Plague is endemic in Colorado/Utah/Arizona/New Mexico. Two years ago, two people in Colorado died from it. As far as I know, just about every human case in the southwestern US has been caused exactly this way: domestic pets (the vast majority have been cats) out roaming around in areas where prairie dogs live, and coming back home sick, and passing it to their owners/vets.
There are areas in Fort Collins, where the vet hospital mentioned is located, that have plastic fence surrounding prairie dog villages with "warning plague danger" signs hung on the fence.