Mapping the Risk of Snakebite in Sri Lanka - A National Survey with Geospatial Analysis.

Dileepa Senajith Ediriweera,Peter John Diggle,Andrew Dawson,Arunasalam Pathmeswaran,Emanuele Giorgi,Anuradhani Kasturiratne,Buddhika Asiri Wijayawickrama,Geoffrey Kennedy Isbister,Shaluka Francis Jayamanne,Hithanadura Janaka De Silva,David Griffith Lalloo,Nipul Kithsiri Gunawardena

doi:10.1371/journal.pntd.0004813

Abstract

BackgroundThere is a paucity of robust epidemiological data on snakebite, and data available from hospitals and localized or time-limited surveys have major limitations. No study has investigated the incidence of snakebite across a whole country. We undertook a community-based national survey and model based geostatistics to determine incidence, envenoming, mortality and geographical pattern of snakebite in Sri Lanka.Methodology/Principal FindingsThe survey was designed to sample a population distributed equally among the nine provinces of the country. The number of data collection clusters was divided among districts in proportion to their population. Within districts clusters were randomly selected. Population based incidence of snakebite and significant envenoming were estimated. Model-based geostatistics was used to develop snakebite risk maps for Sri Lanka. 1118 of the total of 14022 GN divisions with a population of 165665 (0.8%of the country’s population) were surveyed. The crude overall community incidence of snakebite, envenoming and mortality were 398 (95% CI: 356–441), 151 (130–173) and 2.3 (0.2–4.4) per 100000 population, respectively. Risk maps showed wide variation in incidence within the country, and snakebite hotspots and cold spots were determined by considering the probability of exceeding the national incidence.Conclusions/SignificanceThis study provides community based incidence rates of snakebite and envenoming for Sri Lanka. The within-country spatial variation of bites can inform healthcare decision making and highlights the limitations associated with estimates of incidence from hospital data or localized surveys. Our methods are replicable, and these models can be adapted to other geographic regions after re-estimating spatial covariance parameters for the particular region.

Highlights

Bites of venomous snakes cause significant morbidity and mortality in the rural tropics
To get a truer picture of the situation in Sri Lanka, where snakebites are an important cause of hospital admission, we undertook an island-wide community survey to determine the number of bites, envenomings and deaths due to snakebite in the previous 12 months
We found that there were more than 80,000 bites, 30,000 envenomings and 400 deaths due to snakebite, much more than claimed by official statistics

Summary

Introduction

Bites of venomous snakes cause significant morbidity and mortality in the rural tropics. The main reason for this was the paucity of robust epidemiological data on the disease burden associated with snakebite. The paucity of reliable data is partly related to inherent methodological difficulties, which include: poorly developed reporting and recording systems in countries with the highest burden, limitations in hospital-based data that often under-estimate the problem [2][3][4][5], and seasonal and geographical variation in bite incidence [6][7], all of which make extrapolations unreliable. There is a paucity of robust epidemiological data on snakebite, and data available from hospitals and localized or time-limited surveys have major limitations. We undertook a communitybased national survey and model based geostatistics to determine incidence, envenoming, mortality and geographical pattern of snakebite in Sri Lanka

Objectives

Methods

Results

Discussion

Conclusion