Canine distemper typically starts with a fever and respiratory signs like coughing and nasal discharge, then progresses through gastrointestinal and potentially devastating neurological stages. Symptoms usually appear 1 to 4 weeks after exposure, with most dogs showing the first signs around 10 to 14 days. The disease moves through the body in phases, and recognizing each stage early can make a significant difference in a dog’s chances of survival.
Early Signs: Fever and Respiratory Problems
The first thing most owners notice is a discharge from their dog’s eyes and nose. This often starts watery and becomes thicker and more yellow-green as the infection takes hold. Alongside the discharge, dogs develop a cough that can range from mild to severe, difficulty breathing, and sometimes pneumonia. Fever is one of the earliest markers, and distemper actually produces a characteristic two-phase fever: the temperature spikes, drops back to near-normal for a few days, then rises again as the virus spreads to other organ systems.
Dogs in this early stage often lose their appetite and seem unusually tired. Because these signs look a lot like kennel cough or a basic upper respiratory infection, distemper can be easy to miss in the first few days.
Gastrointestinal Symptoms
As the virus moves beyond the respiratory tract, it attacks the lining of the digestive system. Vomiting and diarrhea are common, and together with the loss of appetite, they can cause rapid dehydration, especially in puppies. This stage sometimes overlaps with the respiratory phase, so a dog may be coughing and having diarrhea at the same time. In young or immunocompromised dogs, the combination of respiratory and GI symptoms can become life-threatening quickly.
Skin Changes: Hard Pad Disease
One of the most distinctive signs of distemper is a thickening and hardening of the nose and paw pads, a condition historically called “hard pad disease.” The skin in these areas becomes dry, rough, and overgrown with excess tissue. This happens because the virus directly infects the cells that produce the outer layer of skin, causing them to multiply abnormally. Not every dog with distemper develops this sign, but when it appears alongside respiratory or neurological symptoms, it’s a strong clinical indicator of the disease.
Neurological Symptoms
The neurological stage is the most serious phase of distemper, and it’s the one that causes the most lasting damage. It can develop while a dog is still showing respiratory and GI symptoms, or it can appear weeks later, after those earlier signs have apparently resolved.
The hallmark neurological signs include seizures, muscle twitching (especially in the jaw and front legs), and repetitive chewing motions sometimes called “chewing gum fits.” Dogs may also develop an unsteady gait, walk in circles, press their heads against walls, or pace compulsively. Changes in behavior and awareness are common: a dog may seem confused, unusually aggressive, or mentally dull.
In more advanced cases, dogs can lose coordination in all four legs, ranging from mild weakness to near-complete paralysis. Some dogs develop what looks like a constant, rhythmic jerking of specific muscle groups. This involuntary twitching can persist even during sleep and, in many cases, becomes permanent.
Long-Term Damage in Survivors
Dogs that survive distemper often carry permanent reminders of the infection. The neurological twitching and seizures can persist for life, even after the virus itself has been cleared. Hard pad changes to the nose and feet may also remain.
Puppies that contract distemper while their adult teeth are still forming can develop a condition called enamel hypoplasia, where the permanent teeth come in with pitted, discolored, or irregularly shaped enamel. This happens because the fever and viral infection disrupt the cells responsible for building tooth enamel during a critical developmental window. The damage is cosmetic in mild cases but can make teeth more prone to decay and sensitivity.
A rare long-term complication called old dog encephalitis can appear in adult dogs, sometimes years after the initial infection or even in dogs with no obvious history of distemper. It causes progressive neurological decline, including loss of coordination, compulsive movements like head pressing or constant pacing, and cognitive changes.
Which Dogs Are Most at Risk
Unvaccinated puppies between 3 and 6 months old are the most vulnerable. At that age, the protective antibodies they received from their mother are fading, and their own immune systems are still developing. Adult dogs that have never been vaccinated or have lapsed on boosters are also at significant risk. The disease spreads through airborne droplets and direct contact with an infected animal’s saliva, urine, or nasal secretions, making shelters, boarding facilities, and dog parks common transmission points.
Distemper isn’t limited to domestic dogs. Raccoons, foxes, skunks, and ferrets all carry the virus, so dogs with access to wildlife or rural areas face additional exposure risk.
How Distemper Is Diagnosed
Veterinarians often suspect distemper based on the combination of respiratory illness, GI upset, and neurological signs in an unvaccinated or under-vaccinated dog. To confirm the diagnosis, they typically test samples from nasal or eye discharge, blood, or urine for the presence of the virus’s genetic material. This type of test can identify the virus even in early stages before some of the more dramatic symptoms have appeared. Antibody testing on blood samples can also help, though interpreting results is trickier in dogs that have been partially vaccinated.
The hard pad changes, when present, are a strong supporting clue. A young dog with pneumonia, diarrhea, and thickened foot pads raises immediate suspicion for distemper even before lab results come back.
What to Expect With Treatment
There is no antiviral drug that kills the distemper virus. Treatment is entirely supportive, meaning the goal is to keep the dog alive and as comfortable as possible while their immune system fights the infection. That typically means managing dehydration with fluids, controlling vomiting and diarrhea, treating secondary bacterial infections that take advantage of the weakened immune system, and managing seizures if they develop.
Recovery depends heavily on the dog’s age, vaccination status, and how far the disease has progressed. Dogs that develop only mild respiratory and GI symptoms have a much better outlook than those that reach the neurological stage. Once seizures or paralysis set in, the prognosis becomes significantly worse, and many of these cases are ultimately fatal or result in permanent disability. Puppies and dogs under 5 years old with pneumonia-like signs face the highest fatality risk. Dogs that do recover from the acute illness can take weeks to months to regain strength, and some neurological deficits may never fully resolve.