Above: Image © OldGreyMan, iStockphoto.com

Are you afraid of snakes? Real snakes aren’t as frightening as the ones in the movie Snakes on a Plane. But venomous snakes can be very dangerous. About 600 of the approximately 3000 snake species in the world are venomous. These snakes are not only dangerous, but also interesting. This is because their venom holds clues to medical discoveries that can save human lives. 

How venom works

Snakes mainly use venom to subdue their prey, but they sometimes also use venom to defend themselves. Snake venom is produced in the back of the snake's head in the salivary glands (the parts of the head where saliva is made). To deliver venom, snakes have hollow fangs that act like hypodermic needles. When a snake bites, muscles in its head squeeze the venom glands. This pushes the liquid through the fangs and into the flesh of the prey.

The exact “recipe” for snake venom varies from one species to the next. Sometimes, it can even be different for snakes of the same species that live in different locations.

Once the toxins are injected, they can work in several ways. How the toxins work depends on the type of snake. Different toxins target the nervous system (neurotoxins), the blood (haemotoxins), or muscles (myotoxins). Neurotoxins prevent neurons in the brain from transmitting signals. This causes paralysis. Haemotoxins can cause red blood cells to burst, cause blood to clot, or severely lower blood pressure. Myotoxins cause tissue death (necrosis) in muscles and prevent muscle contraction.

Did you know? The longest venomous snake in the world is the king cobra, which can grow to over 4 metres long! It rarely bites, and its venom is not as toxic as that of most other cobras.

Treating human victims

Every year, between 421,000 and 1.84 million people worldwide are bitten by venomous snakes. And between 20,000 and 94,000 of those people die after being envenomated (injected with venom). Most incidents occur in Asia and Africa. Why? Because these places have lots of venomous snake species, long distances between hospitals, and large numbers of agricultural workers who come in contact with snakes.

To treat snake envenomations, medical researchers have developed antivenoms. Antivenoms contain antibodies that neutralize the dangerous proteins in venom. To develop an antivenom, a host animal (usually a horse) is injected with larger and larger amounts of venom. Eventually, the horse’s body generates an immune response. This is when the horse’s immune system causes plasma cells to produce antibodies (proteins). These antibodies defend the body by attaching to the harmful proteins in the venom. The antibodies are then extracted from the host animal’s body, processed, and purified so they can be given to snakebite victims.

Different kinds of antivenom are usually specific to a single snake species or a group of related species. They can also be very expensive, especially in the United States, where patients can be charged thousands or even tens of thousands of dollars for a single vial! Most snakebites need to be treated with multiple vials.

Helpful venom

Although the toxins in snake venom can hurt humans, they can also be used as medicine. As you know, many compounds in snake venom affect systems that control blood pressure and blood clotting. These compounds can be used to develop new drugs to treat illnesses. In fact, the proteins in snake venom have been used to treat many conditions including cancer, pain, high blood pressure, heart attacks, strokes, Alzheimer's disease, and Parkinson’s disease. The venom of other animals, such as spiders and scorpions, has also been used to develop important drug treatments.

A lot of time, effort and money is required to develop new drugs from snake venom. To develop these drugs, proteins in snake venom are purified. This process helps scientists identify compounds with useful medical applications, such as the ability to block pain receptors. Next, scientists try to develop a synthetic version of the compound. They then test the compound in small doses on animals. Finally, scientists create a version of the drug for humans. They test it, then put it on the market once they’re sure it’s safe.

Did you know? Poison refers to toxins ingested, inhaled, or absorbed by touch, such as from the skin of a poison dart frog. Venom refers to toxins injected into the body, such as by a snake’s fangs.

* * *

Snake venom is a very powerful tool for snakes to subdue their prey, but also for doctors to treat illnesses and snake bites. The development of new antivenoms will hopefully decrease the number of people who die from snake bites. And the discovery of next-generation drugs to combat heart attacks, strokes, and even cancer may rely on hidden secrets contained in snake venom.

This article was updated by Let's Talk Science staff on 2016-06-22 to improve readability by reducing the reading grade level.

Learn more!

Websites with general information on venomous snakes found in Canada and the United States:

Frequently Asked Questions About Venomous Snakes (2012)
Steve A. Johnson, University of Florida

Snakes of Canada
Maria Macrae, Canadian Wildlife Federation

Fast Facts: Prairie rattlesnake
Canadian Geographic

Scientific article and public health website with information on antivenom:

Snake Antivenoms: Antivenoms (2003)
D. G. Lalloo & R. D. G. Theakston, Journal of Toxicology: Clinical Toxicology 41
Link to abstract. Registration or subscription required to view full text.

Snake Antivenom Immunoglobulins
World Health Organization

News articles and scientific article on the medical importance of snake venom:

The Bite That Heals (2013)
Jennifer S. Holland, National Geographic

V is for Venomous Snake (2015)
University of Cambridge

Venomous Cures (2008)
PBS Nature

Snake venom components and their applications in biomedicine (2006)
D. C. I. Koh, A. Armugam & K. Jeyaseelan, Cellular and Molecular Life Sciences 63
Link to abstract. Registration or subscription required to view full text.

James Paterson

I am a PhD student at the University of Ottawa studying lizard ecology in southern Arizona. I did my undergraduate degree in Zoology at the University of Guelph and then moved on to a Master's degree at Laurentian University studying turtles in Algonquin Park. Before starting my PhD I worked for Ontario Nature on reptiles, amphibians and citizen science where I got to combine my love of conservation biology with science outreach. When not working, I love to camp, canoe, hike, bird-watch and explore natural areas.

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