Overview 

Canine distemper virus (CDV) is a highly contagious and potentially fatal disease of dogs and other carnivores such as ferrets, raccoons, skunks and foxes. While found worldwide, CDV is more likely to spread in communities with low vaccination rates and high dog populations.  

Clinical signs vary in severity from sub-clinical to rapidly life-threatening. Young or unvaccinated dogs are most susceptible; however, vaccination is very effective at preventing CDV, and it is a core vaccination for every dog. 

Cause 

Dogs are most commonly infected by CDV when exposed to air containing droplets of the virus — usually when a nearby infected animal coughs, sneezes or barks. The virus can also be transmitted through direct contact with infected dogs or other bodily fluids, such as saliva, urine or feces.  

Once a dog is infected, the virus quickly spreads throughout the entire body and significantly weakens the immune system, leaving them susceptible to secondary infections. The skin, respiratory, gastrointestinal (GI) and central nervous systems can all be affected. 

Infected dogs become contagious to other dogs several days before they show any signs of illness, which can vary from less than a week up to six weeks. Even mildly affected dogs can look well but shed significant amounts of the virus.   

Diagnosis 

Initially recognizing CDV may be a challenge because CDV clinical signs appear similar to other common diseases. A PCR test is a diagnostic tool to determine the presence of the virus’s genetic material, and a quantitative PCR is considered to be the current test of choice. PCR or virus isolation tests can be used to confirm an infection and determine if recovered dogs are likely to be still infectious to other dogs.  

Another useful test for determining whether an exposed dog might be vulnerable examines their blood antibody levels, also called serology. High antibody levels paired with a negative PCR indicate that a dog is likely immune to infection.  

Veterinarians may also recommend blood work or chest X-rays for affected dogs to assess their overall health and investigate any contributing or secondary infections.  

Treatment 

There is no specific treatment or cure for canine distemper, and antivirals are not recommended. The goal of treatment is to manage symptoms and prevent secondary infections.  

Treatment may include: 

• Antibiotics to protect dogs with weakened immune systems  

• IV fluids 

• Palatable, easy to digest food 

• Anti-nausea medications for GI symptoms 

• Anti-seizure medications in mild neurological cases 

• Humane euthanasia for severe or unmanageable cases  

Outcome 

CDV can be a devastating disease, and some dogs may not recover, despite treatment. The prognosis depends on several factors, primarily involving the dog’s immune response to infection. If a dog recovers from CDV, they are likely immune to reinfection for a prolonged time, perhaps even for life.  

Some dogs that recover from CDV may have residual muscular twitches or seizures. Others may develop neurologic signs in the weeks following recovery or years later, in a syndrome called “old dog distemper.” 

Prevention 

The most effective way to prevent CDV is through vaccination. CDV is recommended as a core vaccine for dogs living in homes starting at 6-8 weeks of age, and it should be repeated every 3-4 weeks until 16-20 weeks of age. The vaccine is then repeated after 1 year and generally every 3 years after that. This frequency is often modified for dogs living in shelter settings or other high-risk populations.  

Until the initial vaccination series is complete, owners should be careful when bringing puppies to high-risk locations where other dogs congregate, such as dog parks.  

Infected dogs must be identified and isolated from other dogs to prevent further spread of the virus. Sanitation practices should include good hygiene and thorough cleaning, as most household disinfectants easily kill the virus. Caretakers should wear disposable PPE, including gowns, gloves and booties when interacting with the infected dog or cleaning their space, and they should discard these items and wash their hands before visiting other dogs.  

Generally, dogs shed the virus through their bodily secretions for about one month, but the exact timeframe can range from between 2 weeks to 3 months. However, some dogs (especially those with neurological signs) may continue to shed the virus for 6-8 months. Although the correlation between PCR detection and virus shedding is unclear, these dogs should be kept away from public spaces until cleared by a veterinarian.