Browsing by Author "Lalloo, D."

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Envenoming Snakebite Risk Map for Sri Lanka
(Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) Ediriweera, D.; Kasturiratne, A.; Pathmeswaran, A.; Pathmeswaran, A.; Gunawardena, N.; Jayamanne, S.; Wijayawickrama, B.; Isbister, G.; Giorgi, A.D.E.; Diggle, P.; Lalloo, D.; de Silva, J.
Snakebite is a neglected tropical disease. Hospital based statistics often underestimate snakebite incidence because a significant proportion of victims seek traditional treatments. Since geospatial risk assessments of snakebite envenoming are rare, health care resources are distributed based on administrative boundaries rather than on a need analysis. The aim of the study was to develop a snakebite envenoming risk map for Sri Lanka. Epidemiological data was obtained from a community-based island-wide survey. The sample was distributed equally among the nine provinces. 165,665 participants living in 1118 Grama Niladhari divisions were surveyed. Model-based geostatistics was used to determine the geographical distribution of envenoming bite incidence. The Monte Carlo maximum likelihood method was used to obtain parameter estimates and plug-in spatial predictions of risk. A predictive model was developed with natural and social environmental variables to construct an estimated envenoming bite incidence map and a probability contour map (PCM) to demonstrate the spatial variation in the predictive probability that local incidence does or does not exceed national envenoming snakebite incidence (i.e. 151 per 100,000). Envenoming bite incidence had a positive association with elevation up to 195 meters above sea level, with incidence dropping at higher elevations. The incidence of envenoming was higher in the dry zone compared to intermediate and wet climatic zones and decreased with increasing population density. Developed risk maps showed substantial within-country spatial variation in envenoming bites. Conclusion: The risk maps provide useful information for healthcare decision makers to allocate resources to manage snakebite envenoming in Sri Lanka. We used replicable methods which can be adapted to other geographic regions after re-estimating spatial covariance parameters for each region of interest.
Evaluating Spatiotemporal Dynamics of Snakebite in Sri Lanka
(International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Ediriweera, D.; Diggle, P.; Kasturiratne, A.; Pathmeswaran, A.; Gunawardena, N.; Jayamanne, S.; Lalloo, D.; de Silva, J.
Snakebite data has shown spatial and temporal variations in many countries and regions. Yet, no study has evaluated spatiotemporal patterns of snakebites across a country in detail. We used data from the National Snakebite Survey (NSS), which sampled 0.8% of the national population (165665 people) living in 1118 clusters representing all the provinces. Explanatory variables of previously published spatial and temporal models for the NSS data were considered as candidate explanatory variables for our spatiotemporal models. Spatial prediction models for snakebite incidence was a geostatistical binomial logistic model and the temporal prediction model was a Poisson log-linear model, which predicted snakebite incidence at the national level. These spatial and temporal models could not explain locally varying temporal patterns in the country. Therefore, we constructed spatiotemporal models at the provincial levels. The NSS was conducted for 11 consecutive months, and different clusters were surveyed in each month. Therefore, the NSS can be considered as a set of 11 repeated cross-sectional surveys at different locations. NSS captured bite events that occurred in the survey month and in the 12 preceding months. Hence, each individual provided information regarding the number of bites experienced in each of 13 months. In the NSS data, the location of each sampled individual was fixed at the cluster centroid and the data contain the month of each recorded bite, if any, over a 13 month period covering the survey month and each of the preceding 12 months. We modelled the data from each cluster as an inhomogenous Poisson process with cluster-level explanatory variables and estimated the model parameters by maximising the pooled log-likelihood over all. The fitted cluster-level spatiotemporal models were aggregated so as to predict the province-level monthly bite incidence rates in Sri Lanka. Snakebite incidence showed complex spatiotemporal patterns in Sri Lanka. Models fitted for Southern, North Central, Uva and Sabaragamuwa provinces showed both spatial and temporal variation in snakebites. The geographical extent of the high-risk areas (i.e. hotspots) in these provinces dynamically changed over a period of a year. The remaining five models (i.e. Western, Central, North Western, Northern and Eastern) did not show any spatio-temporal interaction, in risk, i.e. the geographical extent of the hotspots persisted throughout the year. Southern, Sabaragamuwa and North Central provinces showed triannual seasonal trends. High snakebite incidences in Southern and Sabaragamuwa provinces were noticed in April followed by December and August to September. Peak incidences in North Central province were seen in November and another two smaller peaks were observed in April and July. Uva province showed a biannual trend with highest incidences in June followed by December. These findings can inform healthcare decision-making at local level, taking account of the seasonal variations in order to prevent and manage snakebites in Sri Lanka
The Global Challenge of Snakebite: where are we in 2016?
(Faculty of Medicine, University of Kelaniya, Sri Lanka, 2016) Lalloo, D.
OBJECTIVE: To understand the ongoing challenges to improving outcomes following snakebite around the world. The existing state of our knowledge about the epidemiology and management of snakebite around the world will be reviewed, including identifying the major contributions made to the literature by Sri Lankan researchers. The future research agenda and the inherent challenges in achieving improved outcomes will be highlighted and discussed.
Prevention of acute adverse reactions to snake antivenom after snakebite: multi-centre, randomized, controlled clinical trial
(Sri Lanka Medical Association, 2009) de Silva, H.A.; Ranasinha, C.D.; Pathmeswaran, A.; Jayamanne, S.; Kalupahana, R.; Ratnathilake, G.A.; Ariyasena, H.; Uluwatte, W.; Lalloo, D.; Armitage, J.; Aronson, J.K.; de Silva, H.J.
BACKGROUND: Antivenom is the most effective treatment for snakebite envenoming. Acute adverse reactions to the polyvalent antivenom (PAV) are common; anaphylactk reactions are particularly serious. OBJECTIVE: To determine whether promethazine, hydrocortisone, and low-dose adrenaline, alone and in all possible combinations, prevent reactions to antivenom. METHODS: The study was conducted in 3 hospitals in Sri Lanka from March 2005 to April 2008. It required 1000 patients to detect a 25% reduction in reactions at p<0.01 with 80% power. After informed consent, patients were randomized in a 2x2x2 factorial blinded design to receive each active intervention versus matching placebo immediately before administration of PAV. They were monitored for adverse reactions categorized as mild, moderate, severe, for at least 96 hours. The pre-specified primary analyses were of effects of each intervention on the incidence of severe reactions over 48 hours. Results: Of 1007 randomized subjects 776 (77.2%) were males, mean (sd) age 36.5 (13.6) yrs. Median time between snakebite and PAV administration was 4.25 hours. 752 (75%) patients developed acute reactions to PAV; 9% mild, 48% moderate and 43% severe. None of the drugs significantly reduced severe reactions to PAV at any time point. However, there was an 18% reduction in the rate of severe reactions at 1 hour with adrenaline (p-0.052) and a 33-3% reduction in signs of allergy (pruritus, urticaria, facial oedema, bronchospasm) with promethazine at 1 and 24 hours (p<0.001). CONCLUSIONS: Pre-treatment with promethazine, hydrocortisone, and low-dose adrenaline alone and in different combinations do not significantly reduce acute reactions to PAV.