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

Background There 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 Findings The 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/Significance This 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.

[1]  S. Fox,et al.  Underestimation of snakebite mortality by hospital statistics in the Monaragala District of Sri Lanka. , 2006, Transactions of the Royal Society of Tropical Medicine and Hygiene.

[2]  Peter Dalgaard,et al.  R Development Core Team (2010): R: A language and environment for statistical computing , 2010 .

[3]  P J Diggle,et al.  Spatial modelling and the prediction of Loa loa risk: decision making under uncertainty , 2007, Annals of tropical medicine and parasitology.

[4]  Christopher R. Panabokke,et al.  Soils and agro-ecological environments of Sri Lanka , 1996 .

[5]  P. Diggle,et al.  Model‐based geostatistics , 2007 .

[6]  P. Jha,et al.  Snakebite Mortality in India: A Nationally Representative Mortality Survey , 2011, PLoS neglected tropical diseases.

[7]  Sanjib K. Sharma,et al.  Impact of snake bites and determinants of fatal outcomes in southeastern Nepal. , 2004, The American journal of tropical medicine and hygiene.

[8]  R. Snow,et al.  The prevalence and morbidity of snake bite and treatment-seeking behaviour among a rural Kenyan population. , 1994, Annals of tropical medicine and parasitology.

[9]  K. Maduwage,et al.  Revisiting saw-scaled viper (Echis carinatus) bites in the Jaffna Peninsula of Sri Lanka: distribution, epidemiology and clinical manifestations. , 2011, Transactions of the Royal Society of Tropical Medicine and Hygiene.

[10]  R. Theakston,et al.  INCIDENCE AND MORTALITY OF SNAKE BITE IN SAVANNA NIGERIA , 1980, The Lancet.

[11]  K. Maduwage,et al.  Epidemiology and clinical effects of hump-nosed pit viper (Genus: Hypnale) envenoming in Sri Lanka. , 2013, Toxicon : official journal of the International Society on Toxinology.

[12]  P. Diggle,et al.  Bivariate Binomial Spatial Modeling of Loa loa Prevalence in Tropical Africa , 2008 .

[13]  A. Kasturiratne,et al.  The Global Burden of Snakebite: A Literature Analysis and Modelling Based on Regional Estimates of Envenoming and Deaths , 2008, PLoS medicine.

[14]  Anjana Silva Dangerous snakes, deadly snakes and medically important snakes , 2013, Journal of Venomous Animals and Toxins including Tropical Diseases.

[15]  R Core Team,et al.  R: A language and environment for statistical computing. , 2014 .

[16]  A. Milton,et al.  Annual Incidence of Snake Bite in Rural Bangladesh , 2010, PLoS neglected tropical diseases.

[17]  L. Ranasinghe,et al.  Deadly venomous land snakes of Sri Lanka. , 1983, The Ceylon medical journal.