August 20, 2012


As most participants on an EcoTraining course are taught, poison is inGESted and venom inJECted. This is just one of a plethora of facts that get shared and imparted by the highly trained and experienced instructors at all our different wilderness camps. We also make use of experts in their respective fields to divulge the finer details of their field of expertise.

Like Johan Marais of Reptile Ventures and also author of A Complete Guide to Snakes of Southern Africa.

He clears up the confusion around envenomation and venom types in snakes:

The majority of snakes have full control over their venom glands and can therefor regulate the amount of venom injected when biting. There are exceptions – snakes like the boomslang and vine snake have Duvernoid’s glands and have little control over these glands. In such instances the amount of venom injected depends largely on the amount of pressure applied to the glands when the snake bites. For this reason these snakes chew on their prey once caught so that they can inject as much venom as possible.

But back to snakes like mambas, cobras and adders that have control over their venom glands – these snakes can bite and inject no venom whatsoever. We refer to such bites as “dry” bites.

Otherwise there could be mild envenomation, also referred to as a warning bite, during which enough venom is injected to cause some symptoms but not enough to be life-threatening. This is also quite common and of people hospitalised after a bite from a potentially deadly snake, only about 20% of them require anti-venom.

Lastly there is severe envenomation when a snake injects far more venom than what is required to kill a human. These cases are very serious and victims need to be hospitalised for treatment urgently.

Snake venoms are complex in their structure and we generally talk of neurotoxic, cytotoxic and hemotoxic venoms. But some venom may combine some or all of these toxins while others may also contain other toxins, including myotoxins, cardio toxins, etc.

The neurotoxic venom affects the nervous system, causing drowsiness, vomiting, slurred speech and difficulty in swallowing and breathing. Swelling is usually minimal and victims have little pain. Most cobras (except the spitting cobras) and the mambas have neurotoxic venom.

Cytotoxic venom causes immediate burning pain, swelling and local necrosis that may require skin grafts or even lead to amputation. The puff adder, Gabon adder, rinkhals, Mozambique spitting cobra and the stiletto snake have predominantly cytotoxic venom.

Both the boomslang and vine snake have potent hemotoxic venom that affects the blood clotting mechanism, causing oozing from the fang punctures, severe headaches and eventually (in untreated cases), severe internal bleeding. Hemotoxic venom is quite slow in acting, allowing most victims enough time to get to medical care.

With regards to snake bite, always bear in mind that over 98% of snake bite victims that are hospitalised survive the ordeal.

(Thank you Johan Marais for this important information!)
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