HERPES VIRUS INFECTION AS A TRIGGER OF
ANIMAL HEALTH PROBLEMS
FELINE HERPES VIRUS
Feline herpes virus (FHV-1) is found worldwide
and is a very common disease of cats. Approximately 50 to
70% of adult cats have antibodies to the virus and the infection
rate can be up to 100% in susceptible, unvaccinated cats.
Mortality, however, is usually quite low, with the exception
is in kittens, where the mortality rate can reach 30%. Mortality
is higher with stress or concurrent infections.
FHV-1 causes acute respiratory illness
known as rhinotracheitis. Rhinotracheitis is characterized
by a variety of respiratory symptoms, including sneezing,
nasal discharge, and rhinitis (inflammation of the nose).
Rhinotracheitis is part of the feline upper respiratory
infection complex, a group of viral and bacterial
infections (e.g., Calicivirus, Chlamydia, Bordetella and
Mycoplasma) that cause sneezing and discharge from the eyes
and nose. FHV-1 is one of the most common. Cats often have
two or more of these upper respiratory infections at the
same time. This occurs because the herpes virus enters and
challenges the animal’s immune system, causing the
host to become more susceptible to all other infections
more readily than an uninfected cat. HealthGene's Feline
Upper Respiratory Profile (test code: FP6) can
help a veterinarian to detect most common pathogens which
are responsible for this problem.
Also, FHV-1 can cause conjunctivitis and
keratitis in cats. It is important to know that FHV-1 conjunctivitis
and/or keratitis cannot be cured, only controlled. Often,
the medical history and the clinical signs present are sufficient
to aid in diagnosis, but special tests are needed. These
tests include (but are not limited to): collection of conjunctival
and/or corneal cells for culture, or special DNA tests for
FHV-1 infection (Feline Extraocular Infection Profile,
test code: FP14).
CANINE HERPES VIRUS
Canine herpes virus (CHV) infection can
be devastating to the breeding kennel, resulting in decreased
fertility, small litter sizes, and puppy death. CHV is quickly
killed by sunlight or heat, and therefore most transmission
occurs when dogs are in close contact as a result of licking
secretions or coughing. Herpes virus may be passed to unborn
pups in the uterus, or may infect newborn puppies as they
pass through the birth canal and come in contact with vaginal
cervical secretions. CHV may also be transmitted during
mating. Dogs are most susceptible to infection when under
stress, such as during pregnancy (especially three weeks
prior to whelping), in the neonatal period (especially the
first three weeks of life), in a boarding kennel, or when
competing in events. Also any dog undergoing immunosuppressive
therapy (cancer treatment or steroid use) is at a higher
risk of herpes virus infection. Once infected, the dog usually
remains infected for life, and may be capable of shedding
virus whenever stressed.
In the adult bitch, herpes virus infection
usually results in vaginal infection (vaginitis), and may
form pustules (also known as "dog pox"). Fertility
is decreased, and abortion or birth of premature puppies
is common. Males will show similar 'pox-like' lesions on
the base of the penis and prepuce. Many males will have
a preputial discharge. Upper respiratory signs may also
be noted.
Infection of newborn puppies commonly results
in death. Puppies infected with herpes virus at the time
of birth will generally start to show clinical signs of
infection at four to six days of age. Infected puppies will
persistently cry, have a diminished suckling response, exhibit
yellow green diarrhea and have abdominal pain. Fever is
usually not present. Death frequently occurs within 48 hours
after clinical signs are noted. One or all pups in a litter
infected at birth may show signs of herpes virus infection.
Puppies older than two weeks of age are usually fairly resistant
to infection and may show mild signs or no signs at all.
To control and monitor CHV infection in
a dog population, HealthGene Laboratory is offering two
DNA profiles: one for the bitch (Canine Lost Pregnancy
Profile, test code: CP16) and for the sire (Canine
Semen Profile, test code: CP10). Both profiles
can be used to test animals before breeding.
EQUINE HERPES VIRUS
Equine herpes viruses types 1 and 4 (EHV-1,
EHV-4) are closely related viruses, spread via the respiratory
route. Initial infection occurs in the respiratory tract
and the virus then infects blood cells and is hence carried
around the body to other sites of infection. The outcomes
of infection (either following primary infection or reactivation)
vary between mild respiratory disease to the induction of
abortion in pregnant mares and occasionally severe neurological
disease including paralysis. EHV-4 infection predominantly
results in respiratory disease whereas EHV-1 can induce
both abortion and paralysis; in both cases, however, the
majority of infected horses do not show overt signs of disease.
After an infection, the virus can remain latent in the body
and the animal is said to be a "carrier" of the
virus. These animals may be the source of an outbreak of
disease. Diagnosis in live animals can be confirmed by PCR
(DNA test) from nasopharyngeal swabs and blood samples.
If an animal dies, diagnosis can be made on post mortem
examination through characteristic histopathology and PCR
of DNA extracted from tissues.
