IPRC - 2019
Permanent URI for this collectionhttp://repository.kln.ac.lk/handle/123456789/20881
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Item Mosquito Breeding Habitat Diversity and Distribution of Species in Selected Areas in the Districts of Kurunegala, Gampaha, Kegalle and Kandy in Sri Lanka(International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Ranasinghe, H.A.K.; Gunathilaka, P.A.D.H.N.; Amarasinghe, L.D.; Udayanga, N.W.B.L.Sri Lanka has been suffering from mosquito-borne diseases since ancient times with the high prevalence of malaria, filariasis and Japanese Encephalitis (JE). As a result of successive efforts in control programs, Sri Lanka has received remarkable achievements. However, with all these successful efforts some arbovirus infections majorly the dengue has increased rapidly over last few decades. Some control programs only target the specified vectors for that disease and report of other vector species is ignored. The prevalence of different mosquito species from surveillance has been limitedly document is Sri Lanka which is grossly inadequate in providing evidence for potential health risks. The present investigation attempts to cater for this knowledge gap by documenting the prevalence of mosquito species in four selected districts of Sri Lanka. Entomological surveys were conducted from a total of 160 temporary and permanent mosquito breeding habitats identified in selected areas, in the districts of Kurunegala, Kegalle, Kandy and Gampaha from June 2017 to October 2018. Mosquito immature stages were sampled using standard dipping, siphoning or pipetting methods according to the nature of breeding habitat and collected specimen were identified up to the species level. Chi-square test of independence was used to evaluate the significance in the distribution of different mosquito species among different breeding sites in the studied districts. The diversity indices for breeding habitats were subjected to a Kruskal Wallis test followed by Dunn’s Multiple Comparison to identify the significance in the variations of diversity indices across breeding sites and studied districts. A total of 4663 mosquito larvae belonging to seven genera and fifteen species of mosquitoes were collected from natural and artificial water holding macro and micro habitats located in study sites. The relative distribution of different mosquito species differed significantly among the four studied districts (X2=143.248; df= 33; P< 0.001). Mosquito assemblages in the districts of Gampaha and Kandy indicated a similarity of 83.16%, while the district of Kegalle shared a similarity of 75.45% with the above cluster. A total of 21 permanent/temporary key breeding sites were found from the study areas. As suggested by the Kruskal Wallis statistics (P < 0.05 at 95% of significance), all the diversity indices for immature stages of mosquitoes varied significantly across different breeding sites recorded during the study. Meanwhile, none of the diversity indices indicate significant differences in terms of locality. The highest values of Pielou's Index (2.01 ± 0.6), Menhinik's Index (3.34 ± 0.83) and Margelef Index (0.59 ± 0.19) and highest species richness (4.0 ± 2.82) in terms of mosquito larvae were shown by paddy fields within the studied four districts. Findings of the current study would be useful to identify the entomological potential for disease transmission and facilitate implementation of appropriate vector control interventionsItem Bacterial Diversity in the Midgut of Field Caught Culex tritaeniorhynchus(International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Ranasinghe, H.A.K.; Gunathilaka, P.A.D.H.N.; Amarasinghe, L.D.; Rodrigo, W.W.P.Ingestion of blood meal by female mosquitoes triggers a series of physiological processes in midgut where symbiotic microbes also exist. These symbiotic microbes can be engineered to produce molecules that inhibit pathogens; through paratransgenic approach. Little is known about the midgut microbes of Culex mosquitoes and no attempt has been made so far in Sri Lanka. Cx. tritaeniorhynchus mosquitoes were separated from the entomological surveys conducted at Kelaniya Medical officer of Health (MOH) area from June – August 2019. Unfed adult female mosquitoes were sacrificed using a cold shock and were surface sterilized using 70% ethanol followed by rinsing with phosphate buffer saline (PBS). Midgut of mosquitoes were dissected and midgut of ten mosquitoes were pooled in sterile PBS (250 μL) to make a homogenized lysate. A dilution series (100- 10-7) was made from lysate. 100 μL from each dilution was plated on Plate Count Agar (PCA) and were incubated for 48 hours at 37 0C. Pure cultures for each microbe were obtained from the primary plates using streak plate method, sub culturing in Nutrient Agar. The experiment set up was repeated 25 times with ten mosquito pools at each effort. Colony separation was done based on phenotypical differences and basic biochemical tests. Stab cultures of isolates were sequenced for 16S ribosomal RNA partial gene. To identify the closest related sequence, obtained sequences were analyzed by Bioedit software package and completely aligned sequences were compared with the BLAST database. The evolutionary history was inferred using the neighbor-Joining method and the evolutionary analyses were conducted in MEGA X. A total of eight bacterial strains namely; Staphylococcus pasteuri, Bacillus megaterium, Staphylococcus cohnii, Pantoea dispersa, Staphylococcus chromogenes, Bacillus aquimaris, Staphylococcus arlettae, Staphylococcus scuiri was isolated from Cx. tritaeniorhynchus (n=250). All of these species were belonged to two phyla; Firmicutes and Proteobacteria. Phylum Firmicutes was the dominant phyla which include seven species. The evolutionary distances which were computed using Tajima-Nei method were used to infer the phylogenetic tree. It represented a close relationship between the species of two genera; Staphylococcus and Bacillus while the relationship was distant for genus Pantoea. The present data strongly encourage further investigations to explore the potential usage of these microbes through the paratransgenic approach which is a novel eco-friendly vector control strategy