Feline coronavirus (FCoV) Feline Infectious Peritonitis (FIP) antibody tests Feline coronavirus (FCoV) Feline Infectious Peritonitis (FIP) antibody tests

Feline Coronavirus (Feline Infectious Peritonitis) Antibody tests

Diagnosis of feline infectious peritonitis (FIP) is very complex (see FIP diagnosis) and requires a thorough clinical examination and a number of veterinary tests, amongst which are assays for feline coronavirus, (FCoV) antibodies: a negative FCoV antibody test (if sensitive enough) rules out a diagnosis of FIP. On this page we examine the uses of FCoV/"FIP" antibody tests and compare available FCoV/FIP antibody tests.

Prof. Neils Pedersen once famously said that more cats had died of FIP tests than of the disease.

Taking a sample for a test is perfectely safe, but a diagnosis of FIP often results in euthanasia. Many so-called FIP tests are actually tests for antibody to the virus which causes FIP: feline coronavirus, (FCoV) or for the virus itself. However, many healthy cats and sick cats with non-FIP illnesses are also positive on these tests and can be mis-diagnosed as having FIP.

A healthy cat should NEVER be euthanased because of a positive test for feline coronavirus - even if the test has been mis-named a FIP test!

This page is written for veterinary surgeons and veterinary students, I apologise for there being no equivalent page for lay persons at this time.

Some basic facts about FCoV antibodies:

Seroconversion to FCoV takes place 18-21 days post infection.

Maternally derived antibody (MDA) to FCoV usually wanes between 5-7 weeks of age.

The question of whether the antibody is against FECV or FIPV is irrelevant for most purposes of antibody testing.

Why tests for feline infectious peritonitis (FIP) antibodies are really feline coronavirus (FCoV) antibody tests

Feline coronavirus (FCoV), feline enteric coronavirus (FECV), feline infectious peritonitis (FIP) - which test do I choose?

Uses of feline coronavirus (FCoV) and feline infectious peritonitis (FIP) antibody tests

Use a reliable feline coronavirus (FCoV) antibody test

Which FCoV (or so-called FIP) antibody tests are available for use in the practice?

FCoV/FIP antibody tests from commercial laboratories
What should I look for in FCoV/FIP antibody tests from my laboratory?
What is the FCoV antibody prevalence in various groups of cats?

What can affect FCoV antibody titres, other than FCoV infection?

Catvirus.com assessment of FCoV antibody tests

Recommended laboratories for FCoV and FIP antibody testing

List of references

 

Why tests for feline infectious peritonitis (FIP) antibodies are really feline coronavirus (FCoV) antibody tests

FIP occurs when the cat's immune system reacts inappropriately to feline coronavirus (FCoV) infection. FIP is the name of the disease, FCoV (sometimes called feline enteric coronavirus, FECV) is the name of the virus. The vast majority of cats simply become infected, shed FCoV for some months, mount a successful 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.

At time of writing, there is no such thing as a single FIP test, except histopathology of a biopsy, or autopsy. Good veterinary surgeons use an algorithm to assess the likelihood of FIP in a living cat, using various tests available in the veterinary surgery and mailed to reference laboratories. The nearest thing to a single non-invasive test to diagnose FIP would be a positive FCoV RT-PCR test on an effusion.

Download free FIP diagnosis algorithm.

 

Feline coronavirus (FCoV), feline enteric coronavirus (FECV), feline infectious peritonitis (FIP) - which test do I choose?

Don't let the complex nomenclature mislead you - all antibody tests, whether labelled FCoV, FECV, FIP or FIPV antibody are just tests which detect antibody to feline coronavirus. No antibody test can tell how virulent the virus is, or indeed whether a seropositive cat is actually infected! (Only 1 in 3 cats with FCoV antibodies are actually shedding virus at any time. And seronegative cats are uninfected - but only if the test is sensitive enough!) What matters in choosing a test is its reliability, specificity and sensitivity.

 

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Use a reliable feline coronavirus (FCoV) antibody test

There is little point in doing a test unless the test works properly and the people running it know how to use it, especially when something as important as a cat's life hangs on the result. Tests which habitually give false negative or false positive results, or where the starting dilution of sample is too high, are worse than useless. A scientist once told me that she took a series of samples, split them into 5 and sent them to 5 veterinary laboratories in the USA, and received back 5 different results (Postorino-Reeves, personal communication).

A list of available FCoV antibody tests is given below, it is by no means exhaustive, but features mainly tests known personally to, and assessed by, the author (Dr Diane D. Addie). FCoV antibody tests are currently being assessed at my FIP research laboratory, the Feline Institute Pyrenees, and all manufacturers of FCoV antibody tests are invited to participate - for details see below. (The results of the first comparison were published in the Journal of Feline Medicine and Surgery.)

Make sure that the test you use, either in your veterinary surgery, or in the laboratory you mail your samples to, is one that has been assessed, and approved of, by the veterinary scientific community. You will know this because it will feature in published papers in good quality refereed journals - don't be shy to ask for evidence that the FCoV test your lab is using really works. In the list of FCoV antibody tests given in the FCoV/FIP antibody test section, references are given where they exist.

 

Uses of FCoV antibody tests

1. Exclusion of a diagnosis of FIP

2. Monitoring a cat being treated for FIP

3. Diagnosis of feline coronavirus enteritis

4. Testing cat(s) who have been in contact with a cat with FIP or a FCoV excretor

5. Testing a cat prior to mating

6. Screening a household for the presence of FCoV

7. Screening a cat for introduction into a FCoV free household, cattery or country

8. Monitoring cats where FCoV is being eliminated

9. Screening a cat prior to a stress such as surgery or rehoming

10. Screening a cat prior to immunosuppressive treatment or commencing medicines for oestrus suppression

11. Screening a cat prior to blood transfusion

 

1. Exclusion of a diagnosis of FIP

In a nutshell:

  • FCoV antibody tests are primarily useful to EXCLUDE a diagnosis of FIP: a negative result allows the veterinarian to discount FIP and move on to consider other diagnoses
  • in a case of effusive FIP, the antibody titre would usually be high, but it can be variable, especially if the test is performed on the effusion: false negative results can occur, especially with some of the less sensitive rapid immunomigration tests
  • in a case of non-effusive FIP, the FCoV antibody titre would usually be very high

Important 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.

If you'd like to read more details, this is for you ......

Feline infectious peritonitis (FIP) is a diagnostic challenge for even the most gifted clinician. It must always be remembered that cats with conditions other than FIP may coincidentally have antibodies to FCoV, especially if the cat is pedigree (purebred) or has recently been in a shelter. Whatever a laboratory or test may claim, there is currently no such thing as an FIP test - a diagnosis of FIP is arrived at after working through a thorough clinical examination and a series of tests as shown in the catvirus.com algorithm:

Download free FIP diagnosis algorithm.

A version of this algorithm was published in the European Advisory Board of Cat Disease recommendations on FIP (Addie et al, 2009). The catvirus.com FIP diagnosis worksheet, used along with the algorithm, can help you to decide whether or not your own particular case is suffering from FIP:

Download free FIP diagnosis worksheet for veterinary surgeons.

Only one film of working through a case using the algorithm is presently available on YouTube for continuing professional development or veterinary undergraduate training, but more films are being made:

Does Pancho have non-effusive FIP?

See also the webpage on FIP diagnosis.

Good FCoV antibody tests are incredibly useful in the diagnosis of FIP, most FIP cases have very high titres and a negative test, provided it is sensitive enough, rules out a diagnosis of FIP (Addie et al, 2009; Addie et al, 2014; Hartmann et al, 2003). However, of course the usefulness of the test depends on the reliability of the antibody test used (see above).

Occasionally, an effusive FIP sample will appear to be antibody negative (Norris et al, 2005; Sparkes et al, 1991) because there is so much virus in the cat that all the antibody is bound to it and is not available to bind to the virus in the test (Meli, 2013). If this is suspected, send the effusion for an RT-PCR test: effusions from FIP cats are sometimes, strangely, negative by RT-PCR but in these FIP cats with negative antibody tests, the RT-PCR signal is usually huge (Meli, 2013).

A frequently asked question is: can antibody tests differentiate feline enteric coronavirus (FECV) from FIP virus? It's not a good question, because wherever FCoV is, FIP can develop.

Dr Addie occasionally gives masterclasses on FIP diagnosis - see home page for details of when and where the next class will be available.

 

2. Monitoring a cat being treated for FIP for FIP

In a nutshell:

  • repeat the FCoV antibody tests only every 2-3 months (use AGP, globulin, lymphocyte count on a more frequent basis)
  • FCoV antibody tests are most useful in this situation at the end of treatment, when assessing if it is safe to discontinue the interferon, etc.

More information:

There is very little information published about cats being treated for FIP, so what I write here is from personal experience.

FCoV antibody testing is useful at the time of initial diagnosis, but there is little point in monitoring it more frequently than once every 2-3 months once treatment has begun - antibody titres are slow to change. Bear in mind that corticosteroid treatment may suppress the antibody titre, causing it to be artificially low. The most useful tests for assessing response to treatment in the early stages are AGP, globulin, haematocrit, and lymphocyte count (see FIP treatment). FCoV antibody titre and FCoV RT-PCR on faeces are useful for knowing when to discontinue treatment - if a cat has fully recovered, he or she will stop shedding virus, then eventually become seronegative. However if he or she is only in remission, the antibody titre will likely stay high, and treatment should only be withdrawn cautiously, if at all.

 

3. Diagnosis of feline coronavirus enteritis

In a nutshell:

  • a negative FCoV antibody test rules out a diagnosis of gastrointestinal signs being caused by FCoV and allows the veterinarian to move on to discover the real cause (bear in mind that although FCoV shedding begins 2 days post-infection, seroconversion takes about 3 weeks, so a negative FCoV antibody test does not rule out FCoV as a cause of diarrhoea in kittens of a few weeks of age)
  • a positive FCoV antibody test only shows that FCoV MAY be a cause of the clinical signs, since many cats are co-incidentally FCoV seropositive. Keep open to the possibility that the diagnosis may be something else and consider doing RT-PCR of the faeces or a rectal swab to see if the cat really is shedding FCoV or not

More information:

FCoV can cause diarrhoea for a number of reasons:

  • at initial FCoV infection diarrhoea may occur as the virus infects the small intestine epithelial cells: it can be mild or severe. FCoV infected kittens develop diarrhoea usually around 5-7 weeks of age
  • a colonic form of FIP can occur, with either diarrhoea or constipation (see What is FIP for more details)
  • FCoV chronic carrier cats, who remain asymptomatic for many years, can develop a large intestinal type diarrhoea / incontinence, as they get into their teens

If feline coronavirus is suspected of causing gastrointestinal signs, a quick in-house test will reveal whether or not antibodies are present, and if so, a faecal sample or rectal swab can be sent out to a laboratory to determine whether the cat really is shedding FCoV. As with FIP, a negative FCoV antibody test rapidly excludes a diagnosis of FCoV-associated gastrointestinal signs, so a negative result is more useful than a positive result, therefore test sensitivity is important.

 

4. Testing cat(s) who have been in contact with a cat suspected of excreting FCoV

In a nutshell:

  • these cats are very likely to have antibody to FCoV, since it is an extremely infectious virus. Re-test every 2-4 months until the cat becomes seronegative, optimise nutrition and keep stress to a minimum. Consider RT-PCR testing faeces to establish if virus is being shed
  • a negative FCoV antibody test rules out the presence of FCoV infection

More information:

Cats who have shared a litter tray with a FCoV infected cat, or a cat with FIP, are very likely to have antibody to FCoV, since it is an extremely infectious virus - therefore you almost know without testing that the cat will be seropositive. However, testing can be useful to obtain an antibody titre which can be used for comparison, when in 2-4 months a repeat test is taken to determine whether the antibody titre is declining.

Knowing that a cat is FCoV antibody positive can enable you to reduce stress on the cat in an attempt to prevent FIP and to advise the guardian to delay getting a new cat until their existing cat has become seronegative. In general 33% of FCoV seropositive cats sheds virus, though the higher the FCoV antibody titre, the more chance that they are shedding FCoV in their faeces, until at a FCoV antibody titre of 640 or over there is a 75% chance of shedding virus (Addie & Jarrett, 2001; Pedersen et al, 2008).

Obviously if the cat's antibody titre is less than 10 (i.e. negative) it is good news - the cat will not develop FIP and isn't shedding FCoV, so it is safe to get a new feline friend to keep him or her company!


5. Testing before mating with a known positive or negative cat

It is important that cat breeders know the FCoV infection status of their cats and 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.

In a nutshell:

  • negative antibody test - these cats are FCoV free, provided your test was sensitive enough. Safe to continue with the mating and kittens will be FCoV free and not develop FIP
  • positive antibody test - may be shedding FCoV and FCoV is present in the household, retest the cat in 2-4 months and consider testing faeces by RT-PCR

More information:

For more details on how to avoid FCoV transmission at mating and to kittens see the FCoV prevention page.

Since rapidity of result may be required it is likely that an in-house FCoV antibody test will be chosen for this purpose, at time of writing (2014) my recommendations are for the FCoV Immunocomb, the Speed F-Corona or the FASTest FIP in house tests, since these are the most sensitive of the in-clinic tests (Addie et al, 2014).

 

6. Screening a household for the presence of FCoV

In a nutshell:

  • negative antibody test - these cats are FCoV free, provided your test was sensitive enough
  • positive antibody test - FCoV is likely present in these cats, retest in 2-3 months and consider testing faeces by RT-PCR

More information:

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 one or two cats in 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 a negative group to prevent re-infection. In these programs, cats are usually also monitored for virus shedding in the faeces.


7. Screening a cat for introduction into a FCoV free household, cattery or country

In a nutshell:

  • negative antibody test - fine, safe to introduce new cat (provided your test was sensitive enough)
  • positive antibody test - safer to wait until the cat has ceased shedding virus and become seronegative. Retest in 2-3 months and consider testing faeces by RT-PCR

More information:

Once a household is FCoV-free, it is vital to stay that way, so all new cats and kittens need to be tested FCoV antibody negative before being introduced. It may even be sensible to quarantine and test cats coming back from stud or shows for 2-4 weeks to be sure they are not shedding virus and so will not infect the other cats. You may also test faeces by FCoV RT-qPCR but repeat tests are necessary to be sure that a cat is uninfected, whereas a single negative antibody test (i.e. less than a titre of 1:10) indicates that the cat is not infected (unless the cat became infected for the first time within the 3 weeks prior to the test).


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8. Monitoring cats where FCoV is being eliminated

In a nutshell:

  • negative antibody test - this cat has eliminated FCoV (provided your test was sensitive enough)
  • positive antibody test - consider testing faeces by RT-PCR, the seropositive cat has approximately a 1 in 3 chance of being actively infected (i.e. 66% of seropositive cats are actually NOT shedding virus at any one time). The higher the antibody titre, the greater the chance that the cat is shedding virus. Retest antibody titre in 2-3 months (in kittens less than 6 months retest in 1 month).

More information:

See the FCoV prevention page.

9. Screening a cat prior to a stress such as surgery or rehoming

In a nutshell:

  • negative antibody test - safe to proceed with the stressful event
  • positive antibody test - stressing this cat may not be safe, since stress can lead to FIP developing. If possible, delay for 2-3 months and retest. If delay is not possible, consider testing faeces by RT-PCR, the seropositive cat has approximately a 1 in 3 chance of being actively infected (i.e. 66% of seropositive cats are actually NOT shedding virus at any one time). The higher the antibody titre, the greater the chance that the cat is shedding virus.

More information:

See the FCoV prevention page.

 

10. Screening a cat prior to immunosuppressive treatment or commencing medicines for oestrus suppression

In a nutshell:

  • negative antibody test - safe to proceed (except that most medications for oestrus suppression are in themselves inherently unsafe - immunosuppressive and often carcinogenic, especially megestrol acetate).
  • positive antibody test - immunosuppressing this cat may not be safe and could lead to FIP developing. If possible, delay for 2-3 months and restest. If delay is not possible, consider testing faeces by RT-PCR, the seropositive cat has approximately a 1 in 3 chance of being actively infected (i.e. 66% of seropositive cats are actually NOT shedding virus at any one time). The higher the antibody titre, the greater the chance that the cat is shedding virus.

More information:

There are a number of considerations when immunosuppressing a cat, in addition to FCoV/FIP: for example 80% of cats is latently infected with feline herpesvirus (FHV) and immunosuppressive drugs can cause viral recrudescence with upper respiratory signs such as sneezing and ocular discharge. It would be wise to also perform an antibody test for toxoplasmosis and, in countries where Leishmania is endemic, to screen for that too.

 

11. Screening a donor cat prior to blood transfusion

In a nutshell:

  • negative FCoV antibody test - safe to proceed
  • positive antibody test - preferable to use a FCoV antibody negative blood donor, if available

In laboratory experiments, cats who were passively given FCoV antibodies were more likely to develop FIP on exposure to the virus, therefore it would be prudent for blood donor cats to be FCoV seronegative.  Provided it is sensitive enough, an in-house test can be used.

 

 


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Which FCoV (or so-called FIP) antibody tests are available for use in the practice?

 

FCoV (FIP) Immunocomb

Speed F-Corona rapid immunomigration

FASTest FIP antibody

Anigen Rapid FCoV antibody

FCoV IC (Biopronix, Agrolabo)

 

If you have an in clinic FCoV/FIP antibody test which you would like mentioned here, please contact the author by emailing draddie@btinternet.com. Assessment will be blinded and strictly confidential: manufacturers and laboratories are given the option not to have their results included in this webpage once they have seen their results. However, when the Angelica Trust, or another party, pays for an assessment of your tests then it will be published here. 

Statement of independence/vested interests - please note that neither the author of this website nor any of her colleagues or family hold any shares or directorships or any vested interests of any kind in any of the tests discussed here with the following exceptions: first, the author currently works for the University of Glasgow diagnostic laboratory on a regular basis and secondly BVT commissioned an independent assessment of their Speed F-Corona test for which the author was paid a fee. However the majority of this project was funded by the Angelica Trust and the author has performed most of the assessments pro bono. Donations by individual companies is noted in the relevant section.

 

Speed F-Corona rapid immunomigration

Amount of sample required: 40ul

Type of sample: effusion, plasma, serum, heparin or EDTA blood

Type of test: in house (in clinic, in practice) FCoV antibody RIM

Time to perform test: around 15 minutes

Store tests: at room temperature

 

 

The Speed F-Corona (BVT, Virbac, France) is a rapid immunomigration test (RIM). It has the advantages of rapidity and of not requiring complex equipment - everything you need comes in the package (except the syringe for taking the sample). This is a useful initial test for screening cats pre-mating, pre-stress, for possible FIP diagnosis etc. but for tests requiring an antibody titre (for example monitoring cats in a household in which you are eradicating FCoV) use an IFAT.

Download Speed F-Corona instruction leaflet.

Contact your local Virbac supplier to purchase Speed F-Corona tests.

The author (D. Addie) assessed this test for the company who make it, using samples supplied by BVT (this was a paid commission). However, the company were happy for their assay also to take part in a completely independent assessment using the catvirus.com assessment samples and they generously supplied more Speed F-Corona test kits without charging for them. In the most recent assessment, the Speed F-Corona was the best of the in-house RIM tests on account of it being the most sensitive overall and working in the presence of virus (Meli et al, 2013).

In the catvirus.com assessment (Addie et al, 2014):

  • specificity was 100% (46 samples)
  • sensitivity was 92.4% (49/53 samples)
  • sensitivity in presence of virus: 84.6% (11/13 samples)

On a personal note: I like the ethos of the BVT company, when I met its founder, Dr Gerard Papierok, he said to me that he didn't see why HIV rapid tests could be bought for one dollar but cat tests were costing more than 10 times that, so he sought to introduce economical rapid in-house tests for animals. In an independent study, their in-house FeLV test came out as the best (Hartmann et al, 2007). This company has been very supportive of catvirus.com projects, donating tests for the Falkland Islands FCoV eradication/prevention project; the project to assess the impact of virus on FCoV antibody tests and the current FCoV antibody test assessment. They really seem to grasp that the eradication of FCoV worldwide depends on good FCoV antibody tests. In addition, they were willing to change the name of their test from Speed FIP to Speed F-Corona, showing that the welfare of cats was important to them.

 

FCoV (FIP) Immunocomb

Amount of sample required: 5ul

Type of sample: effusion, plasma, serum, heparin or EDTA blood

Type of test: in house (in clinic, in practice) FCoV antibody ELISA

Time to perform test: around 40 minutes

Store tests: in fridge

The Immunocomb is an in-house FCoV antibody test. It has the huge advantages of not requiring complicated equipment - just a refrigerator to store it in. It also requires only 5ul of sample, which is great when there isn't much sample. It can be used on whole blood, serum, plasma or effusion. In the catvirus.com assessment project there were effusion samples in which antibody was bound to virus, which fooled other tests: the Immunocomb was able to detect the antibody.

This test produces grey spots which can be read in an ordinary photograph scanner, with software provided by the manufacturer. Results are given in a scale of 1 – 6, depending on the intensity of the colour of the spots. The absence of a spot gave a result of zero, correlating with a FCoV IFAT titre of <1:10, which was deemed to be negative. In the first published assessment of the Immunocomb* (Addie et al, 2004) sensitivity was 95% and specificity 83%. However, since that time, Biogal have introduced a software programme that takes out the subjectivity of assessing the result spots (as described by Bell et al, 2006), In the present study the spots were read using an ordinary domestic scanner (Epson 4000), which increased the precision of the tests, i.e. the repeatability of the results, since the analysis of scanned images is probably more reproducible and objective that a visual analysis that is operator dependent and may suffer also from variables (e.g. sources of light).

In the catvirus.com assessment this was the best test overall, so long as a scanner, rather than the naked eye, is used to score the spots:

  • specificity was 100% (121 samples)
  • sensitivity was 100% (78 samples)
  • sensitivity in presence of virus: 100% (14/14 samples)

Download FCoV/FIP Immunocomb instruction leaflet.

Suppliers:

UK: Complete Veterinary Care (CVC)

France: Kitvia http://www.kitvia.fr/fr/

Par Tel : +33(0)5 61 88 88 54
Par Fax : +33(0)5 61 88 88 55
Par e-mail : kitvia@kitvia.fr

Other: contact Len Small at Biogal

Biogal Galed Laboratories (Israel) were the first commercial laboratory, other than that of the University of Glasgow, to correctly name their Immunocomb antibody test as a FCoV test, rather than an FIP test. Unfortunately, the authorities in the USA insisted they change the name back to FIP Immunocomb to sell in that country, therefore it is known by two names, depending on which country it is available in.

*Note: Biogal did fund the first study in which their test was evaluated at the University of Glasgow, but in the full understanding that we would publish our 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. Biogal have freely donated test kits to take part in the current assessment - evidently they are confident in their product!

 

FASTest FIP antibody

The FASTest FIP antibody test (MegaCor, Austria) is a rapid immunomigration test (RIM) for the detection of antibodies to feline coronavirus (FCoV). It is not, of course, a test for feline infectious peritonitis (FIP). It has the advantages of rapidity and of not requiring complex equipment - everything you need comes in the package (except the syringe for taking the sample). This is a useful initial test for screening cats pre-mating, pre-stress, for possible FIP diagnosis etc. but for tests requiring an antibody titre (for example monitoring cats in a household in which you are eradicating FCoV) use an IFAT.

 

Amount of sample required: 40ul

Type of sample: serum, plasma, heparin or EDTA blood. The instructions do not list effusions, but the test works perfectly well on effusions.

Type of test: in house (in clinic, in practice) FCoV (mis-labelled FIP) antibody RIM

Time to perform test: around 10 minutes

Store tests: at room temperature

FASTestFIP

The company supplied a small number of tests freely for assessment, and in addition I was given a donation of 100 tests so was able to make an independent assessment. I liked the use of 7 drops of sample buffer, meaning that it was uncommon for a device not to work. In our assessment 5 tests gave faint signals, which made it the best test overall for clarity of signal. As with all RIM tests, you have to be wary of tiny clots of blood or effusion clogging up the membrane. I highly recommend this in-house RIM test, in sensitivity it is second only to the Speed F-Corona test and it performed very well overall.

In the catvirus.com assessment:

  • specificity was 100% (46 samples)
  • sensitivity was 84.6% (44/52 samples)
  • sensitivity in presence of virus: 84.6% (11/13 samples)

Download FASTest FIP instruction leaflet.

In the UK, you can obtain these tests from VetLab Supplies.

In other countries, please contact MegaCor to find your local distributor.

 

Anigen Rapid FCoV antibody

The Anigen Rapid FCoV antibody rapid immunomigration test is made by Bionote. The company supplied some tests and I was given a donation of a larger number of tests which allowed a meaningful assessment. It was the second best test in terms of requirement of amount of sample, needing only 10 microlitres (the FCoV Immunocomb required 5 microlitres which isn't significantly less).

Amount of sample required: 10ul

Type of sample: plasma or serum but also worked, to some extent, on effusion

Type of test: laboratory or in house (in clinic, in practice) FCoV antibody RIM

Time to perform test: 10 minutes

Store tests: room temperature

In the catvirus.com assessment:

  • specificity was 100%
  • sensitivity was 64.1%
  • sensitivity in presence of virus: 53.8%

 

Download Anigen Rapid FCoV antibody instruction leaflet. (Note - it will appear in a new window.)

 

FCoV IC (Biopronix, Agrolabo)

The FCoV IC antibody rapid immunomigration test is an in house test made by Agrolabo, who are well known for their excellent blood typing kits. The kits are beautifully and stylishly made, but lack a place to write the cat's name or reference number. The company generously supplied a large number of tests.

Amount of sample required: 10ul

Type of sample: plasma, serum, whole blood

Type of test: laboratory or in house (in clinic, in practice) FCoV antibody RIM

Time to perform test: read between 10 and 20 minutes

Store tests: room temperature

 

In the catvirus.com assessment:

  • results withheld at manufacturer's request

 

FCoV/FIP antibody tests from commercial laboratories

Indirect immunofluorescent antibody test (IFA or IFAT) - using Feline Coronavirus

Indirect immunofluorescent antibody test (IFA or IFAT) - using transmissible gastroenteritis virus (TGEV)

Enzyme-linked immunosorbent assay (ELISA)

Kinetics based (KELA)

 

Indirect immunofluorescent antibody test (IFA or IFAT) - using Feline Coronavirus

The indirect immunofluorescence antibody test (IFA) is useful because it generates antibody titres (IFAT) which correlate well with virus excretion (Addie & Jarrett, 2001; Pedersen et al, 2008).  It is clear that seronegative cats, as determined by a reliable diagnostic test, do not shed FCoV (Addie & Jarrett, 1992; Addie & Jarrett, 2001, Foley et al 1997) whereas approximately one in three FCoV-seropositive cats do shed virus (Addie & Jarrett, 1992). Cats with higher antibody titers are more likely to shed virus, (Addie & Jarrett, 2001; Foley et al 1997; Pedersen et al, 2008) although cats with relatively low indirect fluorescent antibody (IFA) titers of 1:40 to 1:80 have a 26% to 39% chance of shedding FCoV. (Addie & Jarrett, 1992; Addie & Jarrett, 2001).

Many laboratories make their own IFA test using either feline coronavirus or transmissible gastroenteritis virus (TGEV) of pigs. Other laboratories buy ready-made IFA plates from VMRD, who sell plates of cells pre-infected with either type I or type II FCoV. Most strains of FCoV in the field are type I, but since antibodies in cats are polyclonal (i.e. against many viral proteins, not just the spike) this usually doesn't matter too much unless the assay contains only type II FCoV spike.

A spokesperson from VMRD told me this:

"Our FIP-1 and FIP-2 slides are suitable for detecting antibody.  To determine FIP disease status, we recommend screening samples on both slides at a dilution of 1:6400.  If fluorescence is detected on either antigen, FIP disease is indicated.  Since FIP-1 is far more prevalent than FIP-2, cost savings may be realized by using only the FIP-1 substrate at the risk of missing an occasional FIP-2 case.  Cat sera may be screened for antibody to either antigen at a dilution of 1:400.  The usefulness of such screening is highly debatable; almost every cat has antibody."

There is obviously a lot of knowledge about FIP at VMRD, and I believe that their product is unique in differentiating types I and II FCoV antibody. However, screening samples at a dilution of 1:400 or 1:6400 will miss a lot of seropositive cats - even with FIP. And it is not correct to say that a positive at 1:6400 indicates FIP. It is also untrue to say that almost every cat has antibody (see prevalence section below). So far, VMRD declined to take part in the catvirus.com FCoV antibody assessment.

 

What to watch out for in an IFA test:

  • make sure your laboratory uses an initial dilution of your sample at no more than 1:10
  • make sure your laboratory has an internal negative control in every well
  • find out whether your laboratory is using FCoV or TGEV or even some other virus - if TGEV, be on the lookout for false positive results, possibly due to ANA

Negative results will be reported as 0, <1:10 or <1:25 (or less than whatever the laboratory's starting dilution is).

Positive result will usually be stated as an antibody titre - e.g. 640, 2560. What this means is that there was fluorescence of your sample at a dilution of e.g. 1 in 640 or 1 in 2560.

 

Indirect immunofluorescent antibody test (IFA or IFAT) - using Transmissible gastroenteritis virus (TGEV)

The coronavirus Transmissible Gastroenteritis Virus (TGEV) of pigs can be used to detect antibodies to feline coronavirus (Kummrow et al, 2005). 

What has emerged from the Catvirus.com assessment of FCoV antibody tests so far is that extreme care must be taken to distinguish fluorescence from true detection of antibodies to FCoV from non-specific fluorescence caused, for example, by antinuclear antibodies (ANA) and that this appears to be more of a problem in TGEV IFA compared with FCoV IFA (Addie et al, 2012; Addie et al, 2014).  ANA can be present because of concurrent infections, (e.g. FIV,  Ehlrichia canis), autoimmune disease, recent vaccination or certain treatments for hyperthyroidism (i.e. thiamazole, felimazole, methimazole).  Therefore inclusion of a negative control of uninfected cells for each serum, plasma or effusion is essential. 

 

Enzyme-linked immunosorbent assay (ELISA)

Plate enzyme-linked immunosorbent assays (ELISAs) are used in commercial and research laboratories. There is very little in the veterinary or scientific refereed press about these tests. Many laboratories develop their own (e.g Pratelli et al, 2008; Pratelli et al, 2009) which are not available elsewhere. Roughly, a plate is coated with virus or viral antigen, the sample is added to the plate, then a conjugate with anti-cat antibody is applied. Results may be read by eye or in an ELISA plate reader. What is often lacking is a control to measure non-specific adherence of the cat's sample to components of the kit other than the coronavirus. Another disadvantage is that usually you do not receive an antibody titre.

Commercially available tests include:

7B FIP ELISA

ViraCHEK CV (Synbiotics)

CELISA

Coronase ELISA

 

7B FIP ELISA

FCoV antibody tests based on the 7b protein are misguided and based on an old publication which found deletions in the 7b gene of the less virulent strain  laboratory enteric coronavirus strain FECV 70-1683, while the highly virulent laboratory strain FIPV 79-1146 had an intact 7b gene (at that time the gene was called 6b) (Vennema et al, 1992).  The same eminent group who wrote the first paper later showed that this finding was actually a laboratory artefact:  FCoVs in cell culture frequently develop deletions in their 7b gene (Herrewegh et al, 1995), showing that this gene is not essential for viral replication, indeed is superfluous in the absence of a host.  And a later study showed that both cats with FIP and healthy cats have antibodies to the 7b protein (Kennedy et al, 2008).

 

ViraCHEK CV (Synbiotics)

Amount of sample required: 1ul

Type of sample: plasma or serum

Type of test: laboratory or in house (in clinic, in practice) FCoV antibody ELISA

Time to perform test: around 30 minutes

Store tests: in refrigerator

Download ViraCHEK®/CV instruction sheet

I have not yet experienced this test, but it is cited in some published papers (Foley et al, 1997; Foley et al, 1997).

 

CELISA

I was unable to find out much about this test, it may not even be available now. It was mentioned in Norris et al, (2005).

 

Coronase ELISA

I was unable to find out much about this test, it may not even be available now. Levels of greater than 1:400 are considered suspicious of FIP in this test (see above - FIP diagnosis - it must always be remembered that healthy cats and cats with conditions other than FIP are frequently seropositive). This author is aware of only one account of this test in the literature - where a test on a single cat with FIP gave an antibody titre of 1:800 (Norris et al, 2005).

 

Kinetics based (KELA)

The kinetics based  ELISA or KELA (Barlough et al, 1986) is available from the diagnostic laboratory at the University of Cornell, Ithaca.

Download Cornell's own KELA information sheet.

Negative FCoV KELA titre is less than 1:8. Positive titres are reported as between 9 and 2,000.

 

What should I look for in FCoV/FIP antibody tests from my laboratory?

That their test is reliable - ask for the references of publications which cite the test they are using. Check your laboratory's test with the tests listed on this page.

You should be given an antibody titre (titer), not just a positive or negative result.

Find out how your laboratory defines negative - a good laboratory will be making an initial dilution of your sample at around 1:10 or less. Starting dilutions of 1:100 will miss cats who are shedding FCoV.

Ask what negative controls are in place - feline sera are notoriously sticky, you want an individual negative control for the sample YOU SENT - not just that they ran a known negative sample through the test on the same day.

 


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What is the FCoV antibody prevalence in various groups of cats?

FCoV and FIP are endemic in most countries in the world, though the prevalence varies from country to country (Horzinek et al, 1979). In all countries so far examined, type I FCoV is more prevalent than type II FCoV (Addie et al, 2003; Benetka et al, 2004; Hohdatsu et al, 1992; Kummrow et al, 2005).

The seroprevalence is greatest amongst pedigree (purebred) cats in breeding catteries (once in their new homes they eventually lose their antibodies - after months to years) and cats in other multicat environments such as rescue shelters. FCoV is rare to non-existent amongst free-roaming, stray and feral cats.

 

Australia - prevalence in feral cats was 0% (Bell et al, 2006)

Australia - prevalence in pet cats was 34% (Bell et al, 2006)

Falkland Islands (las Malvinas) - prevalence is ZERO! - the cats in these islands are FCoV free, thanks to their vets insisting on screening cats and only allowing antibody negative cats to enter the islands! (Addie et al, manuscript in preparation.)

Italy - prevalence in cats in shelters - 82% (Pratelli et al, 2008).

Sweden - seroprevalence in pedigree cats 65%, in mixed breed cats 17% (Strom Holst et al, 2006).

Turkey - the prevalence of FCoV II antibodies was 62% (95% CI 0.44-0.77) among multi-cat environments, and 4% (95% CI 0.01-0.11) among single cat households (Pratelli et al, 2009).

UK - overall prevalence in cats 17% (Cave et al, 2004)

UK - healthy pedigree cats at shows - 84% (Sparkes et al, 1992)

What can affect FCoV antibody titres, other than FCoV infection?

Antibodies to feline coronavirus (FCoV) appear around 18-21 days after infection with the virus. The FCoV antibody titre (titer) is the measurement of how many antibodies there are in the cat's blood or effusion and different assays measure the antibody titre in different ways. In immunofluorescent antibody tests the virus is presented in a cell culture - usually either feline or porcine - therefore there is the chance that antibodies present in the cat's blood may stick to the cells of the assay, rather than the virus. This would give a false positive result and good tests contain uninfected control cells to alert the assay reader to that. One such confusing antibody in the cat's blood is anti-nuclear antibody (ANA) which can be present because of concurrent infections, (e.g. FIV,  Ehlrichia canis), autoimmune disease, recent vaccination or certain treatments for hyperthyroidism (i.e. thiamazole, felimazole, methimazole) (Addie et al, 2012).

It was reported that antibodies to ruminant sera components were found in 5.9% of serum samples in the USA (Barlough et al, 1984) and this was attributed to recent vaccination. This reactivity disappeared between 6 and 15 weeks after vaccination (Barlough et al, 1984).

 

Catvirus.com assessment of FCoV antibody tests

The purpose of this project is to put together a list of internationally validated FCoV antibody tests which people around the world can use with confidence in the diagnosis and eradication of FIP. In many such studies the test being assessed is compared with a gold standard test, but this project recognises that no test is infallible, so all the tests in the trial are being used to give a consensus result on the bank of trial samples.

The following is a list of tests either currently being assessed or the responses of companies who were invited to take part:

Antech FCoV antibody test and 7b test - Antech declined to take part

L'école Nationale Vétérinaire d'Alfort - extremely helpful and eager to participate.

Immunocomb FCoV/FIP, Biogal, Israel - company keen to participate and very helpful. Current results in assessment are 100% specific and 100% sensitive!

Speed F-Corona, BVT/Virbac, France - company keen to participate and very helpful.

FASTest FIP, MegaCor, Austria - company sent a small number of tests.

Anigen Rapid FCoV antibody test, Bionote, Austria - company sent a small number of tests to try out.

FCoV IFA - University of Glasgow, Scotland, UK

FCoV IFA - Biobest Laboratory, Scotland, UK - company participated and was very helpful. Results were excellent.

Idexx IFA - in reply to my emails Idexx informed me that they have withdrawn FCoV antibody testing. It appears that they use FCoV antibody tests local to the country in which the Idexx laboratory is situated, making it impossible to make an overall recommendation on how reliable their tests may be.

TGEV IFA - Zurich University Veterinary School - Prof. Lutz and Dr Meli are collaborating with Dr Addie on this project

ViraCHEK CV (Synbiotics) - currently in communication

VMRD FCoV type I and type II IFA - company declined to take part in the study

 

All laboratories are invited to take part, contact the author at draddie@btinternet.com if you would like to participate. The trial is free, though participating laboratories are invited to make a donation to FIP research, and of course to not charge for running their tests or for sending me their kits! The results of the first part of this study are being published by JFMS, a refereed veterinary journal, and will be available on this website if consent is given.

 

Personal note from Diane Addie: I am VERY GRATEFUL to the cats. their veterinary surgeons and guardians, who have supplied samples for use in this study, as well as to the many donors to the Angelica Trust whose generous support is making this independent study possible.

 

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Recommended laboratories for FCoV and FIP tests

I'm sorry that I do not yet have recommendations for laboratories in all countries.

Australia

France

Italy

Switzerland

UK

USA

 

Australia

Veterinary Pathology Diagnostic Services

University of Sydney

George Tsoukalas
Laboratory Manager
Phone: +61 2 9351 3099
Fax: +61 2 9351 7421
Email: G.Tsoukalas@usyd.edu.au

Australian FCoV/FIP expert:

Dr Jacqueline Norris BVSc, MVSt, PhD, Grad Cert Ed Stud (Higher), IVAS Cert Acup.
Senior Lecturer in Veterinary Microbiology
Faculty of Veterinary Science
University of Sydney 2006
Australia

www.vetsci.usyd.edu.au

 

France

IFA using TGEV:

Contact: Dr Sophie de Poder

UMR 1161-Virologie,

Ecole Nationale Vétérinaire d'Alfort,

7 avenue du Général de Gaulle,

94704 Maisons-Alfort,

France.

 

Amount of sample required: at least 100ul

Type of sample: plasma, serum, whole blood, effusion

Type of test: external laboratory TGEV based antibody IFAT

Time to perform test: depends on time for mail to be delivered (minimum 1 day)

Send samples: at ambient temperature by first class or express mail

In the catvirus.com assessment:

  • specificity was 97.5%
  • sensitivity was 98.2%
  • sensitivity in presence of virus: 100%

 

Dr Addie's laboratory:

Feline Institute Pyrenees

Maison Zabal

64470 Etchebar

France

 

Send as much sample as you can (leftover samples are used in research).

 

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)

This laboratory declined to take part in the assessment, however I paid to have a few tests examined - there were some false positive results given.

 

Italy

This laboratory uses their own ELISA cited in Pratelli et al, 2008 and Pratelli et al, 2009 and has the technology to do immunofluorescence, virus neutralisation testing and western blotting. They are also able to differentiate IgA and IgG. I highly recommend this laboratory.

Expert in Italy : Dr A. Pratelli (email: a.pratelli@veterinaria.uniba.it)

Department of Public Health and Animal Sciences,

Faculty of Veterinary Medicine,

University of Bari,

Italy.

 

Switzerland

This is the laboratory of world renowned FCoV/FIP expert Prof. Hans Lutz and is run by another expert and highly efficient scientist: Dr Marina Meli. This laboratory is unique in being able to tell you if a sample has Anti-nuclear antibodies if they detect non-specific fluorescence.

Zurich Veterinary School

Clinical Laboratory,

University of Zurich,

Winterthurerstr. 260,

CH-8057,

Zürich,
Switzerland

Phone +41 44 635 81 11

Fax +41 44 635 89 06

Amount of sample required: at least 50ul

Type of sample: plasma, serum, whole blood, effusion

Type of test: external laboratory TGEV based IFAT

Time to perform test: depends on time for mail to be delivered (minimum 1 day)

Send samples: at ambient temperature by first class or express mail

In the catvirus.com assessment:

  • specificity was 83.3%
  • sensitivity was 100.0%
  • sensitivity in presence of virus: 100%

 

United Kingdom

To submit a sample to the University of Glasgow for FCoV antibody testing or 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:

Veterinary Diagnostic Services
University of Glasgow Veterinary School
Bearsden
Glasgow
G61 1QH
UK

Amount of sample required: they ask for 1 ml but can do the test on far less (minimum 50ul)

Type of sample: plasma, serum, whole blood, effusion

Type of test: external laboratory FCoV type II based IFAT

Time to perform test: depends on time for mail to be delivered (minimum 1 day)

Send samples: at ambient temperature by first class or express mail

In the catvirus.com assessment:

  • specificity was 100.0% (non-specific fluorescence is reported as a matter of course, with follow up immunoblotting provided)
  • sensitivity was 100.0%
  • sensitivity in presence of virus: 100%

Download a sample submission form

Download 2014 price list

 

CTDS laboratory

Blacksmiths Forge
Brookfield Farm
Selby Road
Garforth
Leeds
West Yorkshire
LS25 1NB
UKs

CTDS Ltd
FREEPOST NAT13729
LEEDS
LS25 1YY

Telephone: 0113 287 0175
or 01132 287 6259

Fax: 0113 286 5127

Out of hours emergency telephone:
0788 1711924

email: info@ctdslab.co.uk

 

 

Biobest have their own IFA (a type II FCoV) which works extremely well. This company has generously supported a number of catvirus.com studies and their test featured in 3 publications (Addie et al, 2012; Meli et al, 2013; Addie et al 2014). They can report on non-specific immunofluorescence if you ask them in advance to do so. They also sell IFA plates to other laboratories on request (store test plates in the freezer).

In the catvirus.com assessment:

  • specificity was 100%
  • sensitivity was 96.1%
  • sensitivity in presence of virus: 100%

 

Their contact is Dr Paul Burr.

Biobest Laboratories Ltd
6 Charles Darwin House
The Edinburgh Technopole
Milton Bridge
Nr Penicuik
EH26 0PY

Tel: +44 (0)131 440 2628
Fax: +44 (0)131 440 9587

Email: enquiry@biobest.co.uk

 

United States of America

Lucy Whittier Molecular and Diagnostic Core Facility. This is the veterinary diagnostic laboratory of the legendary Dr Niels Pedersen - the number 1 world expert on FIP! He is also the man who discovered Feline Immunodeficiency Virus! You can download a sample submission form from the website.

Lucy Whittier Molecular & Diagnostic Core Facility
School of Veterinary Medicine
Department of Medicine and Epidemiology
3110 Tupper Hall
University of California, Davis
Davis, CA 95616

Phone: 1 530 752 7991
Fax: 1 530 754 6862

 

FECV FA Cornell University College of Veterinary Medicine

 

 

References

This is not an exhaustive list on publications on feline coronavirus antibody tests, but hopefully gives sources for the statements made on this webpage.

 

Addie D.D., Jarrett O.  1992  A study of naturally occurring feline coronavirus infection in kittens.  Vet. Rec. 130  133-137

Addie, D.D., Jarrett, J.O.  2001. Use of a reverse-transcriptase polymerase chain reaction for monitoring feline coronavirus shedding by healthy cats.  Vet. Rec.    148:649-653.  

Addie D.D, Schaap I.A.T, Nicolson L, Jarrett O. 2003 Persistence and transmission of natural type I feline coronavirus infection. J. Gen. Virol. 84 (Pt 10), 2735-2744

Addie D.D, McLachlan SA, Golder M., Ramsay I, Jarrett O. 2004 Evaluation of an in-practice test for feline coronavirus antibodies. Journal of Feline Medicine and Surgery. 6  2  63-68

Addie D, Belak S, Boucrat-Baralon C, Egberink H, Frymus T, Gruffydd-Jones T, Hartmann K, Hosie MJ, Marsilio F, Lloret A, Lutz H, Pennisi MG, Radford AD,  Thiry E, Truyen U, Horzinek MC.  2009  Feline infectious peritonitis.   ABCD guidelines on prevention and management.  JFMS. 11 7  594-604

Addie DD, McDonald M, Audhuy S, Burr P, Hollins J, Kovacic R, Lutz H, Luxton Z, Mazar S, Meli M. 2012   Quarantine protects Falkland Islands (Malvinas) Cats from Feline Coronavirus Infection. J Feline Med Surg  14 2  171-176.

Addie DD, le Poder S,  Burr P, Decaro N, Graham E, Hofmann-Lehmann R, Jarrett O, McDonald M, Meli ML. 2014  The utility of feline coronavirus antibody tests  J Feline Med Surg

Barlough J.E., 1985  Cats, coronaviruses and coronavirus antibody tests.  J.S.A.P.  26  353-362

Barlough J.E., Jacobson R.H., Scott F.W. 1985  Effect of recent vaccination on feline coronaviral antibody test results.  Feline Practice  15  5  17-26

Barlough J.E., Jacobson R.H., Sorresso G.P., Lynch T.J., Scott F.W.  1986  Coronavirus antibody detection in cats by computer-assisted kinetics-based enzyme-linked immunosorbent assay (KELA): field studies. Cornell Vet. 76  227-235

Bell ET, Toribio JA, White JD, Malik R, Norris JM.  2006  Seroprevalence study of feline coronavirus in owned and feral cats in Sydney, Australia.  Aust Vet J. 84(3):74-81.

Bell ET, Malik R, Norris JM. 2006  The relationship between the feline coronavirus antibody titre and the age, breed, gender and health status of Australian cats.  Aust Vet J. 84(1-2):2-7.

Benetka V, Kubber-Heiss A, Kolodziejek J, Nowotny N, Hofmann-Parisot M, Mostl K. 2004 Prevalence of feline coronavirus types I and II in cats with histopathologically verified feline infectious peritonitis. Vet Microbiol.  99(1):31-42.

Barlough J.E., Jacobson R.H., Pepper C.E., Scott F.W.  1984 Role of recent vaccination in production of false-positive coronavirus antibody titers in cats.  J. Clin. Microbiol. 19  3  442-445

Cave TA, Golder MC, Simpson J, Addie DD. 2004 Risk factors for feline coronavirus seropositivity in cats relinquished to a UK rescue charity.  J Feline Med Surg.  6(2):53-8.

Foley JE, Poland A, Carlson J, Pedersen NC.  1997  Patterns of feline coronavirus infection and fecal shedding from cats in multiple-cat environments.  JAVMA  210  9  1307-1312

Foley JE, Poland A, Carlson J, Pedersen NC.  1997  Risk factors for feline infectious peritonitis among cats in multiple-cat environments with endemic feline enteric coronavirus.   JAVMA  210  9  1313-1318

Hartmann K, Binder C, Hirschberger J, Cole D, Reinacher M, Schroo S, Frost J, Egberink H, Lutz H, Hermanns W.  2003  Comparison of different tests to diagnose feline infectious peritonitis. J Vet Intern Med. 17(6): 781-790.

Hartmann K, Griessmayr P, Schulz B, Greene CE, Vidyashankar AN, Jarrett O, Egberink HF. 2007 Quality of different in-clinic test systems for feline immunodeficiency virus and feline leukaemia virus infection.  J Feline Med Surg.  9(6):439-45.

Herrewegh AAPM., Vennema H., Horzinek MC., Rottier PJM, de Groot RJ.  1995  The molecular genetics of feline coronaviruses: comparative sequence analysis of the ORF7a/7b transcription unit of different biotypes.  Virology.  212:622-631

Hohdatsu T., Okada S., Ishizuka Y., Yamada H., Koyama H.  1992  The prevalence of types I and II feline coronavirus infections in cats.  J. Vet. Med. Sci. 54  3  557-562

Horzinek M.C., Osterhaus A.D.M.E. 1979 Feline infectious peritonitis: a worldwide serosurvey.  Am. J. Vet. Res. 40 1487 - 1492

Kennedy MA, Abd-Eldaim M, Zika SE, Mankin JM, Kania SA. 2008 Evaluation of antibodies against feline coronavirus 7b protein for diagnosis of feline infectious peritonitis in cats.  Am J Vet Res.  69(9):1179-82.

Kummrow M, Meli ML, Haessig M, Goenczi E, Poland A, Pedersen NC, Hofmann-Lehmann R, Lutz H. 2005 Feline coronavirus serotypes 1 and 2: seroprevalence and association with disease in Switzerland. Clin Diagn Lab Immunol. 12(10):1209-15

Meli ML, Burr P, Decaro N, Graham E, Jarrett O, Lutz H, McDonald M, Addie DD. 2013  Samples with high virus loads cause a trend toward lower signal in feline coronavirus antibody tests.  J Feline Med Surg 15 4 295 – 299

Norris JM, Bosward KL, White JD, Baral RM, Catt MJ, Malik R.  2005  Clinicopathological findings associated with feline infectious peritonitis in Sydney, Australia: 42 cases (1990 – 2002).  Australian Veterinary Journal  83  11  666-673

Pedersen NC, Allen CE, Lyons LA.  2008 Pathogenesis of feline enteric coronavirus infection.J Feline Med Surg.  10(6):529-41

Pratelli A. 2008  Comparison of serologic techniques for the detection of antibodies against feline coronaviruses. J Vet Diagn Invest.  20(1):45-50

Pratelli A, Yesilbag K, Siniscalchi M, Yalçm E, Yilmaz Z. 2009 Prevalence of feline coronavirus antibodies in cats in Bursa province, Turkey, by an enzyme-linked immunosorbent assay.   J Feline Med Surg.  11(10):881-4.

Sparkes A.H., Gruffydd-Jones T.J., Howard P.E., Harbour D.A. 1992  Coronavirus serology in healthy pedigree cats.  Vet. Rec. 131  35-36  

Sparkes A.H., Gruffydd-Jones T.J., Harbour D.A. 1994 An appraisal of the value of laboratory tests in the diagnosis of feline infectious peritonitis.  JAAHA.  30  4  345-350

Strom Holst B, Englund L, Palacios S, Renström L, Berndtsson LT. 2006 Prevalence of antibodies against feline coronavirus and Chlamydophila felis in Swedish cats. J. Feline Med Surg.  8(3):207-11.

Vennema H, Rossen JW, Wesseling J, Horzinek MC, Rottier PJ. 1992 Genomic organization and expression of the 3' end of the canine and feline enteric coronaviruses. Virology.  191(1):134-40. 

 

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