities in the district of Gampaha. Pre-treatment, treatment and post-treatment adult C. quinquefasciatus mosquito densities were recorded for 20 consecutive days within the study period between May to December 2008. The study period covered both rainy and dry seasons. The larvicide was applied to three selected treatment sites and three control sites with a backpack sprayer to test the efficacy of Bti treatment. The six Pre-treatment surveillances in the three treatment and three control sites were done once a week in the first month and once in two weeks for the second month. Adult mosquitoes collected were identified in the laboratory to the species level and the numbers were recorded. For each site, 30 households were selected, with a total of 180 households. During the first month, treatment and surveillance cycles were carried out at weekly intervals, and once in two weeks during the next two months. Six posttreatment surveillances were carried out in the same way as the pre-treatment surveillances. According to the results obtained in this study, out of three treatment sites, two sites were shown to have Culex mosquito density reduction of 19% and 4%, while an increase in mosquito density was observed in the third site. Further, the three control sites, showed an average of 17% mosquito density reduction even without the application of Vectobac-WGr treatment. These results suggest that the product Vectobac-WGr is not effective on Culex quinquefasciatus as a larvicide to control filariasis in Sri Lanka.
An Entomological study to plan intervention for prevention of dengue in Gampaha district, Sri Lanka
(Elsevier, 2008) Abeyewickreme, W.; Hapangama, H.A.D.C.; Weerasinghe, I.; Hapugoda, M.D.; Gunawardene, Y.I.N.S.; Gunawardena, N.K.; Wickremasinghe, A.R.
BACKGROUND: Dengue is the most common and fastest spreading human arbo viral disease worldwide. Most control efforts are based not on insecticides but on suppression of vectors by reducing the number of larval breeding habitats. METHODS: Total of 2000 houses in the District of Gampaha in the Western Province which had the second highest transmission of dengue in 2006 was selected using grid sampling technique, based on disease incidences during 2003—2006. Mosquito surveillance was carried out from 0900 hrs to 1400 hrs during June-August, 2007. Larval and pupal surveillances were carried out indoors and outdoors using standard larval surveillance techniques. RESULTS: The House, Container and Breteau indices for Aedes larvae were 49.3%, 26.1% and 26.9% respectively. The common breeding places for Aedes species were discarded containers 27.1% (559/2064), unused bowls 16.2% (334/2064), plant axils 11.7% (242/2064), water storing barrels 11.4% (236/2064) and coconut shells 5.4%(111/2064). Most productive container types for larvae were tyres (44.3%), plant axils (37.6%), ceramic jars (36.6%), discarded containers (29.5%) and fish tanks (25.0%). Most productive container types for pupae were discarded containers (13.4%), fish tanks (10.4%), unused bowls (8.38%), ceramic jars (7.31%) and coconut shells (6.3%). Aedes albopictus (larvae-85.3%, pupae-80.4%) was the most predominant vector in the district. Earthen pots, plant axils, discarded containers and buckets were the main sources for Aedes albopictus while tyres, barrels, tanks and bowls were for Aedes aegypti. Further, mixed breeding was observed in water storage containers and tyres. CONCLUSION: Discarded small bowls/containers were the key containers with the highest pupal index. Natural breeding habitats such plant axils may also significantly contribute to pupal production. Therefore an integrated control effort to include community level awareness programmes, improved solid waste management for small containers and efforts to prevent breeding in plants is suggested for prevention of dengue in the district. © 2008 Elsevier Inc.
Knowledge, attitudes and practices (KAP) on dengue control in Gampaha district.
(Sri Lanka Association for the Advancement of Science, 2008) Abeyewickreme, W.; Hapangama, H.A.D.C.; Gunawardene, Y.I.N.S.; Hapugoda, M.D.; Gunawardena, N.K.; Wickremasinghe, A.R.
Dengue/Dengue Hemorrhagic Fever (DHF) has become a major public health problem in many parts of the tropics. In Sri Lanka, it is endemic in some parts of the country with outbreaks of dengue/ DHF. The present study was done to assess 1) knowledge regarding dengue among the general population in the district of Gampaha, 2) whether simple preventive measures are being practiced in the community. A cross-sectional survey was conducted in selected 2000 households in the Gampaha District from June - August, 2007 using a pre-tested structured questionnaire to assess the level of knowledge, attitudes and practices regarding dengue. The majority of the respondents interviewed were females (65.2%). More than 90% have had secondary education (90.2%). The main source of water supply were pipe borne (43.4%) and well water (40.6%). 64.3% households stored water for washing, drinking and cleaning purposes. More than 95% of the respondents had heard about dengue fever and its transmission. 91.3% cited that their main source of information on dengue was from television/radio. 34.3% had either received advice or participated in a training programme on dengue prevention and 7.8% had received support materials. The main preventive measure used to reduce the mosquito nuisance was personal protection with repellents (73.6%). Most of the respondents (56.8%) felt that no action was taken by the government to control mosquitoes. When respondents views were taken, the suggestions made by them to improve dengue control included, fogging (31.8%), educating people (30.5%), treating water (24.3%) and cleaning the environment (19.5%). When questions were directed at possible methods for community participation for dengue control, the majority were in favour of removing solid waste (84.15%), eliminating stagnant water collections (40.7%), removing larvae (8.75%) and covering all the water containers using lids (8.1%). The community had good understanding on dengue and the main source of information was from the electronic media. However it was found that good knowledge itself does not necessarily lead to good practices. The respondents' attitudes were found to be good and most of them were supportive of control measures. Mass media is an important means of conveying health messages to the public, thus research and development of educational strategies designed to improve behaviour and practices of effective control measures through mass media among the community are recommended. Financial support by World Health Organization TDR/WHO Multi Country Study on "Eco-Bio-Social Research on Dengue in Asia" is acknowledged.
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.
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.
Silent transmission of the dengue fever in Gampaha District, Sri Lanka
(Malaysian Society of Parasitology and Tropical Medicine, 2007) Hapangama, H.A.D.C.; Gunawardene, Y.I.N.S.; Gunasena, S.; Hapugoda, M.D.; Premaratna, R.; Wellawaththage, L.C.; Abeyewickreme, W.
Dengue fever is a major infectious disease in Sri Lanka. Silent transmission of dengue virus has been suggested as a possible risk factor for the increasing incidence of dengue. The present study was carried out in the District of Gampaha using cluster investigation method. A cluster consisted of a minimum of 20 volunteers (family members and immediate neighbours) of a hospitalized serologically/molecular biologically confirmed dengue patient. Serum samples were collected from 148 volunteers in 7 clusters. Samples were tested for anti-dengue antibodies using Dengue Duo IgM and IgG Rapid Strip Test. Of these, positives were further tested for anti-dengue IgG antibody by Haemagglutination Inhibition (HAI) assay, the gold standard test for serological diagnosis of virus infection. Of the 148, 41 had evidence of exposure to dengue virus by Dengue Duo IgM and IgG Rapid Strip Test [positive for IgM: 28(68.4%), IgM & IgG: 7(17%) and IgG: 6(14.6%)]. Of that 41, paired sera were collected from 36 volunteers and tested by HAI assay which confirmed dengue virus infection in 4(11.1%) [confirmed secondary-4(100%)]. Additional 32(88.9%) were diagnosed as recent dengue infections [probable secondary-17(53.1%), probable dengue- 15(46.9%)]. Out of 36 volunteers, 12(33.3%) were symptomatic [confirmed secondary-1(8.3%), probable secondary-10(83.4%), probable dengue-1(8.3%)] and 24(66.7%) were asymptomatic [confirmed secondary-3(12.5%), probable secondary-7(29.2%), probable dengue-14(58.3%)]. Presence of dengue vectors, Aedes aegypti and/or Aedes albopictus were detected around all 7 clusters. The present study serologically confirms the persistence of silent transmission of dengue virus with a trend towards clustering around cases. Presence of vector species in the area further supports this phenomenon.
A Study on cost of caring for patients with dengue fever at Professorial Medical Unit, Colombo North Teaching Hospital
(Sri Lanka Association for the Advancement of Science, 2008) Hapangama, H.A.D.C.; Attanayake, N.; Premaratna, R.; Abeyewickreme, W.
Dengue fever (DF) and Dengue Hemorrhagic Fever (DHF) may constitute a substantial economic burden on both the healthcare system and individual households in Sri Lanka. The objective of this study was to determine cost of caring for patients with DF and to determine the economic impact of DF on households and healthcare institution. The direct economic impact of the healthcare system and on the households of 31 laboratory confirmed dengue patients who were managed in the professorial medical wards of the North Colombo Teaching Hospital, Ragama was assessed during October, 2006 to March, 2007. The institutional cost was calculated using data obtained from relevant departments of the hospital. The cost for the households of each patient was calculated using an interviewer administrated questionnaire. Of the 31 patients enrolled all had DF and none developed DHF. The median and mode for hospital admission of study sample was third day of fever (range 1-7). The mean Direct Household Cost (DHC) for a single day in hospital of a dengue patient was Rs 820.06. Over 90% of DHC consisted of cost for transportation (33.22%), food (30.44%) and for services obtained from outside hospital sources (30.14%). The mean basic institutional cost for a patient-day in a medical ward of the hospital (excluding the cost for specific management of an illness) was Rs.961.81. Total institutional cost of caring dengue patient per day was Rs. 1142.57 which comprised of cost for basic inpatient care (84.2%) and specific management of dengue fever (15.82%). Further, total cost of hospitalization due to dengue for the study sample comprised of 6.5% for drugs, 17% for investigations and 76.5% for accommodation, staff, transportation, food and other expenses. The study shows a considerable economic burden for both hospital and households due to hospitalization with dengue fever. Although this study focused on some aspects of curative care, primary prevention should be regarded as the basis for minimizing the economic and social burden. The rising demand for the laboratory investigations needs to be addressed by the public sector in a more systematic manner. The substantial burden on the household can be reduced by integration of the private sector in to the system in a rational manner and ensuring a pricing policy. "All medical and nursing staff of the Medical Wards of the North Colombo Teaching Hospital and staff of the Molecular Medicine Unit are gratefully acknowledged."
Study on effect of silent transmission and clustering of cases on the transmission of dengue virus in gampaha and kurunegala districts, Sri Lanka
(University of Kelaniya, 2010) Hapangama, H.A.D.C.
Dengue infection has been an important flaviviral infection in Sri Lanka and is considered as an emerging and re-emerging disease causing epidemics from time to time. During the last 20 years hyperendemic transmission has been established over a geographically expanding area. Transmission of dengue virus is known to be influenced by overlapping and reinforcing factors related to human host, virus and mosquito vector. Present study is on the effect of silent transmission, clustering of dengue cases and the role of Aedes vectors on transmission of dengue in Gampaha and Kurunegala Districts of Sri Lanka. The present study was carried out using the cluster investigation method. Index clusters were selected from hospital based dengue cases. Control clusters were selected from low dengue transmission areas. Cluster enrolees recruited were residing within 100 m radius from the index case and blood samples and demographic data were collected. At each household, adult and larval mosquito surveillance was also carried out. Volunteer samples were tested for recent dengue infection by IgM EL1SA. A selected set of sera were tested for dengue Ag by Ag detection ELISA, and for dengue viral RNA by RT-PCR and Semi-Nested PCR. ffA I assay was done as a confirmatory test. Of the 629 volunteers recruited from 30 index clusters, 90 (14.3%) were positive for recent dengue infection while none of the 310 volunteers of 15 control clusters were positive. Of the 90, asymptomatic dengue infection was observed in 49 (54.4%) indicating symptomatic to asymptomatic rate of infection was 1:1.2 in the study locations. Previous dengue infected volunteers were more vulnerable to infection (r2=2.19, p<0.00!) and age was the most important factor determining asymptomatic infections (r=0.672, pO.OOl). Irrespective of the gender, dengue exposed population over 40 years of age were more likely to be asymptomatic (x2==21.87, pO.OOl). Of the 33 paired sera tested by HAI assay, dengue virus infection was confirmed in 4 volunteers, of them 3 were asymptomatic confirming the presence of silent transmission in the study population. Level of IgM antibody was less among asymptomatic volunteers compared to symptomatic volunteers and hospitalized patients (F=16.05, pO.OOl). Study confirmed the clustering of dengue cases around index cases (t=5.06, pO.OOl). Dengue infections were clustered centrally close to the index patient's house (F=5.894, pO.OOl) with a significant trend towards household risk of infection. There was a significant correlation between the presence of dengue infection with breteau index (+0.372) and Aedes albopictus was found in 70% of the localities. Of the 40 adult Aedes mosquito pools (3 Ae. Aegypti and 37^1e. albopctus) collected from index cluster localities, only one pool (Ae. albopictus) was positive for dengue viral RNA and it was found to be of dengue serotype 2 (DEN-2). Study confirms the presence of asymptomatic dengue infections, clustering of dengue cases and the probable role of Ae. albopictus on dengue transmission leading to silent spread of the disease.
Towards an innovative approach to control dengue: Bio-Social study in Gampaha District, Sri Lanka
(University of Kelaniya, 2008) Abeyewickreme, W.; Wickremasinghe, R.; Karunathilake, K.; Hapangama, H.A.D.C.
Transmission study of dengue fever in Gampaha District, Sri Lanka
(Faculty of Tropical Medicine, Mahidol University, 2007) Hapangama, H.A.D.C.; Gunawardene, Y.I.N.S.; Hapugoda, M.D.; Dayanath, M.Y.D.; Abeyewickreme, W.
RATIONALE: Dengue is an important flaviviral infection in Sri Lanka.OBJECTIVES; To determine the effect of possible contributing factors on transmission of Dengue METHODS: A total of 40 households situated around 7 selected dengue cases confirmed by both IgM-IgG ELISA and HAI assay were taken. A minimum of 3 inhabitants from each household were tested for anti-dengue antibodies. At each household, mosquito surveillance was carried out. RESULTS: Of the 40 households, 26(65%) were positive for dengue viral infection. Of the 148 inhabitants, 41 had evidence of exposure to dengue. Of the 41. asymptomatic dengue infection was observed in 25(61%). Paired sera were collected from 36/41 volunteers and tested by HAI assay which confirmed dengue virus infection in 4(11.1%) and were confirmed secondary. Three (75%) of them were asymptomatic. Balance 32(88.9%) was diagnosed as recent dengue infections. Of that 21(65.6%) were asymptomatic probable secondary 7(33.3%), recent dengue 14(66.6%)]. Clustering of cases was observed in all localities varying from 56.5%. There was a significant statistical association between the presence of a definitive dengue infection with the presence of Aedes vectors (x2=3.1, p=0.1). Ae. albopictus were found in all localities 'while Ae. aegypti was found only in one. Breteau index for Ae. albopictus varied from 0-260 while- container index varied from 0-84%. Highest clustering of dengue cases were observed in localities with the highest indices for' mosquitoes. CONCLUSIONS: Study confirms that the presence of asymptomatic infections and clustering of cases. The predominant vector was Ae. albopictus.