Conference Papers
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This collection contains abstracts of conference papers, presented at local and international conferences by the staff of the Faculty of Medicine
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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 Intestinal and Ectoparasites of Human Health Importance among Stray Dogs in Galle District, Sri Lanka.(19th Conference on Postgraduate Research, International Postgraduate Research Conference 2018, Faculty of Graduate Studies,University of Kelaniya, Sri Lanka, 2018) Rathnayake, S.P.; Sudusinghe, H.P.; Nilaweera, T.H.W.T.; Marasinghe, M.A.P.; Sriyalatha, W.A.; Gunathilaka, P.A.D.H.N.Human-animal bond is a reciprocally favorable dynamic relationship which is beneficial to the health and well-being of both. Dogs have close contact with humans and play a pivotal role as definitive hosts or reservoirs for different zoonotic parasites, especially in developing countries. There are only few studies have focused on the zoonotic potential of animals in Sri Lanka. Therefore, the objective of the present study was the determine the intestinal and ectoparasites among dog population that may be important for human health. A total of 40 stray dogs captured for an animal welfare clinic conducted in Galle District of Sri Lanka was recruited for the study. Faecal samples were collected per rectal in to separate vials containing 10% formaldehyde. Ectoparasites of selected dogs were collected using a lose comb and stored in alcohol solution. The stool samples were processed by Kato-Katz techniques and intestinal parasitic stages were morphologically identified. For quantitative analysis, the modified McMaster technique was used to estimate eggs per gram of feces. The ectoparasites were characterized referring to morphological features. The results revealed eight intestinal parasites namely; Ancylostomacaninum (Prevalence: 66.75%; Eggs per gram: 362.82), Toxocaracanis (13.51%; 73.41), Enterobiusvermicularis (9.1%; 49.41), Trichurisvulpis (7.0%; 38.12), Physalopterarara (1.56%; 8.47), Paragonimuskellicotti (1.0% 5.65), Uncineriastenocephala (0.78%; 4.24) and Eucoleusaerophilus (0.26%; 1.41). The high prevalence rates of T. canis may cause visceral and ocular larva migrans to humans, which lead to blindness and A. caninum associated with hookworm related cutaneous larva migrans. Humans can be infected with T. vulpis when they accidentally ingest embryonated eggs, through contamination of infected soil, food or fomites even though it has been recorded as a rare infection. P. rara infection can be caused to humans by the accidental ingestion of arthropod hosts such as German cockroaches. In addition, the P. kellicotti, U. stenocephala, E. aerophilus and E. vermicularis may cause some health issues to humans. Even though present study did not indicate the presence of Echinococcusgranulosus which resides in the small bowel of dogs and other canids may lead to cause echinococcosis in humans. Argaspersicus (Prevalence; 34.18%) was the predominant among ectoparasites followed by Ctenocephalidescanis (32.91%) and Ixodesscapularis (32.91%). A. persicus can cause serious allergies on humans. The bites of I. scapularis may lead to cause human babesiosis (Babesiamicroti), human granulocytic ehrlichiosis (HGE); and tick-borne encephalitis (TBE). The presence of C. canis may indicate the transmission potential of Dipylidiumcaninum to humans as an occasional host. Overall, the investigation indicated that stay dogs in Galle District contain a multitude of ectoand endoparasites, thus posing a risk for the human population.Item Evaluation of the spatial and temporal trends of dengue outbreaks in Akurana, Central Province, Sri Lanka(Sri Lanka Association for the Advancement of Science, 2015) Udayanga, N.W.B.A.L.; Gunathilaka, P.A.D.H.N.; Iqbal, M.C.M.; Kusumawathie, P.H.D.; Najim, M.M.M.; Amerasinghe, U.S.; Abeyewickreme, W.Renowned as the world's fastest growing vector borne disease, dengue has become one of the major health issues in Sri Lanka leading to an alarming concern due to recent outbreaks throughout the country. Despite the immense efforts taken by the relevant authorities to reduce the rate of mortality, the average number of dengue cases recorded in each year remains around 30,000-35,000 without being changed significantly over time in Sri Lanka. Investigation of the trends in spatial and temporal distribution patterns of dengue is often treasured in the drafting and implementation of management/action plans to ensure effective management of dengue epidemics at regional scale. Thus, a statistical and geo informatics based analysis of the recent trends in dengue distribution was carried out to identify spatial and temporal trends in distribution patterns of Dengue in the Akurana Medical Officer of Health (MOH) area. Monthly records of reported dengue cases from 2010 to 2014 of the Akurana MOH area were obtained and were subjected to a scatter plot analysis in MINITAB (version 14.12.0) to identify the temporal patterns in the recorded dengue cases. Spatial maps of the recorded dengue case distribution in each GND for each month and for the whole study period were prepared by using Arc GIS 10.1. The spatial and temporal variations of dengue outbreak distribution within the Akurana MOH (at GND level) were analyzed to identify the recent trends in dengue incidence. Akurana, Bulugahathenna, Dippitiya, Dunuwila, Konakalagala and Neeralla localities could be identified as areas with relatively high risk to dengue outbreaks throughout the study period, while localities such as Balakanduwa, Delgasgoda, Delgasthenna, Malgamandeniya, Marahela, Palleweliketiya and Udawelikatiya emerged as areas with low risk. As suggested by the results of the paired-Chi square test [>Χ2 (30, 0.95) = 43.773], the emergence of dengue outbreaks indicated a significantly declining trend of recorded dengue cases in most of the GNDs (Aswadduma, Delgasgoda, Kurugoda, Malgamandeniya, Palleweliketiya and Walahena etc.) during the recent years. The evaluation of the trends in temporal and spatial distribution of dengue outbreaks at the localized level, could be recommended as a useful tool in the planning and implementation of action plans to control the rise of dengue, while evaluating the efficacy of already implemented control measures at regional scale.Item Characterization of the sibling species status of Anopheles culicifacies breeding in polluted water bodies in Trincomalee District of Sri Lanka(Sri Lanka Association for the Advancement of Science, 2015) Gunathilaka, P.A.D.H.N.; Prashath, K.; Abeyewickreme, W.Anopheles culicifacies, the major vector of malaria in Sri Lanka, is known to breed in clean and clear water. However, recent findings have confirmed breeding in waste water containing drains. However, no study has been conducted to identify whether it is vector or non vector siblings. Therefore, the objective of the study was to identify the sibling species status of An. culicifacies breeding in waste water containing drains. An. culicifacies adult samples (Reared from larvae) were obtained from the Padavisiripura Entomological team attached to Tropical and Environmental Diseases and Health Associates (TEDHA) Malaria Elimination Program in the Trincomalee District. The collected mosquito specimens were processed for the extraction of genomic DNA individually. The PCR amplifications were carried out using different primer combinations for differentiating species A from D, species B from C, species B from E, and species B, C, and E from each other. The results obtained from the gel electrophoresis were compared with the marker, and band sizes of 359 bp, 248 bp, 95 + 248 bp, 166 + 359 bp and 178 + 248 bp were used to identify the sibling species A, B, C, D and E respectively. The molecular biological identification of the field caught An. culicifacies samples indicated that only 6.25% (1/16) represented sibling species B. About 93.75% (15/16) of the samples were An. culicifacies sibling species E. According to the results, the majority of the species belongs to sibling species E which is considered as the vector sibling species of An. culicifacies. This is the first time that An. culicifcicies E breeding in waste water was confirmed by a molecular method. However, malaria control programs focus on rural communities as a result of bio-ecology of Anopheles mosquitoes. Therefore, unusual breeding habitats such as waste water collections may mislead the current vector controlling programs. These results reconfirm that An. culicifacies has adapted to breed in water bodies including waste water collections. Since a majority of them belong to sibling E, which is considered as the vector, this may adversely affect the current malaria elimination program. Therefore, new strategies should be adopted to control malaria vector breeding in these unusual breeding habitats under the current malaria elimination program in Sri Lanka.Item Entomological investigations on malaria vector studies in earlier conflict areas of Sri lanka after 30 years(University of Peradeniya, 2014) Gunathilaka, P.A.D.H.N.; Fernando, M.A.S.T.; Hapugoda, M.D.; Wijeyerathne, P.; Wickremasinghe, A.R.; Abeyewickreme, W.Entomological investigations on the abundance of malaria vector mosquitoes have not been studied in northern and eastern parts of the Sri Lanka over the past 30 years due to the separatist war. The main aim of this study was to explore diversity and abundance of Anopheles mosquitoes in earlier conflict areas in Sri Lanka. Monthly entomological monitoring was carried out at 60 possible malaria sensitive localities situated approximately 12 km apart in 15 selected sentinel sites in Ampara (4), Batticaloa (3), Mannar (3) and Trincomalee (5) districts for 32 months (June 2010 to August 2013). Adult mosquitoes were collected by WHO recommended techniques. Out of 701,356 anophelines collected, An. culicifacies was noted only in Ampara, Batticaloa and Trincomalee Districts. Although the main vector An. culicifacies (n= 1,876) was low in numbers, the presence of secondary vectors including An. subpictus (n= 205,594) were high in these areas. An. nigerrimus (n= 227,057), An. barbirostris (n= 35,150), An. vagus (n= 21,161), An. pallidus (n= 17,403), An. annularis (n= 4,882), An. varuna (n= 3151), An. tessellatus (n= 718) and An. aconitus (n= 591) were the other species reported. There was a change in breeding habitats of An. culicifacies and An. subpictus. They were found more conducive to breeding in built wells, brackish water habitats and waste water collections which were below 3 mg/l of dissolved oxygen (2.85 ± 0.03). These results indicate that particularly An. culicifacies has adapted to breed in wide range of water bodies including waste water collections although they were earlier considered to breed in clean and clear water with high dissolved oxygen. The adaptation of the major and subsidiary vector mosquitoes to widespread water bodies (along with increase in imported cases) could be a potential factor for the increase in the incidence of malaria in the future even though reported cases are low at present. Further, entomological surveillance detected the presence of An. jeyporiensis from the country after 106 years. Hence, more classical entomological studies are required to describe species currently found in the country; revision of morphological identification keys is a step in this direction. Financial assistance given by the Global Fund for Aids, Tuberculosis and Malaria (GFATM-Round 8-SRL809G11M.) through TEDHA malaria elimination program is acknowledged.Item Trends in densities of Anopheles culicifacies (Giles) and other potential malaria vector mosquitoes in the district of Trincomalee(Sri Lanka Association for the Advancement of Science, 2013) Gunathilaka, P.A.D.H.N.; Fernando, M.A.S.T.; Hapugoda, M.D.; Wijeyarathne, P.; Wickremasinghe, A.R.; Abeyewickreme, W.Item Some observations on abundance and breeding habitats of Anopheles sp. in Trincomalee, Sri Lanka(Sri Lanka Association for the Advancement of Science, 2010) Gunathilaka, P.A.D.H.N.; Fernando, M.A.S.T.; Hapugoda, M.D.; Wijeyerathne, P.; Wickremasinghe, A.R.; Abeyewickreme, W.Malaria is one of the most serious vector-borne diseases affecting millions of people in the world annually. More than 90% of the deaths, resulting from malaria occurred particularly in children aged 1-5 years. Despite the huge burden and the absence of an effective vaccine, few tools are available to control malaria. Malaria is transmitted by Anopheles mosquitoes. The abundance of Anopheles mosquitoes was not studied in some parts of the island, especially in North and East areas over 30 years because of the ethnic conflict. The main aim of this study was to explore the habitat range and distribution of Anopheline species in the Trincomalee district. Five hundred and seventy one Anopheles larvae were collected from different breeding sites in 5 areas (Sirajnagar, Hatharaela, Paraipanchankulam, Indiwewa and Uppuweli) in Trincomalee district in March 2010 using standard larval collection techniques. These areas were situated about 10 km apart from each other. Collected mosquito larvae weretransferred to the laboratory and reared. Emerged adult Anopheles mosquitoeswereidentified using taxonomic keys. Nine anopheline species wererecorded: Anophelesculicifacies 6% (32/571), An. subpictus 25% (145/571), An.vagus 23% (134/571), An. peditaeniatus 5% (28/571), An. nigerrimus 35% (200/571), An. barbirostris 2% (14/571), An.jemesi 1% (7/571), An. pallidus 0.3% (2/571) and An. varuna 0.3% (2/571). Overall, Anopheles nigerrimus, An. subpictus and An. Vagus were the most prevalent, and An. culicifacies, An. peditaeniatus, An. barbirostris, An. jemesi, An. varuna and An. pallidus were the least prevalent species. Paddy fields, burrow pits, field channels, ponds, irrigation channels, edges of tanks, mud pools and marshy lands were the main breeding sites of Anopheles mosquitoes in selected areas in Trincomalee district. The presence of some Anopheline mosquitoes which can act as potential malaria vectors may cause malaria epidemics in these areas. Acknowledgements: Financial assistance from the Global Fund for Aids, Tuberculosis and Malaria (GFATM) (Round 8)Item Species succession of malaria vector mosquitoes and physicochemical factors affecting their abundance in rice ecosystems in Trincomalee, Sri Lanka(University of Kelaniya, 2013) Gunathilaka, P.A.D.H.N.; Ranathunge, R.M.T.B.; Fernando, M.A.S.T.; Hapugoda, M.D.; Wijeyerathne, P.; Wickremasinghe, A.R.; Abeyewickreme, W.Background: Mosquito-borne diseases are a major public health threat in Asia. The present investigation was carried out to study the ecology of vector mosquitoes in Sri Lanka, in order to explore effective mosquito control strategies in rice ecosystems from the ecological point of view. Method: As part of investigations on potential linkages between irrigation and malaria transmission, all surface water bodies in and around 20 selected villages along an irrigation distributary in the District of Trincomalee, Sri Lanka, were surveyed for anopheline mosquito larvae (Diptera: Culicidae) from January 2012 - June 2013. Breeding sites were characterized according to exposure to sunlight, substratum, and presence of vegetation, fauna, inorganic matter and physical water condition (clear/turbid). Dissolved Oxygen (DO), conductivity, salinity, pH, temperature, Total Dissolved Solids (TDS) and turbidity were recorded. Results: A total of 3914 Anopheles larvae of twelve morphological types were collected from 685 breeding habitats. Anopheles peditaeniatus (n= 1041), was the most abundant, followed by An. subpictus (n= 893), An. nigerrimus (n= 808), An. barbirostris (n= 581), An. pallidus (n= 184), An. annularis (n=124), An. jamesii (n= 80), An. varuna (n= 76), An. vagus (n= 56), An. barbumbrosus (n= 48). An. culicifacies (n= 22) and An. aconitus (n= 1). The four most abundant species were significantly associated with waterlogged paddy fields. Anopheles culicifacies was noted only from irrigational canals with vegetation. Conductivity, salinity, and TDS were positively correlated with larval densities of An. peditaeniatus (Pearson correlations= 0.04, 0.17, 0.33: P= 0.94, 0.77, 0.58), An. subpictus (Pearson correlations= 0.6, 0.68, 0.56: P= 0.19, 0.20, 0.31), and An. vagus (Pearson correlations= 0.6, 0.42, 0.17: P= 0.28, 0.47, 0.77). However all physicochemical variables were negatively correlated with An. culicifacies densities. Conclusion: Major malaria vector of An. culicifacies complex occurred at relatively low densities, mainly in irrigated and waterlogged fields. These findings support understanding of mosquito ecology and will support future mosquito control strategies in rice ecosystems in Sri Lanka.Item Resting behavior of malaria vectors in Mannar District of Sri Lanka with reference to zooprophylaxis(University of Kelaniya, 2013) Gunathilaka, P.A.D.H.N.; Fernando, M.A.S.T.; Hapugoda, M.D.; Wijeyerathne, P.; Wickremasinghe, A.R.; Abeyewickreme, W.Background: The most important factors for effective zooprophylaxis in reducing malaria transmission are the presence of predominate populations of a strongly zoophilic mosquitoes and domestic animals for their blood-meal. Methods: Resting behavior of anopheline mosquitoes was evaluated using indoor and outdoor mosquito collection techniques. Mosquitoes were captured using 389 outdoor cattle-baited traps and indoor hand catches in 5672 houses at 12 possible malaria sensitive areas situated 12 km apart; Pesali, Keeri, Erukkallampeddi, Moor, Vankalai, Narawallikulam, Vanchiyankulam, Arvanum, Arrippu, Kokkupadayan, Koolankulam and Pandaraveilli for 12 months (June 2012 to June 2013) on a weekly basis. These areas had mostly homogenous characteristics in vegetations and house type. All collected mosquitoes were identified using standard taxonomic keys. A hypothesis test was conducted to determine whether there is a difference between indoor and outdoor collections. Results: A total of 3986 anopheline mosquitoes were collected from both indoor (n= 3122) and outdoor (n= 864) collection techniques. Anopheles subpictus was found to account for over 97.5% (n= 3887) of Anopheles species collected in the study areas. Other species were; 1.4% An. peditaeniatus (n= 57), 0.6% An. varuna (n= 22), 0.3% An. pallidus (n= 10), 0.2% An. nigerrimus (n= 7), 0.05% An. tessellatus (n= 2), and 0.03% An. aconitus (n= 1). Only 3 species namely, An. subpictus (n= 485), An. tessellatus (n= 2) and An. aconitus (n= 1) were recorded from indoor hand catches. In experimental cattle-baited hut trials, An. subpictus (n= 3026) was found to have the highest exophilic tendency (96.9%) compared to other anophelines encountered. The hypothesis test suggests that there was a significant difference of An. subpictus attracted to cattle-baited traps and human dwellings (P = 0.008). Although the main vector An. culicifacies was absent, the presence of the secondary vector An. subpictus was observed in high numbers in the District. Conclusion: Exophilic and zoophilic tendencies of An. subpictus are conducive for zooprophylaxis. The study further indicates that zooprophylaxis may be a potential strategy for malaria control. It is recommended that in areas with a predominant An. subpictus population, cattle could be kept close to human dwellings to maximize the effects of zooprophylaxis.Item Breeding of Anopheles culicifacies in different waterbodies in the district of Trincomalee(University of Kelaniya, 2012) Gunathilaka, P.A.D.H.N.; Fernando, M.A.S.T.; Hapugoda, M.D.; Wijeyerathne, P.; Wickremasinghe, A.R.; Abeyewickreme, W.Introduction: Anopheles culicifacies (Diptera: Culicidae), the major vector of malaria in Sri Lanka is known to breed in clean and clear water. This study was focused to understand the larval habitats of the major malaria vector with the eco system changes in the Trincomalee district of the Eastern Province. Method: Potential larval habitats for Anopheles mosquitoes were surveyed on a monthly basis for 17 months (January 2011 –June 2012) in 4 different selected sampling sites (Murthankulam, Kommnaimottai, Paranamadawachchiya and Kokmotawewa). Collected larvae were identified using standard taxonomic keys. The species Distribution (C) and Density (D) were calculated. Results: A total of 2996 larval specimens representing 13 Anopheles species were reported from 16 different breeding habitats namely, waste water (n= 635), built well (n= 1229), earth well (n=149), agricultural well (n=9), rain water collection (n=89), animal hoof print (n=17), burrow pit (n=256), rock pool (n=10), canal (n=15), irrigation canal (n=27), lake margin (n=27), tank margin (n=448), pond margin (n=15), marshy land (n=13), paddy field (n=15) and slow moving water (n=42). An. culicifacies was observed as the most predominant species throughout the survey. According to Density criterion, An. culicifacies (44.0%), An. subpictus (19.2%), An. barbirostris (13.2%), An. peditaeniatus (10.28%) and An. nigerrimus (8.7%) were within the dominant class; (D > 5%). Two species (An. vagus, An. pallidus) were in the subdominant class (1< D <5%). Only An. annularis, An. varuna, An. barbumbrosus, An. pseudojamesi, An. jamesii and An. tessellatus were the satellite species (D < 1%). An. nigerrimus, An. subpictus and An. peditaeniatus can be regarded as constant according to distribution (C= 80.1-100%). Only An. vagus was the most frequently reported (C= 60.1 – 80%) species. All other Anopheles including An. culicifacies were observed as infrequent species (C= 20.1 – 40%) and no species was identified as sporadic appearance (C= 0 – 20%). Most productive breeding site for An. culicifacies were drains covered with waste water (Density= 81.57%) in remote areas. Interpretation & conclusion: These results indicate that An. culicifacies has adapted to breed in a wide range of water bodies including waste water collections although they are considered to breed in clean and clear water. The survival of the major vector mosquito in widespread water bodies could be responsible for the increase in the incidence of malaria in the future.