Epidemiology of snakebites

Map showing the approximate world distribution of snakes.
Map showing the global distribution of snakebite morbidity.

Most snakebites are caused by non-venomous snakes. Of the roughly 3,700 known species of snake found worldwide, only 15% are considered dangerous to humans.[1][2][3] Snakes are found on every continent except Antarctica.[1] There are two major families of venomous snakes, Elapidae and Viperidae. 325 species in 61 genera are recognized in the family Elapidae[4] and 224 species in 22 genera are recognized in the family Viperidae,[5] In addition, the most diverse and widely distributed snake family, the colubrids, has approximately 700 venomous species,[6] but only five genera—boomslangs, twig snakes, keelback snakes, green snakes, and slender snakes—have caused human fatalities.[6]

Since reporting is not mandatory in many regions of the world,[1] snakebites often go unreported. Consequently, no accurate study has ever been conducted to determine the frequency of snakebites on the international level. However, some estimates put the number at 1.2 to 5.5 million snakebites, 421,000 envenomings, resulting in perhaps 20,000 deaths, but the actual number of deaths may be as high as 94,000.[7] Many people who survive bites nevertheless suffer from permanent tissue damage caused by venom, leading to disability.[8] Most snake envenomings and fatalities occur in South Asia, Southeast Asia, and sub-Saharan Africa, with India reporting the most snakebite deaths of any country.[1] An analysis cross-referencing exposure to venomous snakes and accessibility of medical treatment identified that 93 million people worldwide are highly vulnerable to dying from snakebite.[9]

Available evidence on the effect of climate change on the epidemiology of snakebite is limited but it is expected that there will be a geographic shift in risk of snakebite: northwards in North America and southwards in South America and in Mozambique, and increase in incidence of bite in Sri Lanka.[10]

Worldwide, snakebites occur most frequently in the summer season when snakes are active and humans are outdoors.[1][11] Agricultural and tropical regions report more snakebites than anywhere else.[1][12] In North America, the victims are typically male and between 17 and 27 years of age.[2][11][13] Children and the elderly are the most likely to die.[2][14]

Number of Snakebite Envenomings per Year
Region Low Estimate High Estimate
Asia 237,379 1,184,550
Australasia 1,099 1,260
Caribbean 1,098 8,039
Europe 3,961 9,902
Latin America 80,329 129,084
North Africa / Middle East 3,017 80,191
North America 2,683 3,858
Oceania 361 4,635
Sub-Saharan Africa 90,622 419,639
Total: 420,549 1,841,158
Number of Deaths from Envenoming per Year
Region Low Estimate High Estimate
Asia 15,385 57,636
Australasia 2 4
Caribbean 107 1,161
Europe 48 128
Latin America 540 2,298
North Africa / Middle East 43 78
North America 5 7
Oceania 227 516
Sub-Saharan Africa 3,529 32,117
Total: 19,886 93,945
  1. ^ a b c d e f Winkel, Ken; Kasturiratne, Anuradhani; Wickremasinghe, A. Rajitha; de Silva, Nilanthi; Gunawardena, N. Kithsiri; Pathmeswaran, Arunasalam; Premaratna, Ranjan; Savioli, Lorenzo; Lalloo, David G; de Silva, H. Janaka (2008). "The Global Burden of Snakebite: A Literature Analysis and Modelling Based on Regional Estimates of Envenoming and Deaths". PLOS Medicine. 5 (11): e218. doi:10.1371/journal.pmed.0050218. PMC 2577696. PMID 18986210.
  2. ^ a b c Gold, Barry S.; Richard C. Dart; Robert A. Barish (1 April 2002). "Bites of venomous snakes". The New England Journal of Medicine. 347 (5): 347–56. doi:10.1056/NEJMra013477. ISSN 0028-4793. PMID 12151473.
  3. ^ Russell, F. E. (1990). "When a snake strikes". Emerg Med. 22 (12): 33–4, 37–40, 43.
  4. ^ "Elapidae". Integrated Taxonomic Information System. Retrieved 27 November 2006.
  5. ^ "Viperidae". Integrated Taxonomic Information System. Retrieved 10 August 2006.
  6. ^ a b Mackessy, Stephen P. (2002). "Biochemistry and pharmacology of colubrid snake venoms" (PDF). Journal of Toxicology: Toxin Reviews. 21 (1–2): 43–83. CiteSeerX 10.1.1.596.5081. doi:10.1081/TXR-120004741. S2CID 86568032. Archived from the original (PDF) on 2010-06-02. Retrieved 2009-09-26. Estimates of the number of venomous colubrids approach 700 species. Most may not produce a venom capable of causing serious damage to humans, but at least five species (Dispholidus typus, Thelotornis capensis, Rhabdophis tigrinus, Philodryas olfersii and Tachymenis peruviana) have caused human fatalities
  7. ^ Kasturiratne, A; Wickremasinghe, AR; de Silva, N; Gunawardena, NK; Pathmeswaran, A; Premaratna, R; Savioli, L; Lalloo, DG; de Silva, HJ (4 November 2008). "The global burden of snakebite: a literature analysis and modelling based on regional estimates of envenoming and deaths". PLOS Medicine. 5 (11): e218. doi:10.1371/journal.pmed.0050218. PMC 2577696. PMID 18986210.
  8. ^ Gutiérrez, José María; Bruno Lomonte; Guillermo León; Alexandra Rucavado; Fernando Chaves; Yamileth Angulo (2007). "Trends in Snakebite Envenomation Therapy: Scientific, Technological and Public Health Considerations" (PDF). Current Pharmaceutical Design. 13 (28): 2935–50. doi:10.2174/138161207782023784. PMID 17979738. Archived from the original (PDF) on 2011-04-28. Retrieved 2009-07-01.
  9. ^ Longbottom, Joshua (August 25, 2018). "Vulnerability to snakebite envenoming: a global mapping of hotspots". The Lancet. 392 (10148): 673–684. doi:10.1016/S0140-6736(18)31224-8. PMC 6115328. PMID 30017551.
  10. ^ Bhaumik, Soumyadeep; Beri, Deepti; Jagnoor, Jagnoor (October 2022). "The impact of climate change on the burden of snakebite: Evidence synthesis and implications for primary healthcare". Journal of Family Medicine and Primary Care. 11 (10): 6147–6158. doi:10.4103/jfmpc.jfmpc_677_22. ISSN 2249-4863. PMC 9810950. PMID 36618235.
  11. ^ a b Wingert W, Chan L (1 January 1988). "Rattlesnake Bites in Southern California and Rationale for Recommended Treatment". West J Med. 148 (1): 37–44. PMC 1026007. PMID 3277335.
  12. ^ Cite error: The named reference Gutierrez2006 was invoked but never defined (see the help page).
  13. ^ Parrish H (1966). "Incidence of treated snakebites in the United States". Public Health Rep. 81 (3): 269–76. doi:10.2307/4592691. JSTOR 4592691. PMC 1919692. PMID 4956000.
  14. ^ Gold BS, Wingert WA (1994). "Snake venom poisoning in the United States: a review of therapeutic practice". South. Med. J. 87 (6): 579–89. doi:10.1097/00007611-199406000-00001. PMID 8202764. S2CID 37771848.