‘In one case a stray eel found its way through the man’s genitals and into his kidney, and he ended up needing a three-hour operation,’ Nixon told the conference. ‘This is the sort of procedure that is coming your way.’

The alarming example is reportedly that of Zhang Nan, a 56-year-old man from Hubei province in China.

‘I climbed into the bath and I could feel the eels nibbling my body,’ Mr Nan said shortly after the incident two years ago.

‘But then suddenly I felt a severe pain and realised a small eel had gone into the end of my penis.’