Had something like this with our Dane about 2 months ago. By the time we realized what was going on, we couldn't get a vet appt for 10 days. By then, he'd cleared up. It affected our Dane/Mastiff mix for about 2 days, and our Bullmastiff not at all. It's been well over a year since they were boarded, and they haven't left our property since then.