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The blood of a US man who deliberately injected himself with snake venom for nearly two decades has led to an "unparalleled" antivenom, say scientists.

But Mr Friede's 18-year mission could be a significant step in finding a universal antivenom against all snakebites - which kill up to 14,000 people a year and leave three times as many needing amputations or facing permanent disability.

Antivenom is currently made by injecting small doses of snake venom into animals, such as horses.

But venom and antivenom have to be closely matched because the toxins in a venomous bite vary from one species to another.

There is even wide variety within the same species – antivenom made from snakes in India is less effective against the same species in Sri Lanka.