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FELINE HERPESVIRUS
Feline herpesvirus (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 herpesvirus 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 HERPESVIRUS
Canine herpesvirus (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. Herpesvirus 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. Canine Herpesvirus 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 herpesvirus infection. Once infected, the dog usually
remains infected for life, and may be capable of shedding virus whenever stressed.
In the adult bitch, herpesvirus 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 herpesvirus 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 herpesvirus 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 Canine Herpesvirus 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 HERPESVIRUS
Equine herpesviruses 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.
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