Canine distemper is a virus that causes serious illness. There is no known cure and the virus affects dogs and certain species of wildlife, such as raccoons, wolves, foxes, and skunks. The virus is spread through the air and by direct contact with an infected animal. The virus does not persist in the environment and is very easy to kill with most disinfectants. If a dog becomes infected with distemper, the virus first travels to the dogs lymphatic system and replicates itself for approximately a week. The canine distemper virus then spreads to other parts of the body, such as the respiratory, urogenital, gastrointestinal, and nervous system.
The initial signs of a canine distemper infection include a fever, ocular and nasal discharge, poor appetite, and coughing. After infecting the respiratory system, the distemper virus continues to travel through the body and causes gastrointestinal signs, such as vomiting and diarrhea. Some dogs, especially immunocompromised puppies, will die during this phase, called the mucosal phase. If a dog survives the mucosal phase, the distemper virus will travel to the central nervous system. A classic central nervous system sign from canine distemper is a chewing gum fit. It starts with tremors or snapping of the jaw and progresses to convulsions of the whole body. Other central nervous system signs of canine distemper are instability and weakness. Ultimately, most dogs that are infected with the distemper virus will die. If a dog survives the initial distemper infection the virus will hide within the nervous system and skin. If this occurs, these dogs can develop chronic seizures and callusing of foot pads.
Most cases of canine distemper involve unvaccinated dogs. The colostrum that puppies get from nursing from their mom during the first few days of life contain antibodies that protect the puppies from the distemper virus. As the maternal antibody levels wane during the first 4 months of a puppies life the puppy will need to be vaccinated for distemper in order to continue to be immune from the distemper virus. If a puppy is not vaccinated for distemper their immunity will be very low making them susceptible to a distemper infection.
There are multiple tests for the distemper virus, such as serology and polymerase chain reaction (PCR). However, these tests do not confirm the absence or presence of a distemper infection. The reason being is that these test modalities do not differentiate the vaccinal strain versus an infective strain of distemper. Presently, the distemper PCR test on urine is often recommended. It is easy to perform and the results are reliable in a dog that has not been vaccinated for distemper during the past 3 weeks. The PCR test can also be performed on blood, but that is more likely then the urine test to be affected by prior distemper vaccination.