I didnt think it bothered adult dogs much either...(Pulled this off a website about Parvo)...Canine Parvovirus is carried by dogs. Adult dogs may be infected, but without showing any clinical signs - they merely act as carriers. Dogs with the typical diarrhea that parvovirus causes shed the virus as well.
Parvo is extremely contagious. It is passed in the feces or vomit of an infected dog. It can be brought into your yard on your tires, on your feet or clothing after handling an infected animal (and this is probably why it spread worldwide so quickly after it first appeared). It can be passed from yard to yard by birds carrying the virus on their feet or people going "kennel-hopping" carrying the virus on clothing or shoes.
The Parvovirus is hard to kill and is shed in large numbers by infected dogs. One ounce of feces can carry millions of particles of the virus. This means a fly can land in an infected area then land in your yard and infect that space. Some kennel owners ask that their visitors bleach the bottom of their shoes, wash their hands in bleach water and put gowns on before allowing contact with the puppies. These are excellent precautions to take, and reduce the risk, but they are not a guarantee that the puppies will be protected from the Parvovirus. Many kennel owners who have taken these precautions still end up occasionally contracting Parvo in their kennel. We have seen this situation many times.
A parvoviral infection can therefore be picked up anywhere, although it is easier to pick up an infection in an area where an infected dog has been present simply because of the larger amounts of virus present in a contaminated area.
Whether an individual dog gets infected or not depends primarily on the number of viral particles that the dog experiences, but also on what kind of immune experience the dog has had with the virus before (e.g. has it been vaccinated, has it previously been infected, how much past exposure has it had), and the individual dog's overall health, which is affected by factors such as diet and stress.
For some reason, Doberman Pinschers, German Shepherds, Pit Bulls, Labrador Retrievers and Rottweilers, as well as other black and tan breeds seem to be particularly prone to Parvo, and seem to succumb to it faster and with a lower chance of recovery than any other breed.
Conversely, Toy Poodles and Cockers appear to be at a reduced risk of contracting this disease (**).
It is important to remember, however, that any breed can get Parvovirus, so be sure to keep your dog's vaccinations up to date.
