IPRC - 2018
Permanent URI for this collectionhttp://repository.kln.ac.lk/handle/123456789/19163
Browse
4 results
Search Results
Item 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 breaksItem 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.Item 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.