Research Article: The Global Burden of Snakebite: A Literature Analysis and Modelling Based on Regional Estimates of Envenoming and Deaths

Date Published: November 4, 2008

Publisher: Public Library of Science

Author(s): Anuradhani Kasturiratne, A. Rajitha Wickremasinghe, Nilanthi de Silva, N. Kithsiri Gunawardena, Arunasalam Pathmeswaran, Ranjan Premaratna, Lorenzo Savioli, David G Lalloo, H. Janaka de Silva, Ken Winkel

Abstract: BackgroundEnvenoming 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 burden due to snakebites.Methods and FindingsThe 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 Global Burden 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, deaths were 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 that envenoming occurs in about one in every four snakebites, between 1.2 million and 5.5 million snakebites could occur annually.ConclusionsSnakebites cause considerable morbidity and mortality worldwide. The highest burden exists in South Asia, Southeast Asia, and sub-Saharan Africa.

Partial Text: Venomous snakes are found throughout most of the world (including many oceans), except for a few islands, frozen environments, and high altitudes [1]. Envenomings and deaths resulting from snakebites, however, are a particularly important public health problem in the rural tropics. Populations in these regions experience high morbidity and mortality because of poor access to health services, which are often suboptimal, and, in some instances, a scarcity of antivenom, which is the only specific treatment. A large number of victims survive with permanent physical sequelae due to local tissue necrosis and, no doubt, psychological sequelae. Because most snakebite victims are young [2], the economic impact of their disability is considerable. Despite the scale of its effects on populations, snakebite has not received the attention it deserves from national and international health authorities, and may therefore be appropriately categorized as a neglected tropical disease.

The methodology consisted of two components, data retrieval and estimation.

The review of published literature generated 3,256 citations on snakebite. Data on incidence and/or mortality of snakebite were available in 160 publications.

We estimate that at least 421,000 envenomings and 20,000 deaths occur worldwide from snakebite annually. These figures may be as high as 1,841,000 envenomings and 94,000 deaths. On the basis of the estimation that the total number of snakebites is two to three times the number of envenomings, we estimate that 1,200,000–5,500,000 snakebites may occur globally. The vast majority of the estimated burden of snakebite is in South and Southeast Asia, sub-Saharan Africa, and Central and South America, as identified in previous estimates of the global burden. Despite accounting for nearly one-fourth of the global snakebite incidence, mortality due to snakebite is relatively lower in Central and South America when compared to other high incidence regions. Mortality may be lower because of better snakebite management systems, including the development of locally effective antivenoms, in many Latin American countries. The lower estimates of snakebite incidence in sub-Saharan Africa are probably a reflection of under-reporting from many parts of this region; we found it particularly difficult to find reliable data for this region, especially for East Africa. India, with its population of over a billion people, accounted for the highest estimated number of bites and deaths for a single country.



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