Symptoms usually begin with a high fever, lethargy, depression, and loss of appetite. Secondary symptoms appear as severe gastrointestinal distress, such as vomiting and bloody diarrhea. In many cases, dehydration, shock, and death follow. Parvovirus is characterized by severe, bloody diarrhea and vomiting, high fever and lethargy. The diarrhea is particularly foul smelling and is sometimes yellow in color.
Parvo can also attack a dog's heart causing congestive heart failure.
This complication can occur months or years after an apparent recovery from the intestinal form of the disease. Puppies who survive parvo infection usually remain somewhat un-healthy and weak for life. Canine parvovirus is carried by dogs. Adult dogs may be infected carriers without showing any clinical signs. Dogs with the typical diarrhea that parvovirus causes shed the virus as well.