Symposium on Dengue - 2015
Permanent URI for this collectionhttp://repository.kln.ac.lk/handle/123456789/10378
Papers presented at the Symposium on Current Research Activities on Dengue, organized by the Molecular Medicine Unit, on 13th of November 2015
Browse
16 results
Search Results
Item Biology and diversity of Copepods in Sri Lanka and their potential use as predator of Aedes larvae(Moleclar Medicine Unit, Faculty of Medicine, University of Kelaniya, Sri Lanka, 2015) Anukulan, J.W.; Ratnayake, R.M.A.S.; Perera, R.S.M.; Hapukotuwa, R.B.; Iqbal, M.C.M.BACKGROUND: Dengue is a major viral disease in tropical and subtropical countries. Although chemical control of the vector is efficient it causes much damage to the natural environment including destroy of other useful insects. There are many natural predators that prey on mosquito larvae such as copepods, dragonfly, damselfly and larvivorous fish. Among them the use of fish has been practiced extensively to control mosquito larvae. Another potential predator of mosquito larvae is a small aquatic organism called copepod, which is extensively used for biological control in South East Asian countries. We are conducting a preliminary survey on the copepods in Sri Lanka and their ability to prey on larvae of dengue vector Aedes spp. METHODS: Water collected from reservoirs in Kandy (species A), Batticaloa (species B) and Kurunegala (species C) were sieved with a net with 50μm mesh size. The trapped copepods were collected into sampling bottles by washing the net thoroughly. The copepods were observed under a stereo microscope to determine their size. The predation studies were conducted with two ratios: 25 first instar Aedes larvae and 5adult copepods(5:1) and 50 first instar Aedes larvae and 5 adult copepods (10:1). The 5:1 ratio was replicated four times while applying the 10:1 ratio thrice. RESULTS: The body length of the Batticaloa (species B) copepods were larger than the Kandy and Kurunegala copepods. The total mortality of larvae (TM) from the study of 5:1 was species A TM=45, species B, TM=70 and species C, TM=49. The average mortality (AM) was, speciesA, AM=11.25±5.6, species B, AM=17.5±3.1 and species C, AM=12.25±2.5.Mosquito larva predation rate per day by a copepod was, species A 2.25±1.12, species B 3.45±0.62 and species C 2.45±0.5.In the second study with a ratio of 10:1, the total mortality was, species A, TM= 86, species B, TM= 123 and species C, TM= 108. Average mortality was, species A, AM= 28.67±14.17, species B, AM=41±6.24 and species C, AM=39.33±14.53. Mosquito larval predation rate per day by a copepod was, species A, 2.87±1.42, species B, 4.1±0.62 and species C, 3.93±1.45. CONCLUSION: Species B from the Batticaloa, which were with larger in body size showed a better predation ability of Aedes when compared with species A (Kandy) and C (Kurunegala).Item Awareness on dengue and solid waste management among selected school students in Gampaha District of Sri Lanka(Moleclar Medicine Unit, Faculty of Medicine, University of Kelaniya, Sri Lanka, 2015) Radhika, N.M.L.; Gunathilaka, P.A.D.H.N.; Abeyewickreme, W.; Kasturiratne, K.T.A.A.BACKGROUND: Community mobilization is often respected as a powerful tool in ensuring the effective controlling of dengue via promoting effective and sustainable dengue vector control strategies. The current study attempts to investigate the level of awareness on dengue and solid waste management, among selected school students in Gampaha District which is the second highest dengue reported district in Sri Lanka. METHODOLOGY: Awareness programmes on dengue (transmission, vector ecology and preventive measures) and solid waste management were conducted in 10 schools belong to Kelaniya Medical Officer of Health (MOH) area selecting a minimum group of 200 students from each school within the age of 13 - 15 years. Tools such audio-visual presentations, leaflets and videos were used for the awareness programmes. A questionnaire was given to each student prior to the awareness and after the awareness programs as pre and post evaluations respectively in order to assess the general awareness on dengue and solid waste management before and after the awareness programme. One-Way ANOVA, paired t-test and multiple regression techniques were utilized in evaluation of the degree of awareness and key factors affecting the level of awareness, prior and after the conducting the awareness programmes. RESULTS: The degree of initial awareness on dengue and solid waste management of the target school community was recognized to be significantly characterized by the grade of the students and the Education Zonal Category [EZU] (into which their school belongs to) in accordance with One-Way ANOVA (p < 0.05). A significant increment in post awareness of the target school community was recognized due to the conducting of awareness programmes in accordance with the statistics of paired t-test (p < 0.05). Furthermore, based on the multiple linear regression modelling, the post awareness was significantly influenced by the grade of the students and the initial awareness (p < 0.05), regardless of the EZU (p > 0.05). CONCLUSIONS: The awareness of school students on dengue and solid waste management is significantly affected by the grade of the students and EZCs. Awareness programmes are an effective media of raising the awareness of school communities on dengue and solid waste management, while motivating them to actively contribute for the controlling of dengue, via establishing a strong inter sectorial network among schools and other relevant institutions within the Gampaha District.Item Engineering miR-shRNA based molecule to interfere replication of dengue virus in transgenic Aedes aegypti mosquitoes: Bioinformatics approach(Moleclar Medicine Unit, Faculty of Medicine, University of Kelaniya, Sri Lanka, 2015) Ramyasoma, H.P.B.K.D.; Dassanayake, R.S.; Gunawardene, Y.I.N.S.; Kajan, M.; Abeyewickreme, W.BACKGROUND: The genus Flavivirus of the family Flaviviridae includes several vector-borne viruses to which the four serotypes of dengue viruses (DENV-1,-2,-3 and 4) belong to and DENV viruses have a messenger like positive polarity, single-stranded RNA genome approximately 11kb in length which encodes three structural proteins (C-prM-E) and seven Non-Structural proteins (NS1-NS2A-NS2B-NS3-NS4A-NS4B-NS5). RNA interference (RNAi) and its properties as a tool has heralded a new era in functional genomics and short double stranded RNAs mediated by RNAi has become a powerful tool for post transcriptional gene silencing. Therefore, this study took the advantage the latter biological phenomenon and designed a multiple miR-shRNA (multi-mir-shRNA) molecule using bioinformatic approach to be effective to block the replication of all dengue serotypes of Sri Lanka. METHODS: Genome sequences of DENV strains belonged to serotypes 1 and 3 isolated from Sri Lanka deposited in GenBank were analyzed for potential sequences for the best siRNA target sites and identified two such sites from DENV 1 and DENV 3 from non structural protein coding sequence of NS5 and structural protein coding sequence of prM consensus regions, respectively. Two more siRNA targets reported from previous study chosen from upstream and downstream of non coding region effective for silencing all DENV serotypes were also used in designing mir-shRNA sequences. The stem region of miR1175 pre-miRNA sequence (miRBase ref: MI0013470) of Aedes aegypi was then replaced with each selected siRNA targets to generate the DENV effective miR-shRNAs and generated miR-shRNAs connected together by placing restriction endonuclease sites between each other to obtain multi-mir-shRNA containing four loop and stem structures. The transgenic gene cassette containing Ae. aegypti carboxypeptidase A promoter, multi-miR-shRNAs and poly adenylation signal of Simian Virus 40 Major Capsid VP1 was then constructed. Expression of this effecter molecule can be achieved by the induction of Ae. aegypti carboxypeptidase A (AeCPA) promoter following blood meal which then ensures activation of RNAi at the time of virus enter into the midgut of mosquito. RESULTS: Folding patterns of the transcript of the designed multi-mir-shRNA cluster were analyzed using online bioinfomatic tool, mfold and the secondary structure of this transcript shown to have optimum endogenous miRNA cleavge/processing with the lowest -ΔG indicating the ability of this design to exert RNAi in mosquito Ae. aegypti. CONCLUSION: Designing multi-miR-shRNA in bioinformatic means an effective way to construct the effector molecule that could exert the maximum RNAi against DENV. However, the effect of design will have to be demonstrated first by transforming to Ae. aegypti mosquitoes and then by evaluating the inhibition of DENV replication in mosquito.Item Maternal transformation of Wolbachia isolated from infected mosquito hosts to Aedes aegypti using micro-injection based procedure: an approach towards integrated dengue vector control(Moleclar Medicine Unit, Faculty of Medicine, University of Kelaniya, Sri Lanka, 2015) Wijegunawardana, N.D.A.D.; Gunawardene, Y.I.N.S.; Chandrasena, T.G.A.N.; Dassanayake, R.S.; Ruanareerate, T.; Kittayapong, P.; Abeyewickreme, W.BACKGROUND: The maternal transformation of Wolbachia (Wb) to Aedes mosquitoes is an approach that has been widely used in Aedes mosquito population control strategies in the integrated dengue vector control efforts. This study details usage of such approach in the maternal transformation of Aedes aegypti using the Wb isolated from infected mosquito hosts using micro-injection based procedure for the first time in Sri Lanka. METHODS: Twenty five ovaries of each adult female Aedes albopictus and Culex quinquifaciatus mosquitoes (14-18 days old) were dissected and Wb was isolated and suspended in 20 μl of 1X Phosphate Buffered Saline (PBS). The isolated samples were kept on ice to maximize the bacteria viability. The exudate was then used in the trans-infection of Ae. aegypti mosquitoes. Infection of Wb into the mosquito Ae. aegypti was carried out by maternal/adult microinjection. To create stable trans-infected lines, the regions near the 3rd leg emerged from the thorax of Ae. aegypti were microinjected to incorporate Wb into the developing germ line and then to facilitate the transmission of Wb to offspring. The volume used for injection based on the swelling of the abdomen, which was monitored throughout the experiment while maintaining the injection pressure, time and number of injecting times. Virgin female Aedes mosquitoes survived after microinjection was fed with 1 ml of 10% sugar solution containing 10,000 units Penicillin/Streptomycin per 100 ml. Survival rate was monitored at 1, 3 and 24 hour/s following microinjection procedure. Survived female mosquitoes resulted from injected line (generation 0 [G0]) was placed in vials with three uninfected male mosquitoes to establish iso-female lines. After egg laying 3 times, G0 females were sacrificed and total DNA was extracted, and PCR was carried out (wsp primers 81F and 691R) using DNA extracted from Ae. aegypti to detect the presence of Wb DNA and its density in the latter mosquito using dilution series of extracted DNA. To select for a stable infection, only offspring from females that came positive for Wb by PCR screening was used as parental stocks. For the samples positive by wsp PCR, strain identification was carried out by performing PCR with 4 different primer sets; wPip, wAlbA, wAlbB and wsp specific for Wb. Females that tested negative for Wb were discarded along with their progeny. The resulting triple infected line will be monitored periodically by PCR to confirm infection status. RESULTS: Wolbachia-triple infected line of Ae. aegypti mosquito was created by using isolated wAlbA+wAlbB+wPip Wolbachia strains. Infection status of newly developed line was monitored by PCR up to G2 and will be continued to G8. Experimental work will be started from G5 to evaluate the use of newly develop Ae. aegypti mosquito line for Wb-based approach under laboratory condition. CONCLUSION: Direct maternal micro-injection technique was used to create Wb infected mosquito line of Ae aegypti, which could be applied in Wb-based dengue vector control activities in Sri Lanka once the line is established.Item Effect of γ-radiation on fertility and survival of Aedes albopictus (skuse) males in the laboratory for Sterile Insect Technique(Moleclar Medicine Unit, Faculty of Medicine, University of Kelaniya, Sri Lanka, 2015) Harishchandra, J.; Abeyewickreme, W.; Hapugoda, M.; Premaratne, R.G.; Gilles, J.R.S.BACKGROUND: It is believed that Aedes albopictus, one of the dengue vectors in Sri Lanka can be controlled using Sterile Insect Technique (SIT) when integrated with other conventional control methods. The objective of this study was to determine the effective dose of gamma radiation for producing sterile males of Ae. albopictus mosquitoes. METHODS: A batch of male pupae (n=32) aged 24-48 hours in F1 was irradiated using a gamma-ray irradiator (Gamma 220, Atomic Energy of Canada Ltd., Co60) with 25 Gy in duplicates. Following the same procedure, different doses (30 Gy, 40 Gy, 50 Gy, 60 Gy and 70 Gy) were given to each pupal batch in duplicates. Then they were transferred to laboratory cages (30 cm X 30 cm X 30 cm) for emergence and supplied with 10% sucrose solution. Adult emergence rate and male longevity were recorded. Virgin females from the same cohort (F1) were introduced into each cage for mating and fed blood starting 5 days after emergence. Females were then isolated in to individual tubes and hatching rate of individual egg batches was determined after two weeks of egg maturation in hatching solution containing 0.25 g BNB, 0.05g BY in 700 ml distilled water. Spermachecae of female mosquitoes were dissected and insemination rates were calculated after egg laying. RESULTS: Male mosquito pupae in F1 showed low mortality (0-3.12%) immediately after exposing to radiation (0-48 hours). After 21 days of the irradiation, probability of survival of male mosquitoes in F1 were 0.578, 0.494, 0.453, 0.313, 0.328, 0.381 and 0.219 at 0Gy, 25 Gy, 30 Gy, 40 Gy, 50 Gy, 60 Gy and 70 Gy respectively (Kaplan Meier survival analysis). Log Rank test indicated significant differences of survival of control males with males irradiated at 40Gy, 50 Gy, 60 Gy and 70 Gy. The survival of males irradiated at 25 Gy and 30 Gy did not differ from each other and from the control. The survival of males irradiated at 40 Gy, 50 Gy, 60 Gy were not significantly different among each other. The mean hatching rate (Mean+SE) of the F2 progeny of Ae. albopictus males (F1 progeny) were 10.89+2.76%, 7.36+1.75%, 3.09+0.71%, 0.79+0.27%, 0.66+0.23% and 0% when irradiated at 25 Gy, 30 Gy, 40 Gy, 50 Gy, 60 Gy and 70 Gy respectively. The control group showed a hatching rate of 64.26 + 7.12%. It was found that insemination rate of the irradiated males among different doses and controls were above 90% in F1 based on spermatheca dissection of blood-fed females (F1). CONCLUSION: 50 Gy is recommended as the most suitable γ radiation dose to produce 99% sterility in Ae. albopictus males which has 0.328 survival probability after 21 days of irradiation. This dose can be used to produce sterile males of Ae. albopictus for population suppression.Item Status of dengue vector breeding in pineapple plantations and environmental factors affecting their breeding(Moleclar Medicine Unit, Faculty of Medicine, University of Kelaniya, Sri Lanka, 2015) Dassanayaka, D.M.T.; Aryaprema, V.S.; Jayasooriya, H.T.R.; Abeyewickreme, W.BACKGROUND: Pineapple plantations are believed to have contributed to the transmission of dengue fever in pineapple growing areas in Sri Lanka. Hence, there is a need to introduce effective control methods to reduce dengue vector breeding in leaf axils of pineapple plants, a characteristic larval habitat of dengue vectors. The current study was designed primarily to obtain baseline information required for a much longer study planned to evaluate the use of pyriproxyfen and temephos in leaf axils of pineapple. METHOD: The study was carried out in five pineapple plantations in Medical Health Office area Meerigama in the Gampaha District from December 2014 to June 2015. Ninety plants from the five plantations were selected randomly and the volume of water in each plant and number of leaf axils positive with immature stages of mosquitoes was recorded twice a month. The water contents of leaf axils positive for mosquito larvae were transported to the laboratory and larvae were identified using standard keys. Chemical parameters: pH and temperature were measured in situ in the same samples and a few selected chemical parameters (concentrations of nitrates, phosphates, potassium and total dissolved solids) were measured in the laboratory using standard methods. Climatic data were obtained from the Meteorological Department of Sri Lanka. RESULTS: Eight mosquito species belonging to five genera were identified in leaf axil water of pineapple. Four species of Aedes including Aedes albopictus, the secondary vector of dengue, were identified while the primary vector Aedes aegypti was not recorded during the entire study period. The water volume per plant varied from 2.34 – 25.27 ml and it showed a significant positive correlation with the vector density (r=0.54, p=0.001). The number of rainy days in each month (r=0.76, p=0.000) and the monthly mean rainfall (r=0.53, p=0.001) showed significantly positive correlations with monthly vector density. Although monthly mean pH value showed no correlation with the monthly mean water temperature correlated negatively with the vector density (r= -0.5, p=0.004). None of the chemical factors except the concentration of nitrate (r=-0.45, p=0.016) in leaf water were associated with the vector density. CONCLUSIONS: Ae. albopictus was the most abundant species in all months except in January. The study revealed that the water volume in leaf axils, number of rainy days per month, monthly mean rainfall, water temperature and nitrate concentration of axil water seemed to affect the Ae. albopictus breeding, which are the important data useful in evaluating the use of pyriproxyfen and temephos in leaf axils of pineapple in the future. However, a continuation of the study for another six months to observe seasonal variation within a year is recommended.Item Vector prevalence and insecticide resistance status of Aedes sp. in dengue high and low risk areas in the Colombo District(Moleclar Medicine Unit, Faculty of Medicine, University of Kelaniya, Sri Lanka, 2015) Janaki, M.D.S.; Aryapreme, V.S.; Jayasooriya, H.T.R.; Abeyewickreme, W.BACKGROUND: In areas where dengue transmission is high, space spraying against adult Aedes sp. is practiced to reduce the density of infected mosquitoes and thereby reduce transmission within a very short time. Repeated use of insecticides in this manner, in dengue high risk areas, lead to the development of insecticide resistance in vector populations. The aim of the present study was to determine the prevalence and status of insecticide resistance of Aedes vectors in dengue high risk and low risk areas in the Colombo District. METHODS: The study was carried out in the area of Regional Director of Health Services, Colombo (RDHS area Colombo) and the Colombo Municipal Council area (CMC area), from December 2014 to June 2015. One each of comparatively high risk and low risk MOH area were selected from each study site based on the reported number of dengue cases during last five years. MOH areas Kolonnawa and D3 (Borella) were selected as high risk areas while Padukka and D5(Wellawatta) were selected as low risk areas respectively from the RDHS area Colombo and the CMC area. Ovitrap survey method was used to determine the vector prevalence and to collect Aedes eggs for bio assay tests. Larval and adult bio assay tests were conducted according to WHO guidelines. RESULTS: Both Ae. aegypti and Ae. albopictus were recorded from all MOH areas, except Padukka where there was only Ae. albopictus present. The vector prevalence in terms of Ovitrap Index and Egg Density Index was higher in Padukka (p=0.001 and p=0.029 respectively) than those in Kolonnawa in the RDHS area Colombo. In the CMC area, there was no such significant difference in the low risk and the high risk areas. Vector prevalence and the number of reported dengue cases showed no significant correlation in any of the MOH area. Aedes larvae in all four MOH areas have acquired resistance to diagnostic dosage of temephos (0.012 mg/l). Ae. aegypti in Kolonnawa, Ae. albopictus in Padukka and Ae. aegypti in D3 (Borella) showed possible resistance to 0.025% Deltamethrin while, Ae. aegypti in D5 (Wellawatta) has already acquired resistance. Ae. albopictus in D5 (Wellawatta) was still susceptible to the same insecticide. CONCLUSION: The vector prevalence does not significantly correlate with disease incidence, but further correlations with patients in localities within MOH and the vector densities will reveal reliable information. Despite the comparative status of high and low risk, all MOH areas have acquired resistance to insecticides, specifically to temephos and deltamethrin. Study reveals the emerging trends in resistance development of Aedes sp. in the Colombo District which has to be taken into account when designing further studies on resistance monitoring with a view to design effective control strategies.Item Emerging spatio-temporal trends of dengue incidence in Colombo and Kandy Districts, Sri Lanka(Moleclar Medicine Unit, Faculty of Medicine, University of Kelaniya, Sri Lanka, 2015) Udayanga, N.W.B.A.L.; Gunathilaka, P.A.D.H.N.; Iqbal, M.C.M.; Kusumawathie, P.H.D.; Abeyewickreme, W.BACKGROUND: Dengue has become a prominent challenge to the health sector in Sri Lanka. Prior identification/prediction of possible risk areas with high susceptibility to dengue, could be of major importance in ensuring the effective regulation of dengue epidemics. Therefore, the current study attempts to investigate the spatio-temporal trends in dengue incidence and priority risk factors that characterize dengue epidemics, aiming to stratify the Colombo and Kandy Districts into high, moderate and low risk areas via development of dengue risk maps by devising a statistical and geo-informatics based approach. METHODOLOGY: Socio-economic data of dengue patients and healthy volunteers in selected high risk MOH areas of Colombo (5) and Kandy (5) Districts were obtained through an interviewer administrated questionnaire. Previously reported dengue cases from 2009 to 2014 in each MOH were acquired. The spatio-temporal trends in dengue incidence of studied MOHs, were investigated at the Grama Niladhari Division (GND) level by using Arc GIS (version 10.2). The impacts of gender and age of the community on the disease prevalence were investigated by using normal Chi square test and Paired-Chi square test in SPSS (version 23). RESULTS: At present, 95% and 81% of the overall socio-economic surveillance has been completed in Kandy and Colombo Districts, respectively. Spatial maps on disease outbreaks have been developed for Akurana, Doluwa, Gampola, Gangawatakorale, Kandy Municipal Council (KMC), Kundasale and Poojapitiya MOH areas. According to results of the Paired-Chi square test, the emergence of dengue outbreaks indicated a significantly declining trend in recorded dengue cases in most of the GNDs within the studied MOHs, during the recent years. The Percentage Infected Male:Female Ratio (PIMFR) remained significantly altered throughout the period of study (p=0.001<0.05 at 95% of significance). Within the studied MOHs, males tend to indicate relatively high susceptibility for dengue infection than females (with 58.6: 41.5 of average PIMFR). The age group of 11 – 20 and 21 – 30 years were identified as with highest vulnerability to dengue, while the age > 61 years indicated the least vulnerability in all the MOHs. According to the Paired-Chi square test, the vulnerability of age groups was found to shift significantly throughout the study period [>Χ2 (7, 0.95) = 14.067]. CONCLUSIONS: The KMC and Gampola MOHs indicate relatively high susceptibility to dengue within the district of Kandy. Within all the studied MOHs, males tend to indicate relatively high susceptibility to dengue. Age groups of 11 - 20 and 21 – 30 denote relatively higher vulnerability to dengue, while age group of > 61 emerge as the least vulnerable group for the infection of dengue in the studied MOHs.Item Identification of risk factors affecting transmission of dengue in the District of Gampaha, Sri Lanka(Moleclar Medicine Unit, Faculty of Medicine, University of Kelaniya, Sri Lanka, 2015) Withanage, G.P.W.K.; Abeyewickreme, W.; Hapugoda, M.D.INTRODUCTION: Dengue is the most significant mosquito-borne infectious disease in Sri Lanka, causing more than 35,000 cases annually for last five years. The second highest prevalence of dengue was reported from the District of Gampaha for last 10 years. OBJECTIVE: To identify possible risk factors affecting transmission of dengue in selected high risk areas of dengue in the Gampha District. METHODOLOGY: The study was conducted in four high risk Medical Officer of Health (MOH) areas where the annual number of dengue cases greater than 250 during last ten years. In each MOH area, one Grama Niladhari (GN) division with the highest dengue incidence was selected as study areas. In each study area, a cluster of 150, including house-holds, open areas (barren lands, dump yards, and construction sites), abandoned houses, and religious facilities, was selected. A house-hold and entomological surveys were performed in March, 2015 after obtaining an informed written consent. RESULTS: The selected study areas were Akbar town (Mahara MOH), Eriyawatiya (Kelaniya MOH), Kurana (Negombo MOH), and Welikadamulla (Wattala MOH). The size of study human population was 2,544 in 574 house-holds in the study areas and 53.66% (1,365/2,544) were females. The average size of a homestead was 19.3 perches and more than one house was observed in 21.6% (124/574) of land plots. The type of the house-hold was mostly moderate (67.2%-386/574) and the gender of the house-hold head was male in 77.7% (446/574) house-holds. The average number of dwellers in a house-hold was 4 and 7.35% (187/2,544) of the population has previously infected with dengue. Most of house-holds were individual houses with a small garden (98.9%-568/574) and residential function of the house-hold was mainly residential only (83.4%-479/574). The main source of water was piped water (95.1%-546/574), but 39.5% (227/574) using ground-well or tube-well water daily purposes other than drinking and food processing. The most common mosquito preventive measure was bed nets (31.7%-182/574) and 47.6% (273/574) house-holds were using more than one mosquito preventive measures. Collecting tailors of municipal councils is the main solid waste disposal method, while 16.0% (92/574) using burning, burring in pits, composting or open ground due to lack of proper solid waste collection system. Bushes and small trees were the most common vegetation cover of the homesteads (84.5%-485/574) and potential breeding sites were observed in 97.5% (585/600) premises in the study areas. Main mosquito breeding places were plastic and polythene wares, discarded cans and tins, discarded tyres, plant axils, and aluminum and clay pots. The Breteau Index (BI) for Aedes larvae was 4.88 (28/574). Most prominent adult mosquito species in the areas was Aedes albopictus (92.4%-281/304). Dwellers in the study areas have considerable knowledge of the disease and preventive measures, but they reluctant to pursue preventive measures. DISCUSSION: Possible risk factors for transmission of dengue may be crowded conditions, small house-holds and homesteads, poor water and waste management systems, disfavor to pursue preventive measures, and dependence on government vector control programs. Therefore, immense persuade will be required to control dengue in the areas.Item Encapsulation of essential oil blend in β-CD nanoparticles as a repellent for slow release(Moleclar Medicine Unit, Faculty of Medicine, University of Kelaniya, Sri Lanka, 2015) Jayaweera, V.; Eliyapura, A.; Gunasekara, D.; Weerasinghe, L.; Gunathilaka, P.A.D.H.N.; Abeyewickreme, W.; Karunaratne, V.BACKGROUND: Malaria, dengue, and other tropical diseases carried by arthropods such as mosquitoes, ticks and fleas have greatly affected life expectancy, infant mortality, quality of life and work productivity. Essential oils such as citronella, lemon eucalyptus, peppermint, lemon, eucalyptus, lemongrass, geranium, and lavender are known for their mosquito repellency. Due to high volatility of essential oils, these are needed to be reapplied to the skin every 30–60 minutes. Therefore, development of a long lasting mosquito repellent is needed for effective repellent activity. The aim of this experiment is to develop a new blend which encompasses citronella, lemon eucalyptus, lemon and lavender. This oil blend is encapsulated using β-Cyclodextrin (β-CD) to decrease the volatility of the oil blend and increases the long-lasting repellency. METHODS: Citronella, lemon eucalyptus, lemon and lavender were obtained in 15% v/v, 15% v/v, 1% v/v and 1% v/v respectively for a total volume of 100 ml. These oils were mixed with 0.2% w/v of β-Cyclodextrin for encapsulation. The blend was sonicated for 20 min and dissolved in ethanol. This final encapsulated mixture was subjected to bioassays using 110 adult Aedes albopictus mosquitoes against the control. Sitting and biting mosquito behavior patterns were studied against the releasing time. RESULTS: The bioassay results indicated that the encapsulated repellent product is effective against the mosquitos up to 6 hours with zero sitting and biting comparatively to the control. In the 7th hour showed single mosquito sitting with zero biting. CONCLUSION: The encapsulated repellent is effective against the Ae, albopictus mosquitoes for 6 hour time period. Therefore, it is a long-lasting repellent that protect against dengue fever caused by mosquitoes.