A universal antidote for deadly snake bites could be on the horizon after a breakthrough by British scientists.
It could enable doctors to treat symptoms without having to know the individual species that sank its fangs into a victim.
The World Health Organisation has added ‘snakebite’ to its list of neglected tropical diseases.
Now venom specialists at the Liverpool School of Tropical Medicine have shown it is possible to treat the bite from one snake with antivenom produced from a completely different species.
In particular, they identified an antivenom produced from the saw-scaled viper, one of south Asia’s most dangerous snakes.
It worked in lab experiments on blood and mice following poisoning with a potentially lethal dose of venom from the very distantly related snake, the boomslang.
First author Dr Stuart Ainsworth said: “This work is extremely exciting and we hope provides a basis for looking at antivenom in a new way.
Traditionally, when producing a polyspecific antivenom that could treat the bite of many different snakes, we have done so from a geographical standpoint.
However, we have now shown that it may indeed be of more benefit to look at the specific pathology caused, allowing clinicians an opportunity to treat the symptoms they see without having knowledge of the exact species of snake involved.”
Snake venom is a white or yellow-coloured liquid which is produced in glands behind the snake’s eyes and is pumped down a duct to the fangs when it bites down on something or someone.
The fangs acts like a hypodermic needle, injecting the venom quickly and efficiently into the unsuspecting victim.
Snakes with fangs at the front of their mouths are most dangerous – such as the cobra, puff adder, viper, rattlesnake and mamba, for example.
Antivenoms are usually only effective against bites from the species of snake providing the venom for its manufacture. Historically, they are also made with the venoms of snakes from a single region.
This means there is a need for many different antivenoms across the different parts of the world.
Rather than looking at the problem geographically, the team instead decided to focus on the symptoms caused by a large number of different venoms.
These fall broadly into four categories that either attack the circulatory system, in other words the blood, or the nervous system.
They include coagulopathy, or abnormal blood clotting, haemorrhaging, neurotoxicity which damages the nervous system causing paralysis, and cytotoxicity, where the bite kills cells and destroys tissue.
The team whose findings are published in Communications Biology discovered some antivenoms could prevent the clotting nature of certain venoms from snakes which they were not manufactured from.
The hope is now to progress this research further, to demonstrate if this benefit can be extended to other venoms containing toxins causing similar pathologies.
Senior author Dr Nick Casewell said: “Each geographic area has huge diversity in the types of venomous snakes that cause different pathologies.
Demonstrating here the feasibility of designing antivenoms that target specific pathologies, rather than focusing on a specific region of the world, should enable the development of a suite of pathology specific antivenoms that could be used globally in a modular manner across the world.
This approach should also offer antivenom manufacturers with economies of scale to make snakebite treatments more affordable for the impoverished victims of the tropics who suffer the greatest burden of snakebite.”
The current production of antivenom is very costly and treatment for snakebites can be completely unaffordable to victims who, particularly in the low and middle-income countries, are often disadvantaged subsistence farmers and their families.
Snakes get closer to humans and cause more damage and more deaths than any other venomous animal, including spiders, scorpions and jellyfish.
That’s because venomous snakes are found across large swathes of the planet, typically in rural, tropical areas, like sub-Saharan Africa and south-east Asia. But they also live in Australia and North America.
Added Dr Casewell: “It is about tackling this neglected medical problem with solutions that can make a real difference.
For example, we are also exploring the potential of enzyme inhibitors as inexpensive alternatives to the antibodies currently used in antivenoms.
We hope our work, along with that of our collaborators, could provide a solution which makes a real difference to those individuals living in some of the world’s poorest communities.”
Snake venom is made up of several hundred proteins which all have a slightly different toxic effect on the human body.
Each year, up to five million people worldwide are estimated to be bitten by snakes, with 400,000 left disabled or disfigured by their injuries, on top of those who die.
Anti-venoms are life-saving antidotes made by extracting venom from snakes then injecting it diluted into sheep or horses, which build up antibodies against it. These antibodies are then separated from the animal’s blood.
But those proven to be safe and effective are rare – and few people can afford them.
There are plenty of myths about how to deal with being bitten by a snake. There is no evidence sucking out venom from a snakebite with the mouth or using any other suction device helps.
In fact, experts say it could hasten the venom’s passage into the bloodstream.
Cutting out the venom is not recommended either because it could make the wound much worse.