A music teacher had to have an emergency operation to save his testicle after being attacked by a out-of-control dog.
Joel Goodman, 28, was out on his morning jog in Epping, Essex, when a snarling dog leapt out from an alley and savaged him.
The animal bit his groin, and Mr Goodman was left writhing on the ground in agony, bleeding profusely.
But the owner of the dog, which is believed to be an English Bull Terrier, refused to put it on a lead or give his name and address when challenged by Mr Goodman, and walked away, declaring: "I'm not from round here."
Mr Goodman staggered, covered in blood to a friend's house nearby who put him in a car to take him to hospital, but after getting stuck in rush hour traffic, they managed to flag down a police car which took Mr Goodman to Princess Alexandra Hospital in Harlow.
The operation was a success, but Mr Goodman said he was still living with the psychological scars of the attack.
He said: "The dog came out of an alleyway and went straight for me and I did not even have chance to react.
"I did not even see it and it just took a bite.
"The incident was over so quickly but the consequences are going to last for a lot longer.
"Thankfully the doctors were able to save my testicle but I keep re-living the attack and am suffering from anxiety as a result of it.'
Mr Goodman is now calling for the dog to be caught and put down before it has a chance to attack another innocent person.
He added: 'It is really hard to talk about this but something has to be done.
"I want the dog put down and the owner prosecuted before it happens to somebody else."
Police are trying to track down the owner of the dog, who is described as between 35 and 40.
MP Anne McIntosh has called for tighter dog control legislation after 14-year-old Jade Anderson was attacked and killed by five dogs in Wigan, Greater Manchester in March.