Parvo (or, more accurately, "parvovirus" or "canine parvovirus") is a disease that can be life threatening for dogs.The disease is extremely contagious, passing from dog to dog quite easily. It is typically found in the ground where infected animals have defecated. It can stay alive in that type of environment for long periods of time and can spread when it's picked up by one's shoes or a pet's feet.
Vomiting and diarrhea are both common symptoms of a canine parvovirus infection. Most often these are severe, but in some dogs they can be mild. In addition, infected dogs typically have a fever and are likely to be lethargic, in addition to having swollen lymph nodes. Symptoms alone can warrant testing, but can't diagnose the infection. That's because there are other canine illnesses that produce the same symptoms.
Veterinarians can do blood testing to check for canine parvovirus. More specifically, a complete blood count is the proper procedure. Dogs with the disease have extremely low white blood cell counts. This result won't conclusively confirm canine parvovirus, though. There are other problems that can cause a low white blood cell count, but any of them would also require intensive medical attention. If the count comes back in the normal range, parvovirus can be ruled out.
The next step in testing a dog for parvovirus is a stool test. Generally, the feces will have an extremely strong odor to begin with, so that is another warning sign. Stool test results can be misleading, so this test is always saved for last--if the test is not done properly, it can give a false negative. In addition, dogs that have been recently vaccinated for parvovirus can display a false positive result.
There is no cure for parvovirus, and some dogs will have to be euthanized once infected. However, many dogs recover from it. The main impediments to recovery are dehydration and secondary infections. Most dogs will need to be hospitalized for at least a few days and treated with antibiotics to give their immune system time to work against the infection. Even once a full recovery is made, they should be kept isolated other dogs for at least two months.
The best way to keep your dog safe from parvovirus is to have him vaccinated against it. Disinfect any toys or other items an infected dog came in contact with to keep the virus from spreading. Even a dog that has recovered from parvovirus can get reinfected, so use the same procedure before your dog comes home. While there are specific cleaners designed to disinfect parvovirus-infected areas, a bleach and water solution can also be used.