Dogs with enteritis act like they are in extreme pain. Early symptoms are depression, loss of appetite, vomiting, high fever, and severe diarrhea. Feces can be either grayish or fluid and bloody. Rapid dehydration is a danger, and dogs may continue to vomit and have diarrhea until they die, usually three days after onset of symptoms. Others may recover without complications and have no long-term problems.
Puppies can die suddenly of shock as early as two days into the illness.
The second form of CPV is cardiac syndrome, or myocarditis, which can affect puppies under three months old. There is no diarrhea because the virus multiplies rapidly in muscle cells of the immature heart. Puppies may stop suckling and then collapse and die within minutes or days. No effective treatment is available for cardiac syndrome, and surviving puppies may have permanently damaged hearts. The rapid spread of illness in a group of dogs is another indication that CPV may be the culprit.