-----Feline Immunodeficiency Virus
River Road Veterinary Clinic
Box 309
Norwich, Vermont 05055
Phone: 802-649-3877 Fax: 802-649-1345
email: RRVC@Valley.net.com
www.rrvetclinic.com
Dr. Christine Pinello - Dr. JoAnne Giel - Dr. Kathy Ling Newcomb
Feline Immunodeficiency Virus
Article written by: Alfred M Legendre
Feline immunodeficiency virus (FIV) was first identified in an immunosuppressed
cat in 1986. FIV is a lentivirus (slow virus), so named because of the
slow development of disease. FIV is of the same family of viruses as
human immunodeficiency virus (HIV), which causes acquired immunodeficiency
syndrome (AIDS) in people. It is important to remember that FIV is infectious
only to cats.
Immunodeficiency related to FIV infection occurs most often in free-roaming,
male cats older than 6 years. Transmission of FIV is usually through
cat bites incurred when fighting. Defense of territory explains the
higher incidence of disease in male cats. FIV is occasionally transmitted
to kittens by their mothers.
Random testing of cats seen by veterinarians shows a healthy cat prevalence
of 1 to 2 per cent in the United States and up to 12 per cent in Japan,
where most cats a re kept outside and are not neutered. Twelve to 40
per cent of sick cats are infected with FIV. Once cats develop FIV infection,
they are infected for life. Studies of frozen serum samples from 20
years ago show that the prevalence of FIV infection has not changed.
Cats with FIV, like people with HIV, have an acute phase of illness
that begins 4 to 6 weeks after a bite from an infected cat. Most cats
develop fever, depression, and enlarged lymph nodes that last from weeks
to months. These symptoms are usually mild enough that owners rarely
notice. Kittens infected as newborns may die in the acute phase. After
recovery from the acute phase, these cats may appear completely normal
for 3 years or more. During this asymptomatic period, the FIV virus
is gradually destroying the immune system, limiting the ability to fight
infection.
When the immune dysfunction is relatively mild, cats have bacterial
and viral infections commonly seen in cats, such as mouth infections,
abscesses, chronic nasal and eye discharges, skin infections, ear infections,
and diarrhea. FIV-infected cats have ringworm at three times the expected
rate. These infections respond to the usual treatment, but not as well
as expected, and often recur after treatment is completed.
FIV can also affect the bone marrow, causing anemia. Parasitic
diseases such as toxoplasmosis tat normally cause only mild signs become
life threatening. The FIV has an affinity for brain tissue and can produce
personality changes. Shy cats may become aggressive and outgoing cats
may hide. Malignancy of lymph node cells (lymphosarcoma) may develop.
Cats infected with FIV are also more likely to develop kidney failure.
When immune depression is severe, cats may develop opportunistic infections
(infections that do not usually occur in that species) such as demodectic
mange seen in dogs. During the later stages, standard treatments are
not effective because they require the help of the immune system to
resolve infections. Nevertheless, immunosuppressed cats may live a year
or longer if treated.
When FIV is suspected, a blood test can be done. A negative test usually
excludes a diagnosis of FIV, but an early infection (first 2 months)
could be missed. A positive test with appropriate signs is quite reliable,
but an occasional false-positive
Test can occur. A Western blot test (a more specific and definitive
test) of blood confirms the diagnosis.
A positive test for FIV is not a reason for euthanasia. A study of newly
diagnosed FIV-infected cats showed that 7 of 11 cats were still alive
2 years later. We rarely know when cats become infected. A cat with
early infection may have 3 or 4 more years of disease-free life. FIV-positive
cats should be kept indoors for the safety of other cats and to limit
their exposure to the disease.
The response to treatment of FIV-infected cats depends on the degree
of immune suppression. There are no god antiviral drugs for the cat.
Azidothymidine (AZT), a drug used in people to inhibit virus reproduction,
works against the FIV virus but has a significant toxicity in the cat.
There are other promising drugs but they are not yet available. Most
of the illnesses in FIV-infected cats results from secondary bacterial
infections that can be controlled with antibiotics. Antibiotics can
prolong the cat's life in spite of a poorly functioning immune system.
Prevention with vaccination would be helpful but, as in people, an effective
vaccine has not been developed.