Journal/Magazine Articles
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This collection contains original research articles, review articles and case reports published in local and international peer reviewed journals by the staff members of the Faculty of Medicine
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Item Biocontrol potential of six locally available fish species as predators of Aedes aegypti in Sri Lanka(Elsevier Ltd, 2021) Ranathunge, T.; Kusumawathie, P.H.D.; Abeyewickreme, W.; Udayanga, L.; Fernando, T.; Hapugoda, M.ABSTRACT: This study was conducted to evaluate the potential of six locally abundant fish species to control Aedes mosquito larvae and thereby manage dengue epidemics in a sustainable, cost-effective and environmentally friendly manner. The biocontrol efficacy of six larvivorous fish species, namely, Poecilia reticulata, Rasbora daniconius, Aplocheilus dayi, Oriochromis mossambicus, O. niloticus and Puntius bimaculatus, was evaluated under laboratory and field conditions. Five size-matched fish (of the same species) were introduced into separate tanks (replicates) containing 2 L of dechlorinated water and 200 third instar larvae of Aedes aegypti (L.). The number of larvae consumed by each fish species was recorded at three-hour intervals for 24 h. Acclimatized fish were introduced into a total of eighteen artificial breeding habitats located in the Gampola Medical Officer of Health (MOH) area at the species level with three replications. In addition, three breeding sites without fish were monitored as controls. Aedes larvae were monitored by dipping and siphoning methods in each breeding habitat at weekly intervals for three months and the number of fish surviving in each habitat was tallied. Over 24 h under laboratory conditions, O. mossambicus showed the highest predation rate, consuming 320.2 ± 14.5 larvae per day, with a predatory efficiency of 87.5 ± 3.5%. In comparison, O. niloticus consumed 264.6 ± 12.2 larvae per day with consumption efficiciency of 78.1 ± 3.7%, whereas R. daniconius had the lowest larval consumption (33.2 ± 2.7 larvae per day) and predatory efficiency (33.2 ± 3.2%). Over 12 weeks of observation under field conditions, breeding sites with Ap. dayi had the lowest Aedes larval counts, followed by Po. reticulata. Considering predation efficiency and survival under field conditions, Ap. dayi and Po. reticulata were considered to be the best potential candidates for biological control of Ae. aegypti. Further studies under field settings are warranted to evaluate the survival and predatory potential of the selected candidates under more varied environmental conditions.Item Use of cyclopoid copepods for control of Anopheles (Diptera: Culicidae) mosquito larvae to prevent re-emergence of malaria in Sri Lanka(Malaria Research Centre, Indian Council of Medical Research, 2019) Ranathunge, T.; Abeyewickreme, W.; Iqbal, M. C. M.; Hapugoda, M.BACKGROUND & OBJECTIVES: Although malaria is eliminated from Sri Lanka, there is a possible risk of spread from infected persons coming from malaria endemic countries. The presence of major and potential vectors in several parts of the country along with drug resistance, necessitates the identification of effective and novel control methods. The present study focused on identifying effective biological control agents for anopheline larvae using carnivorous copepods under laboratory and field conditions to prevent re-introduction of malaria in the country. METHODS: Three copepod species, namely Mesocyclops scrassus, Cyclops varicans and C. languides collected from different areas in the country were cultured by adding supplementary food, and their predatory efficacy was evaluated under laboratory and field conditions. RESULTS: Significant variation (p <0.05) was observed in predation rates of studied copepod species. The species M. scrassus showed the highest predacious efficiency, and consumed the highest number of anopheline larvae under laboratory and field conditions. Further, M. scrassus had higher survival rate than C. varicans and C. languides. INTERPRETATION & CONCLUSION: The results of the study suggest that the predatory copepod M. scrassus can be used as a bio-control agent for the control of Anopheles mosquitoes to prevent re-emergence of malaria in the country. Additional research is suggested to identify naturally available copepod species and their predatory efficacy. KEYWORDS: Anopheles; Sri Lanka; biological control; copepods; malaria vectors; predatory efficacy.Item Entomological surveillance with viral tracking demonstrates a migrated viral strain caused dengue epidemic in July, 2017 in Sri Lanka.(Public Library of Science, 2020) Withanage, G.P.; Hapuarachchi, H.C.; Viswakula, S.D.; Gunawardene, Y.I.N.S.; Hapugoda, M.BACKGROUND: Dengue is the most important mosquito-borne viral infection disease in Sri Lanka triggering extensive economic and social burden in the country. Even after numerous source reduction programmes, more than 30,000 incidences are reporting in the country every year. The last and greatest dengue epidemic in the country was reported in July, 2017 with more than 300 dengue related deaths and the highest number of dengue incidences were reported from the District of Gampaha. There is no Dengue Virus (DENV) detection system in field specimens in the district yet and therefore the aim of the study is development of entomological surveillance approach through vector survey programmes together with molecular and phylogenetic methods to identify detection of DENV serotypes circulation in order to minimize adverse effects of imminent dengue outbreaks. Entomological surveys were conducted in five study areas in the district for 36 months and altogether, 10,616 potential breeding places were investigated and 423 were positive for immature stages of dengue vector mosquitoes. During adult collections, 2,718 dengue vector mosquitoes were collected and 4.6% (n = 124) were Aedes aegypti. While entomological indices demonstrate various correlations with meteorological variables and reported dengue incidences, the mosquito pools collected during the epidemic in 2017 were positive for DENV. The results of the phylogenetic analysis illustrated that Envelope (E) gene sequences derived from the isolated DENV belongs to the Clade Ib of Cosmopolitan genotype of the DENV serotype 2 which has been the dominant stain in South-East Asian evidencing that a recent migration of DENV strain to Sri Lanka.Item Appearance of Anopheles jeyporiensis James from Sri Lanka; a new species to the mosquito checklist(The Japan Society of Medical Entomology and Zoology, 2015) Gunathilaka, N.; Abeyewickreme, W.; Hapugoda, M.; Wickremasinghe, A.R.Previous records of Sri Lankan Anopheles were most imperfect, and even the number and names of the species present were very doubtful. There was no systematic study conducted for Sri Lankan adult anophelines since 1990. Therefore, the objective of this study was to explore the species abundance and morphological variations of anopheline mosquitoes in Sri Lanka. Entomological surveys were conducted on a monthly basis from June 2010 to December 2013 in Trincomalee District, using five entomological techniques. Entomological surveys identified a total of 131,804 mosquito specimens belong to 18 anopheline species. One of which was An. jeyporiensis, a species that was not in the checklist in Sri Lanka. Its basic morphological features are similar to the members in Myzomyia series under the subgenus Cellia. Following characteristics were used to confirm the species as An. jeyporiensis; Centre of the scutum covered with short oblong white scales extending back to scutellum; Vein R 1 usually with accessory pale spot on preapical dark (PD) area; Foretarsomere 1 with apical pale band nearly 2.0 width of tarsomere diameter.Item Rare hemoglobin variants: Hb G-Szuhu (HBB: c.243C>G), Hb G-Coushatta (HBB: c.68A>C) and Hb Mizuho (HBB:c.206T>C) in Sri Lankan families(Informa Healthcare, 2015) Perera, P.S.; Silva, I.; Hapugoda, M.; Wickramarathne, M.N.; Wijesiriwardena, I.; Efremov, D.G.; Fisher, C.A.; Weatherall, D.J.; Premawardhena, A.In this short communication, we describe the clinical presentation of unusual hemoglobin (Hb), variants in three Sri Lankan cases under study for β-thalassemia intermedia (β-TI). We believe this is the first report on their occurrence in Sri Lanka as well as from the Indian subcontinent. During a molecular study performed on β-TI patients, we identified three unusual Hb variants as Hb G-Szuhu (HBB: c.243C>G), Hb G-Coushatta (HBB: c.68A>C) and Hb Mizuho (HBB: c.206T>C) in three unrelated families. Hb G-Szuhu and Hb G-Coushatta were found in combination with the common β-thalassemia (β-thal) mutation, IVS-I-5 (G>C). Both probands had mild anemia with greatly reduced red cell indices and had non palpable livers and spleens, however, by ultrasound, both were observed to be enlarged. The final Hb variant, Hb Mizuho, was identified as a heterozygous mutation found in both proband and his mother. Both family members had severe anemia and were regularly transfused and had increased red cell parameters.