I would venture to say seizure or some kind of poison, i.e. insect, reptile or chemical. Parvovirus takes bout a week after exposure, then a couple days for signs to start showing, then a day or so later they start pooping a bloody stool, vomiting, lethargic, white gums and hide slowly dropping instead of like normal, fall almost immediately, which is caused from dehydration. The foul smelling bloody stool is caused from the stomach lining being stripped away, which is also why they can't hold food down and puke it back up. did you quarantine the rest of the pups?
No bite marks of any kind visible and he had been inside except to go to the bathroom in the yard. He went from playing energetically to deep sleep and then death. He wasn't kept around any of my other pups.
