Feline Virus Infection
Copyright
©1996, 1997 HomeVet
Feline
Leukemia Virus: What Is It?
Feline leukemia
virus (FeLV) is one of the most common and destructive
of all cat viruses. It is highly contagious and is spread
primarily by saliva during cat fights, grooming or mating.
The virus is also spread by blood, urine and feces.
Kittens may become infected while still in the womb,
during birth or during nursing.
Not all cats
exposed to FeLV become infected. About 40 percent of
exposed cats have immune systems that destroy the invading
virus. The remainder of exposed cats become persistently
infected (30 percent) or develop a latent infection
(30 percent).
The latter group
has inactive virus in the bone marrow, and these virus
particles may later become active when the cat becomes
ill from another disease, stress or certain drugs.
Of the cats persistently
infected, about 25 percent will die within one year
and 75 percent will die within three years. Some may
live a normal life but tend to have various chronic
illnesses.
There are no
signs specific for FeLV infection. The main effect of
the virus is to disrupt the cat's immune system. While
anemia is the most common disorder caused by the virus,
cancer and various other diseases are common.
Disorders commonly
associated with FeLV infection include chronic respiratory
disease; chronic infection of the mouth, gums and tongue;
chronic eye disease; frequent or chronic skin disease;
disease (abortion, stillbirths and kitten deaths); frequent
or chronic urinary tract infections; chronic digestive
tract disease; and other systemic diseases (infectious
peritonitis, hemobartonellosis, toxoplasmosis, polyarthritis).
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How
Can I Protect My Cat From FeLV?
Vaccination before
exposure to the virus is the best means of preventing
FeLV infection. Without vaccination, isolation from
other cats is the only means of prevention.
Outdoor cats
have a high risk for developing FeLV infection (if they
encounter other leukemia-infected cats). Indoor cats
are at low risk for developing FeLV infection. Keep
indoor unvaccinated cats away from outdoor cats, or
have them vaccinated. Because infected cats are at high
risk for developing cancer or other life-threatening
diseases they should be maintained as indoor cats.
Currently, there
is no uniformly effective treatment for cats infected
with FeLV. Immune stimulation with various natural therapies
may help improve quality of life and the disease-free
interval.
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Feline
Immunodeficiency Virus (FIV): Is It the Same Virus That
Causes AIDS in People?
No. The Feline
Immunodeficiency Virus (FIV) is also called the Feline
AIDS Virus. It is likened to the AIDS virus that affects
humans because of the similarities in the two diseases
which result. Fortunately, most viruses are species-specific.
This is the case with the human AIDS virus and with
FIV. The AIDS virus affects only humans, and the FIV
affects only cats.
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How
Do Cats Get FIV?
The FIV is transmitted
primarily by the biting that occurs in cat fights. Other
interactions of cats, such as sharing common food and
water bowls or grooming each other, have not been shown
to be significant in transmission.
Evidence of exposure
to the FIV can be detected by a simple blood test. A
positive test means the cat has been exposed to the
virus and will likely be infected for the remainder
of its life. A negative may mean that the cat has not
been exposed; however, false negatives occur in two
situations:
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From the
time of initial virus inoculation into the cat,
it may take up to two years for the test to turn
positive. Therefore, for up to two years, the test
may be negative even though the virus is present
in the cat.
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When some cats become terminally
ill with FIV, the test may again turn negative.
This occurs because antibodies (immune proteins)
produced against the virus become attached and bound
to the large amount of virus present. Since the
test detects antibodies which are free in circulation,
the test may be falsely negative. This is not the
normal occurrence, but it does happen to some cats.
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What
Does a Positive FIV Test Result Mean in a Kitten?
The vast majority
of kittens under four months of age who test positive
have not been exposed to the virus. Instead, the test
is detecting the immunity (antibodies) that were passed
from the mother to the kitten. These antibodies may
persist until the kitten is about six months old, when
the kitten should be retested. If the result remains
positive, the possibility of true infection is much
greater. If the kitten tests negative, there is nothing
to worry about.
If a kitten is
bitten by an FIV infected cat, it can develop a true
infection. However, the test will usually not turn positive
for many months. If a mother cat is infected with the
FIV at the time she is pregnant or nursing, she can
pass large quantities of the virus to her kittens. This
means of transmission may result in a positive test
result in just a few weeks.
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What
Type of Disease Does FIV Cause?
An FIV infected
cat will generally go through a prolonged period of
viral dormancy before it becomes ill. This incubation
period may last as long as six years. Thus, we generally
do not diagnosis an FIV sick cat at an early age.
When illness
occurs, we usually see a variety of severe chronic illnesses.
The most common illness is a severe infection affecting
the gums. Abscesses from fight wounds that should heal
within a week or two may remain active for several months.
Respiratory infections may linger for weeks. The cat
may lose weight and go through periods of not eating
well; the hair coat may become unkempt. The cat may
have episodes of treatment-resistant diarrhea. Ultimately,
widespread organ failure occurs, and the cat dies.
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Is
There a Treatment or a Vaccine for FIV?
There is no treatment
that will rid the cat of the FIV. Sometimes, the disease
state can be treated and the cat experiences a period
of recovery and relatively good health. This can be
promoted by use of proper nutrition and supplementation
with immune system enhancers. However, the virus will
still be in the cat and may become active at a later
date. Therefore, the long term prognosis is not good.
If you have a
cat that tests FIV-positive but is not ill, it is not
necessary to euthanize it immediately. As long as it
does not fight with your other cats or those of your
neighbors, transmission is not likely to occur. However,
if it is prone to fight or if another cat often instigates
fights with it, transmission is likely. In fairness
to your neighbors, it is generally recommended to restrict
a FIV-positive cat to your house. Owners of infected
cats must be responsible so that the likelihood of transmission
to someone else's cat is minimized.
Unfortunately,
there is no vaccine available against FIV.
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Feline
Infectious Peritonitis (FIP): What Causes It?
Feline Infectious
Peritonitis (FIP) is a severe disease of domestic cats
and some exotic cats. It does not affect non-feline
species, such as dogs. It is caused by a coronavirus.
The incubation
period is controversial. In experiments with the virus,
cats will develop the disease within two weeks of infection.
However, in household situations, it appears that the
virus may be dormant in some cats for several months,
or even years, before the disease occurs.
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What
Are the Clinical Signs of FIP?
FIP is a chronic,
wasting disease that results in poor appetite, fever,
and weight loss over several weeks; it is ultimately
fatal. Because various organs may be affected (i.e.,
liver, kidneys, brain, eyes, etc.), a variety of clinical
signs may be associated with this disease. For example,
blindness or seizures may occur in one cat, while another
will have signs of liver disease (jaundice).
There are two
forms, the wet (effusive) form and the dry form. The
wet form results in accumulation of large quantities
of fluid in the chest or abdomen. If it occurs in the
chest, the cat will experience difficulty breathing.
When it occurs in the abdomen, a large, bloated appearance
will result. The dry form affects the target organs
in a similar fashion, but no fluid is produced. If enough
time passes without the cat dying, the dry form may
progress into the wet form. Diagnosis of FIP is much
easier if fluid is present.
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How
is FIP Diagnosed?
Diagnosis of
FIP may be difficult and frustrating. There are no specific
tests which are reliable in all cases. Although organ
biopsy is the most reliable, this requires surgery.
For obvious reasons, surgery may not be advisable in
a sick cat. The following tests are usually used on
cats with suspicious clinical signs.
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Coronavirus
Test This test detects antibodies to any
coronavirus. Antibodies are the circulating defense
agents of the immune system. There are two coronaviruses
that affect the cat: the FIP virus and the enteric
coronavirus. If positive, this test indicates that
one or both of those viruses WAS or IS present in
the cat. However, we do not know which virus is
reacting to the test. Since antibodies may persist
even if the virus is no longer present, a positive
test can be misleading in some cases. Also, terminally
ill cats may have their antibodies "tied up" when
large amounts of the FIP virus are present. This
can result in a false negative test result. Therefore,
this test must be interpreted in conjunction with
results of other tests. These tests are listed below.
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Polymerase Chain
Reaction (PC) This new test is more specific
for the FIP virus than the coronavirus antibody
test; however, it is still just a test for the presence
of the FIP virus. A positive test means the virus
is present, but does not necessarily mean the disease
is present. This test is also subject to some false
negative results.
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Serum Protetin
Levels If the total serum protein is elevated
AND the A:G ratio (ratio of two different blood
proteins ) is less than normal, FIP becomes a more
likely diagnosis. A few other diseases may also
cause this, but these are also very severe and usually
fatal. These findings occur in 50 percent of the
cases of FIP.
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White Blood Cell
Count If the white blood cell count is
greater than 25,000 cells/ul, FIP becomes a stronger
possibility. However, several other diseases may
cause this and some of these are not fatal. Also,
many cases of FIP have a normal white blood cell
count (less than 18,000 cells/ul).
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Abdominal Chest
Fluid Presence If fluid is present, this
is a very meaningful test. If the characteristics
of the fluid are appropriate and the cat has the
correct clinical signs, a diagnosis can be made
with greater assurance. Unfortunately, this fluid
is not present in the dry form of FIP.
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Fine Needle Aspiration
of the Liver or Kidneys A few cells may
be aspirated from the liver or kidney without stressing
the cat (i.e., with a local anesthetic in the skin).
FIP produces a particular inflammatory pattern in
these organs which, although not diagnostic, is
strongly suggestive for the disease. This helps
to rule out other diseases.
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Radiographs (X-Rays)
of the Chest or Abdomen Radiographs serve
to identify enlargements in organs and the presence
of fluid in the chest or abdomen. They are helpful
but not diagnostic and are used to decide which
other tests are appropriate.
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A Combination of
Three Blood Tests Cats with the combination
of a low lymphocyte (a white blood cell) count,
a high blood globulin (protein) level, and a positive
coronavirus antibody test have been shown to have
a 94 percent chance of having FIP.
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Organ Biopsy Organ
biopsy is the only test which is diagnostic of FIP.
However, it is not always possible since the organ
involved may be the eye or the brain.
A case workup
in the absence of organ biopsy often includes several
or all of the above tests. Strongly suggestive findings
with several tests often provides the basis for a presumptive
diagnosis of FIP.
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Is
FIP Contagious?
As with other
viruses, spread of infection to other cats is a concern.
However, there are three stages of FIP infection, and
significant risk to other cats occurs in only the first
two stages.
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The first
stage is initial infection. During the two- to four-week
period following viral infection of the cat, a large
amount of virus is shed; other cats in direct contact
with virus will be exposed.
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The second stage is one
of dormancy. The virus is inactive within the cat,
so it causes no disease. If the cat is stressed
during this stage, some virus shedding may occur.
Otherwise, the cat is not contagious. This stage
may last a few weeks to several years.
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The third stage is clinical illness.
It usually lasts a few weeks and terminates in death
of the cat. As a rule, the cat is not contagious
during this stage.
What
Is the Treatment and Prognosis for a Cat With FIP?
Many treatments
have been tried for cats with FIP, but none have been
consistently successful. Apparently, an occasional cat
will recover, but this is the exception rather than
the rule. Removing fluid from the chest or abdomen in
cats with the wet form will make them comfortable for
a short while, and a few drugs will make some of them
feel better. However, there is no known curative treatment.
The prognosis
for a cat with FIP is very poor. Once a reasonably reliable
presumptive diagnosis has been made, euthanasia
is often the most appropriate course of action.
[If you jump to "euthanasia," use your browser's BACK
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Is
There a Way to Disinfect the Premises or Otherwise Protect
Against FIP?
The coronavirus
may live for up to three weeks in the environment. If
viral shedding into the environment seems likely, a
l:30 mixture of household bleach and water (i.e., 1
cup of bleach in a gallon of water) should be used to
disinfect food and water bowls, litter pans, cages,
bedding material, and items that will not be adversely
affected by household bleach.
A preventive
vaccine against FIP is available, but neither veterinarians
nor the manufacturer recommend that the vaccine be given
routinely to all cats. The vaccine is generally recommended
for cats living in households that have had a cat with
FIP. Initially, two doses are given at a 2-4 week interval.
An annual booster is needed to maintain immunity.
Please note:
The information provided here is meant to supplement
that provided by your veterinarian. Nothing can replace
a complete history and physical examination performed
by your veterinarian. - Dr. Jeff
I greatly value your feedback. Please let me know what
you think of this site and what you would like to see
on it. drjeff@homevet.com
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