Canine Herpesvirus
October, 1997
Infection with Canine Herpesvirus can be devastating to a
Litter of newborn puppies, but, fortunately, is not a very common
occurance. It is seen in dogs only and is found worldwide.
When adult dogs come in contact with the virus, it sets up
infection in the respiratory tract, the genitals, or both.
Respiratory infection may cause a mild runny nose or cough, but
the majority of dogs which harbor this virus in the nose or
throat have no signs of disease. Similarly, the virus may cause
vesicles of the vagina or prepuce, but the majority of adult
genital infections are also asymptomatic. The length of the
Latency period is unkown and variable, but may be years.
Infection of puppies usually occurs at or soon after birth, but
the virus has the potential to cross the placental barrier during
late pregnancy. When this occurs, it Leads to abortions or
stillbirths. More commonly, infection occurs during passage
through the birth canal or from contact with infected littermates
or the dams’ respiratory secretions. The virus may also be
carried on objects and clothing, but it doesn’t survive long
outside the dogs’ body and is not considered an
environmental contaminant.
The virus enters the puppies’ body through the nose and
mouth and then spreads to nearly every tissue in the body. Signs
usually occur between 1 and 3 weeks of age. Infected puppies
appear dull and depressed, lose interest in nursing, and may pass
soft, yellow-green feces. They cry persisently, are restless, and
may have runny eyes and nose. Other, more rare, signs that may be
seen include bleeding tendencies and seizures. Fevers do not
occur, and rectal temperatures usually drop below normal prior to
death, which usually occurs within 24 to 48 hours from the
beginning of outward signs. The progression of the disease is so
rapid that dog owners may only notice sudden death of apparently
healthy puppies.
When exposure occurs during the first week of life, the mortality
rate is high. When occuring after 2 weeks of age, infection
causes only mild disease or no signs at all. There are several
reasons for this abrupt development of resistance. The virus is
easily killed by higher temperatures, but body temperature
regulation and the ability to produce a fever are not well
developed until 2 to 3 weeks of age. Also, normal rectal
temperature at this age is I 3 degrees Farenheit lower than adult
dogs.
The degree of immunity acquired from the dam also appears to be
important in the survival of infected pups. Bitches that have
given birth to an affected litter will develop immunity by their
next heat and, with rare exceptions, future litters are normal.
Diagnosis is usually based on history and clinical signs (rapid
death of puppies 1-3 weeks of age) and can be confirmed by
autopsy. Any puppy that dies should be kept cool until a
verterinarian is consulted. Antibodies can be detected in the
bloodstream, but their significance is difficult to determine.
That is, carriers of the virus may or may not have a measurable
antibody titer. After antibodies do deveop, they may persist
after infection is gone.
Treatment is generally unsuccessfUl, but can be attempted.
Supportive care is used, especially elevating the temperature of
the puppy’s environment with heating pads or lamps. If
administered before exposure to the virus, injections of
antiserum can supply protective antibodies. This is obtained by
collecting blood from bitches that have recently lost litters to
Canine Herpesvirus infection, and is not frequently available.
A kennel with an existing problem with this virus can take a few
precautions. Because puppies that survive the infection (usually
those over 3-4 weeks old) can excrete the virus for several
weeks, isolation and rigorous disinfective procedures
can decrease viral spread. There is nova cination available and
it is not likely one will be developed soon. No screen ing test
is available to reliably differentiate ate carriers from
non-carriers. As men tioned previously, bitches that have ha an
infected litter can safely be bred again Delaying the breeding of
all other adul who may have been exposed to the vir may allow
time to develop immunity Breeding potentially exposed males to fe
males frOm another kennel can be a prob lem because of the
possibility of venere transmission.
Because infections rates can approac 100% in some kennels, rapid
eliminati of the problem is an unrealistic goal, b with time,
good disinfective practices, an some common sense, the number of
new born puppies that succumb to Canine Her pesvirus infection
can be decreased.