You Have Been Bitten by a Snake … Now What?

You’ve been bitten by a snake … now what?

It’s crossed everyone’s mind that has ever ventured into the more rural areas of Australia. You are there enjoying the view, but suddenly you feel a sharp, excruciating pain, look down and see a snake slithering away. Thought’s suddenly flash through your head. How worried should you be? Are you going to die? What should you do? What will happen if you ever make it to hospital? What is antivenom? These are all answers you want to know because it may well be the difference from life and death.

So, dear reader how worried should you be of dying of a snake bite? Well in Australia there has been on average 2 deaths each year between  2000 and 2016 [1]. That means that there is a 0.00013 % chance that your inevitable demise will come from the contents of a snake’s fangs.

Ok let’s just say you have been bitten by a snake, what symptoms should you expect? Well in order to make assessment of symptoms by doctors easier there is a four grade system used to describe different levels of envenomation[2]. A grade 1 bite is where no envenomation occurs, colloquially known as a ‘dry bite’. A dry bite can never be 100% confirmed but is usually suspected when a patient receives a bite from a known venomous snake but presents no symptoms. Now you would probably think in these cases antivenom would be given as a precaution, but this in not actually the case. Anti- venom is used sparingly for two main reasons, the first being that the supply is scarce for reasons that will be discussed later and the more drastic reason is that anti-venoms can actually make a patient really sick through an anaphylactic, or really severe allergic, reaction. This is often known as serum sickness[3] and this can lead to symptoms such as a bad rash and muscle weakness but like all anaphylaxis can potentially be fatal. This can turn 12 – 24 hours of hospital observations for a dry bite to a 2 week stay[4]. A grade 2 is known as a mild envenomation and is where there is swelling and pain in the area around the bite. A grade 3 or moderate envenomation encompasses a spread of swelling beyond the limb or body segment of the bite site and severe local and systematic pain. The highest grade, a grade 4, is known as a severe envenomation. Symptoms that should be expected are severe bleeding from the bite site or any other recent breaks on the skin, intense swelling all over the body and really dark urine caused by kidney failure [5].

Now you know what to expect, but what should you do immediately after receiving a bite? The first thing to remember is not to panic, it may be easier said than done but this will only make the situation much worse. Traditionally a tourniquet was thought to be the best option as it stopped blood from flowing further into the body, whilst this is true, it can also cause many more problems than it solves. First worry of course is that cells in the affected limb my die if they do not receive blood for an extended period. A second worry is the risk of infection of the wound site that can lead to septic shock [6]. Current guidelines for the first aid of a snake bite is the use of a pressure immobilisation bandage[7]. This technique involves wrapping a compression bandage around the affected limb (the assumption is that a bite has occurred on a limb which almost all do. If you are bitten on the trunk you are in huge trouble.) starting at the digits, leaving them exposed to monitor blood flow, and wrapping all the way to either the armpit or bottom of the pelvis. This should not be too tight that the fingers or dose start to become discoloured but should be tight enough to compress that skin around the bite site. It is also important not to wash the bite site or suck the venom out as the venom from the site will be used at the hospital in order to identify the snake [8]. It is also a very good idea to minimise the movement of the affected limb by using a splint and minimising the amount of movement the victim has to do as not to spread the venom through the lymphatic system.

Below is a video with some St John’s Ambulance officers explaining to the Sunrise crew what first aid techniques to perform in a situation where either yourself or someone else has been bitten by a snake.

 

The final step know is the anti-venom. You are probably expected this anti venom to be made in a sterile lab by people in lab coats, but what might surprise you is that this anti venom is actually made by the immune system of a horse. Horses are used thanks to their immune system being very similar to ours. Also, due to their larger body mass than us can be introduced to a dose snake venom that would likely kill a human and show very little symptoms. The horse immune system produces antibodies to fight the compounds in snake venom, these are then isolated and injected into the unlucky person who was bitten by a venomous snake [9]. The main issues of antivenom’s are serum sickness as previously mentioned and the scarcity of available anti venoms. The production of anti-venom is  a very inefficient process, as first a venomous snake needs to be caught, kept in captivity to be ‘milked’ and then this venom needs to be injected into a horse in order to finally isolate the specific antibodies. Overall this makes antivenoms quite expensive [10].

The point of this blog post is not to scare you about what can happen with possible encounters with snakes but rather reassure you that you will probably be fine and help you make good choices in order to give yourself the best chance of survival.

 

1. Welton, R.E., D. Liew, and G. Braitberg, Incidence of fatal snake bite in Australia: A coronial based retrospective study (2000–2016). Toxicon, 2017. 131: p. 11-15.
2. Naik, B.S., “Dry bite” in venomous snakes: A review. Toxicon, 2017. 133: p. 63-67.
3. Ryan, N.M., M.A. Downes, and G.K. Isbister, Clinical features of serum sickness after Australian snake antivenom. Toxicon, 2015. 108: p. 181-183.
4. de Silva, H.A., et al., Low-Dose Adrenaline, Promethazine, and Hydrocortisone in the Prevention of Acute Adverse Reactions to Antivenom following Snakebite: A Randomised, Double-Blind, Placebo-Controlled Trial. PLOS Medicine, 2011. 8(5): p. e1000435.
5. Wüster, W., Venomous snake systematics: implications for snakebite treatment and toxinology. Toxicon, 1996. 34(2): p. 143.
6. Yanamandra, U. and S. Yanamandra, Traditional first aid in a case of snake bite: more harm than good. BMJ Case Reports, 2014. 2014: p. bcr2013202891.
7. Stewart, C.J., Snake bite in Australia: first aid and envenomation management. Accident and Emergency Nursing, 2003. 11(2): p. 106-111.
8. Sutherland, S.K., Venomous creatures of Australia. A consideration of the animals, their potential lethality to man and mode of action of their toxins. Toxicon, 1983. 21: p. 433.
9. Fernandes, I., H.A. Takehara, and I. Mota, Isolation of IgGT from hyperimmune horse anti-snake venom serum: Its protective ability. Toxicon, 1991. 29(11): p. 1373-1379.
10. Pandey, D.P., et al., A season of snakebite envenomation: presentation patterns, timing of care, anti-venom use, and case fatality rates from a hospital of southcentral Nepal. Journal of Venom Research, 2016. 7: p. 1-9.