Canine Distemper

Canine distemper is a disease that primarily affects the lungs,
intestinal tract, and nervous system of dogs. Among the
virus-induced diseases in dogs, the mortality rate of distemper
is second only to that of rabies. The virus is highly contagious
and is passed directly from dog to dog by close contact. The
virus is easily killed by detergents and heat. The virus dies
within minutes in a warm environment but can persist for weeks
at near-freezing temperatures.

Young, unvaccinated dogs 3 to 6 months of age are most often
infected with distemper. Nasal discharges containing virus are
aerosolized by sneezing, thereby spreading the virus. The virus
establishes itself in the nasal passages of a susceptible dog,
multiplies, and spreads through the body. Dogs develop a fever a
week after infection but this fever may not be noticed.

Two weeks after infection, the virus produces severe damage to
the cells of the nasal passages, eyes, lungs, and intestinal
tract. These damaged tissues commonly become secondarily
infected with bacteria. This combined infection with virus and
bacteria produces loss of appetite, fever, snotty nose, thick
discharge from the eyes, pneumonia, and diarrhea. The virus
infects the pads of the feet, producing a hard, scaly thickening
referred to as “hard pad” disease. The virus also damages the
immune system, thereby interfering with the body’s ability to
fight off the infection.

If the bacterial component of the infection can be controlled
with antibiotics, the dogs will appear normal for 2 to 3 weeks
until signs of brain and spinal cord disease occur. Half of the
dogs with distemper develop neurologic disease. The canine
distemper virus is attracted to and grows well in nervous
tissue. The damage done to the brain and spinal cord results in
epileptic seizures and localized seizures of the head often
called “chewing gum fits.” Damage to the spinal cord can produce
weakness and paralysis. Nerve damage may also produce
involuntary twitching of the legs. Most dogs with neurologic
disease die or are euthanized.

Making a definite diagnosis of distemper can be difficult if the
dog does not develop the typical snotty nose-pneumonia syndrome.
After the initial 14 days of the infection, the virus is
difficult to identify in swabs of infected tissues. Increasing
antibody titers against distemper in dogs that have not been
vaccinated strengthen the suspicion of distemper. It is
especially difficult to diagnose distemper in dogs with nervous
system signs that have not had the other typical signs of
distemper.

Currently, no drugs are available to treat the distemper virus,
so treatment with antibiotics is aimed at controlling the
secondary bacterial infection. The antibiotic treatment relieves
many of the signs of disease but does not prevent the virus from
entering and damaging the brain and spinal cord. Nursing care;
good-quality, palatable food; and a stress-free environment are
helpful in improving appetite and general well-being. Because
the treatment options are limited, prevention by vaccination is
the prime strategy.

Vaccines against distemper should be started when puppies are
weaned. If the mother has been vaccinated or recovered from an
exposure to distemper, she will pass protection (antibodies)
against distemper to her puppies in her milk. These maternal
antibodies protect the pups for a few weeks after birth. The
amount of antibodies passed from the mother to her pups depends
mainly on the level of the mother’s antibodies. The antibodies
not only protect the pups from distemper but also interfere with
the pups’ response to vaccination. As long as the pups have
maternal antibodies, they cannot be successfully vaccinated.

By 6 weeks of age, half of the litters of pups no longer have
enough antibodies to interfere with vaccination. As the pups
grow, the antibodies obtained from the darn are gradually broken
down, and by 13 weeks of age more than 95 per cent of the pups
are susceptible to distemper and can be protected by
vaccination. It is not economically feasible to measure
antibodies in the pups, so a vaccine schedule has been developed
to protect pups optimally against distemper.

Vaccines should be started soon after weaning, at 6 to 7 weeks
of age, and given every 2 to 3 weeks until the puppies are 14
weeks of age. The pups should be kept away from other dogs until
the vaccination schedule is complete. This scheme of vaccination
has proved effective in preventing this lethal disease.

The above is general veterinary information. Do not begin
any course of treatment without consulting your regular
veterinarian. All animals should be examined at least once every
12 months.