Note: this section is intended for veterinary surgeons only and should NOT be used by cat guardians to attempt to treat cats themselves. However, before leaving the page, guardians please download the following to take to your veterinary surgeons:
FIP diagnosis algorithm (this will open in a new window)
Note - these downloads should open in a new window and in some browsers will simply automatically download.
Click here for printer friendly version (i.e. black writing on white background) (this version is still the old page: until that is updated, you'd be better with the FIP treatment summary which is a printable pdf giving drugs and doses)
February 2019: Dr Pedersen found the cure for FIP!
When I first came to Feline Infectious Peritonitis research, FIP was regarded as an incurable condition. Many reported "recoveries" were probably curable conditions wrongly diagnosed as FIP. However, it is my experience that if diagnosed early enough, some cats with FIP can be cured. With the introduction of feline interferon and more recently, GS-441524, the RNA nucleoside analogue, we now have hope for more than remission of weeks to months - we have hope of complete recovery for some cats, especially those diagnosed in early infection. However, more work requires to be done: even in human beings there is no reliable treatment for chronic inflammation. Therefore the emphasis must still be on totally preventing cats ever developing FIP in the first place, and on accurate diagnosis, so that cats with non-FIP conditions are not needlessly euthanased.
This webpage represents only the personal opinions of the author, not all opinion leaders agree with me. Disclaimer: this website and webpage are for information purposes only, I accept no responsibility for how you decide to use this information.
Remember that many treatments listed here would be off label and that you must inform your client of this fact and have your client sign your practice's legal disclaimer form.
Updates on treatment will appear in the English version of the website before the translated pages.
1. DOUBLE CHECK THE DIAGNOSIS: 80% of cats diagnosed with non-effusive FIP actually have some other disease
To see me working through FIP diagnosis algorithm on a real life case, watch "Does Pancho Have FIP?" or Does Tommy Have FIP? (These films will count towards your Continuing Professional Development /Veterinary Continuing Education.) Subscribe to my YouTube, Bitchute and dTube channels to see new cases when they are uploaded. Also see the FIP diagnosis webpages.
You can only be really confident of an FIP diagnosis if you have a positive FCoV RT-PCR result on the effusion of a wet FIP case, or a MLN FNA or aqueous humour in a non-effusive FIP case. Note that cats without FIP can have viral RNA (i.e. a positive RT-PCR result) in their CSF: that is NOT diagnostic of FIP. Do NOT send blood samples for FCoV RT-PCR testing, even if the laboratory asks for that sample.
The beauty of altering nutrition immediately is that it will help in any condition, not just FIP—and it is safe. If you have read The China Study, watched Forks Over Knives, or heard Dr Michael Greger’s famous top human killer diseases lecture, you will already be familiar with the enormous impact diet has on preventing, and even curing, most of the main reasons for human deaths - the situation in cats and dogs may well be similar.
It is my opinion that feeding as varied and natural a diet as possible to cats with FCoV infection and FIP is essential: avoiding highly processed, pro-inflammatory grain-based commercial foods (even the expensive so-called “veterinary” diets are usually cereal based).
Unlike humans, arginine is an essential amino acid in the cat (Morris & Rogers, 1978): this is why they are obligate carnivores. Arginine is essential not only for the urea cycle but also for the normal functioning of monocytes and endothelial cells. To see an animation of feline coronavirus infecting a monocyte/macrophage, and wet FIP developing, visit: http://www.youtube.com/watch?v=6RyI2LI9R9Q
Give real meat daily to augment arginine levels: even just a tablespoonful a day will make a difference to FCoV infected cats. It is important that the meat or liver come from free range animals because they will have eaten grass which is rich in omega 3. Alternatively, regularly use commercially available real meat based cat foods e.g. Applaws (MPM products, available from the Zooplus website in Europe); Wild Kitty Cat Food.
Cereal based foods contain too much omega 6 polyunsaturated fatty acids and too little omega 3, leading to a state of chronic inflammation – we have seen this in human beings over the past couple of decades: an unprecedented rise in inflammatory conditions such as allergies, asthma and arthritis. We see a similar rise in inflammatory conditions being recognised in the cat.
Remember to instruct the cat’s guardian in a gradual changeover of the food: to change it over a period of weeks otherwise the cat will wolf down the new food for a few days, then get sick of it and never touch it again! The way to introduce a new food is to give it for one meal, then go back to the customary diet for the next few meals, then give a little of the new food again, and so on, gradually increasing the frequency of the new foods, until giving a different food every meal becomes the norm for the cat. To introduce new foods gradually properly will take at least a month.
FCoV associated diarrhoea helped by chicken and pumpkin cat food
Interferon / Virbagen Omega
My FIP treatment protocol at time of writing (2019) is as follows: Virbagen Omega (s/c for effusive FIP, oral in non-effusive FIP); meloxicam, Itraconazole, weekly Vitamin B12 injections and other treatments tailored to each individual cat.
GS-441524 is a nucleoside analogue that terminates the RNA chain of viral RNA-dependent RNA polymerase. There were promising results in vitro and in one in vivo experimental study, Murphy et al., 2018 and now the eagerly awaited clinical trial has been published. (Pedersen et al, 2019) Thirty-one cats were enrolled in the field study: 17 of 20 with effusive FIP, 2 developed neurological signs and were euthanased and one died due to cardiomyopathy. Eleven other cats were treated: 4 died shortly after treatment commenced, and of the remaining cats, 3 with presumptive non-effusive FIP recovered as did 4 dry-to-wet cases. Thus of the 31 cats treated, 24 survived by time of writing up the paper.
Detractors of the work may criticise that FIP diagnosis was not vigorous, nor was there a placebo control group. However, effusions were tested by FCoV RT-PCR and most would agree that it would have been unethical to have a placebo control group since that would have condemned to death the cats unfortunate enough to be selected to be a part of it.
Dose: GS-441524 treatment at a dosage of 4 mg/kg SC sid for at least 12 weeks, repeating the course if clinical signs recur. The dose can be safely increased to 5mg/kg Murphy et al., 2018 in severe cases and 10mg/kg in ocular cases.
In the field study, about one third of the cats required subsequent courses of treatment and one cat appeared to have a virus which was resistant to the drug.
Remember that this treatment would be off label and that you should have your client sign your practice's legal disclaimer form. There is no veterinary preparation yet available: one awaits news from Gilead Sciences, CA, USA. Some people have found GS-441524 on the DC Chemicals website, but their website states that their product is not for human or animal treatment. Check with your own regulatory body for advice about the legality of its use in your own country.
Side effects: the treatment stings on administration and injection site reactions occurred in 16 of 26 cats treated. (Injection site reactions are worrisome in cats, because they can lead to fibrosarcoma formation.) However, no other toxic side effects have been reported so far, in fact, Dr Pedersen stated that it was "remarkably safe". (Pedersen et al, 2019)
Cost: At time of writing (2019) the price on the DC website is: 650 USD/10mg, 1100 USD/25mg, 2700 USD/100mg; 3500 USD / 600mg; 4300 USD / 1 gram
Email firstname.lastname@example.org for further information on their product.
Other people have found GS-441524 advertised on the Glixxlabs website, but they have too long a delay in supply and again, their product is not licensed for use in animals.
Toll-Free #: (855) Go-Glixx (855-464-5499)
To obtain a consultation with me, please visit the www.catvirus.com home page.
A report of Dr Pedersen’s presentation can be found here: www.vin.com/apputil/Project/DefaultAdv1.aspx?pId=99&catId=102069&id=8124390.
Watch Dr Pedersen’s SOCK website for news of updates and new clinical trials. www.sockfip.org
There is an article about a cat called Luna, who was in Dr Pedersen's GS 441524 treatment trial here: https://pethelpful.com/cats/Hope-for-Feline-Infectious-Peritonitis-aka-FIP-Lunas-Story
This link will take you to the UC Davis clinical trials page (will open in a new window).
GC376 is a 3C-like protease inhibitor antiviral drug, not currently commercially available. In my opinion, it has been eclipsed by GS-441524 (see above), and also Itraconazole. In the most recent field trial, 6 of 20 cats experienced remission. Here is a figure from the publication by Prof Pedersen et al:
As you would expect, the anti-viral was most effective against cats with the acute form of FIP, effusive FIP, but less so against non-effusive FIP. One advantage of GC376 over GS-441524 is that it can be dissolved in water, so the injections aren't as nasty.
Interferons are the broad-spectrum antivirals that the body produces. They are fairly species specific, so it is more effective to use feline interferon than human interferon, although the latter is better than nothing. Until GS-441524 becomes commercially available, Feline Interferon Omega (Virbagen Omega) remains my go-to treatment for cats with FIP.
interferon omega (Virbac, France)
IFN omega was initially given subcutaneously at 1 MU/kg every other day, and then twice every week for variable period if remission was seen.
(dexamethasone 1 mg/kg intrathoracic or intraperitoneal injection
once only) or prednisolone. Oral prednisolone was initially given
at 2 mg/kg once daily, and the dosage was gradually tapered to 0.5
mg/kg every other day after remission. However, my personal modification of this protocol would be to use meloxicam instead of prednisolone.
I am working alongside vets in practice in the UK to monitor a number of cats being treated with this product. It seems to be very important to begin treatment as soon as possible after the onset of clinical signs. We are seeing success in younger cats too, and even cats with non-effusive FIP. Some cats are being treated orally using 100,000 Units a day. Once diluted (in water or saline) IFN Omega maintains its potency in the fridge for up to 3 weeks, so keep most IFN Omega in the freezer until needed.
Remember that reconstituted, diluted Virbagen Omega
lasts only up to 3 weeks in the fridge.
Suppliers: Virbagen Omega can be obtained from your Virbac representative. From abroad, it can be bought at Abbeyvet, who can be contacted at email@example.com.
In the USA, Virbagen Omega is stocked by The Animal Medical Centre, 510 East 62nd Street, New York, NY 10065. Telephone: (212)-329-8724
In effusive FIP 30 i.u./daily can be used, or larger doses of interferon can be given by intramuscular injection daily (104 - 106 i.u. per day). By 6-7 weeks, if the cat is still alive, interferon will no longer work at this dose because the cat will make antibodies against it.
To obtain human interferon-alpha (Roferon or Intron A), write a prescription for your local pharmacist. Obviously, in areas where feline interferon is available it is preferable as it is likely to have more effect than the human interferon.
Diluting human interferon
*In the UK: 2ml tubes are available from Sarstedt, supplier's ref: 72.694.006. Fax: 0116 236 66099 Tel: 0116 235 9023.
To get 104 i.u./ml put 1 x 1 million i.u. vial of Intron A or Roferon into 99ml sterile saline and divide into 1ml doses and freeze. For 105 i.u./ml use 9mls saline and proceed as above. For 106 i.u./ml use the whole vial.
Itraconazole is an anti-fungal but was recently reported to be able to reduce type I feline coronavirus in the laboratory. (Takano et al, 2019) Unlike GS-441524, there is a commercially available veterinary preparation for cats. Although no clinical trial has yet been published, I know of two cats with FIP who are doing well on this, meloxicam and VIrbagen Omega feline interferon.
Dose: 10mg/kg orally
Do NOT use Entyce along with Itraconazole.
Because FIP is an immune mediated disease, therapy sometimes includes suppressing the immune response, for example, with glucocorticoids, which can have lethal consequences if the diagnosis is erroneous (e.g. in toxoplasmosis, or bacterial peritonitis or pleurisy). Before embarking on any of the following therapies, it is essential to ensure that the diagnosis is correct. See Diagnosis of FIP Cats receiving immunosuppressants should also receive antibiotic cover to protect them against other infections. It is also important to maintain the cat's general nutrition status, by adding real meat, vitamins and antioxidants.
Presnisolone is relatively safe and tends to make the cat feel better, it stimulates his or her appetite; prednisolone is inexpensive and available everywhere. However, prednisolone suppresses both the humoral and cell-mediated immune response and it is possible that alternative anti-inflammatory treatments would be more effective in the treatment of FIP: Hugo and Reading (2015) reported prolonged survival—787 days—in a 4 year old cat with effusive FIP, who they treated with meloxicam and one month of metronidazole and Tramadol.
When prednisolone is used, it is absolutely essential that the doses BE REDUCED: I am frequently shocked to learn of veterinary surgeons who forget the halve the dose of corticosteroids every 7-10 days: for example, this was not done in the Ritz study and 13 of the cats died of secondary bacterial infections.
Prednisolone has the advantage of also being the treatment for lymphocytic cholangitis, which can be mistaken for FIP, so where the diagnosis is in doubt between FIP and lymphocytic cholangitis, prednisolone can be given anyway: the cat with lymphocytic cholangitis has a good chance of recovery, the cat with FIP unfortunately will die. Prednisolone should never be used in cats with toxoplasmosis, or leishmaniasis, neither is it safe in cases of septic peritonitis or pleurisy, which is why cytology is a very important part of effusive FIP diagnosis, as there will be many more white blood cells in the effusion of a cat with sepsis, and a good cytologist will detect the bacteria or fungi.
Dose: 2 mg/kg/sid given by mouth for 10-14 days
Prednisone is not effective in catsHugo and Reading, 2015) Meloxicam, rather than glucocorticoids, was also used in 10 experimentally-infected cats who recovered using an antiviral called GS-441524 (not yet commercially available). (Murphy et al, 2018)
Dose: 0.05 mg/kg BW, PO, q24h
Be sure to obtain the owner's consent for using a drug not licenced for cats.
Dose: 50-100mg at night. CANNOT BE USED IN PREGNANT CATS as it is teratogenic.
My go-to protocol to treat effusive FIP is to drain the effusion, give Virbagen Omega to the site of the effusion, then s/c eod after resolution of the effusion, and meloxicam as the anti-inflammatory of choice. If you can obtain the anti-FCoV nucleoside analog GS-441524 (Murphy et al, 2018), that would be the treatment of choice.
Feline interferon omega: 1 million units/kg/sc/eod until recovery
Meloxicam (provided blood pressure and kidney function are normal): 0.05 mg/kg per os, sid.
My go-to protocol for non-effusive FIP therapy is Virbagen Omega at 100,000 units per cat per day per os and meloxicam, provided the cat's kidney function and blood pressure are normal. I have I have little personal experience of Polyprenyl Immunostimulant, my mind is open about its efficacy, but I would love to hear from veterinary surgeons willing to share case histories with me: contact me at draddie [at] catvirus [dot] com.
Show the cat's guardian how to withdraw 0.5mls of the diluted interferon (which now has 100,000 units of interferon per dose). Get the cat's guardian to do the syringe filling and the dosing in front of you: we vets are so used to handling syringes that we forget that most people have never handled a syringe in their lives. Some cats will take the interferon on food, but to be certain the cat gets the dose, tilt the head with the mouth closed and introduce into the commisure of the lips, wait until you see the cat swallow before releasing the head.
Remember that reconstituted, diluted Virbagen Omega lasts only up to 3 weeks in the fridge.
PPI is NOT recommended in effusive (wet) FIP.
I found the following video made by a cat's guardian, demonstrating how she doses her pet:
Apologies -t his section is under construction.
Vitamin B1 (thiamine)
Vitamin B complex
Multivitamins B are a good appetite stimulant and can be obtained from health food shops or chemists (I particularly like the one from Boots). Dose: paediatric dose.
Dose: 10mg/kg every 48-72 hrs per os.
Avoid amoxycillin/clavulanic acid because it can inhibit interferon-gamma, which is essential for FIP survival.
Choose from the following
(in the UK):
Remember to warn the owner
that the cat's urine could become more strong smelling with this
For AGP testing see Companion Animal Diagnostics.
Staging for effusive FIP prognosis to help you to assess whether treatment has a chance of helping or not
In this staging system shown in the video below the severity of effusive FIP can be worked out, which will give you an idea of whether or not it is worth obtaining special drugs to treat, or whether it is worthwhile continuing treating a case. Look at the parameter in the left hand column, then look at where the result of your case falls in the range, then put the score for that parameter into the next free column in the grey shaded cells. Finally work out the total score for your case. You can download the excel file here: http://www.catvirus.com/downloads.html: the total score will automatically fill in the cell at the bottom.
Interpreting the total score for your case:
While this isn’t an absolutely exact predictor, it does give a ballpark indicator of prognosis.
L-lysine should NEVER be given to a cat with FCoV infection or FIP because it is antagonistic to arginine which is essential for immune function.
Thromboxane Synthetase Inhibitors
Two cats with abdominal effusions
were treated with ozagrel hydrochloride with success (Watari et al, 1998). However, follow up studies failed to confirm the usefulness of this compound.
""Feline Infectious Peritonitis and Coronavirus" - download an ebook written for cat guardians or purchase the physical version from Amazon.
I should very much like to conduct a clinical trial on the effectiveness of various treatments for FIP, but unfortunately don't have the funding to do so. I'd like to thank Mr Wayne Carr, Maria Bonino and all the other donors to the Angelica FIP trust, to the catvirus subscribers and the EndFIP group, whose generous donations made preliminary investigations possible. Enormous thanks go to the human families of cats who have had FIP, who have generously given of their time, and samples from their cats, to make my research possible and a BIG THANK YOU also to all the veterinary surgeons who have contributed to my studies.
Addie D.D., 2004 Feline Infectious Peritonitis. Veterinary Interferon Handbook. Ed: Karine de Mari. Virbac. 108-117
Addie D.D.2008 Feline infectious peritonitis – therapy and prevention. Kirk’s Current Veterinary Therapy XIV Edited by: John D. Bonagura, DVM, MS, DACVIM, David C. Twedt, DVM, DACVIM. Saunders, Elsevier.1295 – 1299
Addie, D.D.. Feline coronavirus. 2012 Infectious Diseases of the Dog and Cat. 4th edition. Editor: Greene, Craig. Published by W.B. Saunders Elsevier Company, 11830 Westline Industrial Drive, St. Louis, Missouri 63146, USA. ISBN 978-1-4160-6130-4 92-108
Hartmann K, Ritz S. 2008 Treatment of cats with feline infectious peritonitis. Vet Immunol Immunopathol. 123(1-2):172-5.
Legendre AM, Bartges JW. 2009 Effect of Polyprenyl Immunostimulant on the survival times of three cats with the dry form of feline infectious peritonitis. J Feline Med Surg. 11 624-626
Legendre AM, Kuritz T, Galyon G, Baylor VM, Heidel RE. 2017 Polyprenyl Immunostimulant Treatment of Cats with Presumptive Non-Effusive Feline Infectious Peritonitis In a Field Study. Front Vet Sci. 4:7.
Maunder CL, Day MJ, Hibbert A, Steiner JM, Suchodolski JS, Hall EJ. 2012
Murphy BG, Perron M, Murakami E, Bauer K, Park Y, Eckstrand C, Liepnieks M, Pedersen NC. The nucleoside analog GS-441524 strongly inhibits feline infectious peritonitis (FIP) virus in tissue culture and experimental cat infection studies. Vet Microbiol. 2018 Jun;219:226-233.
O'Brien, DP & Packer, RA (2010) Metabolic encephalopathy: organic acidurias. In August, JR (Ed): Consultations in feline internal medicine. Vol 6. Elsevier Saunders, Philadelphia. pp:595
Pedersen NC, Kim Y, Liu H, Galasiti Kankanamalage AC, Eckstrand C, Groutas WC, Bannasch M, Meadows JM, Chang KO. Efficacy of a 3C-like protease inhibitor in treating various forms of acquired feline infectious peritonitis. J Feline Med Surg. 2017 Sep 1:1098612X17729626.
Pedersen NC, Perron M, Bannasch M, Montgomery E, Murakami E, Liepnieks M, Liu H. Efficacy and safety of the nucleoside analog GS-441524 for treatment of cats with naturally occurring feline infectious peritonitis. J Feline Med Surg. 2019 Feb 13:1098612X19825701.
Simpson KW, John Fyfe, Angelyn Cornetta, Amy Sachs, Dalit Strauss-Ayali, Stephen V. Lamb, Thomas J. Reimers 2001 Subnormal Concentrations of Serum Cobalamin (Vitamin B12) in Cats with Gastrointestinal Disease J Vet Intern Med 15:26–32
Swann JW, Szladovits B, Glanemann B: Demographic Characteristics, Survival and Prognostic Factors for Mortality in Cats with Primary Immune-Mediated Hemolytic Anemia. Journal of Veterinary Internal Medicine 2016, 30:147-156.
Takano T, Hohdatsu T, Hashida Y, Kaneko Y, Tanabe M, Koyama H. 2007b A "possible" involvement of TNF-alpha in apoptosis induction in peripheral blood lymphocytes of cats with feline infectious peritonitis. Vet Microbiol. 119(2-4):121-31
Takano T, Azuma N, Satoh M, Toda A, Hashida Y, Satoh R, Hohdatsu T. 2009 Neutrophil survival factors (TNF-alpha, GM-CSF, and G-CSF) produced by macrophages in cats infected with feline infectious peritonitis virus contribute to the pathogenesis of granulomatous lesions. Arch Virol. 154(5):775-81.
Takano T, Akiyama M, Doki T, Hohdatsu T. Antiviral activity of itraconazole against type I feline coronavirus infection. Vet Res. 2019 Jan 18;50(1):5.
Watari T, Kaneshima T, Tsujimoto H, Ono K, Hasegawa A. 1998 Effect of thromboxane synthetase inhibitor on feline infectious peritonitis in cats. J Vet Med Sci. 60(5):657-9.
Weiss Richard C. 1994 Feline
Infectious Peritonitis Virus: Advances in Therapy and Control in
Consultations in Feline Internal Medicine
2. Edited by John R. August. Published by W.B. Saunders Company.
Harcourt Brace Jovanovich, Inc., The Curtis Center, Independence
Square West, Philadelphia, PA 19106. pages 3-12
Dr Diane D. Addie 14 May 2019