Snake bites more lethal than previously thought

Written by Thomas Hesselberg

Tuesday, 11 November 2008

The Eastern Green Mamba (Dendroaspis angusticeps) has one of the most venomous bites. From Wikimedia Commons (Photo by user Danleo)

Many people have an innate fear of snakes, which probably stem from our evolutionary history. A new analysis of the research literature and reports on snake bites from around the globe suggest that this fear is well-founded indeed. The study estimates that between 1 and 5 million people are bitten by snakes every year.

Snakes are limbless reptiles which can be found almost everywhere on the globe although the diversity is far greater in the tropics than everywhere else. Most snakes are poisonous and use the poison to paralyze prey, which typically include rodent, lizards and amphibians. However, the poison is also used for self-defence against larger predators and although only few species are dangerous to humans these often possess a significant threat to humans working in rural tropical settings.

Researchers from the University of Kelaniya in Sri Lanka and the Liverpool School of Tropical Medicine in the United Kingdom have published a survey of snakebites in PLoS Medicine. They base their findings on published scientific literature as well as on reports from United Nation organisations and the World Health Organisation.

The most reported snake-bites come from Asia and Southeast Asia in particular followed by Sub-Saharan Africa and Central and the northern part of South America. Although only a minority of snake bites are lethal many results in necrosis of tissue and cause various permanent injuries. The researchers estimate than snakebites cause between 20.000 and 90.000 deaths annually with the vast majority occurring in South and Southeast Asia. However, more than 400.000 (and as many as 1.8 million) mainly young people in rural areas suffer some kind of disability as the result of snake-bite. From the knowledge that only a minority of snake bites causes permanent injuries they estimate that between 1 and 5 million people are bitten by snakes annually.

Considering these surprisingly large numbers and the economical burden that snakebites cause in many tropical rural areas, the scientists recommend to focus more on this problem and to ensure that the availability of anti-venom in these areas is increased.

Source:
Kasturiratne A, Wickremasinghe AR, de Silva N, Gunawardena NK, Pathmeswaran A, et al. (2008) Estimating the global burden of snakebite: A literature analysis and modelling based on regional estimates of envenoming and deaths. PLoS Med 5(11): e218. doi:10.1371/journal.pmed.0050218

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