Heartbroken dog owners say their beloved pet fell victim to a mysterious virus as they warn others about the illness.
Duke, a Cavalier King Charles Spaniel, was described as a "lovely" pup who was "everybody's best friend" and a regular at the Consett's Duke of Wellington pub, which his owner Alan Marshall runs.
Julie Cox, also his owner, took Duke for an evening walk on January 9 around an industrial estate.
Shortly afterwards, the four-and-a-half-year-old dog became seriously ill.
Julie told ChronicleLive : "It was at ten past 11, he woke me up wanting to go out, and I thought it was a bit strange because he always goes for a long walk in the morning and at night. I took him out and he had diarrhoea.
"I went back to bed after an hour and he woke me up again, it went on like this about every hour until the morning. He didn't want his breakfast and Duke normally really ravishes his food.
"He managed about a 10-minute walk and when we got back as soon as I took his lead off he vomited.
"My daughter, Rebecca, who is training to be a paramedic, said 'mam, this is not normal, it's not right'.
"He was foaming at the mouth and he vomited about four times in 10 minutes.
"I rang the vets and they told me to bring him up straight away. As we were taking him to the vets he became really lethargic."
After vets ran tests, Duke's organs seemed to be okay and he was given medication.
But as soon as they got home, his owners saw Duke was bleeding from his behind.
He was then sent to another vet in Newcastle to be treated overnight, but when they arrived he suffered a heart attack.
Vets did their best to save him, but despite managing to stabilise him, he crashed again, and they were forced to deliver tragic news to Alan and Julie.
The pair have decided to share their story in the hopes of warning other dog lovers about the disease.
Alan said: "They told us that this virus is going round and they don't know what to do to treat it. The vets did everything possible, they were so upset that they couldn't help.
"We just don't want other people to go through this, you'd got to be careful when you take them for walks, of course, dogs are dogs, but maybe clean their paws whenever you get home."
Julie added: "Duke was perfect. He wagged his tail all the time, he was happy all the time, he was as fit as a fiddle, we made sure we kept him healthy and fit.
"All the people who came into the pub loved him, he used to sit on people's laps and watch what was going on. He was my best friend.
"If we could just get the message out to people that there is this unknown virus out there and to be careful until it comes out exactly what it is."
British Veterinary Association President Justine Shotton said last week the illness was likely to be a virus, which results in "gastroenteritis-like symptoms" (diarrhoea and vomiting).
Although many cases are milder, there is a risk of serious illness, as happened to Duke.
Dog owners are advised to contact their vets if they spot any of these symptoms.
