A three-year-old boy was bitten by an adder at a family picnic and left "paralysed".
Pictures from hospital show tiny Lewis Wise who was attacked by the venomous snake while searching for his toys in the long grass at a Surrey country park on Sunday.
His distraught dad has given an urgent warning to others parents about the venomous snakes after the "horrifying" incident which saw his boy "in excruciating pain" and left his foot black, swollen and bruised.
The tot from Addleston was attacked at Lightwater Country park on July 12 and his dad - who by coincidence is a snake enthusiast - fears adders and humans' paths will cross more as people return to parks as the coronavirus lockdown eases.
Lewis was playing and "messing about" in the grass searching for his plastic toy insects, which had been lost in the 59-hectare park earlier that day, said his dad.
Seconds later, Daniel, 39, heard "a massive scream". Lewis had been bitten by an adder, which was "perfectly camouflaged" in the foliage.
Daniel told SurreyLive: "We think he may have trod on it by accident and it latched onto his leg. It was instant and then he was in excruciating pain.
"We were trying to keep his heart rate low. You have to keep your children calm because the faster your heart pumps, the quicker the venom goes around your body.
"We took him to St Peter's Hospital.
"His whole leg swelled up and it went all the way up to his groin area. His foot has basically gone black, it's all swollen and bruised."
Lewis spent the night at St. Peter's Hospital and was transferred to St. George's Hospital in Tooting on Monday where he saw a skin specialist.
He was given three vials of antivenom and is on morphine, however it is not known how long he will have to remain in hospital.
Daniel explained that Lewis might need surgery to "relieve the pressure" in his leg and subsequent physiotherapy to help him walk after he has recovered.
He said: "He has been really brave, but the swelling is so big; he is paralysed and can't move at the moment.
"When he comes out of St. George's he will have to go back to St. Peter's again and then maybe even have physio afterwards.
"A lot of people think that adders are not that bad, but if you're bitten, it can be really serious. Everyone reacts differently, but it's serious."
Daniel keeps and breeds snakes as a hobby and explained that adders are Britain's only venomous snake.
He said the snakes are cold-blooded and will typically bask in the sun to gain energy. However, their "amazing camouflage" makes them difficult to spot.
According to the Amphibian and Reptile Conservation Trust, 50 to 100 people are bitten by adders every year, as well as approximately 100 dogs.
Human deaths are rare, with 14 recorded fatalities from adder bites since 1876.
The last was in 1975.
Daniel is now urging all parents to be aware of the potential dangers and wants councils to put up warning signs about adders in parks across the county.
He added: "Due to COVID-19, we have not been going to these places and now all of our paths are crossing again.
"These country parks that you can go to, there are no warning signs and the kids are playing about - it's pretty bad really.
"People should not be going near them or trying to catch them, they should be left alone. Parents need to be aware of the dangers."