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 Annotated checklist of chigger mites (Trombidiformes: Leeuwenhoekiidae, Trombiculidae and Walchiidae) in Sri Lanka(Elsevier, 2022) Ashani, M.L.S.; Gunathilaka, P.A.D.H.N.; Premaratna, B.A.H.R.; Chandrasena, T.G.A.N.; Jacinavicius, F.C.; Silva, R.B.Chigger mites (Leeuwenhoekiidae, Trombiculidae, and Walchiidae) are parasites of any terrestrial vertebrate. The present study updates the list of chigger mite (Trombiculidae, Leeuwenhoekiidae, and Walchiidae) species recorded from Sri Lanka along with taxonomic classification based on previous investigations since 1946 to date and our observations in western and southern parts of the country. This checklist listed 15 species in 9 genera within the three chigger families. For now, murid species were the host most sampledparasitized by chiggers in Sri Lanka. However, further studies are required to increase the diversity of chigger mites in Sri Lanka and probably the description of new species, which will be possible with morphological and molecular characterization.Item Occurrence of major and potential malaria vector immature stages in different breeding habitats and associated biotic and abiotic characters in the district of Trincomalee Sri Lanka(New Delhi : National Institute of Malaria Research, 2020) Ranathunge, R.M.T.B.; Kannangara, D.N.; Gunathilaka, P.A.D.H.N.; Abeyewickreme, W.; Hapugoda, M.D.BACKGROUND & OBJECTIVES: Understanding the effect of biotic and abiotic factors on the biology and ecology of immature stages of anopheline larvae is very important in controlling malaria vector mosquitoes. Therefore, this study was focused on the monitoring of ecological factors affecting the distribution, dynamics, and density of malaria vector mosquitoes in the District of Trincomalee, Sri Lanka. METHODS: Permanent and temporary breeding habitats were identified and selected from five possible malaria sensitive sites in the district of Trincomalee. Anopheles larvae and macro-invertebrates were collected using standard methods for 16 months (from October 2013 to January 2015) and they were identified microscopically. Eight physico-chemical parameters of the breeding habitats were measured. RESULTS: Overall, a total of 4815 anopheline larvae belonging to 13 species were collected from 3,12,764 dips from 18 permanent and temporary breeding habitats. The abundance of anopheline larvae showed a significant positive correlation (p <0.05) with physico-chemical parameters in breeding habitats, such as temperature, dissolved oxygen, and turbidity. A total of 35 macro-invertebrate taxa were collected from the anopheline mosquito breeding habitats. INTERPRETATION & CONCLUSION: This study represents the first systematic update of water quality parameters, macro-invertebrate communities associated with Anopheles mosquito oviposition sites in the District of Trincomalee, Sri Lanka. Rainfall intensity and wind speed are critical meteorological factors for the distribution and abundance of malaria vectors. Knowledge generated on the ecology of Anopheles mosquitoes will help to eliminate malaria vectors in the country. KEYWORDS: Macro-invertebrates; Sri Lanka; malaria vectors; physico-chemical parameters.Item A determination of air pollution in Colombo and Kurunegala, Sri Lanka, using energy dispersive X-ray fluorescence spectrometry on Heterodermia speciosa(The Scientific and Technological Research Council of Turkey, 2011) Gunathilaka, P.A.D.H.N.; Ranundeniya, R.M.N.S.; Najim, M.M.M.; Seneviratne, S.ABSTRACT: Sri Lanka is facing severe environmental problems such as air and water pollution due to rapid industrialisation and urbanisation. Because there have not been many studies on heavy metal pollution in Sri Lanka, the present study attempts to contribute to the literature a determination of metal pollution using indicators found in lichen specimens. Our study utilised energy dispersive X-ray fluorescence spectrometry to determine element concentrations resulting from air pollution in the lichen species Heterodermia speciosa Wulfen. These samples, collected from Colombo and Kurunegala, Sri Lanka, were analysed using the energy dispersive X-ray fluorescence (EDXRF) method in order to determine the concentrations of 13 different elements. A radioisotope excited X-ray fluorescence analysis was applied to the elemental analysis of lichens using the method of multiple standard addition. Our qualitative analysis of spectral peaks showed that the samples contained potassium, calcium, titanium, iron, manganese, copper, zinc, lead, bromine, rubidium, strontium, yttrium, and gallium. Samples from the environment around Colombo, which is a highly congested urban area with much industrial development, were found to be more polluted when compared with Kurunegala, a city that is less congested and without industries. Concentrations of K, Ca, Ti, and Fe were always higher than other elemental concentrations in the lichens we analysed, a fact attributed to the proximity to the sea or exposed earth crustal sources. From the elements reported from the 2 cities, K, Ca, Ti, Fe, Mn, Zn, and Pb were reported at concentrations higher than background levels. Levels of Pb and Zn in samples from Colombo were higher than those from Kurunegala, reflecting the increased vehicular traffic. This study reveals that the common lichen species Heterodermia speciosa can be used as an indicator lichen to analyse the pollution level and other elements in the atmosphere. © TÜBITAK. AUTHOR KEYWORDS: Air; EDXRF; Heterodermia; Lichens; Metal pollution. INDEX KEYWORDS: atmospheric pollution; concentration (composition); fungus; heavy metal; lichen; radionuclide; spectrometry; urban area; X-ray fluorescence, Colombo; Sri Lanka; Western Province [Sri Lanka], Heterodermia; Heterodermia speciosaItem Malaria in Sri Lanka: Investigating causes of the recent elimination and making plans to prevent reintroduction.(Malaria Research Centre/National Institute of Malaria Research., 2019) Perera, W.D.H.N.; Gunathilaka, P.A.D.H.N.; Taylor-Robinson, A.W.ABSTRACT: Sri Lanka is a country that has long suffered from epidemics of malaria. In this historical context, it is remarkable that in 2016 the Indian Ocean island nation was able to officially celebrate the elimination of this parasitic disease of major public health importance. The most devastating outbreak recorded in Sri Lanka was during 1934-35, when close to 80,000 human deaths were reported. Indoor residual spraying with the insecticides, DDT and malathion commenced in 1947 and was successful in causing a rapid decline in malaria incidence. However, poor vector control measures, resistance of mosquitoes to these insecticides and resistance of blood-stage Plasmodium parasites to the prevailing drugs used are considered the principal reasons for the occurrence of subsequent outbreaks. Despite this, Sri Lanka achieved the significant milestone of zero locally transmitted malaria cases in October 2012 and zero recorded deaths since 2007. Vector surveillance, parasitological examination, and clinical case management were collective effective activities that most likely led to elimination of malaria. Yet, there remains a high risk of reintroduction due to imported cases and an enduring vulnerability to vector transmission. In order to prevent re-establishment of malaria, continued financial support, sustained surveillance for vector species present in Sri Lanka and effective control of imported cases through rapid detection and early diagnosis are all required. In addition to these immediate practical priorities, further studies on vector biology and genetic variations that affect vectorial capacity would help to shed light on how to avoid reintroduction. This review affords an insight into the determinants of past malaria epidemics, strategies deployed to achieve and maintain the current status of elimination, lessons learnt from this success and plans to avoid resurgence of infection. KEYWORDS: Elimination; Plasmodium; Sri Lanka; importation; malaria; vector.Item The Diversity of Human Dirofilariasis in Western Sri Lanka(Hindawi Pub. Co, 2019) Chandrasena, T.G.A.N.; Premaratna, R.; Mallawaarachchi, C.H.; Gunawardena, N.K.; Gunathilaka, P.A.D.H.N.; Abeyewickrama, W.Y.; de Silva, N.R.BACKGROUND:Human dirofilariasis is an emerging zoonosis in many countries. Dirofilariasis caused by Dirofilaria repens may present with diverse clinical manifestations in humans due to aberrant localization of worm lesions causing diagnostic dilemmas. The aim of this retrospective study was to describe and update the demography and clinical spectrum of human dirofilariasis in western Sri Lanka. Nematode or nematode fragments isolated from excision biopsies that were confirmed as D. repens at the Department of Parasitology, Faculty of Medicine, University of Kelaniya, Sri Lanka, between 2012 and 2018 were included. Data on age, gender, and clinical details were obtained from case files. Identity of worms was established by morphometry and cuticle characteristics on wet-mount preparation. Specimens from unusual case presentations were further analyzed by PCR with specific primers for internal transcribed spacer region 2 (ITS2) of the ribosomal DNA. RESULTS:Sixteen nematode specimens isolated from subconjunctiva (n=2), subcutaneous (n=13) and intramuscular (n=1) locations were identified as D. repens by morphometry (average length 11.5 cm) and the characteristic longitudinal striations on cuticle visualized by microscopy. The age distribution of cases ranged from 1 to 65 years with a mean of 21.5. Females were more frequently affected (n=10, 62.5%) and worm locations were commonest in the orbital region (5/16) and scrotum (3/16). Imaging techniques were of use in detecting infections in deeper tissue levels. PCR analysis of DNA extracted from a worm in an intramuscular granuloma of the temporal region elicited the expected band at 484bp for D. repens. CONCLUSIONS: Human dirofilariasis is on an upward trend in incidence. Imaging techniques were of use in clinical diagnosis and molecular speciation in establishing the species identity in unusual case presentations. We suggest a more conservative approach in the management of human dirofilariasis and recommend a one health approach for control.Item Annotated checklist and review of the mosquito species (Diptera: Culicidae) in Sri Lanka(Magnolia Press LTD, 2018) Gunathilaka, P.A.D.H.N.Mosquito borne diseases remains as an importance source of morbidity and mortality in Sri Lanka. To better control vectors which transmit the diseases, updated list of the species present in the county is imperative. It is also vital in documenting the diversity of the family Culicidae. Original records were collected from a literature review to compile a list of the species recorded in Sri Lanka. This work illustrates the updated list of mosquito species in Sri Lanka and their current taxonomic status based on previous studies from 1901 to date. A total of 159 species belonging to 19 genera including sibling species, have been included in the revised mosquito checklist in Sri Lanka. The present work includes 13 species, two genera (Lutzia, Verrallina) and 9 subgenera in subfamily Culicinae, tribe Aedini of genus Aedes (Bruceharrisonius, Collessius, Danielsia, Dendroskusea, Downsiomyia, Fredwardsius, Hulecoeteomyia, Neomelaniconion, Phagomyia) in to the checklist which were not included in the previous mosquito checklist published nearly 26 years ago. However, further work is essential to refine this list and to explore the abundance of new species within the country. Improved morphological and molecular identification methods will sanction the refinement of the mosquito catalog in years to comeItem Determination of the efficiency of diets for larval development in mass rearing Aedes aegypti (Diptera: Culicidae)(CABI Publishing, 2018) Gunathilaka, P.A.D.H.N.; Uduwawala, U.M.H.U.; Udayanga, N.W.B.A.L.; Ranathunge, R.M.T.B.; Amarasinghe, L.D.; Abeyewickreme, W.Larval diet quality and rearing conditions have a direct and irreversible effect on adult traits. Therefore, the current study was carried out to optimize the larval diet for mass rearing of Aedes aegypti, for Sterile Insect Technique (SIT)-based applications in Sri Lanka. Five batches of 750 first instar larvae (L 1) of Ae. aegypti were exposed to five different concentrations (2-10%) of International Atomic Energy Agency (IAEA) recommended the larval diet. Morphological development parameters of larva, pupa, and adult were detected at 24 h intervals along with selected growth parameters. Each experiment was replicated five times. General Linear Modeling along with Pearson's correlation analysis were used for statistical treatments. Significant differences (P < 0.05) among the larvae treated with different concentrations were found using General Linear Modeling in all the stages namely: total body length and the thoracic length of larvae; cephalothoracic length and width of pupae; thoracic length, thoracic width, abdominal length and the wing length of adults; along with pupation rate and success, sex ratio, adult success, fecundity and hatching rate of Ae. aegypti. The best quality adults can be produced at larval diet concentration of 10%. However, the 8% larval diet concentration was most suitable for adult male survival.Item Efficacy of blood sources and artificial blood feeding methods in rearing of aedes aegypti (Diptera: Culicidae) for sterile insect technique and incompatible insect technique approaches in Sri Lanka(Hindawi, 2017) Gunathilaka, P.A.D.H.N.; Ranathunge, T.; Udayanga, L.; Abeyewickreme, W.INTRODUCTION: Selection of the artificial membrane feeding technique and blood meal source has been recognized as key considerations in mass rearing of vectors. METHODOLOGY: Artificial membrane feeding techniques, namely, glass plate, metal plate, and Hemotek membrane feeding method, and three blood sources (human, cattle, and chicken) were evaluated based on feeding rates, fecundity, and hatching rates of Aedes aegypti. Significance in the variations among blood feeding was investigated by one-way ANOVA, cluster analysis of variance (ANOSIM), and principal coordinates (PCO) analysis. Results. Feeding rates of Ae. aegyptisignificantly differed among the membrane feeding techniques as suggested by one-way ANOVA (p<0.05). The metal plate method was identified as the most efficient and cost-effective feeding technique. Blood feeding rate of Ae. aegypti was higher with human blood followed by cattle and chicken blood, respectively. However, no significant difference was observed from the mosquitoes fed with cattle and human blood, in terms of fecundity, oviposition rate, and fertility as suggested by one-way ANOVA (p>0.05). CONCLUSIONS: Metal plate method could be recommended as the most effective membrane feeding technique for mass rearing of Ae. aegypti, due to its high feeding rate and cost effectiveness. Cattle blood could be recommended for mass rearingAe. aegypti.Item Composition of malaria vectors and diversity of anopheline breeding habitats in the district of Mannar, Sri Lanka(Central Environmental Authority (CEA), 2016) Gunathilaka, P.A.D.H.N.; Hapugoda, M.D.; Wickremasinghe, A.R.; Abeyewickreme, W.In the malaria elimination phase in Sri Lanka, investigation on biological and ecological factors of malaria vectors are important in planning appropriate vector controlling strategies. Lack of sufficient biological and ecological information on malaria vectors in the Northern Province of the country, a malaria endemic region, is a major constrain in successful implementation of malaria control programmes. Therefore, the objective of this study was to explore the diversity of breeding habitats and species composition of malaria vector mosquitoes in the District of Mannar, Sri Lanka. Potential habitats for Anopheles mosquito larvae were surveyed from June, 2010 to July 20 J2 on a monthly basis in selected sampling sites in the Mannar District: Mannar Town, Vankalai and Silawathiura, within a radius about 20 km. In each site, 4 sub sites were selected A total of 37,788 Anopheles representing ten species was recorded from 12 breeding habitat categories. Built wells and waste water collections were conducive for anopheline breeding. Anopheles subpictus (96.2%, n= 36,351) was the dominant species followed by An. peditaeniatus (1.47%, n= 557), An. barbirostris (1.23%, n= 463), An. nigerriums (0.75%,n = 285), An. varuna (0.19%, n= 74), An. barbumbrosus (0.1%, n= 38), An. vagus' (0.03%, n= 12), An. pallidus (0.01%, n= 4), An.jamesii (0.05%, n= 2) and An. pseudojamesi (0.05%, n= 2). Use of wells and waste water drains as breeding places by potential malaria vectors indicates that both of these habitats act as larval reservoirs during the dry season. Presence of theses habitats in close proximity to human habitats create a potential risk of malaria transmission among humans. Therefore, health authorities need to be vigilant on these new habitats in vector control programmes.Item Breeding habitat diversity and species composition of Anopheles mosquitoes in Trincomalee district, Sri Lanaka(HABITATS Conservation Initiative, 2014) Gunathilaka, P.A.D.H.N.; Fernando, M.A.S.T.; Hapugoda, M.D.; Wijeyerathne, P.; Wickremasinghe, A.R.; Abeyewickreme, W.Entomological studies on the abundance of malaria vector Anopheles mosquitoes have not been studied in some malaria endemic areas of Sri Lanka over past 30 years in view of the security situation. The aim of this study was to explore the habitat diversity and distribution of anopheline species in Trincomalee District in order to prioritize vector breeding habitats for developing timely and cost effective larval controlling measures. Potential larval habitats for Anopheles mosquitoes were surveyed from June 2010 - December 2010, in selected sampling sites in the Trincomalee District; Gomarankadawala, Echchallampaththu, Mollipothana, Thoppur and Padavisiripura, within a radius about 20 km on weekly basis. The species distribution and density were calculated. A total of 3,701 larval specimens representing twelve Anopheles species were reported form 19 breeding habitats (Tank margin, main canal, paddy field, vegetative canal, lake, built well, burrow pit, distribution canal, pond, rock pool, canal, un-built well, common well, river margin, sand pool, animal foot print, rain water collection, quarry pit and marshy land). Ten habitats were categorized under structurally complex group based on the presence of biotic communities. Only An. subpictus can be regarded as constant according to Distribution (C) (C= 80.1-100%).An. nigerrimus, An. peditaeniatus, An. pallidus and An. vagus were frequent (C= 60.1 – 80%). An. varuna, An. barbirostris, An. annularis and An. barbumbrosus were shown as infrequent species (C= 20.1 – 40%) and other namely An. aconitus, An. culicifacies and An. jamesii can be categorized under sporadic appearance (C= 0 – 20%). According to Density (D) criterion, five species (An. subpictus, An. nigerrimus, An. varuna, An. pallidus, An. barbumbrosus) were within the dominant class (D > 5%). Four species (An. vagus, An. peditaeniatus, An. annularis, An. aconitus) were in the subdominant class (1< D <5%). Only An. jamesii and An. culicifacies were the satellite species (D < 1%).