Speedy snakes and their venom

04 June 2019

Interview with 

Steven Allain, University of Kent

SNAKE-ON-PAVEMENT

Snake on Pavement

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A lot of dangerous animals have speed on their side and there’s not a moment to lose when it comes to catching prey or defending your patch. And what better way to do so than producing some fast acting venom or poison to survive in the animal kingdom. Steven Allain from the University of Kent and member of the British Herpetological Society joined Katie Haylor in the studio.

Steven - Okay. A herpetologist is somebody who studies reptiles and amphibians. The word is Greek in origin. The root word is herpetós and essentially it means to creep.

Katie -  Okay. So we're talking reptiles and amphibians?

Steven - Reptiles and amphibians; snakes, frogs, lizards, all that sort of stuff.

Katie - Before we get really into this subject, can you just explain the difference between a poison and a venom?

Steven - Certainly. This is a question I get asked a lot and the main difference is that a poison needs to be ingested or it can also be taken through the skin, where a venom has a delivery mechanism such as stinger, a barb, or fangs.

Katie - Talking of poisons and venoms then, what are some of the most fast acting - this is a show about extreme speed - fast acting, most poisonous, venomous animals?

Steven - Some of the fastest are animals such as the box jellyfish which, its venom can act within 2 to 5 minutes of being stung, although not always, that leads to death by cardiovascular collapse. And then you also have dart frogs with a very strong toxin that also acts within a handful of minutes as well.

Katie - So what's going on then in the bodies of the prey in both of those cases, but also in the bodies of the ones inflicting the trouble?

Steven - In the body of the prey or the person or the animal that has been envenomated or poisoned, the main change is that their nervous system is shutting down. The neurons aren't firing, or they're overfiring which then causes issues with the cardiovascular system which shuts down your lungs and your heart, and then you unfortunately die. In the predators or the envenomaters, they are producing toxins in specialised cells or glands. And in the case of the dart frogs, they sequester their poisons through their diet, and so when you take them out of that natural setting - keep them as pets - they're no longer as toxic because they no longer have the specialised beetles or ants where they get these toxins from.

Katie - And we mentioned the box jellyfish. I imagine that probably lives in the sea, right? Where are we talking?

Steven - It does, yes. It lives in the seas around Australia and although they are extremely dangerous there are very few deaths from box jellyfish stings a) because people avoid them, and b) because there are relatively quick emergency response action plans in place to deal with them if they do occur.

Katie - One animal, I guess, may be stereotyped, or people think of when they think of poison is snakes. So how fast are snakes then at envenomating people?

Steven - When it comes to snake venom it can act very fast. Black Mamba venom, it takes about half an hour to act and then after that you're pretty much done for, unless you seek immediate medical attention. Again, it's a neurotoxin so it acts on the nervous system, although other snakes have venoms that can breakdown blood or create clots which have different effects but are more long ranging and also take longer to undertake than shutting down you nerves.

Katie - We're talking about extreme speed in this show and I guess there's the speed at which the venom or the poison gets to work, but there's also that speed at which you're actually causing that damage, right, so how quickly do snakes spring into action?

Steven - A lot of research has been done on this and it doesn't matter whether you're a venomous snake or a nonvenomous snake, all snakes seem to strike around the same speed. And to just put that into perspective, rattlesnakes have been clocked at going 2.9 metres per second which is 6 1/2 mph. It doesn't sound like much, it's just faster than a brisk walk, but in an enclosed space that's pretty fast. It means that in a strike zone, a snake can strike you in about 75 milliseconds, a human blinks in 200 milliseconds, so they can strike you almost 3 times in the time it takes you to blink.

Katie - So why do snakes need a) so much venom, and b) to be able to get it in someone so fast? What's the point?

Steven - You have to think that a lot of species feed on fast moving prey, particularly quite small prey and the amount of venom and the strike speed has all evolved to be able to immobilise that prey immediately, or extremely quickly so it doesn't wander off and die hundreds of metres away from where the snake is. So it can just get its item of food and disappear off in the undergrowth away from the risk of predation or being exposed to the elements.

Katie - This is pretty extreme stuff we're talking about, what are the chances of survival then? For instance, for human beings, what do you do if you're in this very unfortunate situation?

Steven - If you do suffer a snakebite and you are envenomated by a venomous snake it is imperative that you seek medical attention immediately, and it's also important that you identify which species of snake that envenomated you. There are antivenoms which can counteract the venom of a number of species and these are found particularly in areas such as India where you have a number of species that are highly venomous. But in other countries there's only one or two species where you could come across a snake that may cause damage and so you have more specific antivenom to that one species.

Katie - How do you actually make an antivenom, because you need to understand the venom, the way the chemistry and biology is working? Does that mean you have to extract some out of the incredibly dangerous animal?

Steven - It does, yes. You have to take a lot of safety precautions when it comes to handling venomous animals obviously. And depending on whether you’re working with a snake or a spider there are different procedures to extract that venom. And in terms of creating the antivenom, traditionally sheep or horses are used. Because they are quite large, you can inject quite a lot of venom in them and it doesn't really have any negative effects apart from shortening the lifespan, unfortunately, and then you extract the antibody that's produced from the blood and that goes into the anti-venom.

Katie - And finally, how far away are we from a 'catch all' antivenom then? Is it possible to make something that you could give to someone who had got any particular venom or, indeed, poison?

Steven - At the moment that is impossible, no. Although the World Health Organisation is pumping money into that problem as we speak. They've just announced global snakebite is a neglected tropical disease and they're trying to fund a universal antivenom for anybody around the world by any snake species to be able to treat that by using HIV antibody technology. At the moment is still in its infancy, but it does show some promise for the future.

Katie - So we should be watching this space then?

Steven - We should definitely be watching this space, yes.

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