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The Daily Vet by petMD

The Daily Vet is a blog featuring veterinarians from all walks of life. Every week they will tackle entertaining, interesting, and sometimes difficult topics in the world of animal medicine – all in the hopes that their unique insights and personal experiences will help you to understand your pets.


I recently attended the American Animal Hospital Association’s 2013 conference in Phoenix, AZ. While there, I had the pleasure of listening to feline gurus Dr. Neils Pedersen and Dr. Alfred Legendre. One of the topics these two experts in feline health care covered was feline infectious peritonitis, more commonly known as FIP.

I thought I’d take the opportunity today to bring you up-to-date about what we know about FIP and to present to you a drug that may potentially offer some hope for cats with this deadly disease.

When I say deadly disease, I do mean that literally. It is believed that FIP is 100% fatal for cats that develop the disease. However, the development of the disease is far from simple. There is a complex mechanism that causes FIP in cats. It involves infection with a common and usually non-harmful virus known as the feline enteric coronavirus, a mutation within the virus itself, and a deficiency within the immune system of the affected cat.

We know that all cats infected with FIP are also infected with the feline enteric coronavirus. However, we also know that not all cats infected with the coronavirus develop clinical FIP. Under normal circumstances, the enteric coronavirus causes very few symptoms other a mild transient diarrhea for some kittens. Many display no symptoms at all when infected. There is a mutation that occurs within the virus that makes the virus virulent. Actually, there are two genes that need to mutate in order for the virus to morph into the FIP virus. The FIP virus looks just like the enteric coronavirus but acts much differently because of these mutations.

But a mutation within the virus alone is not enough to cause the clinical disease known as FIP. The immunity of the infected cat also comes into play. Most cats, when exposed, develop antibodies to the virus. Antibodies are proteins within the blood stream and they are a natural part of the body’s immune system. However, there are a number of elements that work together to make the immune system function effectively in ridding the body of a pathogen, or disease-causing organism. Antibodies are only part. Cell-mediated immunity is another part of the equation.

In cats that develop FIP, cell-mediated immunity does not occur as it should. Cats that mount a normal effective cell-mediated immune response do not get the disease. They recover fully and do not become ill. However, cats that do not mount any cell-mediated immune response develop the wet (or effusive) form of FIP. Cats that manage a partial cell-mediated immune response develop the dry (or non-effusive) form of the disease.

Cats with the wet form of the disease develop effusions (a form of fluid accumulation) in the abdominal cavity and sometimes the chest cavity. Cats that develop the dry form of the disease do not typically accumulate fluid but they develop characteristic lesions in various organ systems, including the pleural cavity, abdominal cavity, central nervous system, and the eyes. These lesions and where they occur determine the clinical signs seen in these cats. Both forms of the disease are considered to be fatal though.

Several drugs have been looked at as potential treatments for FIP. Both Dr. Pedersen and Dr. Legendre agreed that pentoxifylline and feline omega interferon are not effective against FIP. However, both also agree that a drug known as polyprenyl immunostimulant (or PI) is showing promise as being helpful at least for some cats with FIP. Dr. Legendre has found that cats with dry FIP treated with PI seem to have an improved quality of life and may even have a longer survival time. The verdict is still out and research on this medication is ongoing but the results obtained so far provide more hope than we’ve had previously.

Dr. Lorie Huston

Image: Seiji / via Shutterstock

Comments  5

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  • FIP
    04/01/2013 08:26pm

    Dear Dr Huston,
    I would like to discuss a cellular immunostimulant that I feel would be very effective against both FIV and FIP.
    It has been shown to be effective against HIV and Hep C, and Epstein-Barr virus.
    Thanks for your article and look forward to talking with you further about this.

  • Vax
    04/02/2013 05:59pm

    I've heard varying opinions on the FIV vaccine. One school of thought is that a cat might develop FIV from the vaccine. The other school of thought is that it might provide some resistance to the virus.

    I understand that there is no definitive test for FIV. It stands to reason that it would be especially helpful in the case of dry FIV because wet FIV sounds pretty obvious.


  • 04/05/2013 12:19pm

    Hi, you seem to be confusing FIV (Feline Immunodeficiency Virus) with FIP (Feline Infectious Peritonitis). FIV is a retrovirus like FeLV (Feline Leukemia) and HIV in humans.

    I'm not a vet or anything but my "hobby" is listening to talks given at veterinary continuing education conferences. I have become friends with one of the leading Infectious Disease specialists in N America, Dr Richard Ford, now emeritus at NC State and a co-author of both the AAFP Feline Vaccination Guidelines and the AAHA Canine Vaccination Guidelines. He feels I have a good grasp of vaccine issues, so let me share a little of what I think I've learned ... which you can discuss with your own veterinarian.

    First, FIV (the retrovirus, not the subject of this blog) is a Killed Virus vaccine. Assuming the vaccine batch is not defective, the virus in the FIV vaccine is DEAD ... so, it cannot give the disease to any cat. It is an adjuvanted vaccine which raises the risk of a Feline Injection Site Sarcoma (cancer) in cats with a genetic susceptibility, but it won't give FIV to a cat.

    The efficacy (whether it works or not) of the FIV vaccine is debated among the experts. One problem is that there are 4 strains (called "clades") of FIV world wide, simply called clades A,B,C & D. The vaccine is made for clades A and D ... but in N America we have clades A & B. So, it is not known if the vaccine will protect against clade B (the manufacturer says "yes" but it hasn't been independently verified and the experts are not confident that it will protect). Given that there is uncertainty whether or not it will protect, combined with being an adjuvanted vaccine that requires 3 initial doses and annual boosters ... the experts who wrote the AAFP Guidelines consider it "Non-Core" and only should be given to cats at high risk of infection ... e.g., outdoor, fighting, unneutered males since FIV is generally transmitted via a bite wound.

    Back to FIP which is the subject of this blog. There is no vaccine for FIP itself. What is called the "FIP vaccine" is a vaccine against the benign enteric (which means "intestinal") coronavirus. The vaccine is a live intranasal vaccine and will only work if given BEFORE the cat/kitten is exposed to the feline enteric coronavirus (FECV). A major problem is that the vaccine is labeled not to be given prior to 16 weeks of age. But the FECV is so very common (in people, the "common cold" is also a coronavirus) that most kittens have been exposed to it by 5-6 weeks of age by their mothers. Once infected with FECV, the vaccine is useless. The FIP vaccine will not protect against the mutation to FIP. For this reason the FIP vaccine (which is really a coronavirus vaccine) is the ONLY vaccine that the experts of the AAFP Guidelines has designated as "Not Generally Recommended". They will say that it is a "safe" vaccine to use (though there were concerns when the vaccine first came out that it might actually enhance the progression of FIP) ... but they simple all agree that it should not be given because it gives no protection against FIP.

    Hope that helps answer some of your questions.

  • FIP Catinallity Cattery
    04/02/2013 10:42pm

    The continuing consequences of the Melanie Lowry AKA "Annie" of Lollimops & Catinallity Catteries disaster.

    Every choice has a consequence. Regardless of who you are or what station you may hold in life – you cannot avoid the consequences of your actions or choices. Sure, you may avoid the consequences for a time, but in the end we must always face the consequences of our choices.

    The consequences of the action of the CFA cat breeders who purchased FIP infected bloodlines from Melanie Lowry AKA "Annie" Westlake. Is that these CFA cat breeders are breeding down instead of breeding up.

    A cat breeder is suppose to breed the most healthist cats together. Not the most sickest cats together. Any cat breeder knows this.

    I want to bring to the attention to the public all the CFA cat breeders catteries who have purchased FIP bloodlines from Melanie Lowry AKA "Annie" and would pray that no one would ever buy cats from the CFA cat breeders who did infact purchase from Melanie Lowry AKA "Annie" in her cattery she is using today which is Catinallity Cattery, http://catinallity.com.

    We do not want the potential buyer of pedigree persians and himalayan kittens or cats to be ripped off from the cat breeders who purchased from Catinallity & Lollimops or who have Lollimops or Catinllity in their pedigree bloodlines.

    Not buying their kittens would protect the potential buyers so they dont have to suffer emotional financial ruin and heart ache.

    I pray this message will be a blessing to your lives and I pray I have saved one person from harms way in direct reference to Melanie Lowry AKA Annie of the Lollimops Cattery & Catinallity Catteries.

    I pray this message will be a blessing to your lives and I pray I have saved one person from harms way in direct reference to Melanie Lowry AKA Annie of the Lollimops Cattery & Catinallity Cattery.

    Perhaps the breeders who are being listed on this complaint should contact Melanie Lowry AKA "Annie" of the Lollimops & Catinallity Catteries along with 9 other AKA catteries and share how you feel about buying from her. AKA 9 Catteries

    I know you must be very upset and this is understandable, but your anger should be towards Melanie Lowry of whom you purchased your foundational breeding stock from.

    And also because Melanie Lowry has done some real bad and terrible things to many of her buyers and is just a plain ordinary crook and dishonest creature. To one cat breeder she called their landlord , that breeder lost their entire cattery and became homeless. You can read about here Lost Cattery & Became Homeless

    You can learn more about her by going to her special page: http://ca-catbreeders.info/articles-catinallity.html

  • Mis-pring on cattery
    04/02/2013 10:43pm


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