Browsing by Author "Lalloo, D.G."

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Adjusting for spatial variation when assessing individual-level risk: A case-study in the epidemiology of snake-bite in Sri Lanka
(Public Library of Science, 2019) Ediriweera, D.S.; Kasturiratne, A.; Pathmeswaran, A.; Gunawardena, N.K.; Jayamanne, S.F.; Murray, K.; Iwamura, T.; Lalloo, D.G.; de Silva, H.J.; Diggle, P.J.
BACKGROUND:Health outcomes and causality are usually assessed with individual level sociodemographic variables. Studies that consider only individual-level variables can suffer from residual confounding. This can result in individual variables that are unrelated to risk behaving as proxies for uncaptured information. There is a scarcity of literature on risk factors for snakebite. In this study, we evaluate the individual-level risk factors of snakebite in Sri Lanka and highlight the impact of spatial confounding on determining the individual-level risk effects.METHODS:Data was obtained from the National Snakebite Survey of Sri Lanka. This was an Island-wide community-based survey. The survey sampled 165,665 individuals from all 25 districts of the country. We used generalized linear models to identify individual-level factors that contribute to an individual's risk of experiencing a snakebite event. We fitted separate models to assess risk factors with and without considering spatial variation in snakebite incidence in the country.RESULTS:Both spatially adjusted and non-adjusted models revealed that middle-aged people, males, field workers and individuals with low level of education have high risk of snakebites. The model without spatial adjustment showed an interaction between ethnicity and income levels. When the model included a spatial adjustment for the overall snakebite incidence, this interaction disappeared and income level appeared as an independent risk factor. Both models showed similar effect sizes for gender and age. HEmployment and education showed lower effect sizes in the spatially adjusted model.CONCLUSIONS:Both individual-level characteristics and local snakebite incidence are important to determine snakebite risk at a given location. Individual level variables could act as proxies for underling residual spatial variation when environmental information is not considered. This can lead to misinterpretation of risk factors and biased estimates of effect sizes. Both individual-level and environmental variables are important in assessing causality in epidemiological studies.
Antivenom for snake venom-induced neuromuscular paralysis (Protocol)
(John Wiley and Sons, 2017) Silva, A.; Maduwage, K.; Buckley, N.A.; Lalloo, D.G.; de Silva, H.J.; Isbister, G.K.
Beliefs and knowledge regarding snakebite in rural Sri Lanka: a qualitative survey
(Sri Lanka Medical Association, 2003) Makita, L.S.; Nandasena, S.; Costa, M.R.A.; Kasturiratne, A.; Pathmeswaran, A.; Lalloo, D.G.; de Silva, H.J.
OBJECTIVES: To identify common beliefs and assess knowledge regarding snakebite in rural Sri Lanka, and their influence on health-seeking behaviour. METHODS: Qualitative methods (focus group discussions and key informant interviews) were used to obtain data in five rural locations in wet, intermediate and dry zones. Data was subjected to "framework analysis" involving familiarisation, identification of thematic frame, indexing and coding, charting, mapping, and interpretation. RESULTS: People are aware of risk-behaviour associated with snakebite, and have reasonable knowledge regarding venomous and non-venomous snakes. However, differences in nomenclature sometimes lead to confusion in identifying species. Beliefs and legends, which are linked to religion, have lead people to respect the cobra. Traditional healers claim they can determine the snake species, clinical manifestations that may occur, and prognosis, based on phenomena, such as, day of the week and phase of the moon when the bite took place. They still employ treatment methods, such as wound incision with broken glass and scalp incision for applying potions. Although there is respect for traditional healing, there is acceptance of the efficacy of western medicine. Beliefs, such as, anti-venom though effective is toxic, long-term effects of snake venom can be completely neutralised only by traditional medicine, and producing the dead snake is essential for treatment in hospitals, lead people to seek treatment by traditional healers rather than in hospitals. CONCLUSIONS: Beliefs and misconceptions influence health-seeking behaviour following snakebite. There seems to be a growing acceptance of western medicine. However, traditional healing methods are still popular, but include harmful^rjractices. This information could form a basis for. educational intervention.
Chronic health effects and cost of snakebite
(Elsevier Ltd, 2021) Kasturiratne, A.; Lalloo, D.G.; de Silva, H.J.
ABSTRACT: The burden of disability among survivors and the socio-economic impact of snakebite have not been adequately researched. We reviewed original research articles, case reports and small case series relating to chronic physical, mental and psycho-social disability and economic burden of snakebite. Both physical and psychological health problems seem common in snakebite survivors and can lead to disability and loss of productivity. Chronic physical health effects, musculoskeletal disability being the commonest, can be largely attributed to limited and delayed access to optimal treatment of acute envenoming. The economic burden is considerable, and includes health system costs, out-of-pocket expenditure and opportunity costs, with regional variations. Health systems should be more responsive to needs and circumstances of bite victims, and a more holistic approach should be developed in the treatment of snakebite which incorporates the management of chronic health effects. KEYWORDS: Chronic health effects; Cost; Physical disability; Psychological effects; Snakebite; Socio-economic burden.
Climate change maladaptation for health: Agricultural practice against shifting seasonal rainfall affects snakebite risk for farmers in the tropics
(Cell Press, 2023) Goldstein, E.; Erinjery, J.J.; Martin, G.; Kasturiratne, A.; Ediriweera, D.S.; Somaweera, R.; de Silva, H.J.; Diggle, P.; Lalloo, D.G.; Murray, K.A.; Iwamura, T.
Snakebite affects more than 1.8 million people annually. Factors explaining snakebite variability include farmers' behaviors, snake ecology and climate. One unstudied issue is how farmers' adaptation to novel climates affect their health. Here we examined potential impacts of adaptation on snakebite using individual-based simulations, focusing on strategies meant to counteract major crop yield decline because of changing rainfall in Sri Lanka. For rubber cropping, adaptation led to a 33% increase in snakebite incidence per farmer work hour because of work during risky months, but a 17% decrease in total annual snakebites because of decreased labor in plantations overall. Rice farming adaptation decreased snakebites by 16%, because of shifting labor towards safer months, whereas tea adaptation led to a general increase. These results indicate that adaptation could have both a positive and negative effect, potentially intensified by ENSO. Our research highlights the need for assessing adaptation strategies for potential health maladaptations.
Community incidence of snakebite and envenoming in Sri Lanka; results of a national survey
(Sri Lanka Medical Association, 2014) Pathmeswaran, A.; Kasturiratne, A.; Gunawardena, N.K.; Wijayawickrama, B.A.; Jayamanne, S.F.; Ediriweera, D.S.; Isbister, G.; Dawson, A.; Lalloo, D.G.; de Silva, H.J.
INTRODUCTION AND OBJECTIVES: We undertook the first ever country-wide community-based survey to determine the incidence of snakebite in Sri Lanka. METHODS: Data were collected through household interviews by trained data collectors.125 clusters were allocated to each of the 9 provinces of the country. Within each province the clusters were divided among the districts in proportion to their population. A Grama Niladhari (GN) division was defined as a cluster for data collection. The clusters were selected using simple random sampling, and in each cluster 40 households were sampled consecutively from a random starting point. RESULTS: Data relating to 165,665 individuals (0.8% of the population of Sri Lanka) living in 44,136 households in 1,118 clusters was collected from June 2012 to May 2013. 695 (males 418) snakebites and 323 (males!93) significant envenomings (local tissue necrosis or systemic envenoming) were reported during the 12 months preceding the interview. The overall community incidence of snakebites and significant envenoming were 398 and 151 per 100,000 population, respectively. 446 (64.2%) bites and 208 (64.4%) envenomings were in people aged 30 to 59 years. There was wide variation between districts, the worst affected being Mullaitivu, Anuradhapura, Batticaloa, and Poionnaruwa, ali in the dry zone, mainly agricultural areas of the country. CONCLUSIONS: Sri Lanka has a high community incidence of snakebite and envenoming with a marked geographical variation.This variation underlines both the inaccuracy of extrapolating data of localised surveys to national or regional levels and the need to prioritise distribution of resources for treatment of snakebite even in small countries.
Comparison of seven commercial antigen and antibody enzyme-linked immunosorbent assays for detection of acute dengue infection
(American Society for Microbiology, 2012) Blacksell, S.D.; Jarman, R.G.; Gibbons, R.V.; Tanganuchitcharnchai, A.; Mammen, M.P.Jr.; Nisalak, A.; Kalayanarooj, S.; Bailey, M.S.; Premaratna, R.; de Silva, H.J.; Day, N.P.; Lalloo, D.G.
Seven commercial assays were evaluated to determine their suitability for the diagnosis of acute dengue infection: (i) the Panbio dengue virus Pan-E NS1 early enzyme-linked immunosorbent assay (ELISA), second generation (Alere, Australia); (ii) the Panbio dengue virus IgM capture ELISA (Alere, Australia); (iii) the Panbio dengue virus IgG capture ELISA (Alere, Australia); (iv) the Standard Diagnostics dengue virus NS1 antigen ELISA (Standard Diagnostics, South Korea); (v) the Standard Diagnostics dengue virus IgM ELISA (Standard Diagnostics, South Korea); (vi) the Standard Diagnostics dengue virus IgG ELISA (Standard Diagnostics, South Korea); and (vii) the Platelia NS1 antigen ELISA (Bio-Rad, France). Samples from 239 Thai patients confirmed to be dengue virus positive and 98 Sri Lankan patients negative for dengue virus infection were tested. The sensitivities and specificities of the NS1 antigen ELISAs ranged from 45 to 57% and 93 to 100% and those of the IgM antibody ELISAs ranged from 85 to 89% and 88 to 100%, respectively. Combining the NS1 antigen and IgM antibody results from the Standard Diagnostics ELISAs gave the best compromise between sensitivity and specificity (87 and 96%, respectively), as well as providing the best sensitivity for patients presenting at different times after fever onset. The Panbio IgG capture ELISA correctly classified 67% of secondary dengue infection cases. This study provides strong evidence of the value of combining dengue virus antigen- and antibody-based test results in the ELISA format for the diagnosis of acute dengue infection.
Delayed psychological morbidity associated with snakebite envenoming
(Public Library of Science, 2011) Williams, S.S.; Wijesinghe, C.A.; Jayamanne, S.F.; Buckley, N.A.; Dawson, A.H.; Lalloo, D.G.; de Silva, H.J.
INTRODUCTION: The psychological impact of snakebite on its victims, especially possible late effects, has not been systematically studied. OBJECTIVES: To assess delayed somatic symptoms, depressive disorder, post-traumatic stress disorder (PTSD), and impairment in functioning, among snakebite victims. METHODS: The study had qualitative and quantitative arms. In the quantitative arm, 88 persons who had systemic envenoming following snakebite from the North Central Province of Sri Lanka were randomly identified from an established research database and interviewed 12 to 48 months (mean 30) after the incident. Persons with no history of snakebite, matched for age, sex, geograpical location and occupation, acted as controls. A modified version of the Beck Depression Inventory, Post-Traumatic Stress Symptom Scale, Hopkins Somatic Symptoms Checklist, Sheehan Disability Inventory and a structured questionnaire were administered. In the qualitative arm, focus group discussions among snakebite victims explored common somatic symptoms attributed to envenoming. RESULTS: Previous snakebite victims (cases) had more symptoms than controls as measured by the modified Beck Depression Scale (mean 19.1 Vs 14.4; p<0.001) and Hopkins Symptoms Checklist (38.9 vs. 28.2; p<0.001). 48 (54%) cases met criteria for depressive disorder compared to 13 (15%) controls. 19 (21.6%) cases also met criteria for PTSD. 24 (27%) claimed that the snakebite caused a negative change in their employment; nine (10.2%) had stopped working and 15 (17%) claimed residual physical disability. The themes identified in the qualitative arm included blindness, tooth decay, body aches, headaches, tiredness and weakness. CONCLUSIONS: Snakebite causes significant ongoing psychological morbidity, a complication not previously documented. The economic and social impacts of this problem need further investigation
Delayed psychological morbidity in victims of snakebite envenoming
(Sri Lanka Medical Association, 2010) Williams, S.S.; Wijesinghe, C.A.; Jayamanne, S.F.; Buckley, N.; Dawson, A.; Lalloo, D.G.; de Silva, H.J.
OBJECTIVES: We assessed delayed somatic symptoms, depressive disorder, post-traumatic stress disorder (PTSD) and impairment in functioning among snakebite victims. The psychological impact of snakebite on its victims has not been systematically studied. METHODS: The study had qualitative and quantitative arms. In the quantitative arm, 88 persons who had systemic envenoming following snakebite from the Polonnaruwa District were randomly identified from an established research database and interviewed 12 to 48 months (mean 30) after the incident. 88 persons with no history of snakebite, matched for age, sex, geograpical location and occupation acted as controls. A modified version of the Beck Depression Inventory, Post-Traumatic Stress Symptom Scale, Hopkins Somatic Symptoms Checklist and Sheehan Disability Inventory, together with a structured questionnaire were administered. In the qualitative arm, focus group discussions among snakebite victims explored common somatic symptoms attributed to envenoming. Results: Snakebite victims had more symptoms as measured by the modified Beck Depression Scale (mean 19.1 vs 14.4) and Hopkins Symptoms Checklist (38.9 vs. 28.2) compared to controls (p<0.001). 48(54%) victims met criteria for depressive disorder compared to 13(15%) controls. 11(12.5%) victims also met criteria for PTSD. 24(27%) claimed that the snakebite caused a negative change in their employment; 9(10.2%) had stopped working. 15(17%) victims claimed residual physical disability, and themes identified in the qualitative arm included blindness, tooth decay, body aches, tiredness and weakness. CONCLUSIONS: Snakebite causes delayed psychological morbidity, a complication not previously documented.
Development and assessment of a psychological intervention for snakebite victims
(Sri Lanka Medical Association, 2014) Wiiesinahe, C.A.; Williams, S.S.; Dolawatta, N.; Wimalaratne, A.K.G.P.; Kasturiratne, A.; Wijewickrema, B.; Jayamanne, S.F.; Lalloo, D.G.; Isbister, G.K.; Dawson, A.; de Silva, H.J.
INTRODUCTION AND OBJECTIVES: There is significant delayed psychological morbidity and negative psycho-social impact following snakebite. However, no psychological support is provided to victims. We aimed to develop and assess the effectiveness of a brief intervention which can be provided by non-specialist medical officers aimed at reducing psychological morbidity. METHODS: In a single blind clinical trial at Polonnaruwa Hospital, 187 snakebite victims were randomised into three arms. One arm received no psychological intervention (Group A; n=59; control). Group B (n=60) received psychoeducation at discharge from hospital. Group C (n=68) received psychoeducation and a.second intervention one month later based on cognitive behavioural principles. All patients were assessed six months after discharge from hospital using standardised tools for presence of psychological symptoms and level of functioning. RESULTS: Compared with Group A, there was a significant reduction in anxiety symptoms measured by the Hopkins Psychiatric Symptom check list (16.9% vs. 5.9%, p=0.047, Chi-Squared test) and a non-significant trend towards improvement in the level of functioning measured by the Sheehan Disability inventory (6.47 vs. 4.69) in Group C, but not in Group B. There was no difference in rates of depression and post-traumatic stress disorder (PTSD) between the three groups. CONCLUSIONS: Our preliminary findings suggest that brief psychological interventions which include psychoeducation plus cognitive behavioural therapy given by non-specialist doctors, but not psychoeducation alone seem to reduce anxiety and facilitate a trend towards improved function in snakebite victims. However, these interventions had no effect on depression or PTSD.
Development of a Snakebite risk map for Sri Lanka
(Sri Lanka Medical Association, 2016) Ediriweera, D.S.; Kasturiratne, A.; Pathmeswaran, A.; Gunawardena, N.K.; Wijayawickrama, B.A.; Jayamanne, S.F.; Isbister, G.K.; Dawson, A.; Giorgi, E.; Diggle, P.J.; Lalloo, D.G.; de Silva, H.J.
INTRODUCTION: Snakebite is a public health problem in Sri Lanka and about 37,000 patients are treated in government hospitals annually. At present, health care resources which are required to manage snakebite are distributed based on the administrative boundaries, rather than based on scientific risk assessment. OBJECTIVES: The aim of the study is to develop a snakebite risk map for Sri Lanka. METHOD: Epidemiological data was obtained from a community-based island-wide survey. The sample was distributed equally among the nine provinces. 165,665 participants (0.8%of the country’s population) living in 1118 Grama Niladhari divisions were surveyed. Generalized linear and generalized additive models were used for exploratory data analysis. Model-based geostatistics was used to determine the geographical distribution of snakebites. Monte Carlo maximum likelihood method was used to obtain parameter estimates and plug-in spatial predictions were obtained. Probability contour maps (PCM) were developed to demonstrate the spatial variation in the probability that local incidence does or does not exceed national snakebite incidence. RESULTS: Individual point estimate snakebite incidence map and PCM were developed to demonstrate the national incidence of snakebite in Sri Lanka. Snakebite hotspots and cold spots were identified in relation to the national snakebite incidence rate. Risk maps showed a within-country spatial variation in snakebites. CONCLUSIONS: The developed risk maps provide useful information for healthcare decision makers to allocate resources to manage snakebite in Sri Lanka.
Estimates of disease burden due to land-snake bite in Sri Lankan hospitals
(SEAMEO Regional Tropical Medicine and Public Health Project, 2005) Kasturiratne, A.; Pathmeswaran, A.; Fonseka, M.M.D.; Lalloo, D.G.; Brooker, S.; de Silva, H.J.
Snake bite is a common cause of hospital admission in Sri Lanka. Despite this, there have been no countrywide studies or national estimates of disease burden due to snake bites in Sri Lankan hospitals. We assessed the disease burden due to snake bite in our hospitals and estimated the frequency of admissions due to bites by different snake species. Sri Lanka was divided into four zones based on climate and topography. Hospital morbidity and mortality data, which are available on an administrative district basis, were collated for the four zones. A survey of opinion among specialist physicians (the Delphi technique) was used to estimate the proportion of bites by different species, and requirements for anti-venom (AV) and intensive care facilities for management of snake bites in hospitals in each of the four zones. A study of hospital admissions due to snake bites in seven selected hospitals was also performed to validate the opinion survey. There was a clear difference in the incidence of hospital admissions due to snake bites in the different zones. Estimates of hospital admissions due to bites by different species also varied considerably between zones. These trends corresponded to estimates of requirements of AV and other supportive health care. Health care planning using data based on environmental information, rather than merely on political boundaries, could lead to targeted distribution of AV and intensive care requirements to manage snake bites.
Estimates of disease burden due to snakebite in Sri Lankan hospitals
(Sri Lanka Medical Association, 2003) Kasturiratne, A.; Pathmeswaran, A.; Fonseka, M.M.D.; Lalloo, D.G.; Brooker, S.; de Silva, H.J.
INTRODUCTION: There have been no country-wide studies or estimates of disease burden due to snakebite in Sri Lankan hospitals. OBJECTIVES: To assess disease burden due to snakebite and estimate relative frequency of the biting species in hospitals situated in different parts of the country. METHODS: Hospital morbidity and mortality data on snakebite was obtained for each administrative district. Sri Lanka was divided into 5 zones based on climate and available data on snake habitat (Zone 1-wet zone altitude <900m; Z2-intermediate zone; Z3-dry zone, Z4-wet zone altitude >900m; Z5-northern and north-western dry zone). Administrative districts were allocated to zones based on their geographical location and population using geographical information systems technology. Hospital morbidity and mortality data were collated for the 5 zones. A survey among physicians (37 physicians in 42 hospitals covering the 5 zones) was used (Delphi technique) to estimate the proportion of snakebites by different species and requirement of hospital resources, in each zone. Results: There was a clear difference in incidence of hospital admissions due to snakebite in the different zones (Z3-3.5 and Z4-0.4 per 1000 population). The distribution of bites by individual species also varied between zones (deadly venomous species Z3-85%, Z2-45%), moderately venomous and mildly-venomous species Z4-100%, Zl-70%). These trends corresponded to estimates of requirements for AVS and other hospital facilities (in 2000, Z3-86100 vials of AVS, 7380 Intensive care unit patient-days; Zl-26400 vials of AVS, 2640ICU patient-days). CONCLUSIONS: Incidence of hospital admissions due to snakebite and estimates of relative medical importance of different snake species show geographic variation within the country. This is reflected in estimates of requirements for facilities. Zoning based on environmental information rather than on political boundaries could lead to better distribution of health care resources for management of snakebite in hospitals situated in different parts of the country.
Estimating the true accuracy of diagnostic tests for dengue infection using bayesian latent class models
(Public Library of Science, 2013) Pan-ngum, W.; Blacksell, S.D.; Lubell, Y.; Pukrittayakamee, S.; Bailey, M.S.; de Silva, H.J.; Lalloo, D.G.; Day, N.P.; White, L.J.; Limmathurotsakul, D.
BACKGROUND: Accuracy of rapid diagnostic tests for dengue infection has been repeatedly estimated by comparing those tests with reference assays. We hypothesized that those estimates might be inaccurate if the accuracy of the reference assays is not perfect. Here, we investigated this using statistical modeling. METHODS/PRINCIPAL FINDINGS: Data from a cohort study of 549 patients suspected of dengue infection presenting at Colombo North Teaching Hospital, Ragama, Sri Lanka, that described the application of our reference assay (a combination of Dengue IgM antibody capture ELISA and IgG antibody capture ELISA) and of three rapid diagnostic tests (Panbio NS1 antigen, IgM antibody and IgG antibody rapid immunochromatographic cassette tests) were re-evaluated using bayesian latent class models (LCMs). The estimated sensitivity and specificity of the reference assay were 62.0% and 99.6%, respectively. Prevalence of dengue infection (24.3%), and sensitivities and specificities of the Panbio NS1 (45.9% and 97.9%), IgM (54.5% and 95.5%) and IgG (62.1% and 84.5%) estimated by bayesian LCMs were significantly different from those estimated by assuming that the reference assay was perfect. Sensitivity, specificity, PPV and NPV for a combination of NS1, IgM and IgG cassette tests on admission samples were 87.0%, 82.8%, 62.0% and 95.2%, respectively. CONCLUSIONS: Our reference assay is an imperfect gold standard. In our setting, the combination of NS1, IgM and IgG rapid diagnostic tests could be used on admission to rule out dengue infection with a high level of accuracy (NPV 95.2%). Further evaluation of rapid diagnostic tests for dengue infection should include the use of appropriate statistical models
Evaluating spatiotemporal dynamics of snakebite in Sri Lanka: Monthly incidence mapping from a national representative survey sample
(Public Library of Science, 2021) Ediriweera, D.S.; Kasturiratne, A.; Pathmeswaran, A.; Gunawardena, N.K.; Jayamanne, S.F.; Murray, K.; Iwamura, T.; Isbister, G.; Dawson, A.; Lalloo, D.G.; de Silva, H.J.; Diggle, P.J.
BACKGROUND: Snakebite incidence shows both spatial and temporal variation. However, no study has evaluated spatiotemporal patterns of snakebites across a country or region in detail. We used a nationally representative population sample to evaluate spatiotemporal patterns of snakebite in Sri Lanka. METHODOLOGY: We conducted a community-based cross-sectional survey representing all nine provinces of Sri Lanka. We interviewed 165 665 people (0.8% of the national population), and snakebite events reported by the respondents were recorded. Sri Lanka is an agricultural country; its central, southern and western parts receive rain mainly from Southwest monsoon (May to September) and northern and eastern parts receive rain mainly from Northeast monsoon (November to February). We developed spatiotemporal models using multivariate Poisson process modelling to explain monthly snakebite and envenoming incidences in the country. These models were developed at the provincial level to explain local spatiotemporal patterns. PRINCIPAL FINDINGS: Snakebites and envenomings showed clear spatiotemporal patterns. Snakebite hotspots were found in North-Central, North-West, South-West and Eastern Sri Lanka. They exhibited biannual seasonal patterns except in South-Western inlands, which showed triannual seasonality. Envenoming hotspots were confined to North-Central, East and South-West parts of the country. Hotspots in North-Central regions showed triannual seasonal patterns and South-West regions had annual patterns. Hotspots remained persistent throughout the year in Eastern regions. The overall monthly snakebite and envenoming incidences in Sri Lanka were 39 (95%CI: 38-40) and 19 (95%CI: 13-30) per 100 000, respectively, translating into 110 000 (95%CI: 107 500-112 500) snakebites and 45 000 (95%CI: 32 000-73 000) envenomings in a calendar year. CONCLUSIONS/SIGNIFICANCE: This study provides information on community-based monthly incidence of snakebites and envenomings over the whole country. Thus, it provides useful insights into healthcare decision-making, such as, prioritizing locations to establish specialized centres for snakebite management and allocating resources based on risk assessments which take into account both location and season.
Evaluating temporal patterns of snakebite in Sri Lanka: The potential for higher snakebite burdens with climate change
(Sri Lanka Medical Association, 2018) Ediriweera, D.S.; Diggle, P.J.; Kasturiratne, A.; Pathmeswaran, A.; Gunawardena, N.K.; Jayamanne, S.F.; Isbister, J.K.; Dawson, A.; Lalloo, D.G.; de Silva, H.J.
INTRODUCTION AND OBJECTIVES: Snakebite is a neglected tropical disease that has been overlooked by healthcare decision makers in many countries. Previous studies have reported seasonal variation in hospital admission rates due to snakebites in endemic countries including Sri Lanka, but seasonal patterns have not been investigated in detail. METHODS: A national community-based survey was conducted during the period of August 2012 to June 2013. The survey used a multistage cluster design, sampled 165,665 individuals living in 44,136 households and recorded all recalled snakebite events that had occurred during the preceding year Log-linear models were fitted to describe the expected number of snakebites occurring in each month taking into account seasonal trends and weather conditions, and addressing the effects of variation in survey effort during the study and due to recall bias amongst survey respondents RESULTS: Snakebite events showed a clear seasonal variation. Typically, snakebite incidence was highest during November to December followed by March to May and August, but this varied between years due to variations in relative humidity, which is also a risk-factor. Low relative humidity levels was associated with high snakebite incidence. If current climate change projections are correct, this could lead to an increase in the annual snakebite of burden of 35,086 (95% CI: 4 202 a€" 69,232) during the next 25 to 50 years. CONCLUSION: Snakebite in Sri Lanka shows seasonal variation Additionally, more snakebites can be expected during periods of lower than expected humidity. Global climate change is likely to increase the incidence of snakebite in Sri Lanka.
Evaluating temporal patterns of snakebite in Sri Lanka: the potential for higher snakebite burdens with climate change
(Oxford University Press, 2018) Ediriweera, D.S.; Diggle, P.J.; Kasturiratne, A.; Pathmeswaran, A.; Gunawardena, N.K.; Jayamanne, S.K.; Isbister, G.K.; Dawson, A.; Lalloo, D.G.; de Silva, H.J.
BACKGROUND: Snakebite is a neglected tropical disease that has been overlooked by healthcare decision makers in many countries. Previous studies have reported seasonal variation in hospital admission rates due to snakebites in endemic countries including Sri Lanka, but seasonal patterns have not been investigated in detail. METHODS: A national community-based survey was conducted during the period of August 2012 to June 2013. The survey used a multistage cluster design, sampled 165 665 individuals living in 44 136 households and recorded all recalled snakebite events that had occurred during the preceding year. Log-linear models were fitted to describe the expected number of snakebites occurring in each month, taking into account seasonal trends and weather conditions, and addressing the effects of variation in survey effort during the study and of recall bias amongst survey respondents. ResulTS: Snakebite events showed a clear seasonal variation. Typically, snakebite incidence is highest during November–December followed by March–May and August, but this can vary between years due to variations in relative humidity, which is also a risk factor. Low relative-humidity levels are associated with high snakebite incidence. If current climate-change projections are correct, this could lead to an increase in the annual snakebite burden of 31.3% (95% confidence interval: 10.7–55.7) during the next 25–50 years. CONCLUSIONS: Snakebite in Sri Lanka shows seasonal variation. Additionally, more snakebites can be expected during periods of lower-than-expected humidity. Global climate change is likely to increase the incidence of snakebite in Sri Lanka.
Evaluation of six commercial point-of-care tests for diagnosis of acute dengue infections: the need for combining NS1 antigen and IgM/IgG antibody detection to achieve acceptable levels of accuracy
(American Society for Microbiology, 2011) Blacksell, S.D.; Jarman, R.G.; Bailey, M.S.; Tanganuchitcharnchai, A.; Jenjaroen, K.; Gibbons, R.V.; Paris, D.H.; Premaratna, R.; de Silva, H.J.; Lalloo, D.G.; Day, N.P.
Six assays were evaluated in this study to determine their suitability for the diagnosis of acute dengue infection using samples from 259 Sri Lankan patients with acute fevers (99 confirmed dengue cases and 160 patients with other confirmed acute febrile illnesses): (i) the Merlin dengue fever IgG & IgM combo device (Merlin), (ii) the Standard Diagnostics Dengue Duo nonstructural 1 (NS1) antigen and IgG/IgM combo device (Standard Diagnostics, South Korea), (iii) the Biosynex Immunoquick dengue fever IgG and IgM (Biosynex, France) assay, (iv) the Bio-Rad NS1 antigen strip (Bio-Rad, France), (v) the Panbio Dengue Duo IgG/IgM Cassette (Inverness, Australia), and (vi) the Panbio dengue NS1 antigen strip (Inverness, Australia). The median number of days of fever prior to admission sample collection was 5 days (interquartile range, 3 to 7 days). Sensitivity and specificity of the NS1 antigen tests ranged from 49 to 59% and from 93 to 99%, respectively, and sensitivity and sensitivity of the IgM antibody test ranged from 71 to 80% and from 46 to 90%, respectively. Combining the NS1 antigen and IgM antibody results from the Standard Diagnostics Dengue Duo test gave the best compromise of sensitivity and specificity (93% and 89%, respectively) and provided the best sensitivity in patients presenting at different times after fever onset. The Merlin IgM/IgG antibody tests correctly classified 64% and 86% of the primary and secondary dengue infection cases, respectively, and the Standard Diagnostics IgM/IgG antibody tests correctly classified 71% and 83% of the primary and secondary dengue infection cases, respectively. This study provides strong evidence of the value of combining dengue antigen- and antibody-based test results in the rapid diagnostic test (RDT) format for the acute diagnosis of dengue.
A fever study at the Colombo North Teaching Hospital (CNTH)
(Sri Lanka Medical Association, 2007) Bailey, M.S.; Wijesuriya, T.; Premaratna, R.; de Silva, N.R.; Wuthiekanun, F.; Peacock, S.J.; Lalloo, D.G.; de Silva, H.J.
OBJECTIVES: To determine the aetiology of febrile illnesses at CNTH, to identify effective laboratory tests for their confirmation, and to develop clinical prediction rules that will assist diagnosis. DESIGN, SETTING AND METHODS: A prospective cohort of in-patients is being studied during a one-year period. Patients with oral temperatures >38°C are eligible for inclusion unless they are aged <16 years, have been admitted for >24 hours or have received antibiotics in hospital. Written consent is obtained and a structured questionnaire is completed. Blood is taken for cultures, biochemistry assays, serology and PCR tests. Urine is taken for assays to detect antimicrobial activity. RESULTS: During the first 4 months, there were 180 eligible patients of whom 138 (77%) were recruited. The mean age was 36 years, the male:female ratio was 2.1 and 90% were from Gampaha district. There were no significant differences regarding age or sex in comparison to patients not recruited. Infections were unlocalised in 67% (50% unconfirmed, 43% dengue fever, 3% leptospirosis, 3% scrub typhus, 1% malaria). Localised infections were respiratory (9%), urinary tract (8%), neurological (4%), gastrointestinal (3%) and skin (2%). Non-infectious causes accounted for 3% of febrile patients. Bacteraemia was found in only 4% despite every patient having 2 high-quality blood cultures. Leucopenia or neutropcnia were useful early markers of dengue fever. CONCLUSIONS: Non-bacterial agents cause most febrile illnesses in Gampaha district. New laboratory tests and clinical prediction rules are required for their diagnosis.
The Global burden of snakebite: a literature analysis and modelling based on regional estimates of envenoming and deaths
(Public Library of Science, 2008) Kasturiratne, A.; Wickremasinghe, A.R.; de Silva, N.; Gunawardena, N.K.; Pathmeswaran, A.; Premaratna, R.; Savioli, L.; Lalloo, D.G.; de Silva, H.J.
BACKGROUND: Envenoming resulting from snakebites is an important public health problem in many tropical and subtropical countries. Few attempts have been made to quantify the burden, and recent estimates all suffer from the lack of an objective and reproducible methodology. In an attempt to provide an accurate, up-to-date estimate of the scale of the global problem, we developed a new method to estimate the disease burdendue to snakebites. METHODS AND FINDINGS: The global estimates were based on regional estimates that were, in turn, derived from data available for countries within a defined region. Three main strategies were used to obtain primary data: electronic searching for publications on snakebite, extraction of relevant country-specific mortality data from databases maintained by United Nations organizations, and identification of grey literature by discussion with key informants. Countries were grouped into 21 distinct geographic regions that are as epidemiologically homogenous as possible, in line with the GlobalBurden of Disease 2005 study (Global Burden Project of the World Bank). Incidence rates for envenoming were extracted from publications and used to estimate the number of envenomings for individual countries; if no data were available for a particular country, the lowest incidence rate within a neighbouring country was used. Where death registration data were reliable, reported deaths from snakebite were used; in other countries, deathswere estimated on the basis of observed mortality rates and the at-risk population. We estimate that, globally, at least 421,000 envenomings and 20,000 deaths occur each year due to snakebite. These figures may be as high as 1,841,000 envenomings and 94,000 deaths. Based on the fact thatenvenoming occurs in about one in every four snakebites, between 1.2 million and 5.5 million snakebites could occur annually. CONCLUSIONS: Snakebites cause considerable morbidity and mortality worldwide. The highest burden exists in South Asia, Southeast Asia, and sub-Saharan Africa. Comment in Estimating the global burden of snakebite can help to improve management. [PLoS Med. 2008]