Canine distemper is a widespread, high-mortality viral disease of dogs. Exposure is considered inevitable during a dog’s lifetime, so canine distemper vaccination is almost always recommended. Puppies and young dogs without immunity are at greatest risk. Canine distemper virus infects various tissues in the dog’s body, producing diarrhea, fever, nasal and ocular discharge, respiratory disease, appetite loss and neurologic signs such as muscular spasms and paralysis. The disease is easily transmitted and often fatal.