Canine distemper
Warning
vaccinations against distemper can trigger a latent
disease
Overview
Canine distemper is a contagious, incurable, often fatal,
multisystemic viral disease that affects the respiratory,
gastrointestinal, and central nervous systems. Distemper is
caused by the canine distemper virus (CDV).
Incidence
Canine distemper occurs worldwide, and once was the leading
cause of death in unvaccinated puppies. Widespread
vaccination
programs have
dramatically reduced its incidence.
CDV occurs among domestic dogs and many other carnivores,
including raccoons, skunks, and foxes. CDV is fairly common
in wildlife. The development of a vaccine in the early
1960s led to a dramatic reduction in the number of infected
domestic dogs. It tends to occur now only as sporadic
outbreaks.
Young puppies
between 3 and 6
months old are most susceptible to infection and disease
and are more likely to die than infected adults.
Nonimmunized
older dogs are also
highly susceptible to infection and disease. Nonimmunized
dogs that have contact with other nonimmunized dogs or with
wild carnivores have a greater risk of developing canine
distemper.
Transmission
Infected dogs shed the virus through bodily secretions and
excretions, especially respiratory secretions.
The primary mode of transmission
is airborne viral particles that dogs breathe in. Dogs in
recovery may continue to shed the virus for several
weeks after symptoms disappear, but they no longer shed
the virus once they are fully
recovered.
It is possible for humans to contract an asymptomatic
(subclinical) CDV infection. Anyone who’s been
immunized against measles (a related virus) is protected
against CDV as well.
Symptoms
Macrophages (cells that ingest
foreign disease-carrying organisms, like viruses and
bacteria) carry the inhaled virus to nearby lymph nodes
where it begins replicating (reproducing). It
spreads
rapidly through the lymphatic tissue
and infects all the lymphoid organs within 2 to 5 days. By
days six to nine, the virus spreads to the blood (viremia).
It then spreads to the surface epithelium (cell lining) of
the respiratory, gastrointestinal, urogenital, and central
nervous systems, where it begins doing the damage that
causes the symptoms.
Early symptoms include fever, loss of appetite, and mild
eye inflammation that may only last a day or two. Symptoms
become more serious and noticeable as the disease
progresses.
The initial
symptom is fever
(103ºF to 106ºF),
which usually peaks 3 to 6 days after infection. The fever
often goes unnoticed and may peak again a few days later.
Dogs may experience eye and nose discharge, depression, and
loss of appetite (anorexia). After the fever, symptoms vary
considerably, depending on the strain of the virus and the
dog’s immunity.
Many dogs experience gastrointestinal
and
respiratory
symptoms,
such as:
• Conjunctivitis
(discharge from the eye)
• Diarrhea
• Fever (usually present but unnoticed)
• Pneumonia (cough, labored breathing)
• Rhinitis (runny nose)
• Vomiting
These
symptoms are often exacerbated by secondary bacterial
infections. Dogs almost always develop encephalomyelitis
(an inflammation of the brain and spinal cord), the
symptoms of which are variable and progressive. Most dogs
that die from distemper, die from neurological
complications such as the following:
• Ataxia (muscle
incoordination)
• Depression
• Hyperesthesia (increased sensitivity to sensory
stimuli, such as pain or touch)
• Myoclonus (muscle
twitching or spasm), which can become disabling
• Paralysis
• Paresis (partial or incomplete paralysis)
• Progressive deterioration of mental abilities
• Progressive deterioration of motor skills
• Seizures that can affect any part of the body (One
type of seizure that affects the head, and is unique to
distemper, is sometimes referred to as a “chewing gum
fit” because the dog appears to be chewing gum.)
Many
dogs experience symptoms of the eye:
• Inflammation
of the eye (either keratoconjunctivitis,
inflammation of the cornea and conjunctiva, or
chorioretinitis, inflammation of the choroid and retina)
• Lesions on
the retina (the innermost layer of the
eye)
• Optic
neuritis (inflammation of the optic
nerve which leads to blindness)
Two
relatively minor conditions that often become chronic, even
in dogs that recover are:
• Enamel hypoplasia
(unenameled teeth that erode quickly in puppies whose
permanent teeth haven’t erupted yet - the virus kills
all the cells that make teeth enamel)
• Hyperkeratosis (hardening of the foot pads and nose)
In
utero infection of
fetuses is
rare, but can happen. This can lead to spontaneous
abortion, persistent infection in newborn puppies, or the
birth of normal looking puppies that rapidly develop
symptoms and die within 4 to 6 weeks.
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Overview
Transmission
Symptoms
Diagnosis
Treatment
Prevention
Prognosis