Bites & Stings

This article was last modified Oct 8th 2009 by Caroline Baugh

This is a huge topic, but there are a few key take-home messages:

• Prevention - as ever, this is key
• Research the hazards in your local area or area of travel
• Educate your team as to the risks and likely hazards
• Treatment – again varies widely
• Research local protocols
• If in doubt treatment is supportive and based on symptoms

Mammallian Bites

• Key management message – think antibiotics, rabies and tetanus

Large carnivores and primates

• Large carnivores cannot be outrun so are better faced. Try shouting, throwing rocks or waving sticks which may confuse the animal and make it back away. Running away is just what the prey would do and could precipitate an attack. Be very careful when camping in big cat country. Don't sleep in a tent with anything that may attract a large creature, bears will rip open tents to get at the contents. There are many dangerous animals to be found roaming freely in parts of Africa and Asia. As well as the big cats, these include rhinos, hippos, elephants and (African) buffaloes which can be particularly aggressive. Large primates like baboons and chimpanzees can be particularly dangerous. It pays to be well informed when travelling into areas where these animals are found. If you are going on a safari to a game reserve, stay inside your vehicle when appropriate and always follow the advice of your guide. When travelling close to rivers in Africa, South America and parts of Australia beware of crocodiles which can be lurking in shallow water near to the river bank. 

Domestic Animals

• Because we have so much contact with domestic animals, we are much more likely to be injured by them than by wild animals. Travellers have been injured by cats, dogs, cattle, pigs, camels, water buffalo, elephants, etc. Be wary of any domestic animals you do not know. By far the most common domestic animal responsible for attacks on humans are dogs. Worldwide they are responsible for hundreds of deaths annually. In many countries they often run wild and may respond aggressively when approached. In the US, dogs bite over 4 million people resulting in the hospitalisation of 6000 to 13000 people each year in the United States. Rarely deaths may occur after an attack. A recent study published in WEM 2009 showed males and children less than 10 years of age had the highest rate of death from attacks and that the number of deaths and death rate from dog attacks appear to be increasing. Dog bites not only inflict severe injury but can also spread dangerous infections like tetanus or even rabies. Always remember antibiotics for bite management – risk of infection is reduced by nearly half. (Cummings P. Antibiotics to prevent infection in patients with dog bite wounds: a meta-analysis of randomized trials. Ann Emerg Med 1994;23(3):535-540)

 
Rabies

• Rabies is present worldwide - except in the United Kingdom, parts of Scandinavia, Japan, Oceania, Antarctica, Australia, New Zealand, Malta and some of the Caribbean islands. It can be transmitted to humans in several ways, but most commonly via the bite of an infected domestic dog. Rabies, if left untreated, will always cause death! Rabies vaccination before travel reduces the need for access to Rabies Immunoglobulin if bitten, but the victim will still need to receive a further course of rabies vaccination as soon after  bite occurs as possible.  Rabies vaccine is in short supply and it may not be available for  pre-exposure vaccination because it is held for use in post-exposure vaccination for victims of bites.   For more - http://www.cdc.gov/RABIES/

Snake Bites

Most species of snakes are harmless and over half of the venomous species do not have the capability or temperament to be harmful. Even aggressive and venomous species will very often inflict a "dry bite" which is venom free. Snakes do not like to waste their venom on anything other than prey species. Remember; only one in a thousand people bitten by a snake actually dies as a result as most bites are from harmless snakes or dry bites. But – there are still up to 1.8 million envenomings and 94000 deaths a year globally so it is a significant problem. For more information – see:

http://www.who.int/neglected_diseases/integrated_media_snakebite/en/index.html

Most deaths from snake bites occur on the Indian subcontinent where they are often forced into contact with humans.  Some deaths are sudden, however in fact it is uncommon to die within four hours of a snake bite.

Snakebite venom is broadly divided into:

• Neurotoxin - affecting the nervous system - Neurotoxin venom kills the specialist cells, known as neurons, which make up the nervous system. This can result in symptoms of muscle weakness, or numbness, paralysis, loss of memory, confusion, and vision and hearing problems. At a high enough dose, neurotoxins can cause brain damage, and may paralyse the respiratory system, or heart, which can be fatal.
• Cytotoxin - affecting local tissues - Muscle destruction from cytotoxic toxins is not uncommon and may not be associated with muscle tenderness; it may lead to renal failure and should be specifically looked for, because early treatment with antivenom will reduce its severity.

• Haemotoxin - affecting blood cells - venom kills red blood cells and disrupts the blood's ability to clot. At a high enough dose, haemotoxins can cause a massive drop in blood pressure, resulting in tissue and organ damage, unconsciousness and, ultimately, death.

Initial management

• Keep the casualty calm and still
• Remove rings and watches
• Swab bite site – if venom detection kits are locally available
• Immobilise limb below heart
• Consider applying pressure bandage
• Consider antivenom if available

• There is no evidence for sucking devices or electrical cattle prods!

Snake venom travels primarily via the lymphatic system. Therefore, to prevent the spread of venom the movement of lymph needs to be restricted. This is achieved by immobilising the bitten area (usually a limb), keeping it level with or just below the heart and / or by the application of a pressure bandage.

Much of the research on pressure bandages has been done in Australia, where there are predominantly Neurotoxic snakes. There is good evidence there for its efficacy, although it has never been subjected to formal clinical trials. The evidence is less compelling for Haemotoxic snake bites (more commonly found in North America), as there is a concern about the potential to intensify local injury. The jury is still out really – but the method is widely used outside the US (particularly for non-necrotising neurotoxic bites) so it is worth being aware of. The "pressure-immobilisation" technique is currently recommended by the Australian Resuscitation Council, the Royal Australasian College of Surgeons and the Australian and New Zealand College of Anaesthetists. For more details and diagrams of bandaging techniques, please see the link to the AVRU website. Again this highlights the need for research of the local area and potential hazards before travelling.

Antivenom – in remote settings

Local knowledge of types of antivenom available is vital. There are two types of antivenom in use today. Polyvalent antivenom is used when the species of snake has not been identified, whereas Monovalent can be used for a specific species. They are derived from antibodies created in the blood of a horse or sheep when the animal is injected with snake venom.

Preparations are given IV or IM (IV more effective - diluted over 30 minutes) and you may need >1 ampoule. Because it is obtained from horses, snakebite victims who are sensitive to horse proteins must be carefully managed. The danger is that they could develop an allergy or anaphylaxis so have an Epipen close at hand. It is a potentially lethal drug so all attempts should be made to reach a medical facility for administration by qualified personnel.

Newer kinds of antivenoms derived from sheep have been studied, and one (CroFab) is now licensed for use in the United States. This sheep antibody preparation has been digested with an enzyme to reduce the risk of allergic reactions. The enzyme treatment also allows the antivenin to be cleared from the body more rapidly, so that additional treatments may need to be given.

There is a severe shortage of antivenom in Africa currently, largely due to poor epidemiology therefore drug companies are hampered by a lack of knowledge of which to provide, where to source the venoms necessary for production, and the likely volume levels required.

Spider Bites

Although most spiders are venomous, very few species are able to penetrate human skin and inject venom. Of those that can, only a few species in Australia and South America cause neurotoxicity requiring specific anti venom treatment. The Black Widow bite gives rise to painful muscle spasms which can last up to two days

Bites from the truly poisonous spiders such as Funnel Webs should be treated like snake bites and medical assistance should be sought as soon as possible. The spider should be killed and taken along to the doctor for identification. The spider bite victim should be transported as quickly and as passively as possible to the nearest place where they can be seen by a medically-trained person

Scorpion Stings

These are generally painful rather than life-threatening…but some are potentially lethal so again it is important to research the area of travel. Lethal scorpions tend to be neurotoxic and their victims need to receive anti-venom quickly  Children are at greater risk of developing severe cardiac, respiratory, and neurological complications. For most bites the management is simple: antihistamines, analgesia and seek help if needed.

Marine Creatures

Sea creatures can cause various injuries.  Jellyfish, corals and sea anemones can cause stings.  Their venom is contained in stinging cells (nematocysts) that stick to the victim’s skin, and this is released when the cell ruptures.  The spines of sea urchins or weever fish may puncture the skin, if trodden on, and become embedded in the foot, usually causing a painful local reaction, though serious general effects are rare.  In some parts of the world, severe degrees of poisoning can occur, giving rise to severe allergic reaction (anaphylactic shock), or paralysis of the chest muscle.  These cases, rarely, may be fatal.

Treatment of Marine Puncture Wounds

Place the injured part in water as hot as the casualty can bear for at least 30 minutes, topping up the water as it cools, and taking care not to scald the casualty. The casualty should be taken or sent to hospital, where any spines remaining in the skin can be removed.

Treatment of Marine Stings

1. Rinse wound initially with sea water – do not rub. For most jellyfish – washing off tentacles with sea water or fingers is enough.
2. Vinegar is treatment of choice for Box Jellyfish toxin – interrupts envenomation. For other species there may well be more effective substances (eg sodium bicarbonate for sea nettle), isopropyl alcohol, olive oil, sugar etc. It is no longer recommended to use pressure-immobilisation technique. Avoid alcohol as may stimulate discharge of nematocysts in vitro. Used to use Stingose (Aluminium Sulphate and anionic surfactant) but largely fallen out of favour in Australia now.
3. Avoid systemic drugs unless you need antihistamines for allergic reaction or Adrenaline for anaphylaxis.
4. Hot water (40-41C) – not generally recommended although some research evidence in box jellyfish
5. Once soaked with decontaminant (e.g. vinegar) – need to remove rest of nematocysts – can use shaving foam, or paste of baking soda, flour or talc. Then scrape skin with razor, shell etc.
6. Can use topical anaesthetic, antihistamine or mild steroid
7. Remember tetanus
8. No need for prophylactic antibiotics

Insect Stings

Venomous insects such as wasps, hornets, bees and ants tend to sting or bite as a defence mechanism, injecting their venom via stings. Principles of management include sting removal and be aware of risk of anaphylaxis. Non venomous insects are potentially far more dangerous, due to the diseases they carry, as discussed in the separate area - Vector Bourne Disease.