What makes snakes terrifying is the ability of some to kill by injecting venom. The only known antidote is anti-venom serum, which is made by using venom. For centuries, man has recognised that the snake's deadly cocktail of toxins and enzymes may also contain a range of medications. Most modern therapeutic products developed from venom are used to treat diseases affecting the nervous system, the cardiovascular system and blood, the very systems that venom targets to kill prey.
Many drugs, such as captopril (treats hypertension and congenitive heart failure) from the venom of a South American pit viper called Jararaca, eptifibatide (for a blood disorder) from the Pygmy Rattlesnake of the U.S. and ancrod (treats stroke patients) from the Malayan Pit Viper, are already on the market. Last month, another drug ximelagatran, derived from cobra venom, was launched to prevent stroke and treat people undergoing orthopaedic surgery. A protein isolated from the Gila Monster's toxic saliva is now being prescribed to combat Type 2 Diabetes.
In early December, I attended the First National Conference on Animal, Microbial, Plant Toxins and Snakebite Management in Kolkata, and was amazed by venom's range of medical possibilities. A variety of animals, from caterpillars, wasps and cone snails, to snakes, toads and jellyfish, produces venom. (Venom is animal-based while poison is plant-based. Calling snakes “poisonous” is like calling plants “venomous”!)
Perhaps, the most unlikely death-dealing creature is the Lonomia caterpillar. In 1989, an epidemic of envenoming took place in Brazil. This caterpillar bunches together in groups and brushing against them can set off serious consequences. One case history illustrated at the conference was of a young Canadian tourist who stepped on five caterpillars in Peru. The initial symptoms seemed minor, but she died of multiple-organ failure a few days later. The venom is known to cause internal haemorrhaging, renal failure and haemolysis (rupturing of the red blood cells). Amazingly, there is an anti-venom being made by Instituto Butantan in Brazil.
Glenn King's research on one of the world's four deadliest spiders, the Funnel Web in Australia, may lead to a natural insecticide that is capable of affecting even DDT-immune mosquitoes and pesticide-resistant cotton bollworms. After all, spiders have been in the business of successful insect assassinations for millions of years longer than humans!
Manjunatha Kini's lab at the National University of Singapore has been working on king cobra venom, and some truly miraculous compounds have been discovered. One is the only natural occurring toxin to lower heart rate and blood pressure: -cardiotoxin. The team also discovered haditoxin, an extraordinary painkiller that is 200 times more powerful than morphine. The synthesised peptide can be taken orally, and it is non-addictive, unlike morphine. Elements in cone snail and an Israeli scorpion venom have similar painkillers.
For years, Bill Haast, Rom's former boss, had been promoting the use of snake venom in treating multiple sclerosis. In the absence of clinical trials, the U.S. Food and Drug Administration was having none of it. A few years ago, a patient with multiple sclerosis experienced several months' relief from her debilitating symptoms after being stung by a scorpion. Researchers in America who read about this case investigated further, and have identified a toxin produced by sea anemones that can be used to treat autoimmune disorders. But, this is still several hoops away from being on the market.
Perhaps the ancient Greeks had a premonition of all these wonderful drugs to come when they designed the Rod of Asclepius. Today the motif of a serpent coiled around a staff is the insignia of most medical organisations around the world. Some, however, suggest that it better illustrates the act of a physician pulling out a guinea worm from under the skin of a patient. But, that is another story.
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