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Item 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 managementItem 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.Item 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.Item Sterile Insect Technique for Controlling Aedes albopictus (Skuse); Sex Separation and Mating Competitiveness(19th Conference on Postgraduate Research, International Postgraduate Research Conference 2018, Faculty of Graduate Studies,University of Kelaniya, Sri Lanka, 2018) Harishchandra, J.; Hapugoda, M.; Premaratne, R.G.; Abeyewickreme, W.Sterile Insect Technique (SIT) introduced by Edward F. Knipling in 1950s has been shown as an effective and sustainable genetic approach to control populations of selected pest insects in area wide integrated pest management programmes. Successfulness of this approach depends on the availability of an efficient sexing method and production of sterile males competitive enough to compete with wild males. In the context of developing SIT for the control of dengue vector Aedes albopictus (Skuse) in Sri Lanka, a method for separation of male pupae was tested and mating competitiveness of irradiated males against wild males was evaluated under laboratory conditions. Male pupae of the F42 generation of Ae. albopictus (Gampaha strain) were separated from female pupae using mechanical sieving method. A set of three stainless steel sieves of mesh sizes 1.4, 1.25 and 1.12mm were placed one on the other in descending order of size towards the bottom, forming a column immersed in a water jar. All pupae were poured on to the top sieve and shaken gently for seven minutes. Pupae were collected from each sieve and the male and female counts were taken after emergence of adults. Male and female pupae used for the competitiveness assessment were separated by the above sieving method. Male pupae (F42, age 28-40hours) were exposed to Gamma radiation (Gamma 220, Atomic Energy of Canada Ltd., Co60) at a dose of 50Gy by placing 300 male pupae in each plastic vial with 10ml of water. Dosimetry was performed using Frickey method. Wild fertile males and females reared from field-collected eggs from Gampaha (F1) were used to compete and cross with irradiated males respectively in different ratios. Two days after the emergence, the adult mosquitoes were caged (Bug Dorm 30X30X30cm) with ratios of irradiated males: wild males: wild virgin females 1:1:1, 3:1:1 and 5:1:1 (females, n = 100). Fertile control was set with wild males and wild virgin females 1:1. and an irradiated control was set with irradiated males with wild virgin females 1:1. Mosquitoes were allowed to mate for 3 days with access to 10% sugar solution. Then the mosquitoes were fed with cattle blood and engorged females were isolated in oviposition tubes. After 4 days, females were returned into cages and the filter papers containing eggs were allowed to dry. Eggs were hatched after one week and the hatching rates were compared. From the pupae retained in the sieve of mesh size 1.12mm, 98.3% were males. The mean hatch rates of fertile and irradiated controls and with ratios of irradiated males: wild fertile males: wild virgin females 1:1:1, 3:1:1, 5:1:1 were 80.24%±1.63SEM, 2.42%±0.57SEM, 56.74%±5.79SEM, 37.33%±4.76SEM and 34.23%±4.73SEM respectively. Fried Competitive Index (C) of irradiated males compared to controls was 0.43. Results show sieving method can be used for separating male pupae for irradiation with 98% accuracy. Irradiated males were less than 50% competitive as wild males under laboratory conditionsItem Potential Use of a Combined Sterile Insect Technique (SIT) and Wolbachia-Based Approach for the Control of the Dengue Vector Aedes albopictus in Sri Lanka(19th Conference on Postgraduate Research, International Postgraduate Research Conference 2018, Faculty of Graduate Studies,University of Kelaniya, Sri Lanka, 2018) Wijegunawardana, N.D.A.D.; Chandrasena, T.G.A.N.; Abeyewickreme, W.; Dassanayake, R.S.; Xi, Z.; Bourtzis, K.; Gunawardene, Y. I. N.S.This study addresses the possibility of using a novel and environmental friendly strategy of combined sterile insect technique (SIT) and a Wolbachia-based approach in Aedes albopictus population control efforts in Sri Lanka. The above strategy combines irradiation and the intracellular endosymbiont bacteria Wolbachia, in insects which are vertically transmitted from mother to offspring. Releasing sterile male mosquitoes in the wild will introduce sterility for suppression of Ae. albopictus wild mosquito population. The strategy aims at the releasing of sexually incompatible Wolbachia triple infected and irradiated male mosquitoes on a large scale to the natural environment. By integrating irradiation, any accidentally released female mosquito will be made fully sterile, and hence the risk of population replacement of the target population with triple infected mosquitoes is eliminated. Therefore, the combined SIT/IIT approach offers a safe and bio-secure strategy for the population suppression of Ae. albopictus in Sri Lanka. The overall work involved assessment of the density and species abundance of wild mosquito populations, introgression, and characterization of Wolbachia triple infected Ae. albopictus line in a Sri Lankan genetic background and determination of minimum sterility dose for the males and females of the introgressed line. Results revealed that Ae. albopictus mosquito was the dominant vector species in the study area (Narangodapaluwa PHI area) with an average ovitrap index of 75.25% (range; 56.9% - 94.7%) over the study year. The frequency of Wolbachia infection among the mosquito population was ~17% (13/78). The most prominent Wolbachia super group infecting the wild mosquito species was the B group and Ae. albopictus was naturally infected with both strains A and B. Eighty-five new alleles and 8 complete allelic profiles were submitted to the Wolbachia MLST database. All sequencing data were deposited in the Genebank under the accession numbers MH447376-MH470292 and MH756095-MH777430. Successful transfer of Wolbachia triple infection to Ae. albopictus into Sri Lankan genetic background was achieved through an introgression experiment and characterization of the newly developed Ae. albopictus line expressed partial CI and revealed competitive fitness cost for fecundity, fertility, and longevity compared with wild-type while there was no cost for pupation rate, adult emergence and sex ratio. Therefore, integration of an irradiation (dose; 30Gy) is recommended to achieve complete male and female sterility prior to mosquito release (minimum sterility dose for males - 28 Gy and females - 30 Gy). This minimum sterility dose is lower than the irradiation dose applied for SIT and had not resulted in a significant effect on male competitiveness. Therefore, a combined SIT and Wolbachia based approach in Ae. albopictus dengue vector control is recommended as an additional tool in integrated vector management in Sri Lanka.Item 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.Item Optimization of Critical Threshold Values for Aedes Mosquitoes based on Breteau Index in Kandy District of Sri Lanka.(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.; Kusumawathie, P.H.D.; Abeyewickreme, W.Many countries, including Sri Lanka, mainly depend upon Stegomyia indices,such as Premise Index (PI), Breteau Index (BI),Container Index (CI), and Pupal Index (PI) for routine entomological surveillance of dengue. Among them, BI remain as the most widely used larval index for vector management prior to and during epidemic incidences. Properly defined threshold values for BI are of essence, to assist the prediction of dengue epidemics and as a leading indicator for vector control. However, Sri Lanka still lacks effective thresholds for BI to initiate and drive dengue vector management activities. Hence, the present study attempts to define threshold values for BI based on an empirical modelling approach for the Kandy District of Sri Lanka.Item Characterization of a Dengue Positive Population in Colombo Municipal Council (CMC) Medical Officer of Health (MOH), Colombo(Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) Lakmal, M.G.K.; Udayanga, N.W.B.A.L.; Gunathilaka, P.A.D.H.N.; Fernando, S.D.; Karunathilaka, K.; Abeyewickreme, W.Dengue that has caused 29,777 suspected infections in 2015 has emerged the most challenging health issue faced in Sri Lanka. Approximately 51% of dengue infections are reported from the Western Province. The susceptibility of a population to dengue is influenced by a combination of socio-economic, environmental and epidemiological factors. The current study was conducted to characterize a population of dengue patients residing in a high dengue risk area in terms of their socio-economic appearance. An interviewer administrated questionnaire was used to collect information on the socio-economic aspects of a group of 140 randomly selected dengue positive patients residing in Colombo Municipal Council (CMC) Medical Officer of Health (MOH) area. Out of 140, a majority (63.6%, n=89) were females, while the age groups of 31-40 and 21-30 years were recognized as the most susceptible age groups for dengue. High proportion of the patients (79.3%, n=111) were having an educational level below secondary school (O/L) with a total family income below 20,000 LKR (80.7%, n=113). All the homesteads were smaller (<5 perch) in size, with small roads for access (77.1%, n=108) and/or a footpath (22.9%, n=32) as the access route. Majority of the households (69.3%, n=97) were temporary with moderate conditions (51.4%, n=72), that were mainly utilized for both residential and commercial purposes (63.5%, n=89) at once. In a majority of households’ solid waste was disposed within 7 days (62.1%) via the Municipal Council or by keeping near the main roads (37.9%). Source separation of waste, home gardening and composting by the study population was minimal (n=137, 97.9%). Pipe water remained as the only water source while approximately 27.9% (n=39) households were lacking sanitary facilities. Use of mosquito coils and bed-nets were the most preferred mosquito biting prevention methods. Low educational level, income, poor living conditions and limitations in solid waste disposal methods were recognized as potential risk factors for high infection rates of dengue in this population. Special focus should be given to these key areas by the relevant vector controlling authorities in order to facilitate controlling of dengue outbreaks within the CMC area.Item Eliminating female Aedes mosquitoes by spiking blood meals with toxicants as a sex separation method in the context of the sterile insect technique and Incompatible Insect Technique(Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) Ranathunga, R.M.T.B.; Gunathilaka, P.A.D.H.N.; Udayanga, N.W.B.A.L.; Wijegunawardena, N.D.A.; Abeyewickreme, W.Ivermectin and spinosad have longevity reducing effects in several insect species, including disease transmitting mosquitoes after feeding blood contaminated with above toxicants on hosts. Therefore, this approach could play an enormous role in mosquito control operations by its use in the female elimination process during mass-rearing, enabling the release of only sterile males in the context of the sterile insect technique (SIT) and incompatible insect technique (IIT) with Wolbachia bacterium. Blood meals of cattle origin were spiked with diffeerenct concentrations (2, 4, 6, 8 and 10 ppm) of Ivermectin (Ivotec, 1% w/v) and Spinosad (Spinosyn, 12% w/v) and offered to a batch of adult Ae. aegypti (n = 300) and Ae. albopictus (n = 300) having 1:1 sex ratio in order to obtain an optimal dose for quick and total female elimination. After 24 hours all remaining females and males were aspirated out and transferred in to new cages separately. An additional blood meal with the initially fed concentrations of ivermectin and spinosad was provided after 24 hours, followed by a 48-hour observation of mortality. This experiment was repeated by feeding cattle blood containing a mixture of ivermectin and spinosad in 1:1 ratio from each concentration. Spiked blood with 8 ppm ivermectin and spinosad killed all the fed females of Ae aegypti and Ae. abopictus within 24 to 48 hours. It was observed that the number of fed females gradually increased, when decreasing the toxicity in combination of ivermectin and spinosad (1:1) in blood for both species. Male mortality did not show any significant differences during the study. Mixed feeding of blood with 8 ppm ivermectin and 8 ppm spinosad have shown as the viable treatment to eliminate female Ae aegypti and Ae. abopictus from laboratory colonies.Item Prevalence of dengue vector breeding habitats among selected Schools in Gampaha District of Sri Lanka(Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) Radhika, N.M.L.; Gunathilaka, P.A.D.H.N.; Kasturiratne, K.T.A.A.; Abeyewickreme, W.Aedes aegypti and Aedes albopictus are the vectors responsible for the transmission of dengue viruses in Sri Lanka. Gampaha District has been ranked as the second most Dengue affected area. Recently, health authorities have identified that over 54 percent of schools have dengue mosquito breeding sites. However, the entomological information on the dengue vectors in School premises are not available. Therefore, the present study was carried out to identify the different breeding sites of dengue vector mosquitoes within school premises of randomly selected schools in Gampaha District of Sri Lanka. The premises of the selected schools (n= 34) were surveyed from May to October in 2016 for the availability of potential breeding habitats and the presence of vector breeding through entomological surveys. Collected vectors were identified morphologically and categorized inn to species level. All data on breeding habitats and number of vectors identified were recorded. According to survey, out of 34 schools surveyed; infested water-holding containers by Ae. albopictus were observed at 16 schools (47, 05%). Tree holes (Bridelia retusa tree), leaf axils of banana tree and fallen leaves were observed as natural breeding sites while, discarded plastic food containers plastic paint containers, broken pet bottles, tire marks on the ground, water retaining flower pots and plastic barrels were observed as artificial breeding sites. Breeding of Ae. aegypti was not identified among the school premises surveyed. Improper management of solid waste has affected positively in creating suitable habitats for vector breeding. Therefore, continuous monitoring of dengue vector breeding habitats and school based vector controlling interventions should be implemented through proper awareness and active participation for eliminating breeding habitats.