{"id":185,"date":"2019-07-04T15:15:03","date_gmt":"2019-07-04T15:15:03","guid":{"rendered":"https:\/\/randomthoughtsltd.com\/?p=185"},"modified":"2024-04-06T16:27:03","modified_gmt":"2024-04-06T16:27:03","slug":"a-vipers-nest-of-treasures","status":"publish","type":"post","link":"https:\/\/randomthoughtsltd.com\/?p=185","title":{"rendered":"A Viper\u2019s Nest of Treasures"},"content":{"rendered":"\n
First published in the NASGP Newsletter in September 2018 <\/strong><\/em><\/h5>\n\n\n\n
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Since the antihypertensive captopril went on the market in 1981 captopril has probably saved many more lives than have been lost to the venom of pit vipers from which it was derived.<\/h5>\n\n\n\n

I\u2019ve\n watched snake charmers capitalising on our fear of snakes, and I have \nobserved blood trickling for an hour from my leg where a leech had \nfastened itself, but I have only ever seen one venomous snake in the \nwild. Walking along a Cornish beach after a weekend on call, I came \nacross an adder sunning itself on the sand. In Britain the only deaths \nfrom snake bite in the last 40 years have been from exotic pets. But, as\n makers of horror films know, snakes alarm most people, a response which\n may have proved evolutionarily advantageous for our forebears.<\/p>\n\n\n\n

Some creatures are merely poisonous \u2013 passively producing a toxin to \ndefend themselves, for instance, when you tread on them. A venomous \nbeast is one which actively wounds another animal and inserts a toxin \ndesigned to achieve its aim of acquiring a meal. Apparently, we are \nnever far from one. Most phyla in the animal kingdom have venomous \nmembers, even mammals. The slow loris is cuddly-looking, but if you are \ntempted to hug it when it stretches out its arms, be aware a venom gland\n in its elbow produces a nasty allergic reaction.<\/p>\n\n\n\n

Few, if any, animals evolved their venom to attack humans; we are \ncollateral damage in an evolutionary arms race. There are no accurate \nstatistics, but venomous snakes probably kill more than 100,000 people \nevery year and 400,000 undergo amputation. Deaths due to scorpions, \nalready high, are likely to increase now that they have discovered the \nadvantages of city living.<\/p>\n\n\n\n

Few, if any, animals evolved their venom to attack humans; we are collateral damage in an evolutionary arms race.<\/p><\/blockquote><\/figure>\n\n\n\n

The venomous animal overwhelmingly responsible for most deaths is the\n malarial mosquito. But it isn\u2019t just blood feeders that use \nanticoagulants and analgesics. Venoms are a mixture of hundreds of \ncompounds, each of which is tailored to meet the attacker\u2019s objective. \nAdd vasodilators and hyaluronidases and venom will more easily reach its\n target.<\/p>\n\n\n\n

No wonder that man has used venomous animals to his own ends, from \nancient tribes in Iraq who threw pots of scorpions at their enemies to \nradical pastors demonstrating God\u2019s power, and their own, by handling \nrattlesnakes \u2013 until the rattler demonstrates its power by biting them. \nNo wonder that most cultures have traditional remedies \u2013 ineffective and\n some downright dangerous. And modern snake oil salesmen still sell \nprotection and treatment.<\/p>\n\n\n\n

Inevitably rural people in poor countries suffer most, because their \nlifestyle exposes them to venomous animals. Health services are a long \nway off and an appropriate antivenom, even if available, is \nprohibitively expensive. Antivenoms are now on WHO\u2019s list of essential \nmedicines, and, in response to pressure from affected countries, \nenvenoming has been raised to the status of a neglected tropical \ndisease. But however sound WHO\u2019s advice for managing the problem, for \nmany countries implementation is unrealistic.<\/p>\n\n\n\n

To produce an antivenom, you need the venom. There are \nwell-established techniques for milking snakes, but how do you obtain \nvenom from small sea creatures? Then, you have to analyse those hundreds\n of compounds. Then, making the antivenom currently involves injecting \nhorses and collecting the immunoglobulins they produce. Testing the \nantivenom isn\u2019t straightforward either, because what kills a human may \nnot damage other animals. Add the problems of cost and the distribution \nof appropriate antivenoms to areas where venomous snakes abound.<\/p>\n\n\n\n

Making antivenoms isn\u2019t profitable, but venoms are a treasure trove \nfor scientists and, as captopril shows, a potential goldmine for \npharmaceutical companies. Probably more than quarter of a million \nspecies are venomous. Where to start looking? At victims\u2019 sufferings and\n deaths, and at traditional communities\u2019 use of animal toxins. These \ndays traditional knowledge is protected, at least in theory, by \nbiopiracy laws.<\/p>\n\n\n\n

The sodium channel blocker tetrodotoxin has been invaluable in \nresearch on nerve conduction since the 1950s. One source is the \npufferfish, a popular delicacy in Japan where chefs require a licence to\n cook it. (Even so, one professor of physiology declined to taste it.) \nCalcium channel blockers from spider venoms are a tool in cell membrane \nstudies. And kraits have aided neuroscience research as the \n\u03b1-bungarotoxin in their venom binds to nicotinic acetyl choline \nreceptors at the neuromuscular junction.<\/p>\n\n\n\n

More generally, studying how venoms achieve their aims can help us \nunderstand the pathways involved and so design better therapies. And \nmuch might be learned from studying the ingenious devices that animals \nhave evolved to penetrate cuticle, hide or scales to insert venom into \ntheir victims.<\/p>\n\n\n\n

Even when a compound in a venom has been characterised and revealed \npotentially clinically useful properties, there is a long road to \ndevelop a safe and effective medication. But some drugs have made that \njourney. The glucagon agonist exenatide was developed from a chemical in\n the venom of the Gila monster, a New World lizard. Eptifibatide, \nderived from an anticoagulant in the venom of a rattlesnake, and \ntirofiban, from saw-scaled viper venom, are i.v. antiplatelet drugs. \nSome patients with severe chronic pain benefit from intrathecal \nziconotide, developed from cone snail venom.<\/p>\n\n\n\n

There is a lot of interest in exenatide\u2019s neuroprotective effects for\n Parkinsons Disease, cobra venoms for multiple sclerosis, motor neurone \ndisease and cancer, and a sea anemone neurotoxin for psoriasis. Bee \nvenom penetrates the blood-brain barrier so could be a vehicle for \ntherapies. So does chlorotoxin, a paralytic in the venom of the aptly \nnamed deathstalker scorpion, and it shows a preferential attachment to \nglioma cells. With a fluorescent marker attached, it is undergoing phase\n II clinical trials of its potential as a diagnostic aid and a guide for\n the neurosurgeon\u2019s scalpel. And a spider venom constituent which \ninduces priapism could lead to a treatment for erectile dysfunction.<\/p>\n\n\n\n

The tiny emerald cockroach wasp has perhaps the most disturbing modus\n operandi. It turns its much larger cockroach victim into a zombie, \nalive but passive, which can be led by its aggressor to its nest and \nwhere it lays its eggs in its victim to serve as a living larder for its\n larvae. It\u2019s not, I trust, the horror story scenario that fascinates \nscientists, but the zombie state it produces. It resembles encephalitis \nlethargica, so the wasps\u2019 venom might provide shed light on dopamine and\n other pathways which are affected by movement disorders.<\/p>\n\n\n\n

The research is expensive and challenging. Being peptides, most toxins are broken down by digestion, so they need substantial modification before they can be used orally. But, venomous animals are a source of unlimited opportunities for medical development. Like the snake charmer\u2019s cobra they excite our awe and fear. But let us, safe in Britain, not forget those for whom venomous animals are a daily threat. They need antivenoms.<\/p>\n\n\n\n


The Natural History Museum\u2019s website has<\/strong> <\/strong><\/a>information and links about venomous animals.<\/strong><\/p>\n\n\n\n

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First published in the NASGP Newsletter in September 2018 Since the antihypertensive captopril went on the market in 1981 captopril has probably saved many more lives than have been lost to the venom of pit vipers from which it was derived. I\u2019ve watched snake charmers capitalising on our fear of snakes, and I have observed … <\/p>\n

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