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    A Fuzzy Linear Model Using Possibilistic Linear Regression with Least Squares Method: An Application to Dengue and Rainfall Data
    (International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Attanayake, A.M.C.H.; Perera, S.S.N.; Liyanage, U.P.
    Fuzzy linear models deal with vague and imprecise phenomenon in order to represent better models. These type of models are especially suitable in modelling and predicting dengue disease as the disease associated with various unknown and uncontrollable factors. Further, modelling and predicting the dengue disease is important as it is one of the leading diseases in the world which reports higher number of deaths. This study focuses on modelling reported dengue cases in the Colombo district, Sri Lanka. Particularly, Possibilistic Linear Regression with Least Squares (PLRLS) Method was applied as the modelling procedure. This method was proposed by H. Lee and H. Tanaka in 1999 to deal with crisp inputs and fuzzy output. The rainfall as one of the leading climatic factors that associated with dengue disease included in the model as an independent variable. Data consists of weekly reported dengue cases and weekly average rainfall in the Colombo district from 46th week of 2009 to 12th week of 2015. 2009 to 2014 data were used for model development and rest of the data for model validation. Cross correlation analysis revealed that the rainfall with 10 lags was associated with the reported dengue cases. By considering dengue and rainfall data as crisp inputs, the upper approximation model and lower approximation model were obtained to reflect the fuzziness of the dengue count in the district. The developed coefficients of the fuzzy linear regression were in the form of non-symmetric triangular fuzzy numbers. The left and the right spreads of the central value determined the lower and upper boundary of the interval, respectively, where the corresponding degree of membership equals to 0. The predicted values from the fuzzy regression model and the actual values of the validation set were within the upper and lower approximation models which indicated the possibility of the dengue prediction through PLRLS method. The authors are in the process of testing additional fuzzy linear models by changing fuzzy input/output combinations with incorporating more independent variables.
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    Prediction of Dengue Incidence Based on Time Series Modelling in the District of Colombo, Sri Lanka
    (International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Udayanga, L.; Herath, K.; Gunanthilaka, N.; Iqbal, M.C.M.; Abeyewickreme, W.
    Timely implementation of intervention activities, is essential in controlling dengue epidemics. This requires the prediction of dengue epidemics, while respecting the spatial and temporal trends in dengue incidence. However, such aspects are limitedly focused in dengue epidemic management of Sri Lanka. Therefore, the current study was conducted to develop a temporal prediction model for dengue incidence in the district of Colombo in Sri Lanka. Dengue cases reported from 2000 to 2018 in the district of Colombo were collected from the Epidemiology Unit, Sri Lanka. Selected meteorological parameters such as number of rainy days, monthly cumulative rainfall, minimum and maximum relative humidity and temperature corresponding to the same study period were collected from the Department of Meteorology, along with the Oceanic Niño Index (ONI) from the National Oceanic and Administration (NOAA) Centre. All the data were arranged at monthly level. After evaluation of the normality, seasonality, stationarity and seasonal stationarity of the epidemic data, a Seasonal Autoregressive Integrated Moving Average (SARIMA) model was fitted for the prediction of dengue by using the R statistical package. Subsequently, the meteorological factors and the dengue incidence was subjected to a cross correlation analysis to identify the most representative meteorological factors associated with dengue epidemic incidence and an Autoregressive Integrated Moving Average with Exogeneous Input (ARIMAX) model was fitted. The best fitted SARIMA (0, 1, 0) (3, 0, 0)12 model was characterized by an Akaike Information Criteria value (AIC) of -19.04, Bayesian information criterion (BIC) of -5.42, Mean error (ME) of 0.002 and Root Mean Square Error (RMSE) of 0.518. According to the cross correlation analysis, number of rainy days (RD) and Oceanic Niño Index (ONI) denoted a significant negative association with the reported dengue cases in Colombo, while monthly cumulative rainfall (RF), maximum relative humidity (Max_RH), maximum temperature (Max_T) and minimum temperature (Min_T) shared a positive correlation (P < 0.05 at 95% level of confidence). The best fitting ARIMAX model (as indicated below) was characterized by an AIC of -15.74, BIC of -11. 2, ME of 0.006 and RMSE of 0.171. ARIMA (0, 1, 1) + [-0.0006 RDt-3 + 0.0008 RFt-3 + 0.0260 Max_RHt-3 + 0.0766 Min_Tt—4 - 0.0661 ONIt-5] Based on the performance, the ARIMAX model is recommended to be used for the prediction of dengue incidence in the Colombo district to ensure rational allocation of resources for vector control and dengue epidemic management
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    Assessment of Possible Risk Factors Affecting Transmission of Dengue in the District of Gampaha Based on Reported Dengue Cases
    (International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Perera, E.H.L.; Viswakula, S.; Gunawardene, Y.I.N.S.; Subasinghe, U.; Hapugoda, M.D.
    Dengue is a fast spreading arboviral infection transmitted by the bite of infected females of Aedes aegypti (Linnaeus) and Ae. albopictus (Skuse). According to the Epidemiology Unit, the second highest number of dengue cases is reported in the District of Gampaha, Sri Lanka over past ten years. Objective of this study was to investigate the entomological and socio-economic risk factors affecting transmission of dengue in laboratory-confirmed dengue case reported stations in the District of Gampaha. Laboratory confirmed positive dengue patients (n=100) by dengue NS1 antigen test during the period of June, 2018-August, 2019 were selected. Entomological surveillance was conducted by visiting to each patient within one week of notification of a positive case. For the collection of socio-economic data, an interviewer-administrated questionnaire was used. Adult Aedes mosquito samples collected using a back-pack aspirator showed, 98.64% (73/74) of Ae. albopictus and 1.35% (1/74) of Ae. aegypti mosquitoes. Larval collection using standard larval surveillance techniques showed 92.96% (185/199) and 7.04% (14/199) of Ae. albopictus and Ae.aegypti larvae respectively. The highest House Index (55.17%-16/29), Container Index (28.89%-13/45) and Breteau Index (44.83%-13/29) were reported in the month of June, 2019. The major Aedes breeding place was identified as plastic buckets/barrels (48.6%-84/173) that being used to discard waste. Piped borne water (88%-88/100) was the major water source of the house-holds. Water source of tube well (9%-9/100) was the next popular water source and 66.67%(6/9) of tube wells were positive breeding places for Aedes larvae. Average homestead of the premises of dengue patients was 16.14 perches. From the 100 dengue cases, 67 cases were from middle of town areas, while 2 were from rural areas. Vegetation coverage of the 78% (78/100) house-holds were grass, bushes and small trees and 3% (3/100) house-holds didn’t have any vegetation coverage. The major mosquito prevention method was usage of mosquito nets (54%-54/100) and among dengue patients 7% (7/100) of dengue patients weren’t using any mosquito prevention method. High density of Ae. albopictus mosquitoes, was reported although Ae. aegypti is the major vector of dengue. Therefore, it is required to draw more attention about the Ae. albopictus breeding sites in dengue control programmes. Participants from the study sites were well aware about the disease but still there is a lack of knowledge on breeding sites and vector control methods. Drawbacks in the waste disposal methods, lack of cleanliness in gardens, unplanned water sources and neglecting preventive actions could be considered as the possible risk factors.
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    Oviposition Preference of Aedes albopictus (Diptera: Culicidae) at Domestic and Peri-Domestic Settings in Gampaha Medical Officer of Health (MOH) of Sri Lanka
    (19th Conference on Postgraduate Research, International Postgraduate Research Conference 2018, Faculty of Graduate Studies,University of Kelaniya, Sri Lanka, 2018) Dalpadadoa, C.P.R.D.; Amarasinghe, L.D.; Bandaranayake, W.A.C.L.
    There are varying ranges of water filled man-made and natural container habitats with varying physico chemical parameters available for the breeding of Aedes mosquitoes. House to house cross-sectional entomological survey was carried out monthly in Gampaha MOH area from April 2017 to June 2018 in order to investigate oviposition preference of dengue vector mosquitoes in domestic and peri-domestic areas. Larval collections were done indoors and outdoors using random sampling technique for minimum 100 houses within a radius of 300 m and potential breeding places in each site were identified and categorized accordingly. Out of 1500 premises examined, 17.4% (n= 261) premises were found positive for Ae. albopictus and Ae. aegypti was not recorded during the study period. The House Index (HI), Container Index (CI), and Breteau Index (BI), varied from 3 - 39, from 5.4 - 44.4, and from 4 - 67, respectively during the study period and there was a strong correlation between the HI and the number of dengue patients reported in Gampaha MOH area according to pearson correlation analysis. (r = 0.64). Overall 2828 potential breeding places were examined in which 18.2% (n=405) containers were found positive for Ae. albopictus larvae. The result indicates that most of these positive breeding places were located outdoors 91.2% (n=369) and only 8.8 %( n=36) positive breeding places were located indoor which includes non- used cisterns/ commodes and refrigerator trays. There were 26.5% (n=750) discarded receptacles, 22.6% (n=640) temporary removal items, 13.2% (n=373) natural breeding places, 8.6% (n=242) water storage items, 8.3% (n=235) covering polythenes, 6.2% (n=176) pet feeding cups, 4.8% (n=136) ornamentals, 2.8% (n=78) tyres, 2.4%( n=68) non used cisterns and commodes and 1.9%( n=53) refrigerator trays. Results Indicates that tyres (51.9%), non- used cisterns/commodes (47.7%), ornamentals (26.2%) were the most preferred breeding localities forAe. albopictus followed by discarded receptacles (24.3%) irrespective to the number of potential breeding places found. According to the results CI for discarded items, temporary removals and covering items increased drastically prior to dengue epidemics and four to five weeks lag period was identified between increased container index and increased number of dengue patients. Non- used cisterns/commodes and natural breeding places showed year around productivity and positivity for Ae. albopictus which indicated that they contributed to maintain and survival of mosquito vector population between intermediate dry periods. Therefore, this study emphasizes the control of mosquito breeding in key breeding places such as non-used cisterns, commodes and, natural breeding places may be beneficial to reduce vector densities during dry period hence, leading to reduce the spreading mosquito vectors in to other made artificial containers during rainy season leading to major out breaks
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    Isolation of a Potential Microbial Agent for Controlling Dengue Vector Mosquitoes in Sri Lanka
    (19th Conference on Postgraduate Research, International Postgraduate Research Conference 2018, Faculty of Graduate Studies,University of Kelaniya, Sri Lanka, 2018) Induwara, R.; Fernando, M.; Ranathunge, T.; Parakrama, G.; Hapugoda, M.
    Controlling dengue vector mosquito is the most appropriate controlling method for dengue in the absence of an effective drug or a vaccine for dengue viruses. Vector control can be performed using variety of approaches such as environmental management, chemical and biological control etc.; which have been used in recent vector control activities. Due to the development of resistant varieties against chemical insecticides, the present study attempted to identify larvicidal activity of bacteria collected from the natural environment, as an ideal environmental friendly and effective strategy for controlling Aedesaegypti (Linnaeus), a dengue vector mosquito species. Zero dengue infection was reported in Pudumurippu area in the District of Kilinochchi, Northern Province of Sri Lanka in a preliminary survey. Spore forming microbes were isolated through spread plate technique using water and sediment samples collected from a reservoir in Pudumurippu. Larvicidal activity of each isolate was tested by Ae. aegypti third instar Larvae (L3) in vitro. The highest larvicidal activity was observed in an isolated bacterium from a reservoir water sample under laboratory and field conditions. This bacterium was presumptively identified and subjected to 16s-rRNA sequence analysis. Larvicidal activity of this bacterium was compared with a currently used Bacillus thuringiensisisraelensis (Bti). As well as optimum physiological characteristic features of isolated strain was determined by growing the bacteria strain on nutrient agar supplemented with different NaCl concentrations and different pH values. Isolated bacterium was confirmed as a new strain of Bacillus cereus (SL001; MG827268). This bacterial strain showed the highest larvicidal activity at 5% (1×105 CFU/ml), with mean cumulative mortality rate 92±4.1% and 84.2 ±5.3% at 48 hours’ post challenged under laboratory and field conditions respectively. When compared with Bti, this novel strain showed significantly higher (p < 0.05) larvicidal activity. B. cereus (SL001) displayed high growth rate while tolerating wide range of salinity (0-30gL-1) and pH (6-10). Based on the findings, B. cereus (SL001) with the highest larvicide efficiencies could be an ideal candidate for biological controlling of Ae. aegypti dengue vector mosquitoes in Sri Lanka. Further analysis of this bacterium is on going at present.
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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.
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    Laboratory Evaluation of the Bio-control Efficacy of Selected Copepods on Dengue Vectors 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.; Ranathunge, R.M.T.; Iqbal, M.C.M.; Abeyewickreme, W.; Hapugoda, M.
    Among variety of alternatives for management of dengue vectors, biological control remains as a promising approach, due to its high efficacy, sustainability and low impacts on human and ecosystem health. Copepods are considered asa leading predator of mosquito larvae including Aedes vectors. However, the predatory potential of different copepods on bio-control of dengue vectors has been less studied in Sri Lanka. Therefore, the current study aimed to evaluate the predatory success of five locally abundant copepods on both AedesaegyptiandAe. albopictus. Copepod collections were made from water bodies and rock pools located in the Kandy and Gampaha districts by using a plankton net. After morphological identification, single gravid copepods of different species were used to establish copepod cultures under standard laboratory conditions. Five adult copepods of each species were transferred into containers and groups of 200 first instar Ae. Aegypti larvae were introduced in to each container, separately. The number of surviving larvae in each container was recorded at 3 hour intervals up to 24 hours. Five replicates were conducted for each copepod species. Same experimental design was followed for Ae. albopictus. General Linear Modelling technique (GLM) followed by Tukey’s pair-wise comparison was used to make statistical inferences on the significance of average larvalconsumption rates by studied copepod species. SPSS (version 23) was used for the statistical analysis. Five species of copepods, namely Cyclops languides, C. varicans, C. vernalis, Mesocyclopleuckarti and M. scrassus were considered during the study. Average predation rates of 34.9±1.80 and 33.5±1.06 for Ae. aegypti and Ae. albopictus, respectively, were indicated by M. leuckartias the highest predation rates. Meanwhile, M. scrassus showed the second highest predation rates for both Aedes vectors. On the other hand, the lowest predatory efficacy was shown by C. languides with 10.6+1.60 and 8.4+1.10 for Ae. aegypti and Ae. albopictus, respectively. The average consumption rates of different copepod species varied significantly (p<0.05 at 5% level of significance). The type of Aedes species had a significant influence on the predatory efficacy of studied copepods (p< 0.05) under laboratory conditions. In conclusion, M. leuckartiand M. scrassus that reported the highest predation efficacies on both Aedes larvae could be suggested as potential bio-control agents for dengue vector management approaches in Sri Lanka after semi field and field settings.
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    Dengue: The Cost of Illness
    (In: Proceedings of the International Postgraduate Research Conference 2017 (IPRC – 2017), Faculty of Graduate Studies, University of Kelaniya, Sri Lanka., 2017) Kalansooriya, W.
    Dengue is a viral infection transmitted through the bite of infected Aedes mosquitoes. It is an endemic in Sri Lanka especially in urban and suburban settings with higher transmission rates happening during the rainy season. Even though the dengue epidemic has been devastating, its consequences for the people and economy have received a little attention from economists. The economic burden of the dengue disease has many aspects. First, it affects the public budget as the government urged to allocate extra resources to treat dengue patients as well as to control the spreading of the disease. Second, it affects the individual and household budget since they have to face an unexpected expenditure for their treatments. Thirdly, getting illness reduces the number of working days of the people and therefore the overall productivity of the economy. Therefore, this study intends to identify the economic cost of dengue disease in Sri Lanka by taking a sample of 117 dengue affected people in the year 2016. The sample was selected from Maharagama division in Colombo district which is one of the high density Dengue reporting area. The selection of the sample units was on judgment base according to the prevalence data within the year. The study estimated three kinds of costs; direct medical cost, indirect cost, and other costs involved in Dengue disease. Direct medical costs include the cost associated with hospitals, doctors, nurses, use of equipment, laboratory services, prescriptions, and so on. A shadow price method was used to estimate the indirect cost which is their forgone productivity. The other costs include the extra cost bared by the patients and their families due to the illness; such as food, travelling, caring, and so on. The study found that the total cost of prevalence of dengue disease per person is approximately 74000 rupees on average while 74% of this accounts from direct medical cost, 16% from the loss of productivity and 10% from other.
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    Detection of Dengue Co Infections Using a Novel Single Tube Multiplex Reverse Transcription Polymerase Chain Reaction.
    (In: Proceedings of the International Postgraduate Research Conference 2017 (IPRC – 2017), Faculty of Graduate Studies, University of Kelaniya, Sri Lanka., 2017) Jayathilake, E.K.S.; Jayarathne, J.A.J.C.; Muhandiramlage, T.P.; Fujii, Y.; Gunasekara, K.A.D.C.
    Co-infection in individuals by more than one Dengue Virus (DENV) serotype has been reported in regions where multiple serotypes co-circulate. Co-infections can be detected using Polymerase Chain Reaction (PCR). Semi-nested multiplex PCR with Lanciotti’s primers is a widely used PCR method for serotyping DENV and it has also been used for detecting coinfections. Despite of being widely used, Lanciotti’s method may be sub-optimal in detecting co-infections as overlapping primer targets will create a bias in the amplification of the serotype with a low viral load. This could lead to underreporting of co-infections. Nine new non- overlapping primers were designed to independently amplify each serotype with minimal competition between primers to their target.In mixed infections, novel PCR assay exhibited higher sensitivity in detecting the minor serotype compared to Lanciotti’s method. The new method can also detect all four serotypes in viral RNA isolated from viral cultures and patient samples in a single tube multiplex PCR. This enables rapid and cost-effective serotyping with improved sensitivity indetection ofco-infections in clinical samples.
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    Role of Larval Indices on the Incidence of Dengue Epidemics in Akurana, Medical Officer of Health (MOH) Area, Kandy.
    (In: Proceedings of the International Postgraduate Research Conference 2017 (IPRC – 2017), Faculty of Graduate Studies, University of Kelaniya, Sri Lanka., 2017) Udayanga, N.W.B.A.L.; Gunathilaka, P.A.D.H.N.; Iqbal, M.C.M.; Fernando, M.A.S.T.; Abeyewickreme, W.
    As in many other Asian countries, vector control entities in Sri Lanka also depend upon larval indices as the major driving factor of routine entomological surveillance and management of dengue vectors. However, studies aimed at defining the role of larval indices, which reflect the population dynamics of dengue vectors, on the incidence of dengue outbreaks are limited. This is mainly due to restrictions in long-term vector density related data. Hence, the current study attempts to evaluate the role of larval indices on the incidence of dengue epidemics in Akurana, Medical Officer of Health (MOH) area.