Canine distemper is caused by a virus (Morbillivirus), and it is closely related to the virus that causes measles in people. Prior to the development of a vaccine, distemper was the most common infection in dogs. Fortunately, the distemper vaccine has reduced the frequency of this serious and usually fatal disease, but I still see distemper in puppies, unvaccinated adult dogs and pet ferrets. In addition to dogs, the distemper virus can infect wild members of the canine family, including wolves, coyotes and foxes. It can also infect other wildlife, such as raccoons, skunks, bears, mink and endangered black-footed ferrets. Recently, canine distemper has started to infect big cats, including lions, tigers and leopards; most of these big cats have died from it.
Symptoms Of Distemper In Puppies
Four main signs of illness occur with canine distemper:
1. Respiratory Symptoms: When a puppy becomes infected with the distemper virus, the first signs of the disease are usually seen in the respiratory system. A discharge from the eyes and nose is common. The discharge normally starts as a clear liquid, but it soon thickens and turns yellow to green in color. Sneezing and coughing are also common in this early stage of the disease. Most puppies will be less active than normal, eat less than normal and will have a fever at this stage. It is easy to confuse distemper with a routine upper respiratory infection like kennel cough at this point, even for an experienced veterinarian like me. With canine distemper, the respiratory infection will continue to worsen, and pneumonia will soon develop.
2. Gastrointestinal Symptoms: The virus soon causes damage to the stomach and intestinal tract. Vomiting, diarrhea and lack of an appetite are commonly seen. Vomiting and diarrhea are fairly typical in puppies, but many diseases besides distemper can be the culprit. By this time, the white blood cell count is lower than normal, and the puppy’s immune system is suppressed. The combination of respiratory signs and GI signs will make me suspect distemper as the underlining cause.
3. Paw And Nose Symptoms: Some puppies will develop thick, hard pads on the bottom of their paws; this is why distemper is sometimes called “hard pad” disease by dog breeders and older veterinarians. The hard pads are an uncommon problem for puppies without distemper, so it is one of the classic signs that makes me think distemper is causing the illness in a puppy. Frequently, the distal part of the nose will also change and become thick and crusty.
4. Neurological Symptoms: Roughly one to three weeks later, the signs of damage to the brain and central nervous system become noticeable. A rhythmic twitching of the muscles (myoclonus) on the top of the head and limbs is usually the first neurological sign. This is another uncommon problem in puppies without distemper, and another classic sign that makes me think that distemper is very likely. Other neurological signs include weakness in the rear legs and seizures. Blindness due to inflammation and damage to the optic nerve are also possible.
Treatment For Distemper In Dogs
Currently there is no antiviral medication that works on the distemper virus. Thus, treatment is aimed at rehydrating the puppy, treating the bacterial part of the pneumonia and controlling the rest of the clinical signs. Your veterinarian might choose all or some of the following methods to manage symptoms.
- The dehydration can be treated with intravenous (IV) fluids or in some cases with just subcutaneous (SQ) fluids.
- Cerenia, a motion-sickness drug for dogs, can be used to control the vomiting.
- Antibiotics can be used to treat the pneumonia and diarrhea.
- A soft food like Hill’s Prescription Diet a/d Canine can be used to increase the appetite.
- Phenobarbital and potassium bromide can be used to try to control the seizure activity and muscle twitching.
- Vitamin A supplementation has been shown to help reduce the damage from measles in people, so vitamin A supplements might help in puppies.
- Some veterinarians will use immune stimulators like interferon or polyprenyl immunostimulant (PI) to try to stimulate the puppy’s immune system to fight off the virus.
- Some veterinarians will give a blood transfusion from a recently vaccinated dog to the sick puppy. They hope the antibodies from the recently vaccinated dog will help fight off the distemper virus in the puppy. This is similar to the blood transfusions (from an Ebola survivor) that are used to treat Ebola patients. Unfortunately, antibodies from blood transfusions are not likely to actually get into the brain or to repair the damage to the brain or nerves, so it is doubtful that blood transfusions will help if neurological signs are already present.
Survival Of Puppies With Distemper
Distemper is one of the more frustrating diseases for veterinarians to treat. No matter what treatment your veterinarian tries, most puppies who are showing neurological signs will continue to get worse and will eventually be euthanized or die from distemper. Some puppies are extremely lucky and survive. Unfortunately, the survivors will have permanent damage to the brain and to the enamel of their teeth. Some will have occasional seizure activity for the rest of their life, and most will develop uncoordinated movements of the arms or legs (chorea) when they become adult dogs.
Preventing Distemper In Dogs
With such a poor survival rate for canine distemper, it is imperative to prevent your puppy from getting it. Distemper can easily be prevented with proper vaccinations. Vaccination should start when your puppy is 6 to 7 weeks old. Follow this with vaccine boosters that are given every three weeks until your puppy is at least 16 weeks old.
Distemper is highly contagious and easily spread to other dogs via aerosol droplets from an infected dog sneezing or coughing. This is similar to how the human cold virus and the flu virus are spread. In addition, the distemper virus might be spread in the urine, feces, blood or saliva from an infected dog. An infected animal may spread the virus for weeks to possibly months after being exposed. While your puppy is going through the vaccine series, keep him away from other dogs that could be sick with distemper. Until your puppy is fully vaccinated, avoid high-risk areas, such as animal shelters, pet stores, dog parks and flea markets.
Most cases of canine distemper are in puppies less than 6 months of age, but I have seen it in unvaccinated adult dogs, too. Thus, adult dogs need to be properly vaccinated. Consult with your veterinarian on how often your adult dog will need to be vaccinated.