This guest post was written by Professor David A. Warrell, who is currently International Director (Hans Sloane Fellow), Royal College of Physicians, London and Emeritus Professor of Tropical Medicine, University of Oxford, UK. Professor Warrell was the 2015 ASTMH Marcolongo Lecturer.
Threat of snake-bite to indigenous populations
Most parts of the world are inhabited by venomous snakes. Snake-bites are a risk to rural inhabitants whose agricultural and hunting activities expose them and their children to this primeval environmental and occupational disease. Snake-bite is an important cause of death and disability in West Africa, Southeast Asia, the Indian sub-continent, Papua New Guinea, and the Amazonian region. There is good evidence that in India there are 46,000 and in Bangladesh 6,000 snake-bite deaths each year. Survivors often suffer persistent physical and mental morbidity. Meteorological factors affect the incidence of snake-bite. Annual peaks are during the rains (monsoons) and resulting flooding, associated with cycles of snake (reproductive) and human (agricultural) activity. Many bites occur at night and may be inflicted on people sleeping on the floor of their home.
Threat to travellers
Compared to indigenous populations, travellers are exposed to a tiny-but-finite risk of snake-bite. Biologists collecting specimens in rain forests and other habitats richly populated with venomous snakes are at the highest risk but they are likely to be the best prepared (although even expert herpetologists have been bitten in the field). Ordinary tourists have been envenomed in urban surroundings (e.g. a German tourist bitten by a cobra in the garden of a hotel in central Bangkok and a Dutch man spat at by a spitting cobra that was in his bed in Malacca, Malaysia) and in the wilderness (e.g. a British woman bitten by a rattlesnake while walking on the main trail down the Grand Canyon and a schoolboy bitten by a fer-de-lance in a jungle camp in Costa Rica).
Prevention of snake-bites in travellers
Awareness of risk is important. Find out in advance about the venomous snake fauna of the areas to be visited. There are many sources of information on the web, such as the WHO Venomous snakes and antivenoms search interface and other sites listed below. Be prepared to react appropriately if someone in the group is bitten (see below). Although snake-bite is such a small risk to most travellers, it is a common cause of anxiety and misunderstanding. Appropriate, well-informed reassurance can improve your enjoyment of travel and banish nightmares. If you’re travelling in a group that includes a designated medical officer, he/she should acquire basic knowledge about prevention and treatment.
Do’s and Don’ts of snake-bite prevention
Do the following:
- Open and shake out sleeping bags, boots and clothing before use to dislodge snakes (scorpions etc.) that may have taken refuge inside
- Check ground before sitting at the base of a tree.
- Wear boots, socks, and long trousers when walking in undergrowth or deep sand.
- Use a flashlight/torch at night when walking, collecting fire wood or relieving yourself, especially after heavy rain.
- Be aware that banks of streams, rivers and lakes are common snake haunts.
- Travel with a local guide who is much more likely to see camouflaged snakes.
- Sleep off the ground (hammock or camp bed) or use a sewn-in ground sheet and mosquito-proof tent or sleep under a mosquito net that is well-tucked-in under your sleeping bag. This will protect against night-prowling kraits (Asia) or spitting cobras (Africa) which often bite people while they are asleep on the ground.
Do not do the following:
- Do not disturb, approach, corner, provoke, attack, or attempt to handle snakes, even if they are said to be a harmless species, or appear to be dead (some snakes sham death defensively). Even a severed head may bite! If you corner a snake inadvertently, keep absolutely still until it has slithered away. Snakes strike only at moving objects.
- Do not attend snake charmers’ shows (their snakes may not be under control – a boy watching a snake charmer in northern Nigeria was fatally bitten by the performing Egyptian cobra).
- Do not put hands blindly down inside rucksacks (a British man in Sierra Leone opened his bag and was bitten by a green mamba that was inside).
- Do not put hands or poke sticks into burrows or holes. They often harbour snakes (small boys hunting rodents in Africa and Asia are often bitten by snakes).
- Do not put hands up onto branches or ledges that can’t be seen (a South African man climbing in the Drackenbergs was bitten on the hand by a Berg adder as he reached up onto a rocky ledge).
- Do not swim in rivers matted with vegetation in which snakes may be hiding or in muddy estuaries where there are likely to be sea-snakes.
Do’s and Don’ts of snake-bite first-aid
What to do if someone is bitten by a snake or suspects that they have been bitten
Do the following:
- Reassure the victim. Many bites are by harmless snakes and even the most venomous snakes often bite without injecting harmful amounts of venom (‘dry bites’). Usually, if the snake has injected venom, serious effects will not develop for hours or even days, allowing plenty of time for effective medical treatment.
- Apply a pressure-pad (Figure 2a) directly over the bite wound and immobilize the whole patient, especially their bitten limb.
- Remove tight rings, bracelets, anklets, bands, clothing, etc. from the bitten limb.
- Transport the victim to medical care as quickly, safely and passively as possible.
- For pain, give acetaminophen (paracetamol), codeine phosphate or other opioids.
Do not do the following:
- Do not use traditional first-aid methods, such as cutting the bite site, using vacuum extractor suction, applying tight bands (tourniquets) around the bitten limb, or applying electric shock, ice packs, herbal concoctions, black ‘snake stones’, or chemicals on the wound (all are useless and potentially harmful).
- Do not give aspirin or non-steroidal anti-inflammatory agents for pain; they exaggerate bleeding problems.
- Do not attempt to chase or kill the snake, risking more bites.
Pressure-pad immobilisation first-aid method
(Photos courtesy of Dr David J Williams, Port Moresby General Hospital, Papua New Guinea).
If, when the snake-bite victim reaches the hospital, doctors find evidence of envenoming (‘envenomation’), a specific antidote called antivenom may be needed. Antivenoms are expensive and often in short supply, especially in tropical developing countries. When planning travel to snake-infested regions to undertake high risk activities (such as orchid collecting in remote areas of tropical rain forest), it would be worth visiting the local medical facilities in advance, to see if they have antivenom in stock, or, if not, taking your own supply, to be given, if the need arises, at the local hospital (see antivenom websites below). Refrigeration of liquid or freeze-dried (lyophilised) antivenom is not essential for periods of up to one month.
About Professor David A. Warrell
Professor Warrell is actively involved in Australian-funded research on snake-bite in Papua New Guinea and Myanmar. He was formerly Head of the Nuffield Department of Clinical Medicine, University of Oxford and senior editor of the Oxford Textbook of Medicine, OTM-Infection, Essential Malariology and the Oxford Handbook of Expedition and Wilderness Medicine. His career has been as a physician, teacher, researcher, resident and traveller in Africa, Asia, Latin America and Papua New Guinea. He was originally based at the Hammersmith Hospital and, since 1975, in Oxford. He founded the Oxford Tropical Medicine Research Network in 1979. His research publications cover infectious, tropical and respiratory diseases; venomous animals; envenoming; plant and chemical poisoning; and expedition medicine.
Johnson C et al., (Eds.). Oxford Handbook of Expedition and Wilderness Medicine. Oxford, Oxford University Press, 2nd Ed 2015.
South and South-East Asia – Guidelines for the management of snake-bites (PDF)
Worldwide – Clinical Toxinology Resources
Worldwide – Vapaguide
Antivenoms – Snake Antivenom Immunoglobulins
Antivenoms – List of antivenoms