|
|
|
|
|
|
|
Recommended laboratories for FCoV and FIP tests |
|
|
|
|
|
|
|
What clinical signs (symptoms) should I look out for in my cat? |
Feline infectious peritonitis (FIP) is the leading infectious cause of cat death. FIP occurs when the cat reacts inappropriately to feline coronavirus (FCoV) infection. Most cats simply become infected, shed FCoV for a month or two, mount an immune response, eliminate the virus and live happily ever after (see How to eliminate FCoV infection from a cattery or household of cats). However, for reasons that we don't yet fully understand, instead of clearing FCoV infection, an unfortunate few cats develop FIP.
The name FIP is slightly misleading: FIP isn't inflammation of the peritoneum (the lining of the abdomen) it is a vasculitis (inflammation of the blood vessels). The clinical signs which the cat develops depend on which blood vessels are damaged, and on which organ(s) the damaged blood vessels supplied.
Wet
or effusive FIP
This is the acute form of the disease, where many blood vessels
are damaged severely and fluid leaks out of them into the abdomen
or the thoracic (chest) cavity. When the blood vessels in the abdomen
are affected, the cat's tummy swells up with fluid called ascites.
When the blood vessels in the thorax are damaged fluid leaks into
the chest, impairing the ability of the lungs to expand and the
cat shows difficulty breathing.
(Many thanks to Mrs M. for this photograph.)
The cat may bleed into the eye, or white precipitates appear on the cornea (the clear membrane on the front of the eye).
For vets: check the eyes using an ophthalmoscope for vitreous flare and retinal vessel cuffing (see photo below).
(Many thanks to John Mould for this photograph.)
Around 12% of cats with non-effusive FIP develop neurological signs: often they become ataxic (wobbly and falling over when walking), they may have head tremors, fits, their eyes may dart from side to side instead of being focussed.
However, all of these clinical signs can be caused by other, sometimes treatable, conditions, which is why accurate diagnosis is essential.
Diagnosis of FIP –
this section is intended for veterinary surgeons
FIP is a notoriously
difficult condition to diagnose, many other conditions present with
very similar clinical signs. Definitive diagnosis is only possible
at post mortem, or occasionally by biopsy (though for accurate biopsy
results one has to actually biopsy a visible pyogranulomatous lesion,
which may necessitate laparotomy). Only 18% of samples sent to our
laboratory for FIP diagnosis turn out to be FIP. Since cats with
FIP are usually euthanased, it is absolutely vital that FIP is accurately
differentiated from other, treatable, conditions.
In our laboratory at the University of Glasgow, we offer an FIP profile which confirms or rules out a diagnosis of FIP in over 90% of cases. The FIP profile consists of four parts: a feline coronavirus (FCoV) antibody titre, albumin:globulin (A:G) ratio on the effusion or plasma, alpha 1-acid glycoprotein (AGP) level and cytology or haematology.
Effusive (“wet”) FIP profile
Non-effusive (“dry”) FIP profile
To submit a sample to the University
of Glasgow for a FIP profile
Feline coronavirus antibody tests
Virus
detection by RT-PCR
FCoV antibody titre
The presence of antibodies indicates
that the cat has been infected with FCoV, the cause of FIP. Any
FCoV antibody titre can occur in cases of wet or effusive FIP, but
most cats with FIP have extremely high antibody titres (1280 or
greater). Antibody titres of 0 are unusual in FIP cases and are
usually considered as indicating that the cat does not have FIP.
(However, if other parameters suggest a diagnosis of FIP,
despite having an antibody titre of 0, then this is the one situation
where FCoV RNA detection (RT-PCR), performed on a sample of the
effusion, is diagnostic of FIP. In these cats there is so
much virus in the effusion that all the antibody is bound to it,
and none is available to bind to virus in the test.)
Note: many healthy cats and cats with diseases other than FIP have FCoV antibodies. The presence of FCoV antibodies alone is NOT diagnostic of FIP, if the other parameters of the profile do not indicate a diagnosis of FIP.
Total protein in the effusion
and albumin:globulin ratio (A:G)
The total protein concentration in the effusion of
a cat with FIP is usually greater than 35 g/l and this usually consists
of more globulin than albumin, pushing down the A:G ratio. An A:G
of < 0.4 indicates FIP is quite likely; an A:G of >0.8 rules
out FIP; A:G of between 0.4-0.8 - consider other parameters. The
A:G of an effusion is one of the most useful tests to perform in
practice for a quick indicator of whether or not a cat may have
FIP and can be performed on a VetTest machine (divide the albumin
by the globulin values).
In the USA, AGP testing kits can be obtained from Cardiotech Services. Enquiries to Jeff Sarno or call (502)473-7066.
Cytology
In effusive FIP, there are generally
less than 3 x 10 9 nucleated cells per litre in the effusion and
the cells are predominantly neutrophils and macrophages. In bacterial
peritonitis and pleurisy, the white blood cell count in the effusion
is much higher and the cytologist will usually see bacteria (if
they are intracellular, this indicates that they were not simply
contamination of the sample). Cytology of pleural effusions is useful
for differentiation of thymic lymphosarcomas, since the predominant
cell is the lymphocyte and they often appear malignant.
Summary
Thus, a cat with
wet FIP should be FCoV seropositive, the total protein of the effusion
must be over 35g/l and the albumin:globulin less than 0.4 (or at
least less than 0.8), the AGP should be high (over 1500 micrograms/ml)
and the cytology should reveal few nucleated cells which are mainly
neutrophils and macrophages.
Non-effusive (“dry”) FIP profile
FCoV antibody titre
FCoV antibody titres in dry
FIP are usually equal to or greater than 1280. An antibody titre
of zero rules out non-effusive FIP.
Note: many healthy cats and cats with diseases other than FIP have FCoV antibodies. The presence of FCoV antibodies alone is NOT diagnostic of FIP, if the other parameters of the profile do not indicate a diagnosis of FIP. A healthy cat with a high FCoV antibody titre is NOT a cat with dry FIP.
Albumin:Globulin ratio
(A:G)
In FIP
the globulin concentration in serum or plasma is raised to over
40g/l. Consequently the A:G is usually lowered. An A:G of < 0.4
indicates FIP is quite likely, provided that globulins are raised,
remember than a low albumin (e.g. in liver disease) can also artificially
lower the A:G. An A:G of >0.8 rules out FIP; A:G of between 0.4-0.8
- consider other parameters.
AGP level
AGP is an acute phase protein
which is useful in distinguishing FIP from other clinically similar
conditions. In FIP, AGP levels are usually greater than 1500 ug/ml.
In normal cats, it’s up to 500 ug/ml. Bear in mind, however, that
AGP is not specific, and will also be raised if there is viral (non-FIP),
bacterial (e.g. ascending cholangiohepatitis or pyelonephritis)
or fungal infections or recent trauma. AGP measurement is useful
in distinguishing FIP from neoplasia or non-infectious liver disease,
when AGP levels will be normal.
In the USA, AGP testing kits can be obtained from Cardiotech Services. Enquiries to Jeff Sarno Onras43@aol.com or call (502)473-7066.
Haematology
In non-effusive
FIP there is lymphopenia, a non-regenerative anaemia with a haematocrit
of 30% or less and often a neutrophilia with a shift to the left.
Bear in mind that cats with other chronic infections can have similar
haematological changes. Haematology is useful in differentiating
FIP from Haemobartonella
felis infection where
the anaemia is regenerative and there may be organisms visible on
the erythrocytes.
Summary
A cat with dry FIP should have
a high FCoV antibody titre, be hyperglobulinaemic and have a reduced
albumin:globulin ratio. He or she should have a high AGP, lymphopenia,
a haematocrit of less than 30% which is non-regenerative and possibly
a neutrophilia. Clinically, the cat should have lost weight and
will usually have ocular signs such as iritis, retinal vessel cuffing,
keratic precipitates, aqueous or vitreous flare.
Remember: a healthy cat with a FCoV antibody titre is NOT a cat with dry FIP.
Recommended laboratories for FCoV and FIP tests
I'm sorry that I do not yet have recommendations for laboratories in all countries.
FCoV antibody tests:
Dr Joel Godenir
LABORATOIRE
VETERINAIRE DEPARTEMENTAL
105, route des Chappes
BP 107
06902 SOPHIA ANTIPOLIS Cedex
FRANCE
Téléphone:
04 92 96 00 00
Fax: 04 92 96 01 20
Cost: 21 euros HT, (25.12 euros tax included)
RT-qPCR to test for virus:
Scanelis laboraty.
RT-qPCR to test for virus:
To submit a sample to the University of Glasgow for a FIP profile
Note
that the FIP profile is NOT for use in healthy cats. To screen a
healthy cat for exposure to FCoV, simply send a heparin blood sample
for a FCoV antibody titre.
Effusive or wet FIP: send 1ml heparin blood and 1-2ml effusion in plain and EDTA tubes. (Note: sending the effusion will greatly increase the chances of an accurate diagnosis.)
Non-effusive or dry FIP: send 2 x 1ml heparin blood and 1 ml EDTA blood and two air-dried blood smears.
Send samples with a test request form (can be downloaded from Companion Animal Diagnostics or obtained by calling UK 0141 330 5777) or with a note of your address to:
Companion Animal Diagnostics
University of Glasgow Veterinary School
Bearsden
Glasgow
G61 1QH
UK
RT-qPCR to test for virus:
Dr Christian Leutenneger's laboratory, the Lucy Whittier Molecular and Diagnostic Core Facility. You can download a sample submission form from his website.
AGP testing kits can be obtained from Cardiotech Services. Enquiries to Jeff Sarno Onras43@aol.com or call (502)473-7066.
Feline coronavirus
antibody tests
Use a reliable FCoV antibody test
In our laboratory, we found that the FCoV Immunocomb, by Biogal Galed Laboratories, compared very favourably with our antibody test. This finding was presented at the Second International Feline Coronavirus/Feline Infectious Peritonitis workshop and the abstract is available on that website if anybody wishes further information. The full paper is published in the April 2004 edition of the Journal of Feline Medicine and Surgery. The Immunocomb is an antibody test which can be used in the veterinary surgery.
(Please note that although Biogal Galed have a link from this website, I am in no way an employee of theirs, nor a shareholder. They did fund the study in which their test was evaluated, but in the full understanding that I would publish my findings whether or not the results were favourable. I remain impartial - I make no personal gain from Biogal, nor do they donate to my research. Their link is there because I personally approve of their FCoV Immunocomb product. They are charged the same as other advertisers, but their fee goes to the Celia Hammond Animal Trust, a charity which rescues cats.)
Note to FCoV antibody test manufacturers: I am happy to discuss evaluation of your antibody tests at any time.
1. Diagnosis
of FIP
2. Testing cat(s) who have been in
contact with a cat suspected of excreting FCoV
3.
Testing before mating with a known positive or negative cat
4. Screening a household for the presence of FCoV
5. Screening a cat for introduction into a FCoV-free household
1. Diagnosis of FIP (see FIP diagnosis above)
Good antibody tests are incredibly useful in the diagnosis of FIP, most cases of FIP have very high titres and a negative test can often rule out a diagnosis of FIP. Occasionally, an effusive FIP will seem to be antibody negative because there is so much virus in the cat that all the antibody is bound to that and not available to bind to the virus in the test.
A frequently asked question is: can antibody tests differentiate feline enteric coronavirus from FIP virus? It's not a good question, because wherever FCoV is, FIP can develop. No consistent genetic or serological difference has ever been found in viruses from cats with FIP compared with viruses from healthy cats.
2. Testing cat(s) who have been in contact with a cat suspected of excreting FCoV
These cats are very likely to have antibody to FCoV, since it is an extremely infectious virus. However, testing can be useful to obtain an antibody titre which can be used for comparison, when in 2-3 months a repeat test is taken to determine whether the antibody titre is declining. Obviously if the cat's antibody titre is less than 10 (i.e. negative) it is good news - the cat won't develop FIP and isn't shedding FCoV, so it is safe to get a new feline friend to keep him or her company!
Knowing that a cat is FCoV antibody positive can enable you to reduce stress on the cat in an attempt to prevent FIP.
3. Testing before mating with a known
positive or negative cat
It is important that cat breeders avoid infecting their own or another person's cats by only mating antibody positive cats to antibody positive cats, and antibody negative cats to antibody negative cats.
4. Screening a household for the
presence of FCoV
Since FCoV is highly infectious, it is not always necessary to test all the cats in a household to establish whether or not FCoV is present: if the cats are in groups, then only a sample from each group need be tested. Usually, when FCoV is endemic, over 90% of the cats have antibodies. In control programmes, the cats are tested every 2-3 months and as cats' antibody titres decline to zero, they are put in with the negative group to prevent re-infection.
5. Screening a cat for introduction
into a FCoV-free household
Once a household is FCoV-free, it is vital to stay that way, so all new cats and kittens need to be tested antibody negative before being introduced. It may even be sensible to quarantine and test cats coming back from stud or shows.
Virus
detection by RT-PCR
See also What is RT-PCR. RT-PCR detects the FCoV genome,
so indicates presence of the virus. However, interpretation of such
tests is difficult: healthy cats as well as cats with FIP can be
positive for the virus. Also, cats with illnesses other than FIP can co-incidentally have the virus.
In my research survey, I found that it was less useful to use RT-PCR than our antibody test: to show that a cat has eliminated FCoV required only one antibody titre of less than 10 in our laboratory, but required 5 monthly negative RT-PCR tests on faeces. However, RT-PCR remains the only way to detect a carrier cat - a cat who sheds FCoV continually for 9 months or more is likely to be a lifelong carrier.
At time of writing, there is no RT-PCR which can differentiate FIP-causing coronaviruses from coronaviruses which do not cause FIP. The difference between the former and the latter is that in FIP, the FCoV can replicate in macrophages, whereas in FCoV infected cats without FIP, FCoV is not replicating in macrophages. (Replicate means multiply, macrophages are a type of white blood cell.) However, at the Second International Feline Coronavirus/Feline Infectious Peritonitis workshop, a young Dutch scientist, Fermin Simons, presented an RT-PCR he is working on which detects replicating FCoV in macrophages, his abstract is on the SIFFS website. This RT-PCR is not presently commercially available, but is a very promising test for the diagnosis of FIP.
In America, the FCoV RT-qPCR test which I would recommend you use is available from Dr Christian Leutenneger's laboratory. You can download a sample submission form from his website.
Treatment of FIP –
this section is intended for veterinary surgeons
What clinical signs (symptoms) should I look out for in my cat?
Any of the following clinical signs should alert you to the possibility of your cat developing FIP:
weight loss
recurring fevers (usually detected when
your veterinary surgeon takes the cat's temperature)
going off food
the cat becomes even lazier
than usual
sudden swelling of the abdomen
look closely at your cat's eyes regularly,
watch for any change in colour of the iris (the coloured area of
the cat's eye around the pupil) or any cloudiness, or bleeding (look
closely at the cats' eyes in the Dry or non-effusive FIP section to get an idea of what you are looking
for)
difficulty breathing (the cat breathing through his or her mouth)
if the cat
has a fit or seizure
if the cat seems to lose balance, become clumsy
if the cat's
personality changes
If you are a cat breeder, the following signs in your kittens should alert you to the possibility of FCoV being present in your cats:
kittens of uneven size in a litter
diarrhoea
in kittens around 5-7 weeks of age
transient sneezing or discharge from the
eyes in young kittens
Remember that all of the clinical signs described above can occur due to other, curable, conditions, so take your cats to your veterinary surgeon to be checked if any of these signs occur and hope for the best. Remember that 8 out of 10 cats whose samples were sent to our laboratory for FIP diagnosis turned out not to have FIP at all!
last updated 22 Apr 2006
Site ©
2000 - 2005 Dr.
Diane Addie
Site
Design ©
Melody Amundson, Mariposa Creations