The symptoms associated with parvovirus are very broad. And most infected dogs show any symptoms at all. Because of this most dogs that contracted parvovirus die because the owners do not detect the illness early on.
Parvovirus affects mostly dogs less than 6 months of age with the most brutal cases affecting less that 12 weeks of age. There are also significant differences in response to parvovirus infections and vaccines among different breeds of dogs, with Rottweilers, Doberman Pinschers, and Labrador Retrievers being more susceptible than other breeds.
The most common form of the disease is the intestinal form known as enteritis. Parvovirus enteritis is characterized by vomiting (often severe), diarrhea, dehydration, dark or bloody feces, and in severe cases, fever and lowered white blood cell counts. Acute parvovirus enteritis can be seen in dogs of any breed, sex, or age. The disease will progress very rapidly and death can occur as early as two days after the onset of the disease. The presence of gram negative bacteria, parasites, or other viruses can worsen the severity of the disease and slow recovery.
A less common form of the disease causes myocarditis (inflammation of the heart). This disease is very fatal to very young puppies, less than 8 weeks old, since it inflames the heart muscles and necrosis which causes breathing difficult. Older dogs that survive this form have scarring in the heart muscle.
That is so true. Most dog owners have no idea that their dog already has parvo and just see it as a dog that has a bad stomach and not take the dog to a vet for check-up. We had several dogs that had parvo before, some got lucky but others were taken away from us.