Canine Distemper Virus

The typical distemper suspect is a puppy with questionable vaccination history or an as yet incomplete vaccine series displaying symptoms such as:

  • Gooey eye and nose discharge
  • Fever (which often comes and goes unnoticed)
  • Poor appetite
  • Coughing/possible pneumonia
  • Vomiting and diarrhea
  • Callusing of the nose and foot pads (distemper was aka ? hard pad disease)

This is called the ?mucosal phase? of distemper infection. The virus then proceeds to the central nervous system for its ?neurologic phase,? leading to:

  • Seizures, often starting with snapping or tremoring of the jaws that progress to convulsions or muscle tremors.
  • Imbalance or limb weakness.
  • Dogs that survive may have permanent impaired sense of smell, hearing, or sight and partial or total paralysis.
  • Signs may progress to death.
  • Recovery is also possible.
  • The fatality rate can be as high as 90%.

Transmission and Infection

The infected dog typically infects other dogs via coughing infected respiratory secretions though the virus is shed in most other body secretions including urine. Over the course of two weeks the virus has migrated to various internal organs; fevers may develop. The host is mounting an immune response during this time and the outcome depends on how fast and how well this is accomplished; if the response is poor, then the infection will likely progress to the neurologic phase. After clearing from most internal organs, the virus is able to hide out for long periods of time in the nervous system and skin. Because of this phenomenon, callusing of skin or, much worse, seizures may occur long after the infection was thought to be cleared.

Most victims in the U.S. are puppies. The colostrum (early milk) provided in the first day or so of life will provide them with a solid reflection of their mother?s immunity. This immunity wanes at or before age 16 weeks, leaving the puppy vulnerable if vaccines have not been administered for further protection.

Confirming the Distemper Infection

Distemper is usually a clinical diagnosis, which means that rather than confirming infection with a test that is positive or negative, the veterinarian must usually look at the whole picture: what symptoms are there, is the history typical, etc. The virus itself remains elusive so that positive test results are meaningful in confirming the infection, but negative results do not rule it out.

Treatment for Distemper

Distemper is extremely variable in its ability to produce symptoms and recovery may occur at any stage. The only real treatment is supportive care for clinical signs. Euthanasia is best left for progressive, incapacitating neurologic symptoms.

Preventing Infection

If confirming diagnosis and therapy are the pitfalls of distemper, prevention is the easy part. Puppies are vaccinated beginning at age 6-8 weeks and then every 2 to 4 weeks thereafter until age 16 weeks. The next vaccine is one year later with subsequent boosters given every 1 to 3 years.

  • In puppyhood the buds of the permanent teeth are still developing. The distemper infection can leave these tooth buds permanently damaged so that the adult teeth come in with stained and pitted enamel.
  • Callusing of the nose and foot pads tends to be associated with the development of neurologic distemper. As a general rule about 50% of dogs that recover from the mucosal phase will progress to neurodistemper.
  • A recovered dog may shed virus up to 2 to 3 months. It is important to keep this in mind when taking a recovered pet anywhere where other dogs are present. The most intense viral shedding occurs in the first 2 weeks of infection.
  • A condition called ?Old Dog Encephalitis? refers to a dog that lives nearly all its life as a distemper survivor only to break with neurodistemper in old age.

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