World's deadliest snakes and how more victims could be saved
Thursday 16 May 2019 21:39, UK
An incredible 138,000 people die every year from snake bites - and scientists say this is the world's biggest hidden health crisis.
Yet, unless you live in a part of the world with venomous snakes, you may not have all the facts.
Here, biology professor William Hayes - who has been bitten by a snake himself - explains why many snake bite deaths could be avoided.
Is every bite fatal?
"Snakes can kill," said Prof Hayes, of Loma Linda University in California.
"The severity of the bite depends on how much venom is injected, the composition of the venom, size of the patient.
"Smaller patients are more vulnerable. They could kill you quickly, but usually you have ample time to get to a hospital and get the antivenom. But it doesn't always work out that way."
Prof Hayes said he was bitten by a baby rattle snake with a single fang and not enough venom to require antivenom.
"It hurt like a son of a gun," he added. "Not a pleasant experience."
What is antivenom?
Antivenom is comprised of antibodies to a particular species of snakes. It's made by injecting the venom of the species of interest into horses or sheep.
The animal makes a tonne of antibodies (proteins) that float in the blood. Those antibodies will bind the toxins in the venom and neutralise them. It's the best treatment we have.
What are the risks in developed countries?
Professor Hayes studies the behaviour, ecology and toxicology of venomous snakes. He says that in better developed countries, where good antivenom is available, the biggest risk is not so much death, but serious tissue injury or even organ failure.
"You could lose a finger or perhaps the function of your hands or even your kidneys," he said.
Developed countries have excellent supplies of antivenom. For instance, Prof Hayes explains that in the US there may be about 6,000 bites a year but only six deaths.
In less developed countries, the number of bites could be higher - but the rate of deaths will be much higher.
"Statistics can be very ugly," he told Sky News.
Why isn't there more research?
"The big problem we face is that in large portions of the world - underdeveloped countries - there's not a good market for making money, Prof Hayes said.
"A lot of people are dying simply for want of any antivenom."
Developed countries have excellent supplies of antivenom but politics gets in the way of the bidding, according to Prof Hayes.
"Manufacturers are in it for the money," he said.
"Unless there is a substantial social justice drive to improve the situation, we are stuck with that."
Do we really need more antivenoms?
Those currently in use have their limits. They are expensive to make, there are limitations around storage and they only last so long before losing their efficacy.
They also have to be given intravenously, so administration isn't easy.
But as snakebites are designated as a neglected tropical disease, that facilitates funding.
"We have more than 100,000 deaths a year probably and two million cases of envenomation with substantial morbidity beyond the mortality," Prof Hayes said.
"Things are moving in the right direction but not adequately. Anything we can do to reduce that number (100,000) is terrific. It's not just the mortality, it's the very debilitating, long-term injuries that are just as bad or worse than the deaths."
Prof Hayes said that the vast majority of deaths are down to the lack of antivenom available.
He said: "If a farmer has a severe injury to his leg and can't walk comfortably or to his hand and he can't work the fields, that could be the family's livelihood.
"He may survive the bite but be unable to earn a living for his family. There may be over a million who suffer severe morbidity."
He added: "Sometimes (antivenom) is there in the country but not in the local clinic and so you can't get it to the patients."
Are there any alternatives and how are they developed?
Yes. They are known as protease inhibitors and aptamers and researchers are exploring how they can be used.
When making the antibody production, neither the snakes nor the horses or sheep that are used to generate the antibodies are harmed, Prof Hayes said.
"Unfortunately, the antivenom testing involves mice and rats and we would like to see alternatives to spare those animals from being killed," he added.
Nanomolecules are being looked at to see if they could help and there is a protein in the blood of possums, which is being researched.
There are some species of snakes with potent venom for which there is no available antivenom, many of them in developing countries.
You could use an antivenom against snake poison with similarities to snakes in other parts of the world - but while you'd get some protection, it would take research to determine how effective it could be.
"That's where the funding could be very helpful," the professor said.
Most dangerous: Which snakes should you be scared of?
Deaths from snake bites take place mostly in rural Africa, Asia and South America.
The saw-scaled viper probably causes more deaths than anything else because of its wide distribution and very toxic venom.
:: Africa - a variety of cobras, several types of mambas and some large vipers, like the gaboon viper
:: Asia - a lot of particularly dangerous cobras and kraits
:: South America - primarily has large vipers like the bushmaster
:: Australia - has the elapidae family of snakes, which includes the taipan, brown snake and tiger snake
There is also another major family of venomous snakes called viperidae.
"There's bad stuff there," said Prof Hayes.