A cat is not susceptible to Parvo, although it is believed to be
related to a Feline Distemper virus. With that said, a cat can
become exposed to Parvo via feces, etcetera, and carry the virus
back on their paws or fur or in some similar way and infect dogs by
being the transmitting agent. Rodents and the like can also carry
the virus about in this fashion. The virus is very hardy and can
last nine months off host on floors or the like. Proper
vaccinination is the only way to be sure your dog is safe.