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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A Statistical Approach to Define Thresholds for Dengue Epidemic Management in Akurana Medical Officer of Health Area, Kandy District of Sri Lanka
(19th Conference on Postgraduate Research, International Postgraduate Research Conference 2018, Faculty of Graduate Studies,University of Kelaniya, Sri Lanka, 2018) Udayanga, N.W.B.A.L.; Gunathilaka, P.A.D.H.N.; Iqbal, M.C.M.; Fernando, M.A.S.T.; Abeyewickreme, W.
Stegomyia indices, namely; Premise Index (PI), Breteau Index (BI) and Container Index (CI) are used forvector management approaches in Sri Lanka. Properly defined threshold values for larval indices are of higher importance to provide forecasts on dengue epidemics and also for effective larval management of dengue vectors. However, such critical thresholds are poorly defined for Sri Lanka. The present study aimed to define threshold values forabove larval indices for dengue epidemic management in the Akurana Medical Officer of Health (MOH) in the Kandy District. Larval surveys were conducted on a monthly basis from January, 2016 to June, 2018. Four larval indices, namely BI for Aedesaegypti (BIA) and Aedesalbopictus (BIB), PI and CI were calculated. Further, monthly larval indices of AkuranaMOH area from January, 2012 to December, 2015, were obtained from the MOH office, along with monthly reported dengue cases for the entire study period. Receiver Operating Characteristic (ROC) curves in SPSS (version 23) were used to assess the discriminative power of the larval indices in determiningdengue epidemics and thresholds based on larval indices. As indicated by the area of ROC curve (AUC), the BIA (0.661) and PI (0.637) were having a notable discriminative power to forecast dengue epidemics at a two-month lag period. Both BIB (0.397) and CI (0.526) were non-informative influencers at one and two-month lag periods. The BIA and PI were better predictors of dengue incidence than BIB and CI. Based on the ROC curve, three risk thresholds were defined for BIA as Low Risk (BIA≤2.1), Moderate Risk (3.9≤BIA<4.85), and High Risk (BIA≥4.85), with respect to Ae. aegypti. According to the PI, thresholds were defined as Low Risk (PI≤6.2), Moderate Risk (7.7≤ PI<9.9), and High Risk (PI≥ 9.9). Threshold values defined for BI of Ae. aegypti and PI, could be recommended to be considered in implementing vector control efforts in the above study area for effective dengue epidemic management, through pre planned entomological management of dengue vectors.
Predicting acute liver failure in dengue Infection
(American Gastroenterological Association(AGA) Institute, Published by Elsevier Inc., 2013) Ranawaka, C.; Niriella, M.A.; Kumarasena, R.S.; Miththinda, J.K.N.D.; de Silva, A.P.; Premaratna, R.; de Silva, H.J.
BACKGROUND: Dengue infections (DI) can range from being asymptomatic to severe illness. Unusual manifestations such as encephalitis, myocarditis, and acute liver failure (ALF) have been recognized. ALF is uncommon, but has a poor prognosis. The aim of this study was to identify predictors of ALF in DI. METHODS: Serologically confirmed patients with DI who were admitted to hospital from January 2009 to March 2010 were included. Patients consisted of direct admissions as well as referrals, some with deranged liver functions. Data was obtained from patient records. Clinical details and serum biochemistry was evaluated for up to five days from onset of illness. ALF in DI was defined as evidence of coagulation abnormality [International normalised ratio (INR) ≥ 1.5], and any degree of mental alteration (encephalopathy) in a patient without pre-existing cirrhosis. RESULTS: Out of 240 patients [57.7% male, 42.3% female; mean age 35.6 years (SD 15.4 years)], 164 had dengue with warning signs, 27 had dengue without warning signs and 49 had severe dengue. 15/49 severe dengue patients had profound shock. Abdominal pain, persistent nausea and vomiting (PNV), bleeding, hepatomegaly and ascites were present in 125, 92, 39, 129 and 28 cases respectively. Elevated aspartate aminotransferase (AST), serum bilirubin (SB), alkaline phosphatase (ALP) and gamma glutamyl transpeptide (GGT) were observed in 208, 20, 18 and 60 patients respectively. Of the 240 patients 41 had AST .1000 IU/ml (this included 4/ 15 with profound shock). 16/41 patients with AST .1000 IU/ml, including 4 with profound shock, developed ALF while none with AST ,1000 IU/ml developed ALF. In patients with AST .1000 IU/ml, presence of 2 or 3 of elevated SB, elevated ALP or PNV predicted the development of ALF with 93.8% sensitivity, 98.7% specificity, 83.3% positive predictive value and 99% negative predictive value (Fisher's exact test). CONCLUSIONS: Dengue patients with AST,1000 IU/ml are not at risk of developing ALF. Patients with AST .1000 (regardless of presence or absence of profound shock), with 2 or 3 of elevated SB, elevated ALP or PNV seem to be at risk of developing ALF. These findings need to be validated in a larger cohort of patients.
Dengue fever with bleeding manifestations in pregnancy: our experience
(Sri Lanka College of Obstetricians and Gynaecologists, 2004) de Silva, B.A.; Palihawadana, T.S.; Fernando, W.S.; Wijesinghe, P.S.
Dengue fever, a mosquito borne flavivirus infection is endemic in Sri Lanka. An increased number of cases are seen in the recent past. An increase in the number of patients with secondary infection who are prone to develop complications such as bleeding manifestations, are expected due to repeated outbreaks of the disease, We report four cases of serologically confirmed Dengue fever. Different management strategies were adopted in each patient according to the clinical circumstances. Three antenatal mothers presented in 33, 38 and 39 weeks of POA and bleeding manifestations were present in all three of them. One of them died of an intracerebral haemorrhage after Caesarean section to deliver a stillborn following intrauterine death. Post Partum Haemorrhage (PPH) was experienced in another mother following caesarean section. In one patient bleeding manifestation appeared 2 days following normal delivery. She was managed conservatively. Though the clinical presentations may be similar to that of non pregnant patients, there can be many pitfalls in diagnosis and management of dengue fever occurring in pregnancy. Two of the patients described above developed acute dengue viral hepatitis, which needs to be differentiated from HELLP syndrome and acute fatty liver of pregnancy. Serological tests have a special place in diagnosis than in the non pregnant patients. The classical criteria used to identify Dengue Haemorrhagic fever (DHF), such as an increased haemotocrit and postural hypotension were not present in these patients. In management, the administration of intravenous fluids needed to be more closely observed. They seemed to be more prone to develop bleeding manifestations than non pregnant patients and therefore platelet transfusions were required in early stages. Early interventions to deliver the baby, if the other circumstances permit, seem to offer a better outcome in patients presenting in the antenatal period.
Evaluation of the spatial and temporal trends of dengue outbreaks in Gampola, Central Province, Sri Lanka
(University of Peradeniya, 2015) Udayanaga, N.W.B.A.L.; Gunathilaka, H.N.; Iqbal, M.C.M.; Abeyewickreme, W.
Dengue is the world's fastest growing vector borne disease, and it has become one of the major health concerns in many countries including Sri Lanka. Despite immense efforts and control strategies it claims 30,000 - 35,000 deaths per year, making dengue a priority heath issue in Sri Lanka. Investigation of the recent trends of dengue outbreaks on both a spatial and temporal scale is of high importance in drafting and implementing effective management/action plans to ensure successful management and control of dengue epidemics on a regional scale. Hence, a statistic and geo informatics based analysis of the recent trends in dengue distribution was carried out to identify spatial and temporal trends in distribution patterns of dengue in the Gampola Medical Officer of Health (MOH) division. Monthly records of reported dengue cases from 2009 to 2013 of the Gampola MOH division were collected. A scatter plot analysis in MINITAB (version 14.12.0) was devised to identify the temporal patterns in the reported dengue cases. Arc GIS (version 10.1) was devised to develop spatial maps (at the GND level) of the recorded dengue case distribution for each month and for the whole study period, for Gampola. Furthermore, spatial (at GND level) and temporal (annual) variations in dengue outbreak distribution within the Gampola MOH were analyzed to recognize the recent trends in dengue distribution. Gampola East, Gampola West, Illawathura, Keerapane, Kahatapitiya, Egodakalugamuwa and Pussellawa localities emerged as high-risk areas, while Polkumbura, Kurukude, Galgediyawa, Amuhena and Hunukotugama emerged as low risk areas for dengue outbreaks. Further localities, namely Godagama, Kalugalhinna, Kekulanda, Millagaspitiya, Sinhapitiya North, Sinhapitiya South, Pussellawagama, Ranawala and Wanahapuwa remained unchallenged by dengue throughout 2009 - 2013. The paired-Chi square test revealed significant spatial and temporal variations in the emergence of dengue outbreaks within the Gampola MOH throughout the study period \>x2 w. 0.95} = 65.156]. Regionalized evaluation of recent trends in temporal and spatial distribution of dengue outbreaks are recommended in the design and implementation of management plans to control the rise of dengue, and also in the evaluation of the effectiveness of already implemented practices taken to reduce and control dengue outbreaks, by the government sector and other relevant entities.
Establishment and maintenance of laboratory colonies of Aedes albopictus mosquitoes
(University of Peradeniya, 2015) Wijegunawardana, A.D.; Gunathilaka, H.N.; Dassanayake, R.; Gunawardene, Y.I.N.S.; Abeyewickreme, W.
With a mission of "providing authenticated, high-quality Aedes albopictus mosquito rearing information to the research community" maintenance of a Ae. albopictus mosquito colony was started. All environmental facilities inside the insectary were carefully maintained to better suit the Ae. albopictus mosquito colonization. The mean temperature of 27°C (± 0.5°C) was constantly maintained inside the insectary. Wet towels on adult mosquito cage racks were used for proper maintenance of humidity. Lighting was using fluorescent light and regulated with 16:8 hour continuous dark and light period. Pest insect was controlled to ensure essential absence of ants and cockroaches. This was achieved without any harm to the mosquito colonies either directly or by contamination with toxicants transported by pests. An adult mosquito trap placed inside the insectary was used to monitor released mosquitoes. Consistent effort was also made to improve the level of cleanliness inside the insectary. Written guidelines were given to each person responsible for a task. Insectary operations included egg counting, preparation of hatching bottles with boiled distilled water following cooling to room temperature, egg hatching, larvae rearing with International Atomic Energy Agency (IAEA) recommended diet of tuna meal, bovine liver powder, brewery yeast and vitamin complex in a ratio of 37.5:27:10.5:2 g in 1L up to one week, pupae counting and putting into adult emergency cages, adult male feeding with 10% sugar solution with Vitamin complex, adult female blood feeding from 4th day onwards with bovine blood, placing egg laying cups and collecting egg laying cups, drying egg papers and starting next generation from the dried eggs. Adult mosquito cages were blood fed every 4th day after emergence from pupa and for quality control reasons each adult cage was blood fed only 3 times and there after only 10% sugar solution with vitamin syrup was supplemented until all adult mosquitoes died. Documentation for maintenance and data record was maintained and updated daily. Records included larvae feeding records, larvae tray maintenance and cleaning charts, adult feeding records with both sugar solution and blood, insectary cleaning records with time and dates. Number of eggs and percentage of egg hatching, larvae death, pupation, adult emergence, egg laying and adult mosquito death with respect of the sex and time difference were recorded. For bio-safety reasons all discarded material from larvae trays, egg laying cups and adult cages were boiled thoroughly to facilitate total destruction of the contaminated mosquito eggs. All other infectious material were incinerated. Finally, all above conditions facilitated achievement of 100% egg hatching rate within maximum of 24 hours, 100% survival of larvae to pupa (~ 7 days), 100% survival of pupated larvae to adult emergence (~ 2 days) and 95.5% adult survival up to 12 days. No difference was observed on adult longevity between males and females within first 12 days of adult emergence. However, approximate life span for males (-17 days) was lower than the females (~ 25 days) and the mortality was regular through all generations (Fl to F21).
Male isolation of dengue vector Aedes mosquitoes for sterile insect technique by spiking blood with ivermectin
(Sri Lanka Association for the Advancement of Science, 2015) Abeyewickreme, W.; Wijegunawardana, N.D.A.D.; Ranathunge, R.M.T.B.
There is an increasing demand for exploration of the potential for applying the Sterile Insect Technique (SIT) in area-wide integrated vector management (AW-IVM) in many countries. However, because female mosquitoes, unlike male mosquitoes, can transmit disease, means to eliminate them from the mass production process are a critical pre-requisite. In addition, the efficiency of the SIT programme could be increased by not releasing female mosquitoes due to the fact that sterile males can then only focus on wild females to achieve mating. Therefore, mosquito SIT programmes success will depend on exclusive release of sterile males, which is impossible on a large scale without efficient sex separation methods. Many different sex separations for different stages of mosquitoes are currently being attempted to successfully establish a sexing mechanism for the above purpose. Among them, the mostly attempted methods broadly include genetic sexing methods, molecular methods, mechanical methods and behavioral methods. For all blood feeding mosquitoes, sex separation could occur at the adult stage by spiking blood with insecticides (malathion, dieldrin) or other mosquito toxins (ivermectin, spinosad), as behavioral tools. In this study, a veterinary preparation of ivermectin (Ivotec,1% w/v) which is used to treat dogs infested with the filarial worm Dirofilaria repens in Sri Lanka was used as a tool for sex separation of adult Aedes albopictus and Aedes aegypti mosquitoes by feeding on spiked blood. In an initial attempt by spiking blood with 5 parts per million (5 ppm) ivermectin, 40% of the blood–fed females could survive beyond 24 hours post feeding. However, when the dosage of ivermectin was increased to 7 ppm the survival rate decreased below 40%. Since there had been high mortality of both females and males even in the control cages in which mosquitoes were blood-fed without ivermectin it was suggested that the age of the mosquitoes used may be a factor for high mortality of mosquitoes in the control experiment. When the experiment was repeated with 7 ppm ivermectin in blood using 4-5 day old mosquitoes more than 65% mortality could be observed within 12 hours post feeding in the experimental cage with a significant difference in mortality compared to the control
Evaluation of the spatial and temporal trends of dengue outbreaks in Akurana, Central Province, Sri Lanka
(Sri Lanka Association for the Advancement of Science, 2015) Udayanga, N.W.B.A.L.; Gunathilaka, P.A.D.H.N.; Iqbal, M.C.M.; Kusumawathie, P.H.D.; Najim, M.M.M.; Amerasinghe, U.S.; Abeyewickreme, W.
Renowned as the world's fastest growing vector borne disease, dengue has become one of the major health issues in Sri Lanka leading to an alarming concern due to recent outbreaks throughout the country. Despite the immense efforts taken by the relevant authorities to reduce the rate of mortality, the average number of dengue cases recorded in each year remains around 30,000-35,000 without being changed significantly over time in Sri Lanka. Investigation of the trends in spatial and temporal distribution patterns of dengue is often treasured in the drafting and implementation of management/action plans to ensure effective management of dengue epidemics at regional scale. Thus, a statistical and geo informatics based analysis of the recent trends in dengue distribution was carried out to identify spatial and temporal trends in distribution patterns of Dengue in the Akurana Medical Officer of Health (MOH) area. Monthly records of reported dengue cases from 2010 to 2014 of the Akurana MOH area were obtained and were subjected to a scatter plot analysis in MINITAB (version 14.12.0) to identify the temporal patterns in the recorded dengue cases. Spatial maps of the recorded dengue case distribution in each GND for each month and for the whole study period were prepared by using Arc GIS 10.1. The spatial and temporal variations of dengue outbreak distribution within the Akurana MOH (at GND level) were analyzed to identify the recent trends in dengue incidence. Akurana, Bulugahathenna, Dippitiya, Dunuwila, Konakalagala and Neeralla localities could be identified as areas with relatively high risk to dengue outbreaks throughout the study period, while localities such as Balakanduwa, Delgasgoda, Delgasthenna, Malgamandeniya, Marahela, Palleweliketiya and Udawelikatiya emerged as areas with low risk. As suggested by the results of the paired-Chi square test [>Χ2 (30, 0.95) = 43.773], the emergence of dengue outbreaks indicated a significantly declining trend of recorded dengue cases in most of the GNDs (Aswadduma, Delgasgoda, Kurugoda, Malgamandeniya, Palleweliketiya and Walahena etc.) during the recent years. The evaluation of the trends in temporal and spatial distribution of dengue outbreaks at the localized level, could be recommended as a useful tool in the planning and implementation of action plans to control the rise of dengue, while evaluating the efficacy of already implemented control measures at regional scale.
Role of Aedes albopictus in transmitting dengue virus in some endemic areas in Kurunegala District.
(University of Kelaniya, 2003) Hapugoda, M.D.; de Silva, N.R.; Abeysundara, S.; Bandara, K.B.A.T.; Dayanath, M.Y.D.; Abeyewickreme, W.
Abstract Available
A Preliminary study of genetic estimates of population structure of Aedes aegypti populations in three districts, Sri Lanka
(Sri Lanka Association for the Advancement of Science, 2014) Fernando, H.S.D; Hapugoda, M.D.; de Silva, B.G.D.N.K.
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.

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