Medicine
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This repository contains the published and unpublished research of the Faculty of Medicine by the staff members of the faculty
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Item Engineering RNA interference-based dengue virus resistance in the mosquito vector aedes aegypti: The current status and future directions(Springer, 2021) Denipitiyage, S.D.; Gunawardene, Y.I.N.S.; Federico, Z.; Dassanayake, R.S.Dengue is an acute, febrile disease caused by the dengue viruses (DENV) comprising four serotypes and transmitted by the mosquito vector Ae. aegypti. DENV are single-stranded, positive-sense RNA viruses of the family Flaviviridae. Dengue is declared as a current significant challenge in the Southeast Asia, imposing growing burden on infected populations. To date, dengue control has mostly relied on vector control strategies which have largely become ineffective. There is, therefore, an urgent need for novel vector control strategies. Development of genetically modified mosquito vectors to manipulate disease-vectoring populations has gathered increased interest in recent time. RNAi-mediated viral resistance contributes to the suppression of viruses, including DENV in the mosquito vector Ae. aegypti. With recent advances in the field of molecular biology, we and other scientists are continuing to engineer genes that confer virus resistance to reduce transmission rates of DENV and introducing these genes into the mosquito genome. Even though scientists successfully generated mosquito refractory to DENV2–4, no mosquito refractory to all four serotypes has been developed to date. This limitation can be overcome by systematic analysis of the molecular mechanisms of RNAi in the mosquito vector Ae. aegypti. An enhanced understanding of RNAi function in the mosquito vector Ae. aegypti will facilitate the application of RNAi to control the transmission of the dengue disease in the future. Here, based on current understanding of the RNAi, we discuss the mechanisms of RNAi in the mosquito vector Ae. aegypti. We also provide guidelines for optimal design of RNAi experiments in Ae. aegypti with the possible risks associated with them along with proposed solutions.Item Rare case of self-limiting haemolysis associated with Dengue fever in a Sri Lankan female - case report(Royal Society of Medicine,London, 2022) Luke, W.; Lohithalingam, P.; Jayamanne, S.F.A 61-year old female with dengue haemorrhagic fever developed anaemia and rising transaminase levels on the 6th day of illness. She was found to have haemolysis with a negative direct antiglobulin test (DAT), and no red cell fragmentation. She recovered with supportive care. Haemolysis with associated Haemolytic uraemic syndrome (HUS), Disseminated intravascular coagulation (DIC) and cold Auto-immune haemolytic anaemia (AIHA) is reported previously; DAT negative haemolytic anaemia associated with dengue fever has not. This case suggests a need for further studies on other immune mechanisms that can lead to haemolysis with dengue fever.Item Water quality characteristics of breeding habitats in relation to the density of Aedes aegypti and Aedes albopictus in domestic settings in Gampaha district of Sri Lanka(Elsevier, 2022) Dalpadado, R.; Amarasinghe, D.; Gunathilaka, N.In spite of the unavailability of measures to target dengue control in human populations, the promising way of combating the disease is by controlling vector mosquito larvae and their breeding habitats. Water quality characteristics of the breeding habitats of dengue vectors are among the crucial parameters that determine the female mosquito's oviposition and breeding. Therefore, a cross-sectional study was conducted to investigate the habitat characteristics of dengue vector mosquitoes by assessing the water quality of positive breeding habitats using the weighted arithmetic water quality index (WQI). The present study was conducted in domestic areas of the selected medical officer of health areas of the Gampaha district, Sri Lanka, from 2017 to 2019. Water quality characteristics of breeding habituations were measured and analyzed. The relationship between water quality parameters in breeding habitats with the occurrence of mosquito species was assessed using Kruskal-Wallis one-way analysis of variance, followed by pairwise comparison using Dunn's test and Mann-Whitney U test at a 5% level of significance. This study revealed that the temperature of Aedes mosquito breeding water ranged between 25.3 and 39.8 °C, and bred at temperatures as high as 39.8 °C in discarded receptacles. The results indicated that Ae. aegypti was prominent in alkaline water ranging between 7.5 and 8.5 pH, whereas Ae. albopictus was abundant in water with a pH range of 6.5-7.5. Both species of Aedes inhabited waters of low turbidity and TDS level. Ae. aegypti and Ae. albopictus immatures were prominent in water where TDS levels ranged between 250 and 350 ppm. The mean conductivity in the mosquito breeding water was recorded as 228.3 ± 63.9 µs/cm. The study revealed that Aedes mosquitoes could breed in water with a mean dissolved oxygen level of 6.9 ± 0.7 mg/L, ranging between 6.35 ± 1.09 mg/L and 7.28 ± 0.26 mg/L. The water quality indices were calculated for the eight previously identified breeding habitat categories of Aedes mosquitoes.Item Identification of dengue patients with high risk of severe disease, using early clinical and laboratory features, in a resource-limited setting(Springer-Verlag., 2020) Niriella, M.A.; Liyanage, I.K.; Udeshika, A.; Liyanapathirana, K.V.; de Silva, A.P.; de Silva, H.J.ABSTRACT: Only a minority of dengue infections lead to plasma leakage (critical phase [CP]). Early identification of the risk for CP is helpful for triage of patients. This study aimed to identify early clinical predictors of CP that will aid in patient triage during early illness. A retrospective, case-record-based analysis was performed on all microbiologically confirmed (NS1-antigen- or dengue-IgM-antibody-positive), dengue patients (n = 697), admitted to our unit from 01.01.2017 to 30.06.2017. Bivariate analysis was performed to identify clinical and laboratory parameters that predicted CP. Stepwise multivariate logistic regression with backward elimination (p < 0.05) was used to identify independent risk factors for CP. CP developed in 226 (32.4%) patients. Mortality was 1.0%. Predictors for CP (p < 0.05) within the first three days included age category 41-50 years (OR = 1.96), females (OR = 2.09), diabetes (OR = 1.30), persistent vomiting (OR = 2.18), platelet count < 120,000/mm-3 (OR = 1.91) and AST > 60 IU/L (OR = 3.72). On multivariate analysis, other variables except diabetes remained significant. Elevated transaminase levels remained the strongest independent predictor of CP (OR 2.83). The absence of all five risk factors excluded CP (negative predictive value: 97.2%). Age 41-50 years, female gender, persistent vomiting, thrombocytopenia, and elevated transaminases were early predictors of CP in dengue fever. The absence of these can be used to identify patients who may not require hospital admission. Elevated transaminase was the strongest predictor of CP during early illness.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 Early hepatitis is the strongest risk factor for the development of severe dengue infection: A points-based risk-score to predict critical disease in dengue fever(Sri Lanka Medical Association, 2018) Niriella, M.A.; Udeshika, A.K.M.A.; Liyanage, I.K.; de Silva, A.P.; de Silva, H.J.INTRODUCTION AND OBJECTIVES: Some dengue fever (DF) patients develop plasma leakage [critical-phase (CP)], which may progress to multi-organ failure. We attempted to identify early predictors ofCP in DF. METHODS: This was a retrospective, case-record-based study. Clinical, laboratory features in the first three-days (Dl-3) of illness was used to formulate a risk prediction model (RPM). Patients with serologically confirmed DF, admitted to the University Medical Unit, Teaching Hospital, Ragama, from 01.01.2017-30.06.2017 were included. Patients were randomly assigned to training (TD) and validation datasets (VD) of equal size. Stepwise multivariate logistic regression (p<0.05) was used to identify risk factors in TD. Versions of RPM were compared using Akaike criteria and McFadden's adjusted R2. Coefficients from the best RPM were used to derive weighted risk scores. Best RPM was validated in VD using C-statistic. RESULTS: 697 patients were included (mean-age:34.7±16.1 years, females-48.8%, TD=350, VD=346). CP developed inJ27 (32.6%). Mortality was I%. Risk predictors (p<0.05) were: female gender (OR=2.l), diabetes (OR=l.8), vomiting (OR=l.9), platelets60 IU/L (OR=3.3). In multivariate analysis, female gender (score=2), vomiting (score=3), platelets<120,000/mm-3 (score=3) and AST>60 IU/L 3 (score=4) were significant while diabetes was non-significant. Calculated RPM score ranged from 0-12. C-statistic for the TD was 0.78 and VD 0.77 (Hosmer-Lemeshow test: p=0.19 and 0.34 respectively). A cut-off of 5 was selected to maximise sensitivity (0.96), negative predictive value (0.95) with specificity of 0.44. CONCLUSION: This simple risk score seems useful in identifying those at risk ofCP within Dl-3 of the onset ofDF. The early presence of dengue hepatitis was the strongest predictor of CP.Item Delayed anxiety and depressive morbidity among dengue patients in a multi-ethnic urban setting: first report from Sri Lanka(BioMed Central, 2018) Gunathilaka, N.; Chandradasa, M.; Champika, L.; Siriwardana, S.; Wijesooriya, L.I.BACKGROUND: Although the physical consequences of dengue are well documented, delayed psychological co-morbidities are not well studied to date. Therefore, the objective of the present study was to determine the prevalence of depressive, anxiety and stress symptoms among past dengue patients. METHODS: A community-based, case-control study in a multi-ethnic urban setting was conducted in Sri Lanka involving adults who were diagnosed to have dengue fever by a positive dengue IgM antibody response between 6 and 24 months ago. Self-administered Depression, Anxiety and Stress Scale (DASS-21), Centre for Epidemiological Studies Depression Scale (CESD-20) and a structured clinical interview by a psychiatrist were done in the patients and in an age and gender-matched control group. RESULTS: Fifty-three participants each in the patient (mean age 42.9 years, SD 15.5) and control (mean age 41.6 years, SD 15.3) groups were surveyed. The ages ranged from 18 to 70 years and 64.2% were females. The majority (90.6%; n = 48) of the individuals had been diagnosed with dengue fever followed by dengue haemorrhagic fever (9.4% n = 5). Denguepatients had higher DASS-21 mean depressive scores (means 11.7/9.4, SD 6.4/4.0, t = 2.2, p = .028), anxiety scores (means 10.7/7.2, SD 6.8/1.8, t = 3.6, p = .0005), stress scores (means 12.0/8.8, SD 5.3/3.5, t = 3.6, p = .0004) and CESD-20 scores (means 16.1/11.7, SD 9.4/7.3, t = 2.6, p = .008) than controls. The DSM-5 depressive disorder was clinically detected by the psychiatrist among 15.1 and 7.5% in patient and control groups (OR 2.1; CI .5-7.7; p = .22). Limitations: a limitation is the small sample size. CONCLUSION: Patients with past dengue had significantly higher depressive, anxiety and stress symptoms than the control group according to the DASS-21 and CESD-20 tools. To our knowledge, this is the first report on delayed psychological morbidity related to dengue. This may warrant healthcare professionals to incorporate mental counselling for dengue patients.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 Evaluation of a rapid whole blood assay for testing dengue patients at point of care(Sri Lanka College of Microbiologists, 2004) Sunil-Chandra, N.P.; Karunasekera, E.W.S.; Somasiri, D.A.D.H.; Samarakoon, S.M.R.M.; Jayawardena, K.A.T.M.; Fernando, W.M.D.; Wijesooriya, W.R.P.L.I.; Garcia, M.INTRODUCTION: Dengue is the most significant mosquito borne viral disease affecting nations from Asia to the Americas. Symptoms associated with dengue infection range in severity. . The presentation of disease is impacted by age, prior exposure to the virus and the infecting strain of virus. The more severe form of the disease (haemorrhagic fever) can lead to mortality are generally associated with Secondary infections. Clinically, the measurement of dengue-specific IgM and elevated IgG, allows for the detection and differentiation of Primary and Secondary dengue infection. This discrimination is particularly important in situations such as outbreaks where the allocation of resources needs to be directed to those at greatest risk. In cities and major regional centers worldwide clinicians have access to traditional serological techniques such as ELISA and HAI that measure IgM and IgG levels. Unfortunately, clinicians in rural and remote areas generally do not have the resources available for this technology. Hence there is high clinical utility in a field diagnostic device which has the ability to rapidly and accurately detect and differentiate dengue infections. OBJECTIVES: To evaluate a novel dengue whole blood assay (PanBio) having the capacity for qualitative detection of both dengue-specific IgM and IgG, and differentiate between primary and secondary dengue with regard to sensitivity and specificity. To meet the demand for testing at the point of care or in the near patient environment, the test was required to have the capacity to detect antibodies in whole blood. DESIGN, SETTING AND METHODS: This assay device was used at the bed site of patients to evaluate its performance. The test is simply performed by adding the specimen to the sample well followed by running buffer to the buffer well, wait 15 minutes and visually reading the results. No additional materials required. 231 hospital inpatients in the Gampaha district of Sri Lanka, using a finger prick drop of blood as the analyte were assessed against PanBio Dengue Capture IgM and IgG ELISA for the period of 6 weeks starting from 10Ih November 2003. The capacity to detect and differentiate presumptive primary and secondary dengue was evaluated. RESULTS: The whole blood dengue cassette was able to detect 151 positive and 80 negative samples where as the ELISA could detect 126 positive samples and 105 negative patients. The detection of IgM and IgG positive samples by the cassette gave a relative sensitivity of 94.5%, specificity of 86% and 87.1% agreement between the assays. The cassette was able to identify 71% of positive samples as primary infections (IgM positive) and 96.7% as secondary infections (IgG positive with or without IgM) compared to ELISA. CONCLUSION: These data indicate that the Whole Blood Dengue Cassette has good utility in the detection of primary and secondary dengue with a very high accuracy in discriminating patients at greatest risk and represents a valuable field based assay to support the clinical evaluation of patients presenting with symptoms suggestive of dengue fever. ACKNOWLEDGEMENTS: PanBio Ltd, Australia for the financial assistance and Directors of Teaching hospital Ragama and Base hospitals of Negombo, Gampaha and Wathupitiwala.Item A comparison of serological diagnostic techniques in Dengue fever(Sri Lanka College of Microbiologists, 2005) Gunasekera, H.A.K.M.; Senanayake, C.P.; Sunil-Chandra, N.P.; Mendis, L.INTRODUCTION: The Dengue Duo IgM and IgG Rapid Strip test (PanBio Pvt. Ltd., Brisbane, Australia) is a commercially available immunochromatographic test. The Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok Thailand, has developed an in-house anti-dengue/anti-JE IgM and IgG reference enzyme-linked immunosorbent assay (ELISA). OBJECTIVE: To compare the usefulness of the AFRIMS ELISA and PanBio Dengue Duo IgM and IgG Rapid Strip test (PanBio Strip test) in the diagnosis of dengue infections. MATERIALS AND METHOD: 93 non-bacterial undifferentiated fever cases and 50 suspected dengue fever cases were screened for dengue and JE virus infections by the AFRIMS ELISA and also by the PanBio Strip test for dengue. All cases positive for dengue antibodies by either test were also tested by the Haemagglutination Inhibition test. RESULTS: Results were considered conclusive when at least 2 or all 3 of the above tests agreed. The AFRIMS ELISA had a sensitivity of 91.7% and specificity of 100% while the PanBio Strip test has a sensitivity of 93.8% and specificity of 96.8% in diagnosing dengue infections. 91.7% primary and 91.4% secondary infections were correctly classified by the AFRIMS ELISA. The PanBio Strip test identified 100% primary infections and 65.7% of secondary infections. CONCLUSIONS: The PanBio Strip test has a sensitivity and specificity comparable to the AFRIMS ELISA in diagnosing dengue infections although it tends to underestimate the number of secondary infections.