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Friday, May 14, 2021

What lies in the serpent’s arsenal

Snake venom can stun, shock, kill, or even cure you

Written by Ranjit Lal |
April 25, 2021 6:30:34 am
Scientists and biologists have for long been hugely excited and intrigued by snake venom and there are many questions they are still grappling with.

Most people are petrified of snakes — with good reason. Over aeons, snakes have built up a reputation of being venomous and lethal. Apparently, even Cleopatra used the famous asp to end her life. In reality, of course, snakes are more petrified of us than the other way around and would rather wriggle away from us as fast as they can. Unless you’re a rat, it’s simply not worth their while to waste expensive venom on us, because they can’t eat us afterwards. So, if they do bite, it’s out of self-defence.

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They account for over 100,000 global deaths annually, of which about half occur in India. Our instinctive reaction on seeing a snake is to kill it or have it killed, though these days, this attitude appears to be changing. More of us are now calling up professional snake catchers to have them removed. Which is good because of the over 3,000 species worldwide, only 450 can do us damage.

Venom itself is just highly modified saliva and evolved in scaled reptiles (snakes, lizards, iguanas) around 170 million years ago. It’s a cocktail of over 20 proteins and enzymes and other substances that specialise in immobilising (and killing) and digesting prey (even we have digestive enzymes in our saliva — note the way a slice of bread dissolves in your mouth if kept there for a little while). Stored in large salivary glands, behind the eyes and on either side of the face, the venom is delivered via hypodermic-like fangs, squirted out and injected into the victim, when the reptile strikes.

Different species have different modus operandi: many (like the Russell’s viper) strike lightning fast and retreat, waiting for the venom to immobilise the victim. Others bite and cling on bulldog-like, because their digestive enzymes get to work immediately. Notorious serpents like Africa’s famed spitting cobras can even spray their venom up to eight or nine feet, usually aiming for the eyes of the enemy. This, however, is purely an act of self-defence, to buy time to escape.

Venom affects in various ways. All of them extremely unpleasant, some excruciatingly painful and snakes may specialise in which particular lethal cocktail they concoct. Neurotoxins are favoured by king cobras, other cobras, mambas and others, and attack and dismantle the nervous system, blocking the brain from sending signals to the body. You get disoriented, drowsy and may find it difficult to breathe, until your heart stops (if not treated). As with most snake bites, the shock of being bitten is enough to kill you.

The vipers, including Russell’s viper, specialise in venom that messes with the blood. These are called, haemotoxins. There are two awful outcomes: either your blood coagulates and clots, or, it thins, leading to haemorrhage. You bleed not only from the bite site but every bodily orifice, besides feeling nauseous, and disoriented. Africa’s boomslang favours this kind of weaponry.

Cytotoxic venom destroys and basically eats flesh, starting at the site of the bite and spreading through the body. Naturally, the pain from such a bite is excruciating as tissue and even bone are eaten through; the shock from the pain is often enough to be fatal. Puff adders, Gaboon vipers and spitting cobras have this in their arsenals.

Scientists and biologists have for long been hugely excited and intrigued by snake venom and there are many questions they are still grappling with. Are some snakes immune to their own venom or the venom of other snakes? The king cobra is a serial cannibal — eating only other snakes and doesn’t seem to come to harm doing so. Some birds, too, specialise in a diet of snakes and are seemingly unaffected by the venom.

Another great area of research is in the medical field. Already, the venom of snakes such as some vipers is being used in the treatment of cancer as well as in developing drugs to control blood clotting, bleeding and blood pressure. Antidotes for the venom of several species have been developed, saving thousands of lives.

In India, the feared “big four” are the cobra, the Russell’s viper, the saw-scaled viper and the common krait. Cobras, frequently encountered in paddy fields, rear up, flare their hoods, and give fair warning. The Russell’s viper is, perhaps, the most dangerous, especially when threatened, and accounts for most snake-bite deaths. The saw-scaled viper is equally deadly but stays in dry, desert landscapes. And, the common krait slides into your home, kisses you in sleep and, soon, you stop breathing!

But more deadly than all the above, is the venom being spewed out by us — every single day — on social media and the television talk shows all around the world. For which, alas, as yet, there seems to be no antidote.

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