Medicine
Permanent URI for this communityhttp://repository.kln.ac.lk/handle/123456789/12
This repository contains the published and unpublished research of the Faculty of Medicine by the staff members of the faculty
Browse
10 results
Search Results
Item Distribution and seasonal variation of malaria vectors in the Mannar and Jaffna Districts; an entomological investigation during the phase of prevention of re-establishment of malaria in Sri Lanka(Springer Link, 2024) Jude, J.; Gunathilaka, N.; Wijerathna, T.; Fernando, D.; Wickremasinghe, R.; Abeyewickreme, W.Sri Lanka has been declared “malaria-free” since 2016. The presence vectors and the cent establishment of new vectors are key challenges. This study documents the distribution of malaria vectors in previously high malaria endemic areas in Sri Lanka. Three locations were selected in Mannar and Jaffna districts. Entomological surveillance was carried out during January 2019 to January 2020 in both districts using cattle baited net (CBNT), hand collection (HC), and larval collection. The variation of mosquito abundance with selected climatic variables were evaluated using Pearson’s correlation. A total of 44,526 anophelines belonging to 12 species was encountered from both districts. The CBNT was the most productive technique that represented 78.65% (n = 35,022) of the total collection. Anopheles subpictus was the predominant species among adult collections in both districts, while in larval surveys, An. stephensi (60.1%; n = 2963) and An. varuna (40.9%; n = 1026) were observed in Jaffna and Mannar districts, respectively. The adult density indicated significantly strong positive correlations to the rainfall (r = 0.619, P < 0.05) and humidity (r = 0.524, P < 0.05) in both Jaffna and Mannar (rainfall: r = 0.553, P < 0.05; humidity: r = 0.553, P < 0.05). The number of larvae was not directly correlated with climatic variables. The present study reports the presence of An. culicifacies, An. subpictus and An. stephensi. Considering the fact that imported malaria cases are reported across the country the fact that there is an entomological risk to transmit malaria locally is a challenge. This warrants the continuous monitoring of vector population and seasonal variation, especially in previous malaria endemic regions.Item Comparative analysis of the larvicidal activity of temephos (EC50) and novaluaron (EC10) to control Anopheles stephensi in Sri Lanka(Elsevier, 2023) Jude, J.; Gunathilaka, N.; Udayanga, L.; Fernando, D.; Premarathne, P.; Wickremasinghe, R.; Abeyewickreme, W.Background: Anopheles stephensi was first recorded in the coastal area of Mannar District, Sri Lanka, in December 2016. Since then, this vector has been isolated from other districts in the Northern and Eastern Provinces of Sri Lanka. Chemical control is the main arm of vector control that can be used to reduce the vector densities within a short period. Thus, the present study aimed at evaluating the efficacy of using selected insecticides for the control of An. stephensi larvae. Method: The third and fourth instar larval stages of An. stephensi (F2 generation) of field mosquitoes that were caught using cattle baited net trap collections from Columbuthurai, Kurunagar, and Navanthurai areas in Jaffna District, Sri Lanka, were obtained from the laboratory colony established at Jaffna. Batches of 100 larvae were taken for experiments and introduced separately to a concentration series of temephos and novaluron (0.04-400 ppm). A control test was also performed at each setup without introducing insecticides. The mortality rates of An. stephensi larvae exposed to different concentrations of larvicides were recorded at 1, 24 and 48-h intervals. The experiment was replicated five times at individual concentrations for each selected chemical. Data were analyzed using the General Linear Model (GLM) and Probit analysis. Results: The highest mortality rate (100%) at a 1-h exposure period was observed from temephos at >100 ppm. The mortality rates varied significantly for different concentrations and larvicides (p < 0.05). At 24-h of the exposure period, the 100% mortality of An. stephensi larvae were observed from both temephos and novaluron even at 0.04 ppm. Conclusion: Both temephos and novaluron reported 100% mortality rates in An. stephensi larvae at 1-h and 24-h exposure periods. Based on the findings, temephos and novaluron can be recommended as effective larvicides for chemical-based control of An. stephensi in Jaffna, Sri Lanka. Further, it is recommended to conduct a field-based study, where habitat types and water quality are highly heterogeneous and may affect the residual activity.Item Biology, bionomics and life-table studies of Anopheles stephensi (Diptera: Culicidae) in Sri Lanka and estimating the vectorial potential using mathematical approximations(Elsevier, 2023) Jude, J.; Gunathilaka, N.; Udayanaga, L.; Fernando, D.; Premarathne, P.; Wickremasinghe, R.; Abeyewickreme, W.Background: Anopheles stephensi is an invasive mosquito in Sri Lanka that can potentially transmit malaria. The transmission intensity is linked with biology, bionomic and behavioral aspects of a vector that are associated with the Vectorial Capacity (VC). However, the influence of larval conditions eventually affects the vectorial potential of An. stephensi are not well understood. Methods: A colony of An. stephensi was established at the Regional Centre of the Open University of Sri Lanka, Jaffna District. The colony was maintained under confined conditions according to standard protocols. Biotypes of An. stephensi were characterized by referring to the number of egg ridges. Information on (a) biological aspects of eggs (duration for egg hatching, egg development and hatchability), (b) larval development time, larval survivorship pupation success, resting depth of larvae), (c) pupae (adult emergence rate, average time for adult emergence) and (d) adults (biting frequency, mating success gonotrophic cycle, fecundity, duration for egg-laying, percentage of sexes, adult survival/longevity) were evaluated under life-table analysis. Further, selected morphometric characters of each life cycle stage were recorded from the eggs (length and breadth), larvae (head length, width of head, length of thorax, width of thorax, length of abdomen, width of abdomen, and the total length of larvae), pupae (cephalothoracic length and width) and adults (length & width of wing, thorax and abdomen). The VC was calculated using a mathematical-based approach. Descriptive statistics, General Linear Model (GLM) and independent-sample t-test were used for the statistical analysis. Results: All three biotypes were identified based on egg morphology. Mysorensis biotype (47%; n = 470) was predominant followed by type (38.1%; n = 381) and intermediate (14.9%; n = 149). The mean egg length (F(2,997) = 3.56; P = 0.029) and breadth (F(2,997) = 4.57; P = 0.011) denoted significant differences among the three biotypes. The mating success of females observed was 80.7 ± 4.45%. The mean hatching period was 1.9 ± 0.03 days, with a hatching rate of 86.2 ± 0.77%. Overall, 8.0 ± 0.14 days were required for larval development and 30.3 ± 0.14 h were spent in the pupal stage. The pupation success was 94.5 ± 0.37%, and the majority were males (53.1 ± 0.73%). The mean fecundity was 106.5 ± 6.38 eggs and a gonotrophic cycle of 3.4 ± 0.06 days. The female survival rate was 43.2 ± 2.4%, with a mean biting frequency of 66.6 ± 3.5%. The average VC of adult An. stephensi was estimated to be 18.7. Conclusions: The type biotype, which is an effective vector in the Indian subcontinent is present in Sri Lanka. According to the mathematical approximation, An. stephensi found locally has a vectorial capacity of over 18. Therefore, this study warrants the health authorities and vector control programmes to continue the entomological surveys, monitoring of vector densities and implementing appropriate vector control interventions based on biology and bionomic information of vectors.Item A Comprehensive analysis on abundance, distribution, and bionomics of potential malaria vectors in Mannar District of Sri Lanka(Hindawi Publishing Corporation, 2019) Gunathilaka, N.; Hapugoda, M.; Wickremasinghe, R.; Abeyewickreme, W.BACKGROUND:A detailed knowledge of the distribution of the malaria vectors in Mannar district of Sri Lanka has not been studied after 1927. Past records indicated the presence of only seven species of anophelines, namely, An. culicifacies, An. subpictus, An. barbirostris, An. peditaeniatus, An. nigerrimus, An. Jamesii, and An. maculatus. There have been many changes in terms of distribution of Anopheles in the district over time. METHODS: Entomological surveillance was conducted on a monthly basis, comprising indoor hand collection, window trap collection, cattle-baited net collection, cattle-baited hut collection, and larval survey from June 2010 to June 2012 in 12 study areas under three entomological sentinel sites. The relationship between seven abiotic variables of the breeding habitats was measured. Pearson's correlation coefficients were used to determine the associations between climatic variables and anopheline densities. RESULTS:A total of 74,181 mosquitoes belonging to 14 Anopheles species were recorded. An. subpictus was the most predominant species from all techniques representing 92% (n=68,268) of the total anopheline collection. However, Anopheles culicifacies was not recorded from any site during the study period. Larval surveys identified 12 breeding habitat categories including waste water collections, lagoon water collections, and drains which were not recorded as breeding habitats by previous studies. The mean dissolved oxygen level of waste water collections was 3.45±0.15 mg/l. The mean salinity and conductivity of lagoon water collections were 21105±1344 mg/l and 34734±1974 μs/cm, respectively.CONCLUSION: The present study provides the updated knowledge on anopheline distribution and vector bionomics. Therefore, documentation of the current knowledge would be useful for learners and health authorities to design appropriate vector control measures in the prevention of reintroduction of malaria.Item Use of a public-private partnership in malaria elimination efforts in Sri Lanka; a case study(BioMed Central, 2018) Fernando, D.; Wijeyaratne, P.; Wickremasinghe, R.; Abeyasinghe, R.R.; Galappaththy, G.N.L.; Wickremasinghe, R.; Hapugoda, M.; Abeyewickreme, W.; Rodrigo, C.BACKGROUND: In special circumstances, establishing public private partnerships for malaria elimination may achieve targets faster than the state sector acting by itself. Following the end of the separatist war in Sri Lanka in 2009, the Anti Malaria Campaign (AMC) of Sri Lanka intensified malaria surveillance jointly with a private sector partner, Tropical and Environmental Diseases and Health Associates Private Limited (TEDHA) with a view to achieving malaria elimination targets by 2014. METHODS: This is a case study on how public private partnerships can be effectively utilized to achieve malaria elimination goals. TEDHA established 50 Malaria Diagnostic Laboratories and 17 entomology surveillance sentinel sites in consultation with the AMC in areas difficult to access by government officials (five districts in two provinces affected by war). RESULTS: TEDHA screened 994,448 individuals for malaria, of which 243,867 were screened at mobile malaria clinics as compared to 1,102,054 screened by the AMC. Nine malaria positives were diagnosed by TEDHA, while the AMC diagnosed 103 malaria cases in the same districts in parallel. Over 13,000 entomological activity days were completed. Relevant information was shared with AMC and the data recorded in the health information system. CONCLUSIONS: A successful public-private partnership model for malaria elimination was initiated at a time when the health system was in disarray in war ravaged areas of Sri Lanka. This ensured a high annual blood examination rate and screening of vulnerable people in receptive areas. These were important for certification of malaria-free status which Sri Lanka eventually received in 2016.Item Clinical and histopathological characteristics of cutaneous leishmaniasis in a group of military personnel in Sri Lanka(American Society of Tropical Medicine and Hygiene, 2015) Manamperi, N.H.; Fernando, C.S.; Pathirana, A.; Abeyewickreme, W.; de Silva, V.C.; Karunaweera, N.D.Cutaneous leishmaniasis (CL) is a newly established vector-borne parasitic disease in Sri Lanka. Military personnel have an occupational risk for CL due to being stationed in endemic areas and exposure to vectors outdoors. This study describes the clinical and histopathological features of CL in a group of military personnel. Thirty five patients with smear positive for Leishmania amastigotes were included, their data analyzed for clinical features and skin biopsies processed routinely for histology, examined at a conference microscope and classified into 4 groups using modified Ridley criteria for Leishmaniasis as: I-parasitized macrophages with variable lymphocytes and plasma cells; II-parasitized macrophages with lymphocytes, plasma cells and ill formed histiocytic granulomata; III-a mixture of macrophages (with or without parasites), lymphocytes, plasma cells and epithelioid granulomata; IV-epithelioid granulomatous response with a few lymphocytes and plasma cells but no amastigotes. Lesions were categorized by duration, as acute (< 6 months) or chronic (> 6 months). Study group composed of all males with a mean age of 32.6 years (range 22-47) and lesion duration of 5.6 months (range 1-24). Number of lesions varied from 1 to 6 with majority (71.4%, n= 25) having a single lesion. Nodular (37.1%, n=13) and nodulo-ulcerative (25.7%, n=9) lesions in upper limbs (68.6%, n=24) was the commonest presentation. Twenty nine (82.9%) of the biopsies were positive also by histology. Twenty two (62.9%) were acute and 13 (37.1%) chronic. Group I, II, III and IV patterns were seen in 14 (40%), 12 (34.3%), 5 (14.3%) and 4 (11.4%) respectively and 9 (40.9%), 9 (40.9%), 2 (9.1%) and 2 (9.1%) of acute lesions and 5 (38.5%), 3 (23.1%), 3 (23.1%) and 2 (15.4%) of chronic lesions respectively. Necrosis was not seen in any of the lesions. Majority in this group of military personnel with CL had single lesions affecting the upper limbs and sought treatment within 2 years of appearance of lesions. The histological picture varied from diffuse infiltration of parasitized macrophages admixed with chronic inflammatory cells to ill-formed histiocytic granulomata.Item Oviposition preferences of dengue vectors; Aedes aegypti and Aedes albopictus in Sri Lanka under laboratory settings.(CABI Publishing, 2018) Gunathilaka, N.; Ranathunge, T.; Udayanga, L.; Wijegunawardana, A.; Abeyewickreme, W.Investigations on oviposition behaviour of dengue vectors are critical for effective controlling of vector breeding. Therefore, the aim of the present study was to determine the oviposition behaviour of dengue vectors, Aedes aegypti and Aedes albopictus in Sri Lanka. Batches of 1000 adult mosquitoes (1 : 1, male: female ratio) housed in rearing cages were used for each experimental setup from Ae. aegypti and Ae. albopictus. Oviposition responses with respect to the size of the ovitrap, colours of the ovitrap, water source, sodium chloride (NaCl) concentration and presence/absence of larvae were evaluated by enumerating the number of eggs laid in the ovitraps. The analysis of variance and cluster analysis were used to investigate the significance in the variations among oviposition. The number of eggs laid by both species were improved with the increasing size of ovitraps. Ae. albopictus indicated the highest mean number of eggs in 0.2% of NaCl than in the ovitraps filled with distilled water. However, the egg laying preference was reduced with increasing salinity in both species. Drain water with low dissolved oxygen (DO) level (0.43 ± 0.12 mg l-1) was the preferred water source for both species, while a significantly high oviposition rate was observed in ovitraps with larvae. Black colour ovitraps attracted the majority of gravid females, while white was least preferred. There were no significant variations among oviposition behaviours of Ae. albopictus and Ae. aegypti. The ability of these vectors to breed in waste water with low DO levels may lead them to attain wide dissemination in the natural environment, enhancing their potential threat to human life.Item Application of a real time Polymerase Chain Reaction (PCR) assay for the early diagnosis of human leptospirosis in Sri Lanka(Academic Press, Elsevier, 2016) Denipitiya, D.T.H.; Chandrasekharan, N.V.; Abeyewickreme, W.; Hartskeerl, C.M.; Hartskeerl, R.A.; Jiffrey, A.M.; Hapugoda, M.D.Leptospirosis has a major impact on health in Sri Lanka but is probably grossly under-recognized due to difficulties in clinical diagnosis and lack of diagnostic laboratory services. The objective of this study was to establish and evaluate a SYBR Green-based real-time Polymerase Chain Reaction (rt-PCR) assay for early, rapid and definitive laboratory diagnosis of leptospirosis in Sri Lanka. The rt-PCR assay was established and analytical specificity and sensitivity were determined using reference DNA samples. Evaluation of the assay for diagnosis of clinical samples was performed using two panels of serum samples obtained from 111 clinically suspected adult patients. Patients were confirmed as leptospirosis (n = 65) and non-leptospirosis (n = 30) by the Patoc - MAT. Other 16 samples gave ambiguous results. The analytical sensitivity of the rt-PCR was approximately 60 genome copies and no cross-reactivity was observed with saprophytic Leptospira spp. and other pathogenic microorganisms. Based on confirmation with Patoc-MAT on paired samples this corresponds to a diagnostic sensitivity and specificity of 67.7% (44/65) and 90.0% (27/30), respectively. This study showed that rt-PCR has the potential to facilitate rapid and definitive diagnosis of leptospirosis during early phase of infection in Sri Lanka.Item Molecular Diagnosis for confirmation of Infectious Diseases in Sri Lanka in 2009(Sri Lanka Association for the Advancement of Science, 2009) Hapugoda, M.D.; Bandara, K.B.A.T.; Dayanath, M.Y.D.; Wellawaththage, C.; Hapuarachchi, H.A.C.; Abeyewickreme, W.Confirmation of infectious disease outbreaks in Sri Lanka is an important national requirement. Many clinicians as well as general practitioners find it difficult to confirm diagnosis of some infectious diseases only on clinical grounds. Molecular assays can rapidly confirm diagnosis at the early phase of diseases when aetiological agents are present and before antibody titers are at detectable levels. PCR-based assays are more sensitive and more specific than all conventional methods. Overall objective of this study was early, rapid and definitive laboratory confirmation of the aetiology of chikungunya, dengue, Japanese Encephalitis (JE), leishmaniasis, leptospirosis, malaria and West Nile Virus (WNV) through molecular assays. A rapid mobile investigation team equipped with the case definition, questionnaires, sample collection methods and diagnostic methods for each disease was established. This group visited outbreak areas and collected clinical and laboratory information and clinical samples from suspected patients at the early stage of symptoms: 1-5 days. Clinical samples were laboratory tested by disease specific molecular assays (PCR/RT-PCR). Clinical parameters of each disease were analyzed. Only chikungunya, dengue and leptospirosis outbreaks out of the above mentioned diseases were reported during the preceding six months in 2009. The team collected blood samples from clinically suspected cases of chikungunya (n=430), dengue (n=116) and leptospirosis (n=23) from different parts of the island. Molecular assays confirmed infections only in 81% (350/430) for chikungunya, 7% (8/116) for dengue and 9% (2/23) for leptospirosis in selected suspected patients. Reports of the confirmation of the disease outbreak by molecular assay were sent to the relevant health authority within two days to highlight the magnitude of the infection. These results showed importance of aetiological confirmation of infectious diseases by molecular assays. In conclusion, molecular diagnosis using a single clinical sample is important for rapid, definitive and early confirmation of aetiology of a particular infectious disease outbreak when serological methods are of little value at the early stage of infection. This is important for cost effective and efficient control of the outbreaks through proper clinical management.Item Re emergence of Chikungunya virus in South-east Asia: virological evidence from Sri Lanka and Singapore(Cambridge University Press, 2010) Hapuarachchi, H.C.; Bandara, K.B.A.T.; Sumanadasa, S.D.; Hapugoda, M.D.; Lai, Y.L.; Lee, K.S.; Tan, L.K.; Lin, R.T.; Ng, L.F.; Bucht, G.; Abeyewickreme, W.; Ng, L.Chikungunya fever swept across many South and South-east Asian countries, following extensive outbreaks in the Indian Ocean Islands in 2005. However, molecular epidemiological data to explain the recent spread and evolution of Chikungunya virus (CHIKV) in the Asian region are still limited. This study describes the genetic Characteristics and evolutionary relationships of CHIKV strains that emerged in Sri Lanka and Singapore during 2006-2008. The viruses isolated in Singapore also included those imported from the Maldives (n=1), India (n=2) and Malaysia (n=31). All analysed strains belonged to the East, Central and South African (ECSA) lineage and were evolutionarily more related to Indian than to Indian Ocean Islands strains. Unique genetic characteristics revealed five genetically distinct subpopulations of CHIKV in Sri Lanka and Singapore, which were likely to have emerged through multiple, independent introductions. The evolutionary network based on E1 gene sequences indicated the acquisition of an alanine to valine 226 substitution (E1-A226V) by virus strains of the Indian sublineage as a key evolutionary event that contributed to the transmission and spatial distribution of CHIKV in the region. The E1-A226V substitution was found in 95.7 % (133/139) of analysed isolates in 2008, highlighting the widespread establishment of mutated CHIKV strains in Sri Lanka, Singapore and Malaysia. As the E1-A226V substitution is known to enhance the transmissibility of CHIKV by Aedes albopictus mosquitoes, this observation has important implications for the design of vector control strategies to fight the virus in regions at risk of chikungunya fever.