This really seems to be going around right now. I know 5 people with dogs with this at the moment and Leo woke up at 4 am with it as well -- had me up at 4, at 6, and went to the vet along with the new rescue boy Obie this morning after passing blood. Some dogs with this are also vomiting, including vomiting blood.
I was speaking with my vet about this and just want to emphasise again how important it is to get your dog to a vet immediately if s/he is passing bloody stools or pure blood. By the time they are passing noticeable amounts of blood they are usually quite ill and can go badly downhill very fast due to dehydration (as my vet explained, their gut lining gets eaten away by the virus and they cannot retain liquids -- hence they pass runny and watery poops but more seriously, quickly become dehydrated). This vet generally wants to keep any dog that is passing blood like this in on a drip -- that is how serious it can be! She wanted to keep Leo, but as I have dealt with this before and know Leo tends to recover quickly, and also as he hadn't had his pain pills for SM and they don't carry them in the practice and was already starting to scratch, I said I'd bring him in first thing tomorrow if he isn't greatly improved by then and meanwhile make sure he stays hydrated.
Anyway for those in Ireland, keep an eye on your doglets and be sure to contact a vet if yours is passing blood.