The head shaking could be due to neurological activity secondary to hypoglycemia. Early in the course of the disease Parvo tests can be negative. There are also several other viral diseases that cause bloody diarrhea and vomiting (usually less severe than parvo).
Regardless of the cause your dog needs aggressive supportive care--intravenous fluid therapy, intravenous antibiotics and anti-emetics (anti-vomiting) immediately.
Your veterinarian will want to repeat the parvo test as well to completely rule out parvo.
Regardless of the cause your dog needs aggressive supportive care--intravenous fluid therapy, intravenous antibiotics and anti-emetics (anti-vomiting) immediately.
Your veterinarian will want to repeat the parvo test as well to completely rule out parvo.
