The canine distemper virus is a close relative of the human measles virus. Susceptible dogs can pick it up from direct contact with the urine, blood, saliva, food and water of infected dogs, or by breathing air containing droplets coughed or sneezed from infected dogs. According to Cornell University's Baker Institute for Animal Health, even dogs vaccinated against distemper can contract the disease, although immunization makes transmission much less likely. Among adult dogs, distemper is fatal about half the time, but in puppies, the mortality rate shoots up to about 80 percent.
From the time of infection, canine distemper virus spends about 10 to 14 days laying low and generating copies of itself, which spread throughout the dog's body before the first symptoms appear. These vary from one animal to the next but typically include fever, lethargy, sneezing, coughing and thick mucus discharge from the eyes and nose.
As the disease spreads via the bloodstream to various organ systems, existing symptoms worsen and new ones emerge. When the virus reaches the respiratory system, the dog may experience difficulty breathing. Secondary bacterial infections are common in canine distemper, often leading to death by pneumonia. Vomiting, bloody diarrhea and loss of appetite are all indications that the virus has invaded the dog's stomach and intestines.
If a dog with distemper starts to lose muscle coordination and seems disoriented, it suggests that the disease has affected his central nervous system -- the most dangerous and potentially deadly stage of development. When the brain and spinal cord become infected, additional symptoms may include muscle spasms, seizures and partial or complete paralysis.
If a pregnant female contracts the distemper virus, her puppies may be spontaneously aborted, especially if they're still tiny embryos. If this happens before the owner realizes the dog is pregnant, there might not be any evidence, because the embryos are often reabsorbed into the mother's body instead of being expelled.
Even when dogs recover from distemper, the long-term effects can last a lifetime. Erosion of tooth enamel causing severe tooth decay is common among distemper survivors, as is a condition called hyperkeratosis, which causes painful thickening and hardening of the dog's nose and foot pads. If the disease has damaged the central nervous system, the dog may experience seizures, sometimes later in life.
While canine distemper virus can infect foxes, skunks, coyotes and weasels, the most common wildlife host in the U.S. is the raccoon. According to the Tennessee Wildlife Resources Agency, disease outbreaks among wild animals tend to flare in cycles every five to seven years, with symptoms mimicking rabies. You might spot nocturnal animals wandering aimlessly and behaving strangely during daylight hours. They might lose their natural fear of people, become aggressive, convulse, and appear disoriented. If you see a wild animal behaving this way, don't approach it. Call the appropriate authorities immediately.
For more than a century, canine distemper virus has been known as a disease that infected certain animals but not humans. However, since the 1990s, after outbreaks among nonhuman primates began to surface, many experts have been increasingly concerned that the rapidly mutating virus might soon be capable of jumping the species barrier. Virologist Dr. Jürgen Schneider-Schaulies of the University of Wurzburg in Germany is one of the authors of a study, published in the journal "PLoS One" in March 2013, tracing mutations that are bringing the distemper virus closer to humans. Even though no infections have been identified, he says, science would do well to consider a course of action in case they do.
- ASPCA: Pet Care: Distemper
- Cornell University College of Veterinary Medicine: Baker Institute for Animal Health: An Overview of Canine Distemper
- University of Missouri Extension: Canine Abortion
- mBio: Canine Distemper Virus (CDV) in Another Big Cat: Should CDV Be Renamed Carnivore Distemper Virus?
- Tennessee Wildlife Resources Agency: Canine Distemper
- Virology: Canine Distemper Virus with the Intact C Protein Has the Potential to Replicate in Human Epithelial Cells by Using Human Nectin4 as a Receptor
- Provet Health Care Information: Canine Distemper
- University of Wurzburg: Can the Canine Distemper Virus Infect Humans?
- PLoS One: Experimental Adaptation of Wild-Type Canine Distemper Virus (CDV) to the Human Entry Receptor CD150
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