Canine distemper is an aggressive, extremely contagious viral infection with high mortality rates. The virus is acquired through direct contact with an infected animal, or through their respiratory secretions, eye secretions or bodily fluids. Recovery, though difficult, is possible through intensive supportive care. Fully recovered puppies no longer carry the virus, but some infected puppies can be carriers without showing signs of illness.
Susceptibility in Puppies
Unfortunately, puppies are extremely vulnerable to distemper. Puppies under 6 months old who are unvaccinated or only partially vaccinated are particularly susceptible to the virus. Puppies under 3 months old who have not nursed from their mothers and received the benefits of their mother's colostrum -- her immunity-building first milk -- are highly susceptible. Also vulnerable are unvaccinated adult dogs, older puppies and dogs who don't respond to vaccinations, and dogs who are immune-suppressed.
Upon initial contraction, distemper invades the lymphatic tissues of a puppy's lungs and throat, where it replicates itself. Following replication, it infects the rest of the lymphatic system and bone marrow, where it continues to replicate repeatedly for several days. The virus then moves rapidly throughout the puppy's entire body, infecting his urogenital, respiratory, gastrointestinal and central nervous systems, as well as his skin and conjunctival eye membranes.
Early signs that your puppy has been infected with distemper include lethargy, sneezing, coughing, eye and nasal discharge, fever, inappetence, vomiting and diarrhea. If the virus is allowed to progress without medical intervention, your puppy may experience thickening of the foot pads, tremors, slobbering, lack of coordination, respiratory distress, seizures, paralysis and attacks of hysteria.
Diagnosis and Treatment
If you suspect your puppy has been exposed to distemper, take him to a veterinarian immediately. Although distemper tests exist, they are unreliable. Therefore, your vet will probably perform a battery of tests including a urinalysis, biochemical analysis, X-rays, CT scan and MRI. With no known cure for distemper, supportive care is the only treatment available. Your puppy will be hospitalized and given intravenous fluids, antibiotics to treat or prevent secondary infections, and anticonvulsants to control convulsions and seizures.
Life After Distemper
Sadly, the mortality rate of puppies with distemper is about 80 percent. If your puppy survives the infection, he'll no longer carry the virus and won't be a danger to other animals. However, puppies who have survived distemper are often left with lasting ailments such as dry eye, hard pads, scarred lungs, neurological disorders and nerve damage. Many of these post-distemper conditions are treatable; affected animals can live quite normally.
While recovered puppies no longer carry the distemper virus, it's possible for a puppy who has been fully or partially vaccinated to contract the virus and transitorily replicate it without ever becoming sick. An infected puppy who doesn't fall ill and shows no outward or clinical signs of illness is called a carrier. Carriers pose a significant health risk to other animals, as they'll shed infected viral particles into the environment for up to three months. Once the undetected distemper virus has run its course, the puppy will no longer be a carrier.