Introduction
FIP is one of the most mysterious
diseases a wild or domestic cat can get. Cheetahs are particularly
susceptible to this disease because of their lack of genetic
diversity.
FIP is a rare disease, although it
is fatal. It is seen more often in cats less than 2 years of age and
older than 10 years of age. Multiple cat households, along with cats
that spend time outdoors, are most susceptible. The virus that causes
this disease is spread by respiratory secretions and feces. Litter
that is contaminated with the virus is easily trapped on a cats fur,
which is ultimately swallowed when the cat grooms. Cats infected with
FeLV
also are more at risk of developing this disease.
This disease is the subject of
considerable controversy regarding diagnosis and treatment. This is
partially due to the environmental situation that cats are placed in
that causes undue stress on their immune systems, along with the
complicated and variable immune response they develop when
potentially faced with this virus. Like many cat diseases, FIP mimics
other cat diseases, so a diagnosis in many cases does not come
easily.
This page has short QuickTime
movies on a cats with symptoms that could be the result of FIP. You
need QuickTime on your computer to view it- it is available for free
at www.apple.com
Cause
FIP is caused by a coronavirus,
that has mutated from a harmless intestinal virus of cats called the
feline enteric coronavirus (FECV). It is not known why the virus
mutates from the harmless FECV (it can cause a mild intestinal upset)
to the pathogenic FIP.
Risk factors for this disease are multiple
cat households, the presence of normal cats that shed coronavirus, and the development
of FIP susceptible cats in the general cat population. The continual infection
and reinfection of cats with coronavirus in multiple cat households increases
the chance of an individual cat developing FIP. Any cat infected with a corona
virus has the potential of developing FIP. To give you some perspective on the
current situation, 30% of household cats and up to 90% of cattery cats carry
the coronavirus.
Multiple cat households might be
more susceptible due to increased stress, crowding, poor sanitation,
parasites, and other diseases like the FeLV
and the FIV.
Cats can spread the coronavirus in
their nasal and oral secretions, along with the feces. Even though
the virus can remain infective in the environment (contaminated
feeding utensils, etc.,), it is easily destroyed by routine
disinfectants.
This virus poses no health risk
for people.
Pathogenesis
Within 24 hours of ingestion the
virus spreads from the tonsils to the intestines. Within 2 weeks it
has spread to the large intestine, intestinal lymph nodes, and the
liver. From there it can spread to any other body organ. Cats that do
not produce a full antibody response to the virus will end up with
fluid buildup within body cavities, usually the chest or abdomen.
Cats that develop a full immune response to the virus do not get this
disease, although they can harbor a latent version of the virus for a
period of time. The are immune, but carry the pathogenic version of
the coronavirus, so they can potentially spread it to other cats. If
they become immunocompromised for some reason (stress, drugs,
crowding, parasites, other disease like kidney
disease ) their infection
can be reactivated.
This disease has two major
manifestations. The first is called the "dry form". In the dry form
the white blood cells are involved, and cause an inflammatory
reaction to the internal organs. These organs do not function
normally because of this inflammation, and eventually will fail as
the disease progresses.
The other manifestation of this
disease is called the "wet form", and is where the original name of
"peritonitis" (inflammation of the lining of the abdominal cavity)
came from. It is called this because fluid accumulates in the abdomen
or the chest. The fluid that appears in the wet form is straw colored
to yellow in appearance, and has a relatively high protein content.
The fluid originates from small blood vessels that have been affected
by the immune systems response to the virus. This immune response
damages these blood vessels, causing them to leak fluid into the
abdominal cavity usually, or thoracic cavity less often.
Cats that already have FeLV are
more susceptible to the FIP virus. It has been found that Persian and
Birman cats may have a susceptibility to the FIP virus.
Symptoms
Initially there are no or minimal
symptoms after exposure. Some cats might show mild upper respiratory
signs (sneezing) or diarrhea, but are so mild that they can go
unnoticed. When serious symptoms do appear, the signs might be sudden
in the younger cats, or more gradual in older cats.
Cats that have dry form have vague
symptoms that come and go, and can affect many different systems in
the body. They might be lethargic, have poor appetites,weight loss
and look ill. Common organs involved are the eyes, central nervous
system (brain and spinal cord), and internal organs like the liver
and kidney. Other symptoms could include seizures, paralysis,
behavior changes, poor vision, increased sensitivity to touch, and
urinary incontinence.
Another clue to dry FIP is a cat with an ongoing
fever. It might wax and wane, and usually does not respond to antibiotics.
Since many different organs can be
involved with the dry form, the symptoms we see with this form of FIP
can mimic other common diseases of cats, like hyperthyroidism,
liver
disease, sugar
diabetes
and
kidney
disease. Other diseases
like inflammatory bowel disease, cancer, and toxoplasmosis might also
have similar symptoms.
Pets with the wet form of the
disease may have breathing difficulty or distended abdomens, in
addition to some of the symptoms of the "dry form". The onset of
these symptoms is faster than the gradual symptoms noted in the dry
form. The wet form of FIP is much easier to diagnose than the dry
form.
The virus can also infect the
brain or spinal cord. This form of the disease can sometimes be
diagnosed by an eye exam. Changes can be noted in the back of the
eye, especially the retina.
This
cat has neurologic symptoms that could be the result
of FIP. Double Click on the picture to make the movie
play.
Diagnosis
Diagnosis is difficult in many cases, particularly
in the dry form. We do not have a blood test that tells us if the virus is present
like we have with FeLV
and FIV.
The test we do have tells us if antibodies have been made to the category of
virus that FIP belongs to (coronavirus), but it does not tell us if it is the
actual FIP virus or not. There are DNa type tests available that are more specific
in making this diagnosis, the most common one being the polymerase chain reaction
(PCR) test. As we generate more data on this test in sick cats its usefulness
will probably increase.
In addition to specific FIP
antibody or DNa tests, blood
samples, X-rays and fluid
analysis are also used, and are utilized especially in cats that have
the wet form. The only way to be 100% certain of the diagnosis is to
biopsy
one of the abdominal lymph nodes, the kidneys,
or the liver.
Physical
Exam
Cats that have FIP will have
physical exam findings similar to other feline diseases. In the
wet form the fluild buildup in the abdomen becomes apparent as
time goes on.
One
of the ways we check for fluid during an exam is to
look for a fluid wave. Double click on the picture
below and you can see the wave.
Blood
Panel
The white blood cells might be
low, normal or high, depending on how long the problem has been
present and if other problems also exist. The red blood cell count
might be normal or low (anemia).
The biochemistry profile
commonly reveals an elevation in total protein and globulins. This
elevation comes from the inflammatory process occurring as the
body responds to the virus. This increase, called
hyperglobulinemia, occurs more often in the dry form.
In this lab report of an
FIP cat the arrow points to the elevated globulin level
Other tests on the biochemistry profile could
indicate FIP, but not necessarily, since these problems could occur with other
diseases also. As a case in point, if the kidney values are elevated in an
older cat with suspicion of FIP, some of the possibilities are:
- Chronic renal failure along
with FIP (this cat has 2 different diseases)
- Chronic renal failure with
no FIP
- FIP causing kidney
disease
- Dehydration due to
FIP
- Dehydration due to disease
in some other organ
Fluid Analysis
The fluid that builds
up in the wet form of FIP is called ascites when it occurs in
the abdomen, and pleural effusion when it occurs in the thorax.
The fluid is sticky and usually light yellow to golden color,
with a relatively large amount of protein.
This is what the fluid
looks like just after is has been removed from the body. 
This is the report we get from the
pathologist after it has been analyzed
Radiography
The following x-rays are of a normal cat
first, and then one with the wet form of FIP. approximately 100 ml (3 ounces)
of fluid was removed from the chest of the cat with the fluid. After the fluid
was removed it was analyzed because other diseases can cause fluid in the
thorax (pleural effusion) also.
This is an x-ray
of a normal cats thorax. This cat is laying on its right
side, the head is towards the left. You can see the heart
and the black lung tissue in the shape of a triangle. The
diaphragm (arrows) is the vertical line that separates the
thorax on the left from from the abdomen on the right. The
liver
resides in the abdomen.
This
cat has a significant amount of fluid in the thorax
(pleural effusion), making it difficult to identify
normal organs. You cannot see the heart or diaphragm, and
the lung tissue is greatly reduced because of all the
fluid. The lungs are unable to expand fully causing
significant difficulty in breathing. This pet is very ill
and has minimal breathing reserve. It needs immediate
removal of the fluid.
After some of the fluid was removed it is possible to
visualize more of the organs. There is more lung tissue present and
the top of the diaphragm is now visible.
The fluid
found in the wet form of FIP can also occur in the abdomen
(ascites). In this radiograph, the evidence of fluid
accumulation is subtle, but present.
Ultrasound
Ultrasound gives us
additional information on the internal organs, especially if
they are surrounded by fluid.
This
is what ascites looks like during an ultrasound. The dark
areas, marked "abd eff" are the areas of abnormal fluid
buildup in the abdomen.
The ultrasound gave us
additional information we do not normally obtain from
radiography. In this case, an FIP suspect, we found an
enlarged lymph node (Mesenteric- LN) in the center of the
intestines. This does not verify the diagnosis, but makes
it very likely.
Antibody Test
Our routine blood panel in cats can also
include an FIP titer. This titer detects the presence of antibodies to the
corona virus, indicating exposure to the virus at some time in the past. It
does not tell us if this coronavirus is FECV (the nonpathogenic corona virus)
or the FIP virus. This cat might have FIP, but it might not. Also, some FIP
vaccines can cause an elevated coronavirus titer.
We need to see a relatively
high titer, along with the routine symptoms of FIP, to make us
think a cat with a high coronavirus titer indeed has FIP. To
further complicate the picture, cats presented to us in the final
stages of FIP, where the symptoms can mimic many other diseases,
might not have any titer due to their inability to mount any
immune response, hence they do not produce antibodies detectable
by this test./p>
Here
is a typical report from our lab concerning the FIP titer
test. The "FCV" stands for feline coronavirus. The "IFa"
stands for immunofluorescent antibody. This cat had
antibodies at 1:400, but not at 1:1600. This is typical of
many cats we test, and indicates at some time in the past it
was exposed to coronavirus. It does not tell us if the cat
has FIP or not. If the cat was positive at 1:1600 or higher,
and it had all the other signs indicative of FIP, then it
might indicate the cat has FIP.
DNA Test (PCR)
The DNA test for FIP is called the PCR. It stand for polymerase
chain reaction. It can be performed on blood, fluid, and tissue. Not all cats
with FIP have the virus in the bloodstream (called viremia), so a negative
result with this test on the blood does not guarantee the cat does not have
FIP. Also, the FECV (the nonpathogenic coronavirus) can sometimes be found
in the bloodstream leading to a false positive. To further complicate the
problem, cats with the dry form of FIP, (the very cats we run this PCR test
on since we are not sure it is FIP or some other common disease causing the
problem), often do not have the FIP virus circulating in the bloodstream.
In this case, there will be a false negative.
The test is very sensitive, so it will usually
find the FIP if it is there. There is a tradeoff to this
sensitivity though. It is so sensitive that if the lab does not
practice a high level of quality control we might get a false
positive.
What this test does is look for viral
nucleoprotein to the FIP virus. There is a version of this test,
called the 7B protein test, which further tries to differentiate
the nucleoprotein found in FIP from the nucleoprotein found in
FECV.
This is what the test result for PCR looks
like. 
Histopathology
In many FIP cases, especially the dry form, the
only way to confirm the diagnosis is to biopsy an internal lymph
node or internal organ, and look for specific microscopic changes
that occur in FIP. This biopsy can be performed on a live cat
during an exploratory
surgery, or during a necropsy (the
animal version of an autopsy) in a dead cat.
Common organs to biopsy are the liver and
kidney. In addition, the mesenteric lymph
node (remember the ultrasound above
where it was enlarged?) is a good organ to biopsy.
This
necropsy picture shows an enlarged mesenteric lymph
node. Below it you can see the inflammation that has
occurred on the outer surface of the intestines. This
inflammation causes peritonitis (inflammation of the
lining of the abdominal cavity). This is how the
disease became to be known as Feline Infectious
Peritonitis when it was originally discovered.
This autopsy picture shows a
reaction on the surface of the liver. This reaction is
called pyogranulomatous, and is the basis for the
diagnosis.
This is the final
report we received from the pathologist on the above
tissue samples.
Treatment
There is no treatment that will
cure this disease. Over the years many different treatments have been
attempted to alleviate symptoms of this disease. Some of them seem to
work for variable periods of time, so they are worth trying in some
cases. These include antibiotics, antinflammatories, immune system
stimulators, and vitamins. Since it is difficult to confirm the
presence of this disease, especially in the dry form, it is worth the
effort to treat your cat symptomatically. Unfortunately, the long
term outcome is poor. Cats with confirmed cases of FIP usually
succumb within a few months.
Antiviral medications have been tried but do
not appear to alter the course of the disease.
You can find these
treatments
in our section on FeLV, since both diseases are treating the symptoms
of the virus and not the actual virus. The caveats in treating FeLV
also apply to FIP.
Controlling
the Spread
Cats living in households that
already had a cat die of FIP have a less than 5 percent chance of
developing FIP, mostly because they have already been exposed to the
virus and fought it off. Siblings of cats that died of FIP have a
greater chance of developing the problem. The most important factor
in controlling FIP is limiting the number of cats in a house,
preferably to less than 5. In addition, good nutrition, good
veterinary care, and good sanitation, will go along way to preventing
this problem.
Wait at least one month before
introducing a new cat to house that had a cat die of FIP. Cleaning
the litter pan often and preventing litter from tracking throughout
the house may be helpful. The virus can live in the environment for
several weeks, so clean as thoroughly as possible using a 1:32
dilution of household bleach. Remove all cat related products that
can not be thoroughly cleaned.
Vaccination
In recent years a vaccine has been
developed to help prevent this problem. Even though no guarantee can
be given as to the effectiveness of this vaccine due to the
mysterious nature of this disease, it might be indicated for those
cats that go outdoors or are exposed to many cats. It is administered
as drops in the nose.
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