Foamy vomit is not a common symptom of canine parvovirus. Rather, parvovirus vomit may be clear, yellow, brown, or bloody. Your dog's vomiting will be severe if they have parvovirus, whereas foamy vomit because of indigestion will only happen once or twice. Parvovirus also comes with a range of other worrying symptoms. These include lethargy, loss of appetite, fever, diarrhea, and collapse.