13-07-2025
Snakebites kill 130,000 people a year. This UK lab may have the answer
The snake was clearly unhappy. The terciopelo — a species known in its native Latin America as 'the ultimate pit viper' for its aggression and the potency of its venom — darted across the floor of the lab, the tip of its tail rattling as it looked for someone to take out its anger on.
'This one is a big mean old girl,' said Edd Crittenden, a senior animal technician at Liverpool School of Tropical Medicine's Centre for Snakebite Research and Interventions, as he prepared to trap her to extract her venom. 'She has quite an attitude — she doesn't like us some days.'
A bite from this angry snake — 5ft long, with vivid yellow and black markings — has the potential to trigger internal bleeding and cause tissue to wither and die. If untreated, it can be fatal. More than two million people are bitten by venomous snakes around the world each year, and as many as 138,000 die as a result.
The 25 researchers working at the Liverpool snakebite centre, which holds one of the largest collections of tropical venomous snakes in Europe, is aiming to develop new treatments. And they are close to a breakthrough.
Next summer they will start trialling two pills for snakebite victims in Ghana and Brazil. The new approach could have a radical impact on snakebite mortality.
Currently the only treatment for a bite from a venomous snake is an antivenom — a medicine produced by extracting antibodies from the blood of sheep or horses that have been repeatedly dosed with snake venom. But that approach, which dates to the 19th century, is riddled with problems.
'Snake venoms vary from one species to the next,' said Nick Casewell, director of the centre. 'Each antivenom works only against certain snakes, and some of them are actually very poor. Even if they work, they have to be given in a major hospital, because they are given intravenously, via a drip, and people often have adverse reactions to them, so you want to be able to carefully monitor them. But in rural Africa or Asia or the Amazon rainforest, those kinds of facilities are often many hours or even days away.
'So what we're trying to do is develop an oral medication that can be given in the community soon after a bite. It doesn't need to be stored in a fridge like antivenom. And it can be given by anyone: you don't need any specialist training to give a pill.'
Eventually, tourists may be able to carry the pills if travelling in risky areas. Even in Britain, where snakes are often kept as pets, dangerous snakebites occur. Some 300 people, 72 of them children, were bitten by exotic snakes between 2009 and 2020, according to reports to the UK National Poisons Information Service. Antivenom was given in 17 cases, and one person died.
Deaths from native British snakes are far rarer — the last recorded death from an adder was in 1975.
Casewell's team has already carried out a phase 1 trial of one new snakebite treatment, a pill called unithiol, showing that it was safe on healthy patients in Kenya. Next year they will start a phase 2 trial on patients who have been bitten by snakes, alongside another treatment called marimastat. About 200 people will take part in the trial across Ghana and Brazil.
Both medicines were initially developed for other purposes — unithiol to treat poisoning from mercury, arsenic and lead, and marimastat to treat cancer.
They both work by reducing the impact of metalloproteinases — a type of enzyme which is active in metal poisoning, some forms of cancer and also, the team discovered, in snake venom.
'We realised these are a really important component,' said Casewell. 'Terciopelo, the Malayan pit viper, saw-scaled vipers, Russell's viper — they all have a lot of metalloproteinases in their venom. Our drugs are targeting that toxin family.'
He added: 'Our long-term vision is that we would have one pill to deal with some of the toxins and another to deal with some other toxins. And then it doesn't matter so much which snake you're being bitten by, you should be able to delay pathology. We're hoping those drugs will at the very least reduce the severity of envenoming, and buy that patient a lot more time to get secondary treatment.'
David Lalloo, vice-chancellor of the Liverpool School of Tropical Medicine and a world-leading snakebite expert, said: 'Oral treatments would be a game changer — there's no doubt at all.'
But he said a deeper problem is that snakebites have been ignored as a medical problem. 'The response globally has not been anywhere near as extensive or urgent as it needs to be.' As co-chair of a new Global Snakebite Taskforce, a group of doctors, scientists and world leaders formed at the World Health Assembly in Geneva in May, he is trying to raise political awareness and investment.
Until then, the researchers in Liverpool need more venom to test — which is why Crittenden was in the lab trying to trap the angry terciopelo. He had already extracted the venom from a pair of Malayan pit vipers and then a Mozambique spitting cobra — for which he wore a face shield, for fear of its 10ft spitting range.
The furious terciopelo posed a different challenge. Using a long-handled tool, a band of rubber stretched across two prongs, Crittenden pinned the snake against the floor and reached down, grasping it just behind its jaws. It bared its fangs, trying to whip its head around to bite his wrist, but his grip stopped the movement.
Together with his colleague Paul Rowley, who secured the tail, they carried the snake to a beaker with a silicone lid. The viper — which was donated to the centre by a pet shop in Bristol — bit down through the silicone, yellowish venom dripping into the glass.
Crittenden and Paul Rowley trap the angry terciopelo
SUNDAY TIMES PHOTOGRAPHER JAMES GLOSSOP
'What I find really interesting is venom's biological variability,' said Casewell, as Crittenden labelled the beaker to store away. 'You're bitten by one snake and you might bleed. You're bitten by another snake, you might have a breathing paralysis. You're bitten by another snake, you might have none of those and just some really severe local tissue damage.
'Now we're able to apply the knowledge gained to hopefully make a real impact on people who are bitten by snakes.'
