"It was my own dog," said Dr Nel.
"We had been playing a bit rough and he nicked my hand. It was tiny. I cleaned it and forgot about it.
"It was never infected locally or anything like that."
Dr Nel, a psychiatrist who specialises in treating patients with dementia, was at work around two weeks later when he developed flu-like symptoms.
He told his secretary to cancel all of his appointments and went home to bed.
"I started to feel hot and cold. I was shivering yet I could not get warm.
"My whole body was aching. I thought it was the flu so I went home to bed.
"I texted my partner and said I had the flu and was going to bed.
"The next day I was very ill and confused. I wasn't able to ring work and that's when my secretary started to worry.
"I don't even remember the phone ringing. When my partner Michael got home after work I couldn't stand up, my hands didn't work properly and I struggled to speak.
"That's when he called the paramedics and I was taken to hospital."
The paramedics noticed Dr Nel had red blotches all over his skin - a symptom of Sepsis - and immediately started a course of antibiotics as they rushed him to hospital.
When they arrived at A&E, he collapsed and was taken straight to the intensive care unit where he was placed in an induced coma.
People who go into septic shock only have around a 20 per cent chance of survival.
The infection interferes with the body's blood-clotting mechanism, with many smaller blood clots cutting off circulation to parts of the body and causing blood pressure to drop dangerously low.
In Dr Nel's case, his kidneys started to fail and his legs started to turn black as gangrene set in.
"I was lying there in hospital looking at my black, gangrenous legs and fingers. Looking down I knew I was going to lose everything. I could tell the tissue was dead.
"Even though the doctors had played it down, I knew how severe it was."
Four months after being admitted to hospital Dr Nel had both his legs amputated below the knee.
He lost all fingers on his right hand and one on his left hand, and needed reconstructive surgery on his face.
With the use of prosthetic legs, Dr Nel, now 52, has been able to learn to walk again and live independently.
But the facial disfigurement he has suffered has been difficult to come to terms with.
"I am very reluctant to go out because I am so self-conscious," he says.
"While it hasn't stopped me completely from living independently, it has damaged my confidence.
"The hardest part has been accepting that I am now disfigured and that there is nothing I can do about it."
Doctors were initially baffled by what had caused the infection.
Three weeks later, blood tests revealed a bacteria that lives in a dog's mouth.
It meant the couple's cocker spaniel, Harvey, was carrying the harmful bacteria in his saliva.
The findings eventually led to Dr Nel and Michael making the difficult decision to have Harvey put down.
"It was very sad but we were worried about the dog infecting someone else," says Dr Nel.
"The dog doesn't need to bite for that to happen. It can just be passed on through its saliva.
"What if he had infected a child? It could have been terrible.
"Luckily he was an older dog and was coming towards the end of his life.
"There were times when I was very angry and I blamed him.
"But it was still very sad for us. The bacteria was just bad luck."
It is now 18 months since Dr Nel, who moved from South Africa in 2001, contracted Sepsis.
And, while the psychiatrist is still coming to terms with his life-changing injuries, he has been touched by rays of hope.
"My friendships have become much stronger as a result of what happened to me", he says.
"To see how much my friends and family cared for me was a positive. I have realised I have a lot of inner strength because of what I have been through.
"I think I have a lot more to give to my patients in terms of empathy and understanding. I know what it's like to be close to death and to have a disability.
"There's something in me that I need to share and help people. I hope to eventually show people it is possible to overcome so much in life."
