Distemper in puppies is similar to the human measles virus and is the most common canine infectious disease of the nervous system. During their lifetime, most dogs will be exposed to distemper, and puppies have the highest risk. Distemper also infects the wolf, coyote, raccoon, ferret, mink, skunk, otter, and weasel. Wild animals keep the virus alive so even decades of effective vaccination hasn’t stamped out the disease. Vaccines are not 100 percent effective, but provide the best protection for your puppy.
How Distemper Spreads
Distemper is highly contagious and often fatal. The virus is shed in the saliva, respiratory secretions, urine, and feces. Distemper spreads the same way a cold virus spreads in people. The virus is transmitted by sneezing and coughing, or by your pup sniffing contaminated objects.
Increased exposure to other dogs raises the risk, so pups that are kenneled, regularly boarded, shown in competition, or hunted are more susceptible. Pups adopted from stress-filled sources like animal shelters or pet stores most often get sick, especially during the 9- to 12-week age. They can look healthy while they incubate the disease—even after vaccination—and become sick once in their new home. Diagnosis typically can be made based on the signs of disease.
The Incubation Period
Incubation is the time it takes from exposure to the development of signs of disease. Within two days following infection, the virus spreads to lymph nodes and tonsils, and then throughout the body to bone marrow, spleen, and other lymph nodes.
Within five days, the virus begins to destroy white blood cells and puppies develop a fever for a day or two. The virus attacks various body tissues, especially cells that line the surfaces of the body like the skin, eyes, respiratory tract, urinary tract, and the mucous membranes lining the gastrointestinal tract. The virus also infects the kidney, liver, spleen, brain, and spinal cord. Whether or not the infected pup survives depends on the effectiveness of the dog's individual immune system.
By nine to 14 days following infection, 75 percent of dogs that have competent immune systems will defeat the virus and won't become sick. But a young pup won't have a mature immune system. That's why about 85 percent of puppies exposed to the virus when they are less than a week old develop distemper within two to five weeks and die. Older puppies and adult dogs develop fatal disease only about 30 percent of the time.
Signs Of Distemper
Pups suffer a loss of appetite, yellowish diarrhea, trouble breathing, and central nervous system signs such as seizures, behavior changes, weakness, and poor coordination. A characteristic thick white to yellow discharge from the eyes and nose often develops and looks like a runny nose from a cold. Puppies don't catch colds like humans do; this is a serious warning of illness.
Infection of the respiratory system prompts puppies to cough and develop pneumonia. Gastrointestinal infection can cause bloody or mucus-filled diarrhea. Infected eyes may ulcerate or even become blind, and the skin (particularly the footpads) may thicken, crack, and bleed.
Pups with severe symptoms usually die within three weeks unless hospitalized and given supportive care. Owners can provide some nursing care at home.
Stricken dogs may be given antibiotics to combat infections that result from a suppressed immune system. Fluid therapy and medications help control diarrhea and vomiting to counteract dehydration. Anti-seizure medication may be necessary to control seizures. No single treatment is specific or always effective and it may take ongoing therapy for up to six weeks to conquer the disease.
Each pup responds differently to treatment. For some, the symptoms get better and then worsen before recovery. Others show no improvement despite aggressive treatment. Consult with your veterinarian before making the heartbreaking decision to euthanize a sick puppy.
Recovered pups shed the virus for up to 90 days and can infect other healthy dogs. Sick dogs must be quarantined away from healthy animals. The virus can live in a frozen state for many years, thaw out, and still infect your dog. However, it is relatively unstable in hot or dry conditions and can be killed by most disinfectants such as household bleach.
Dogs that survive infection during puppyhood may suffer enamel hypoplasia—poorly developed tooth enamel that's pitted and discolored. Even dogs that recover from infection may suffer permanent damage to the central nervous system that results in recurrent seizures or palsy for the rest of the dog's life. Protect your puppy with preventive vaccinations as recommended by your veterinarian, and prevent contact with other unvaccinated dogs.