Venomous Snakebite

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THE GLOBAL ISSUE OF VENOMOUS SNAKEBITE

Venomous Snakebite:

Snakebite envenomation is a global public health hazard affecting a great number of people and causing tens of thousands of deaths annually. Recently, venomous snakebite was identified by the World Health Organization as one of the world’s majorly neglected tropical diseases of the 21st Century. (1,2) A study conducted by Kasturiratne (2008) (3) to determine the global burden of snakebite estimated that figures may be as high as 1,841,000 envenomings and 94,000 deaths per year. However, the true impact of snakebite may never be known, especially in respect to the fact that most snakebites occur in rural, underserved areas with poor case reporting. The primary burden of snakebite envenomation falls on the inhabitants of developing countries in tropical and subtropical regions. Indeed, the highest morbidity and mortality rates occur in South Asia, Southeast Asia, and sub-Saharan Africa. (3)

Snakebite has also been overlooked as an occupational hazard with most bites occurring on the feet, legs and hands of young male agricultural workers. (2) Women and children are also largely affected groups. (2,4) The high morbidity and mortality rates from snakebite are attributed to the lack of appropriate regionally specific antivenoms in developing countries, poor health services and lack of rapid access to treatment. (5)   

 

Consequences of Snakebite

The bite from a venomous snake resulting in envenomation can have serious consequences causing disability and death. The snake species causing the highest morbidity and mortality rates worldwide are those from the families Viperidae (true vipers, lance-head pit vipers, and rattlesnakes) and Elapidae (kraits, cobras, coral snakes, mambas, Australasian snakes and sea snakes). The species responsible for the most problems differs depending on the geographic region. (1,2)  

Envenomings cause a variety of effects on the body, both local (at the site of the bite and adjacent tissue) and systemic (via circulatory system, involving distant, multiple organs of the body), as well as central nervous system complications. The most critical consequences of snake bite envenoming include shock, spontaneous systemic bleeding, paralysis involving respiratory muscles, generalized break down of skeletal muscle (rhabdomyolysis), acute renal failure and infection of necrotic tissue at the site of the bite. The chemical composition of venom is complex, varying among different species and even within individuals of the same species. The damaging effects of envenomation may occur rapidly after a bite making the time between sustaining the bite and receiving appropriate medical treatment of paramount importance. (1,2)   

Most Viperid snakes inflict extensive local tissue damage caused by the action of toxins on muscle, skin and blood vessels, resulting in pain, edema, blistering, bleeding and necrosis of skin, subcutaneous tissue, and muscle. Bites by some Elapid snakes, such as cobras, may also result in serious local necrosis. 

Serious systemic consequences of Viperid snake venoms include spontaneous hemorrhage into the brain or gastrointestinal tract secondary to microvascular damage, coagulopathy and platelet dysfunction. This may occur together with cardiovascular shock and subsequent renal failure. Systemic effects of Elapid snake venoms are generally exhibited as neurotoxicity, resulting in paralysis of muscles that may lead to respiratory failure. In addition, some venoms may induce systemic myotoxicity, myoglobinuria, hyperkalaemia and either direct or indirect acute renal failure. (1,2) Making such generalizations more difficult are the known and unknown variations in venom composition of snakes of even the same species giving mixed clinical pictures following serious envenomation (this is one of the reasons limiting the efficacy of monovalent antivenoms).


References

1. World Health Organization. (2007). Rabies and envenomings a neglected public health issue. Report of a consultative meeting, World Health Organization Geneva, Retrieved from http://www.who.int/bloodproducts/animal_sera/Rabies.pdf

2. Gutierrez, J.M., Theakston, R.D.G., & Warrell, D.A. (2006). Confronting the neglected problem of snake bite envenoming: the need for a global partnership. Plos Medicine, 3(6), 0727-0731. 

3. Kasturiratne, A., Wickremasinghe, A.R., de Silva, N., Gunawardena, N.K., Pathmeswaran, A., Premaratna, R., Savioli, L., Lalloo, D.G., & de Silva, H.J. (2008). The Global burden of snakebite: a literature analysis and modelling based on regional estimates of envenoming and deaths. PLoS Medicine , 5(11), Retrieved from www.plosmedicine.org

4. Ariaratnam, C.A., Thuraisingam, V., Kularatne, S.A.M., Sheriff, M.H.R., Theakston, R.D.G., de Silva, A., & Warrell, D.A. (2008). Frequent and potentially fatal envenoming by hump-nosed pit vipers (Hypnale hypnale and H. nepa) in sri lanka: lack of effective antivenom . Transactions of the Royal Society of Tropical Medicine and Hygiene, 102, 1102-1126. 

5. Chippaux, J.P. (1998). Snake bites: appraisal of the global situation . Bulletin of the World Health Organization, 76(5), 515-524.       
Warning- Graphic Images

Lateralising neurological signs of intracranial bleeding in this woman bitten by a Russell's viper in Sri Lanka.


Gingival bleeding in a Sri Lankan man bitten by a Russell's viper.


Russell's viper

Swelling and blistering caused by a Hump-nosed viper bite in Sri Lanka.


Hump-nosed viper


Necrosis of the foot caused by a spitting cobra bite in Swaziland.

Necorsis of the hand and loss of digits caused by a spitting cobra bite in Swaziland.


Spitting Cobra