Description
Canine distemper is a highly infectious disease of dogs and other carnivores which can cause mild signs or be fatal in some individuals, and which can lead to debilitating disease in recovered animals. Young puppies and dogs that have not been vaccinated or which have a poor immune response are most susceptible.

Breed Occurrence
There are no breed predispositions to canine distemper, however dogs that are allowed to stray and mix with other feral dogs are most likely to be exposed to field virus.

Signs

Canine distemper virus affects three main organ systems causing signs of disease :

• The Respiratory System
  • Purulent discharges from nose
  • Coughing
  • Difficulty breathing (dyspnoea)
  • Pneumonia
• The Gastrointestinal tract
  • Diarrhoea - may contain blood
  • Vomiting
  • In young animals that survive  normal enamel of the teeth may be affected producing a pitted surface
• The Central Nervous System
  • Depression (often severe)
  • Fits or seizures
  • Muscular twitches and tonic-clonic contractions - uncontrollable muscle contractions
• Other signs include :
  • High body temperature
  • Purulent discharges from the eyes and conjunctivitis
  • Dry eye (keratits sicca)
  • Inappetance
  • Dehydration
  • Thickening of the foot pads in recovered dogs (called hyperkeratosis or "hard pad")
  • Pustules on the skin 
  • Canine distemper virus antigen has been found in the joints of dogs afflicted with rheumatoid arthritis but the origin (vaccine or natural infection) and significance of this finding is not known.
  • Weight loss
  • Death

The disease has an incubation period of about 7 days, and the first sign might be malaise, depression and a high body temperature.  Animals may appear to recover in 2-4 weeks but in some recovered dogs persistent infection can lead to "old dog encephalitis" in later life.

Diagnosis
Diagnosis is based upon the clinical signs in an unvaccinated dog, and sometimes by virus isolation from swabs taken from the conjunctiva of the eye or other sites (eg tonsils, the buffy layer (white cells) of blood samples). However identification can be difficult. At postmortem eosinophilic virus inclusion bodies are found in various tissues including the respiratory tract, lymph tissue and the urinary bladder wall. 

Many dogs have circulating antibodies to canine distemper due to vaccination or natural exposure to the virus, so serological tests are unreliable as a form of diagnostic test.

Treatment
There is no specific treatment for canine distemper. Intravenous fluids are given to correct the fluid and electrolyte losses due to vomiting and diarrhoea, and antibiotics are given to control secondary infections.

 If bitches are fully vaccinated they will pass on passive immunity to their puppies through the first milk (colostrum) and this protection falls off after 8 weeks, so the puppies should be vaccinated from that time. Measles vaccine can be used to give cross-protection to distemper, and this is given to provide some immunity to young puppies (from about 6 weeks to 12 weeks of age) that have been exposed to the disease even though maternal antibodies may be present.

All dogs should be protected by vaccination, and modified live vaccines are widely available. Two vaccines are given at the puppy stage and immunity can last for as long as 7 years in some individuals. However, it is usual to recommend booster vaccines - at 1-3 year intervals.

Vaccinated dogs can still become infected by canine distemper virus but they only show mild or no signs.

Once severe central nervous signs occur euthanasia is usually recommended.

Prognosis
The prognosis is guarded in all animals, and poor in susceptible animals and once central nervous system signs occur.

Long term problems

"Old dog encephalitis"

Updated October 2013