Viral Diseases
Viruses are disease-causing organisms that are even more basic than cells. They are simply packages of proteinDISTEMPER
Distemper is a highly contagious disease caused by a virus similar to the one
that causes measles in people. Worldwide, it is the leading cause of infectious
disease deaths in dogs, although in the United States it occurs only sporadically.
All unvaccinated dogs are at high risk of infection.
Infected animals shed canine distemper virus in all body secretions.
Inhaling the virus is the primary source of exposure. The highest incidence of the disease occurs in unvaccinated puppies 6 to 12 weeks of age, at which
time maternal antibodies fall below protective levels.
Half the dogs who become infected with canine distemper virus show mild
signs of illness or no signs at all. The overall health of the dog has a lot to do
with how ill he becomes. The disease is most severe in dogs who are poorly
nourished and ill-kept
The distemper virus tends to attack brain cells and cells that line the surfaces
of the body, including the skin, the conjunctiva, the mucous membranes
of the respiratory tract, and the gastrointestinal tract. The disease takes a variety
of forms. Secondary infections and complications are common, partly
attributable to the immunosuppressive effects of the virus.
The first signs of distemper appear six to nine days after exposure, and in
mild cases go unnoticed.
First stage is characterized by a fever spike of up to 103° to 105°F (39.4° to
40.5°C). A second fever spike is accompanied by loss of appetite, listlessness,
and a watery discharge from the eyes and nose. These symptoms may be mistaken
for a cold.
ken for a cold.
Within a few days, the eye and nasal discharge becomes thick, yellow, and
sticky. The dog develops a pronounced dry cough. Pus blisters may appear on
the abdomen. Vomiting and diarrhea are frequent and may cause severe
dehydration.
During the next one to two weeks, very often the dog seems to be getting
better but then relapses. This often coincides with the end of the course of
antibiotics and the development of gastrointestinal and respiratory complications
due to secondary bacterial invasion.
Second stage occurs two to three weeks after the onset of the disease.
Many dogs develop signs of brain involvement (encephalitis), characterized by
brief attacks of slobbering, head shaking, and chewing movements of the jaws
(as if the dog were chewing gum). Epileptic-like seizures may occur, in which
the dog runs in circles, falls over, and kicks all four feet wildly. After the convulsive
episode the dog appears to be confused, shies away from his owner,
wanders about aimlessly, and appears to be blind.
In cases with brain involvement in which the diagnosis is uncertain, a
spinal tap and analysis of cerebrospinal fluid may be of assistance. But this is
not always diagnostic. Another indication of brain involvement is distemper
myoclonus, a condition characterized by rhythmic contractions of muscle
groups at up to 60 contractions per minute. The jerking can affect all parts of
the body, but is most common in the head. Myoclonus is first seen when the
dog is resting or sleeping. Later it occurs both day and night. Pain accompanies
myoclonus, and the dog whines and cries. If the dog recovers, the jerking
continues indefinitely—but becomes less severe with time.
Hard-pad is a form of distemper in which the virus attacks the skin of the
feet and nose, producing thick, horny skin on the nose and calluslike pads on
the feet. It first appears about 15 days after the onset of the infection. At one time, hard-pad and encephalitis were thought to be separate diseases, but they
are now recognized as being caused by different strains of the distemper virus.
Hard-pad is much less common than it was in the past, due to better vaccines
and increased use of vaccines.
Treatment:
Distemper must be treated by a veterinarian. Antibiotics are
used to prevent secondary bacterial infections, even though they have no
effect on the distemper virus. Supportive treatment includes intravenous fluids
to correct dehydration, medications to prevent vomiting and diarrhea, and
anticonvulsants and sedatives to control seizures.
The outcome depends on how quickly you seek professional help, the virulence
of the distemper strain, the age of the dog, whether he has been vaccinated,
and his ability to mount a rapid and effective immune response to the
virus.
CANINE HERPESVIRUS INFECTION
Canine herpesvirus is widespread in the dog population and produces a variety
of illnesses. It causes a fatal disease in newborn puppies. It is one of the agents implicated in the kennel cough
complex. It causes vaginitis in bitches and infection of the penile sheath in
males, and it can be transmitted between males and females during breeding.
Bitches with vaginitis develop hemorrhagic areas and blisterlike lesions of
the vaginal mucosa. These lesions may reappear when the bitch comes into
heat. Intrauterine infections that progress from the vagina are associated with
early embryonic loss, abortions, and stillbirths.
Herpesvirus infection can be confirmed by isolating the virus from infected
tissue.
Treatment:
There is no effective treatment. A vaccine is not available in
the United States at this time, but one is being used in Europe.
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