Browsing by Author "Hapugoda, M. D."

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Assessment of the distribution of Aedes breeding sites at the households of district of Gampaha
(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Perera, E. H. L.; Hapugoda, M. D.; Viswakula, S.; Gunawardene, Y. I. N. S.; Subasinghe, U.; Fernando, L.; Manamperi, A.
Dengue is the most important mosquito-borne viral infection in Sri Lanka at present. Integrated Vector Management (IVM) targeting dengue vector mosquitoes has become the main disease control measure. The objective of this study was to assess the distribution of the Aedes breeding habitats in dengue high and low risk areas in the District of Gampaha where the second highest incidence of dengue reported during last 10 years. Negombo Medical Officer of Health (MOH) area was selected based high incidence of dengue cases reported in the District of Gampaha during last 10 years. A dengue high risk (Kurana East) and low risk (Udayarthoppuwa) Grama Niladhari (GN) divisions with similar geographical situation in the same MOH area were selected as study and control areas respectively. Standard larval surveillance was conducted randomly selected 150 houses in each site for 18 months (April, 2018-October, 2019). In the dengue high risk and low risk areas, the proportions of the larvae of Aedes species to the total larval collection were 34.19% (185/541) and 21.68% (147/678) respectively. High densities of Ae. albopictus larvae were reported in both high [171/185=92.4%)] and low [141/147=95.92%) risk areas. Ae. aegypti was present in low abundance in both areas [High risk-7.56% (14/185) and Low risk- 2.72% (4/147)]. In the high-risk site, breeding sites of the Ae. albopictus larvae were reported as plastic buckets/barrels (55.19 %-154/279), waste plastics (35.15%-98/279), metal tins (3.94%-11/279) and tube wells (2.86%-8/279). In low-risk area, the majority of breeding sites for Ae. albopictus larvae was found in coconut shells (76.14%- 201/264) and plastic waste (21.96%-51/264). In both areas, Ae. aegypti larvae was found in plastic buckets/barrels only. There is a significance difference between the Ae. albopictus breeding places in the dengue high and low risk areas (P=0.024). Although Ae. aegypti is considered as the major vector of dengue, Ae. albopictus was reported as the prominent dengue vector species in the high dengue risk area in the District of Gampaha. Even though, municipal council removes solid waste weekly, a large number of breeding sites are available at both areas. As there is a significant difference between Ae. albopictus breeding sites at the dengue high and low risk areas, it is essential to specifically focus on removal of breeding sites for successful vector control measure.
Study on the resting preferences of Aedes aegypti (Linnaeus) and Ae. albopictus (Skuse) adult mosquitoes in the district of Colombo
(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Perera, E. H. L.; Gunawardene, Y. I. N. S.; Hapugoda, M. D.; Ranathunge, T.; Udayanga, N. W. B. A. L.
Aedes aegypti (Linnaeus) and Aedes albopictus (Skuse) are the world’s most widely distributed mosquito species and, act as major contributors to many mosquito-borne diseases. Remarkable behavioral and ecological attributes make these mosquitoes as efficient vectors. Due to the behavioral and ecological plasticity of Ae. aegypti and Ae. Albopictus, it has become a major limitation in vector control and disease management measures in Sri Lanka. The objective of this study was to determine key bionomics aspects, namely resting preferences of Ae. aegypti and Ae. albopictus in the District of Colombo. Three Medical Officer of Health (MOH) areas were selected for the current study based on previous dengue cases. The two high risk areas (Maharagama and Kolonnawa) and a low-risk area (Padukka) were selected as study sites. Adult mosquito surveillance was conducted in outdoor and indoor settings using a mouth aspirator for one year (November, 2019-October, 2020). Adult mosquito collection included the aspiration from all rooms within the home including furniture, behind hanging clothes and curtains, behind and around cooking utensils and from dark and humid places, where mosquitoes were found resting. A total of 658 Aedes adult mosquitoes were collected from both indoor and outdoor resting locations (total number of resting sites= 432). The most abundant vector species was Ae. aegypti (65.0%; n=428), followed by Ae. albopictus (35.0%; n= 230) in Maharagama and Kolonnawa MOH areas. The most and least abundant Aedes mosquito collection MOH areas were Maharagama 44.5% (n=293) and Padukka 23.2% (n=153), respectively. Ae. Aegypti adult mosquitoes denoted an endophilic behaviors (97.1%; n=416), while Ae. albopictus denoted an exophilic resting behavior (81.30% n= 187). In terms of resting places, Ae. aegypti was mostly found in resting places such as bedroom (36.0%; n=154), kitchen (26.2%; n=112) living room (21.3%; n=91), and outdoor vegetation (1.4%; n=06). Meanwhile, Ae. albopictus was conducive to rest on the vegetation (50.4%; n=116), front of the house-external (23.8%; n=109). The highest percentage of Aedes mosquitoes were found resting on wooden surfaces in both indoor and outdoor sites (52.3%; n=344), followed by clothes/curtains (24.2%; n=159) and cement surfaces (17.0%). Resting behavior of vectors is an important fact since they are prerequisites to determine their role in disease transmission in endemic settings. This study revealed that the resting behavior varied between the two Aedes vector species, were Ae. aegypti adult mosquitoes denoted highly endophilic nature, while Ae. albopictus demonstrated exophilic behavior. In this study Ae. aegypti was mainly found resting in bedrooms, living rooms and kitchens and Ae. albopictus was found resting mainly among outdoor vegetation. The outcome of this study facilitates the relevant health authorities who engage with dengue control programs, to successfully eradicate the vector from resting sites.
Use of morphological and molecular methods in identification of Asian bush mosquito, Aedes japonicus (Theobald, 1901), in Sri Lanka
(Faculty of Science, University of Kelaniya Sri Lanka, 2022) Wickramasinghe, T. K. C.; Udayanga, N. W. B. A. L.; Manamperi, A. A. P. S.; Hapugoda, M. D.; Karunarathna, K. H. T.; Ranathunge, R. M. T. B.
Conducting routine entomological surveillance to identify new vectors and changes in the distribution patterns of vectors is important for the management of mosquito borne diseases in Sri Lanka. A recent preliminary entomological survey reported the presence of Aedes japonicus in Sri Lanka in March 2021. Therefore, the current study was conducted to validate the presence of Ae. japonicus in Sri Lanka, based on morphological and molecular evidence. The search for Ae. japonicus breeding sites and developmental stages using standard siphoning methods were conducted in Kosgama and Pallekanugala areas located in the Districts of Colombo and Kegalle, respectively, from May to December 2021. Collected immature stages were reared up to the fourth instar stage or adult, and specimens were identified to species level using standard morphological keys. Further, DNA was extracted from the head, and thoracic regions of the reared mosquitoes and Polymerase Chain Reaction (PCR) was performed. The amplified products were sequenced at a commercial facility (Macrogen Inc. co. Ltd., Seoul, Korea). Subsequently, the sequences were analysed for sequence identity using NCBI BLAST analysis and Geneious Trial (version 7.1.3). Based on the morphological characteristics, larvae of Ae. japonicus were identified from both study areas. Ae. japonicus was reported only from natural breeding containers such as bamboo plants and tree holes in both study areas. The molecular analysis further confirmed the morphological identification. Further, newly reported Ae. japonicus population denoted a close relationship to the Austrian/Slovenian population. Ae. japonicus is well adapted to temperate climates and has been reported to possess a strong tendency to expand and colonies into new territories, which is facilitated by human-mediated, passive transportation. According to Unweighted Pair Group Method with Arithmetic Mean (UPGMA) based hierarchical cluster analysis, newly discovered Ae. japonicus denoted strong affinity to a previously detected Ae. japonicus strain in Eastern Austria/Slovenia. The dispersal and population dynamics of Ae. japonicus should be thoroughly surveyed in Sri Lanka, as this species is a potential vector of Japanese Encephalitis.