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An
Overview of Canine Distemper
Canine
distemper is caused by the canine distemper virus (CDV). Prior to the
arrival of canine parvovirus, CDV was unquestionably the most feared
disease seen in domestic canines. This is a highly contagious, largely
incurable, and often fatal disease that attacks the respiratory
and gastrointestinal
tracts, and, most devastatingly, the central
nervous system (CNS).
Cases
of canine distemper are much less common today due to the advent of
effective vaccines, but puppies and even unvaccinated adult dogs are
still highly susceptible to infection. Even with a conscientious vaccination
program, some dogs still fall victim to this potentially fatal virus.
Why and how might my dog become infected?
Despite
the fact that CDV particles are present in many environments, not every
dog will become infected. This is because several factors influence
the effectiveness of the virus. Host vitality (overall health of the
dog, immune experience, vaccination status), virulence of the virus
(the number of viral particles in a given area), and other environmental
factors (stress, dry weather, cold weather) all interact and ultimately
determine whether or not an individual dog will fall ill. Though the
most important factors seem to be the immune level of the dog and the
number of viral particles the dog is exposed to, if each factor is ‘just
right’, a dog will become infected. When this occurs, a specific
sequence of events is initiated as the virus attacks the body.
CDV travels
about as aerosol particles and enters the body through the nose or mouth
as the dog breathes. There is then a latent period of approximately
10 to 14 days during which the virus is replicating and spreading throughout
the body, but no clinical symptoms have yet become visible. Once in
the respiratory tract, the virus makes its way to the nearby lymph
nodes in the neck. Once secure within the nodes, viral
particles begin replicating and gradually spread through the lymphatic
system, generally infecting all lymphatic tissue within
5 days. By the ninth day post infection the virus has invaded the blood,
from which it will spread into the respiratory and GI tracts and eventually
the CNS.
Canine
distemper is estimated to be fatal in 50% of cases affecting adult dogs,
and in 80% of cases affecting puppies. When the virus does prove fatal,
death is usually a result of damage to the nervous system and ensuing
complications such as seizures.
How will my vet reach a diagnosis of distemper?
Symptoms of distemper can be extremely variable depending upon
the stage of the disease. The initial symptom of infection is fever,
but this is easy to overlook and often goes unnoticed. Other classic
early symptoms of distemper include significant eye and nose discharge,
often accompanied or followed by depression, loss of appetite, nausea,
vomiting, and diarrhea. Pneumonia is sometimes yet another side effect,
but does not appear in all cases. Many dogs experience trouble with
their vision as a result of CDV. Inflammation, lesions, and ultimately
blindness due to swelling of the optic nerve may sometimes be observed.
Symptoms indicating infection of the CNS include encephalomyelitis
– simply put, an inflammation of the brain and spinal cord. It
is this aspect of the virus that is the most deadly, as it often causes
muscle incoordination, muscle spasm, seizure, partial or complete paralysis,
and deterioration of mental faculties.
The early
symptoms of distemper are similar to those exhibited by other diseases.
If however you suspect your dog is exhibiting any symptom that might
indicate infection with CDV, you should contact your veterinarian immediately.
Diagnosis can be difficult but is possible and is based on a variety
of factors including laboratory tests. Because distemper symptoms are
so varied, there is no one test to determine whether or not your dog
is infected. Rather, a wide range of procedures, when used together,
may lead to a diagnosis.
Common
respiratory side effects such as pneumonia may be detected by either
x-ray or CT scan. Cerebrospinal fluid (liquid that surround the brain
and spinal cord) can be examined for the presence of antibodies that
would only be present if CDV were in the body. Similarly, immunofluorescent
assays can detect the presence of viral antigens – immune system
proteins that serve to fight viral invaders. A polymerase
chain reaction (PCR) can be used to determine the genetic
sequence of any virus present, but this is an extremely sensitive, difficult,
and occasionally inaccurate technique. Finally, a microscopic examination
of blood and tissue samples may detect the presence of inclusion
bodies, cellular structures that indicate that CDV particles
are present. None of these techniques can provide a definitive, question-free
diagnosis. Generally a veterinarian will use laboratory procedures in
conjunction with clinical observations and knowledge of the individual
dog’s vaccination history in order to reach a diagnosis of distemper.
What are the treatment options for dogs with distemper?
Treatment
procedures for dogs suffering from CDV are limited to a supportive capacity.
A hospital stay may be necessary, as fluids and nutrients are often
given intravenously and the trained veterinary staff is properly prepared
to care for seriously ill animals. Treatments may vary between individual
cases, but there are certain aspects that are considered vital.
The environment
in which a sick dog resides must be kept clean, warm, and free of chilly
drafts. An effort should be made to keep eyes and nose as free of discharge
as possible. Certain medications may be prescribed to combat the effects
of vomiting and diarrhea. As previously mentioned, the patient should
be monitored closely for dehydration and may have to receive fluid and/or
liquid nutrition intravenously. Dogs having difficulty with their vision
may be administered glucocorticoid
therapy in an attempt to prevent blindness. If the disease progresses
to such a degree that neurological damage occurs, medicinal control
of seizures and muscle spasms may become necessary.
Even if
a dog survives and recovers from a bout with canine distemper, it should
be noted that many animals continue to suffer long term effects. Enamel
hypoplasia, or lack of tooth enamel, is a common affliction
of CDV survivors. This deficiency, if untreated, causes severe tooth
decay. A second long lasting effect of distemper is known as hyperkeratosis,
which refers to an unnatural and uncomfortable hardening of the nose
and foot pads. There is no easy, quick, or surefire cure for canine
distemper.
How do I vaccinate
my pet against canine distemper?
Vaccines
are complicated substances and often raise many questions. For a brief
introduction to vaccines and how they work, please goto An
Introduction to the World of Vaccines.
Since
the advent of effective vaccinations, CDV has become much less of a
threat to domesticated dogs. This does not mean, however, that CDV is
not a serious problem. Vaccination of your dog should not be considered
an option – it is a must. Veterinarians usually administer the
CDV vaccine as part of a combination which includes, among others, the
parvovirus and coronavirus vaccines. These shots are given every 3-4
weeks from the time a puppy is 6 weeks old until he is at least 16 weeks
of age.
How else can I help prevent the disease?
The most
important step in preventing the spread of distemper is vaccination.
Beyond that, however, certain steps may be taken to minimize exposure.
Thankfully, the canine distemper virus is not as tough as the canine
parvovirus and cannot survive for long outside the dog’s body.
The viral particles may be killed by exposure to heat, sunlight, various
detergents and soaps, and an assortment of chemicals. Any potentially
infected dog should be isolated from other dogs. Once the sick dog has
recovered or has left the home, pet owners should wait one month before
introducing a new animal. Further, contaminated objects and areas may
be disinfected using a 1:30 bleach-water solution.
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