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Canine
Herpesviral Infection
Roger Ross DVM
http://animalpetdoctor.homestead.com
Introduction:
Canine herpesvirus is a fatal, viral infection of puppies worldwide.
It also may be associated with upper respiratory infection or a vesicular
vaginitis or posthitis in adult dogs. Only canids (dogs, wolves, coyotes)
are known to be susceptible.
Etiology: The disease
is caused by an enveloped DNA canine herpesvirus (CHV), which is sensitive
to lipid solvents and most disinfectants. CHV is relatively unstable outside
the host. Transmission usually occurs by contact between susceptible puppies
and the infected oral, nasal, or vaginal secretions of their dam or oral
or nasal secretions of dogs allowed to commingle with puppies during the
first 3 wk of life. In utero transmission may occur. Infection of newborn
susceptible puppies results in replication of CHV in the surface cells of
the nasal mucosa, pharynx, and tonsils. If the pups become hypothermic,
viremia and invasion of visceral organs occur.
Clinical Findings: Deaths
due to CHV infection usually occur in puppies 1-3 wk old, occasionally in
puppies up to 1 mo old, and rarely in pups as old as 6 mo Typically, onset
is sudden, and death occurs after an illness of <24 hr. Older dogs exposed
to or experimentally inoculated with CHV may develop a mild rhinitis or a
vesicular vaginitis or posthitis. In utero infections may be associated with
abortions, stillbirths, and infertility.
Diagnosis: CHV infection
may be confused with infectious canine hepatitis, but it is not accompanied
by the thickened, edematous gallbladder often associated with the latter.
The focal areas of necrosis and hemorrhage, especially those that occur
in the kidneys, distinguish it from hepatitis and neosporosis. CHV causes
serious disease only in very young puppies. The rapid death and characteristic
lesions distinguish it from canine distemper. The virus can be isolated
from fresh lung, liver, kidney, and spleen by cell culture techniques. The
tissues should be submitted to the laboratory refrigerated but not frozen.
Control: No vaccine is
available. Infected bitches develop antibodies, and litters subsequent to
the first infected litter receive maternal antibodies in the colostrum. Puppies
that receive maternal antibodies may be infected with the virus, but disease
does not result. Removal of puppies from affected bitches by cesarean section
and rearing them in isolation has prevented deaths under experimental conditions.
However, infections have been noted even in puppies delivered by cesarean
section. Deaths may be reduced when infected puppies are reared in incubators
at increased temperatures (95°F [35°C], 50% relative humidity) and
given adequate fluids and supportive therapy. The prognosis of puppies that
survive neonatal infections of CHV is guarded because damage to lymphoid
organs, brain, kidneys, and liver may be irreparable.
reprinted with kind permission from Roger Ross DVM
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