Parvo (canine parvovirus) spreads through the feces of an infected dog and it is highly contagious to other dogs, especially puppies that spend time in the same vicinity as an infected dog. (Reference 1, page 78) The feces, often thin diarrhea, may be tracked onto grass, bedding or other items, and your dog is at risk of contracting the deadly disease unless he's been previously vaccinated against it. Diagnosing an infected dog consists of the owner's observations and veterinarian tests.
Watch your dog for signs of depression or lethargy. These early symptoms occur between three and 10 days after your dog is exposed to the virus. He may not be his usual playful self and he may sleep more than normal. (Reference 2)
Observe the dog's feces. Parvo often attacks the cells in the intestine, causing watery diarrhea. As a result, a dog with parvo may quickly become dehydrated. (Reference 2)
Look for vomiting episodes with or without signs of abdominal pain. In some dogs, the stomach contracts, causing them to tuck their abdomen in and upward. (Reference 1)
Check very young puppies for the cardio version of parvo. This less-common form of the virus spreads from the mother dog to her unborn pups and they frequently die soon after birth. The virus attacks the young heart muscle, causing cardiac arrest. (Reference 1, page 78)
Take your dog to your veterinarian as soon as you suspect parvo. Some dogs survive the virus if they receive prompt emergency treatment that involves the intravenous fluid replacement. Your veterinarian may order a blood serum test to make a quick diagnosis. (Reference 1)