Owners told to keep pets away from other canines after sickness found in 14 of 18 counties

A mystery sickness has struck dozens of dogs in Norway, killing at least 25 and prompting authorities to warn owners to keep their pets on a lead and away from other canines until the cause is established.

Ten dogs fell ill on Saturday and Sunday, the national food safety authority said, four of which have since died. While most cases have been in the capital, Oslo, the illness has been reported in 14 of the country’s 18 counties, including the far north.

According to the Swedish newspaper GT, a dog in neighbouring Sweden was also being treated in a veterinary hospital after appearing at a show in the Norwegian city of Trondheim last week. All dog shows in Norway were cancelled this weekend.

The Norwegian Kennel Club said owners were so concerned about the spread of the illness over the weekend that its website crashed under the weight of demands for information. There are an estimated 500,000-600,000 dogs in Norway.

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The undiagnosed sickness was clearly “very serious for dogs”, a food safety authority spokesman, Ole-Herman Tronerud, told the public broadcaster NRK. “But we don’t yet know whether this is contagious, or just a series of individual cases.”

The emergency and safety director of the Norwegian veterinary institute, Jorun Jarp, said it was “naturally alarming to have healthy Norwegian dogs dying so quickly. This is a very special situation; I haven’t been in involved in anything like it before.”

The institute said it had ruled out salmonella and rat poison, and also did not believe the illness – which causes severe vomiting and acute bloody diarrhoea – was due to something in the dogs’ food.

“We have seen that many different types of feed have been used in the dogs that are autopsied, and have no reason to believe that it is the cause of one specific feed,” Jarp said. “We are investigating possible viral, bacterial, fungal and parasitic causes.”

A veterinary pathologist, Hannah Jørgensen, told the broadcaster authorities were working systematically and as fast as possible, but the job was “difficult because we have so far not found any obvious common features from our laboratory analyses”.

The dogs that have fallen ill and died came from “many different places in the country, and they have been drinking and eating different things”, Jørgensen said. “At the moment we have no clear test results and so no firm conclusion.”