Venom

Photography: © Ken Griffiths/Shutterstock

Venom is a secretion produced in specialised glands and delivered through an apparatus, such as fangs, spikes or stingers. Venom is not a single substance but a complex mixture of proteins, peptides, and enzymes, each with a distinct physiological target. These components can disrupt nerve signalling, alter blood clotting, destroy tissue, or immobilise prey within seconds, giving venomous animals a powerful advantage in the wild. Venom is produced by many different animals, such as:

snakes
spiders
scorpions
marine creatures (e.g., blue-ringed octopus, stonefish, lionfish, box jellyfish)
insects (e.g., bees and wasps)
lizards (e.g., gila monster)
mammals (e.g., platypus)

There is a difference between venomous and poisonous. Venomous animals inject toxins into another organism, while poisonous animals deliver toxins only when they are touched or eaten. The distinction is based entirely on the method of delivery, not on how dangerous the toxin is.

Snakes can control how much venom they inject and may sometimes deliver a dry bite, where no venom is released. Venom composition varies not only between species but also among individuals of the same species. For example, two eastern brown snakes can have distinctly different venom profiles. Factors such as diet, age, geography, and environmental pressures influence these differences.

Each snake’s venom serves as its biochemical fingerprint, a unique blend of toxins shaped by its hunting, defence, and survival needs within its environment.

How does venom affect the body?

Venoms contain many different components, and each toxin can affect the body in more than one way. The categories below often overlap, so some venom components may belong to more than one group. This section covers only some toxins and their effects:

Neurotoxins affect the nervous system by disrupting how nerves and muscles communicate. Some stop nerve signals from reaching muscles, while others block the release or action of neurotransmitters like acetylcholine. This can gradually weaken muscles or even cause paralysis. People may have drooping eyelids, trouble speaking or swallowing, and, in severe cases, paralysis of the muscles needed for breathing.

Haemotoxins disrupt the body’s blood and blood-vessel systems. Some activate clotting factors and cause widespread clot formation, which can rapidly consume the body’s supply of clotting factors. Others interfere with platelets or break down clotting proteins. This can lead to uncontrolled bleeding or, in some cases, abnormal clotting. Some toxins also damage small blood vessels, causing blood or plasma to leak into nearby tissues.

Myotoxins harm muscle cells, especially skeletal muscles. They can damage cell membranes or disrupt processes inside the muscle fibres. Severe muscle damage can cause pain, weakness, and muscle breakdown, which is called rhabdomyolysis. When this happens, substances from the damaged muscles can enter the blood and may lead to acute kidney injury.

Cytotoxins can harm or destroy cells by damaging their membranes and other parts. Depending on the venom, this may cause pain, swelling, blisters, and tissue death (necrosis) near the bite. Some cytotoxins can also harm cells in other parts of the body, leading to problems like muscle injury and kidney damage.

Cardiotoxins can affect the heart and other cells. The term originally referred to toxins that harm heart muscle, but research now shows that many cardiotoxins mainly disrupt cell membranes, so their effects are not always limited to the heart and may cause cell damage, muscle injury, and heart or blood vessel problems.

Nephrotoxins can harm the kidneys. Some venom components injure the kidneys directly, while others do so indirectly. Kidney damage can result from several venom effects, such as muscle breakdown, blood clotting problems, destruction of red blood cells, low blood pressure, or direct harm to kidney tissue. Severe envenoming can lead to acute kidney injury.

Proteolytic enzymes break down proteins in tissues and in the structures that support blood vessels. This can cause swelling, blisters, bleeding, and tissue damage. Snake venom metalloproteinases are important examples. They break down parts that support small blood vessels, which can lead to bleeding both near the bite and throughout the body.

Why do snakes bite?

Like humans and other animals, snakes have a strong survival instinct that drives them to protect themselves. They don’t usually bite straight away. Most snakes first try to deter a perceived threat by hissing, rattling leaves with their tail, vibrating a rattle, or shifting into a defensive posture such as raising the front of their body, flattening their neck, or forming an S‑shape. Some species will open their mouths as a warning display and may even make striking motions; not to inject venom, but to scare off the threat so they can escape.

When a snake does bite, it is usually because the threat has continued to approach, or because the snake is attempting to secure prey.

Looking at the image below, it’s easy to imagine how intimidating a human must appear from a snake’s perspective. To a small animal with no arms or legs to defend itself, a person standing overhead looks like a giant. Its only options are to flee or to defend itself.

The best way to avoid an accidental bite is to stay aware of your surroundings, wear appropriate footwear and clothing, and give snakes plenty of space.

Humans look enormous from a snake’s perspective. Most bites happen when the snake feels it has no escape.

Photography: © MEDIAIMAG/Shutterstock

Antivenom

Antivenom is a medicine made from antibodies that neutralise the venom of an animal.

In Australia, there is an established antivenom program involving the Australian Reptile Park and the CSL Seqiris Laboratory. It is the only antivenom program in Australia.

The Australian Reptile Park houses around 200 snakes, which are milked every fortnight. Venom is collected either by encouraging the snake to bite onto a plastic‑topped collection cup, so the venom drips into the vessel, or by gently massaging a small pipette over the snake’s fang to draw the venom directly from the gland. Pipettes are normally only used on species that produce small amounts of venom.

How snake antivenom is made

Snake venom is extracted via a cup or pipette and immediately frozen. Image: © Ali Cobanoglu/Shutterstock

The venom is put into a machine that turns liquid venom into powdered venom crystals. Image: © Ken Griffiths/Shutterstock

The venom crystals are sent to the CSL Seqirus in Melbourne.

The venom is rehydrated and tiny amounts are injected into horses, in increasing doses, over a period of 6-9 months. It does not harm the horses.

centrifuge-and-separated-blood_edited.jp

The horses develop antibodies to the venom. Blood is drawn from the horses and placed into a centrifuge to separate the antibody rich plasma. Image: © Roman Zaiets/Shutterstock

New pages coming soon...

This section is just the beginning.

A new page on the medical applications of snake venom will be added shortly. Visit again soon to learn more.

In the meantime, you can explore individual species profiles to see how each snake’s unique venom has contributed to scientific research and medical discovery.

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