Hundreds of dogs have fallen to a mystery illness after taking walks on beaches along the Yorkshire coast. Veterinary nurse Brogan Proud issued a warning to dog owners to avoid the beach on Monday, after noticing a “high increase” of dogs coming into veterinary practices with severe vomiting and diarrhoea. One was Copper, a nine-month-old beagle spaniel, who began vomiting on Monday after enjoying a walk on Fraisthorpe beach in East Riding, Yorkshire, on Sunday. His owner, Ashley Brown-Bolton, from Tadcaster, said she took him to the vet on Tuesday after became increasingly worried about thim. “They gave him an anti sickness jab, which has helped. But it’s just coming out the other end now,” she said. About two weeks ago, Proud and her colleagues began treating dogs that had been walked on beaches including Scarborough, Robin Hood’s Bay, Whitby and Marske-by-the-sea. She issued an alert on Facebook on Monday, which has attracted more than 1,000 responses, with several dog owners sharing similar stories from inland areas and further down the coast in east Yorkshire. The post “blew up”, leading Proud to fear that “thousands” could have been affected by the mystery illness. Many responses were from those who had visited the coast in early January and had now returned home. “Their dogs are then carrying that virus or that bacteria or that problem. And so it’s no longer being kept on the coast as far as I can see, and it is spreading.” Although theories abound on social media, Proud said no vet, agency or authority had been able to establish a cause or a common theme in behaviour, such as eating or chewing anything washed up on the beach, or swimming in the sea. Whatever the cause, according to Proud, “if there’s going to be something spread, dogs will spread it”. She added: “If it’s a virus or a bacteria, it’s going to be spread in their urine or faeces or in the shedding of their fur. And we all know how dogs like to meet and greet each other – nose to nose, touching bums and all sorts. “My advice would be, if you’ve been on the beach, wash your dog in case it’s carrying anything and be vigilant about your dog’s behaviour.” Aaron Yeates and his French bulldog, Ada, from Carlisle, were on holiday in Robin Hood’s Bay over new year. The day after they returned on the 4 January, Ada had severe sickness and diarrhoea. After two trips to the vet, she is only just starting to keep food down again. “She’s lost a considerable amount of weight, her harness barely fits.” Kirsty Salisbury, coastal general manager for East Riding council, said the inspections team had not noticed anything unusual on the beaches. “We have been liaising with external partners during the course of yesterday to try to establish a cause, whilse also liaising with local colleagues, and also nationally. “From reports from local veterinary surgeries, the illness they are seeing within dogs and the tests carried out have not provided any direct links with the use of beaches.” Scarborough borough council also said that while dogs walked on beaches have been affected, other dog owners are reporting the same symptoms from inland locations. “If any vets have information about possible links to a canine virus that could help these investigations, we kindly ask them to contact our dog warden service.” The Department for Environment, Food and Rural Affairs (Defra), said it was aware of the incidents and was in contact with the Animal and Plant Health Agency. “We are not aware of any link with the issue of crustaceans washed ashore in the area late last year,” Defra said.