The Danish Veterinary and Food Administration are quoted on speculating that it may be parvovirus, as it seems to fit the symptoms. I have seen no further reporting or repudiation on that possibility, though.
Or ... maybe it's lupus?
Or ... maybe it's lupus?
The Norwegians probably know more about the details. There are vaccines against Parvo, so it's hard to tell if denial of vaccinations is so bad in Norway, that there is an outbreak with hundreds of dogs...
... and if is parvo, why is not being caught quickly when there are specific diagnostic tests for it?