By: Lena Wang
Picture this: You’re a biologist adventuring into a dense tropical rainforest with a team of scientists. The sun shines through the foliage of the great jungle trees and the beautiful calls of tropical birds sound as the wind blows through the leaves. Suddenly, you hear a hiss and feel a sharp pain on the back of your leg! You were bitten by a venomous snake! You feel the adrenaline coursing through your body as you begin to panic. But have no fear! One of your companions is a toxicologist who specialises in snake venoms!
What is toxicology? Toxicology is a field of science that studies the harmful effects that substances can have on humans and other organisms (1). Venoms are one area of study, but toxicology also considers other toxins–even manmade ones, such as phthalates and pesticides! In order to determine toxicity, toxicologists analyse the actual effects of toxins on the body, in addition to the scale of the impact of specific doses in order to design appropriate treatment plans (2). Your toxicologist colleague tells you that the very snake that bit you will save you. What a paradoxical thing to say!
In this scenario, your colleague needs to identify which of the three types of snake venoms is in your body. However, we should first make the distinction that all venoms have proteolytic effects. This means that the toxins have properties that break down proteins at the initial bite site. These proteins initiate the breakdown of structural components of tissues… so expect some pain (2)!
Snake venom types
Cytotoxic venoms
The root word of cytotoxic is “cyto-”, meaning cell. As you’d expect, these types of venoms act by damaging or destroying body cells (2). This is a very generalised classification that can be made more specific based on the type of cells that are being damaged. For example, myotoxins (“myo-” relates to muscles) damage skeletal muscle fibers and cardiotoxins (“cardio-” relates to the heart) specifically affect cardiac muscle. Generally, these venoms cause apoptosis (cell death) and necrosis (tissue death). Cytotoxins are highly prevalent in most toxin families in general, and are common in the venoms of snakes such as cobras and vipers (3).
Hemotoxic venoms
Hemotoxic (“hemo-” relating to blood) venoms have significant impacts on the cardiovascular system, specifically hemostasis–the stabilisation of blood flow and bleeding. These venoms can cause drastic changes in blood pressure, systemic hemorrhage (blood loss), blood cell death, and issues with normal blood clotting mechanisms (4). Hemotoxicity is commonly associated with vipers, but also includes many species in the Elapoidea superfamily of snakes (3).
Neurotoxic venoms
Neurotoxic (“neuro-” relating to the nervous system) venoms interfere with normal nerve signalling and neuromuscular function (5). By interfering with the binding of neurotransmitters, these venoms can cause paralysis in victims through uncontrollable, repeated stimulation (as seen through muscle tightness and spasms), lack of stimulation (characterized by muscle weakness and inability to contract), or even from physical nerve degradation. These neurotoxins are notorious in sea snakes, but are also present in kraits, mambas, and vipers (3).
The toxicologist recalls the snake species that are native to this jungle and compares them to the characteristics of the one that bit you. After identifying the snake and its venom type, your friend administers an antivenom, which counteracts the effects of that venom (6). You breathe a sigh of relief. You’re safe for now, but as a scientist yourself, you can’t help but wonder: how was this lifesaving antivenom made?
Venom is first harvested through snake milking–a process as glamorous and as dangerous as it sounds. Snakes are positioned to bite down on a jar, forcing venom to drip from their fangs and be collected in a container (7). The harvested venom is regularly injected into animals such as horses and sheep, with doses gradually increasing as the animal builds tolerance through antibody production (6). These specialized proteins are part of the immune system (8), and can neutralize the toxin by simply changing its chemical structure (9)! With high levels of antibodies in circulation, the animal blood is then harvested and purified to produce antivenoms that can improve toxic symptoms in just hours (7)! Though they’re not a stand-alone solution–you’ll likely need more doses and continuous medical monitoring. In the meantime, let’s appreciate these slithering creatures… even if they’re just solving a problem they created in the first place.
References
Toxicology [Internet]. National Institute of Environmental Health Sciences. [cited 2022 Feb 22]. Available from: https://www.niehs.nih.gov/health/topics/science/toxicology/index.cfm
S S. The 3 Types of Snake Venom (Explained) [Internet]. Wildlife Informer. 2020 [cited 2022 Feb 22]. Available from: https://wildlifeinformer.com/types-of-snake-venom/
Toxin Pathologies [Internet]. The University of Melbourne. 2020 [cited 2022 Feb 22]. Available from: https://biomedicalsciences.unimelb.edu.au/departments/department-of-biochemistry-and-pharmacology/engage/avru/blog/toxin-pathologies
Slagboom J, Kool J, Harrison RA, Casewell NR. Haemotoxic snake venoms: their functional activity, impact on snakebite victims and pharmaceutical promise. Br J Haematol. 2017 Jun;177(6):947–59.
The Amazing Science Behind Fatal Snake Bites [Internet]. BBC News. 2015 [cited 2022 Feb 22]. Available from: https://www.bbc.com/news/health-34214029.
Watt A. What is Antivenom? [Internet]. School of Biomedical Sciences. 2019 [cited 2022 Feb 22]. Available from: https://biomedicalsciences.unimelb.edu.au/departments/department-of-biochemistry-and-pharmacology/engage/avru/discover/what-is-antivenom.
Wade L. Here’s How You Milk Snakes to Make Antivenom [Internet]. Wired. 2014 [cited 2022 Feb 22]. Available from: https://www.wired.com/2014/11/how-to-make-antivenum/.
Ghose T. What are antibodies? [Internet]. Live Science. 2020 [cited 2022 Mar 7]. Available from: https://www.livescience.com/antibodies.html.
Antibody [Internet]. Britannica. 2021 [cited 2022 Mar 7]. Available from: https://www.britannica.com/science/antibody.
Eyelash Viper [Internet]. Animalia. [cited 2022 Mar 8]. Available from: https://animalia.bio/eyelash-viper. Image 1.
Cobra [Internet]. San Diego Zoo Animals & Plants. [cited 2022 Mar 8]. Available from: https://animals.sandiegozoo.org/animals/cobra. Image 1.
Atractaspis congica. In: Wikipedia [Internet]. 2022 [cited 2022 Mar 8]. Available from: https://en.wikipedia.org/w/index.php?title=Atractaspis_congica&oldid=1069023686
Frisky & highly venomous sea snakes mistake divers for their mates [Internet]. NBC2 News. 2021 [cited 2022 Mar 8]. Available from: https://nbc-2.com/news/weird/2021/08/24/frisky-highly-venomous-sea-snakes-mistake-divers-for-their-mates/. Image 1.
Adventures Of A Snake Milker: This Herd Has Fangs [Internet]. NPR. 2010 [cited 2022 Mar 8]. Available from: https://www.npr.org/templates/story/story.php?storyId=125036229. Image 3, Ken Darnell milks snakes in his Gordon, Ala., lab.