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Feline Infectious Peritonitis (FIP)

By | Last Updated: 14th July 2020

What is feline infectious peritonitis

FIP or Feline infectious peritonitis is a contagious, immune-mediated [5] viral disease that may affect domestic or wild cats of all age, with the younger (less than two years) and older ones being more susceptible due to their immature and weak immune system [1,2,19]. Felines living in multi-cat households are at a higher risk of acquiring this uncommon and potentially fatal disease [21], with males being more at risk than females, as suggested in a study [1].

Breeds more prone to this condition include Bengal, Birman, Ragdoll, Himalayan, Devon Rex, and Abyssinian cats.

What causes FIP

The FCoV or feline coronavirus has several strains varying in their condition-causing ability [1]. The feline enteric coronavirus (FECV) is the avirulent or harmless strain, which remains in the cat’s intestinal tract leading to mild digestive problems like diarrhea. On the other hand, the virulent feline infectious peritonitis virus strain is responsible for FIP  [1,4].

According to present observation, the harmless strain can mutate to the harmful one, thereby causing the disease [1, 6].

Feline Infectious Peritonitis

What are the signs and symptoms

The initial symptoms as listed below may be difficult to detect, also varying from cat to cat:

  • Lethargy
  • Reduced interest in activities
  • Decreased or no appetite at all
  • Inconsistent fever

Once the virus enters the body of a cat, it takes some time to breed and spread the infection. The incubation period may be within a few days or even months depending on the strain of the virus, organs affected, as well as the effusive/wet and non-effusive/dry nature of the disease [1,2,4].

However, not all cats with coronavirus antibodies in their bloodstream would contract the disease. Those dwelling in single households may even become free of the virus within six months, with their antibody count gradually becoming negative [5].

Dry or non-effusive FIP

The dry form results in inflammatory lesions around the blood vessels, affecting single or multiple organs like the liver, intestine, brain and eyes [1,7]. Signs and symptoms include:

  • Anemia
  • Diarrhea
  • Vomiting
  • Improper growth (in kittens)
  • Depression
  • Jaundice
  • Eye problems like inflammation, white spots, internal bleeding, and uveitis [4]
  • Uncoordinated movements
  • Low vision or blindness [2] (if the infections spreads to the brain)

Wet or effusive FIP

Fluid accumulation in the abdomen (ascites), chest or thorax (plural effusion) and pericardial cavity of the heart (pericardial effusion, rare) gives rise to various evident symptoms [4,8,20]:

  • Diarrhea
  • Swollen abdomen
  • Troubled breathing
  • Runny nose
  • Bad breath
  • Sneezing [2]

The symptoms of the dry form show up at first, while those associated with the wet form are prominent at the latter stage, by which time, most affected cats get pot-bellied.

How is FIP diagnosed

Diagnosis of feline infectious peritonitis may be challenging as some of its clinical signs are common with other diseases like cholangiohepatitis and hepatitis lipidosis [17,18]. The following tests may be necessary to detect the underlying signs and confirm the diagnosis:

  • Routine blood tests like hematology and serum biochemistry [1, 7, 8] to detect abnormalities like an increased serum level, decreased albumin-globulin ratio or reduced lymphocyte count (common to this condition) [8,25].
  • X-rays, to determine fluid absorption in the chest and abdomen [1].
  • Abdominal ultrasound to check the position of the internal organ and if they are surrounded by fluid [15,20].
  • Fluid analysis of the chest and abdominal fluid, for determining the cause behind its accumulation. It may prove useful as the kind of fluid seen in FIP is not common for any other disease [1].
  • A histopathological examination, where samples of the affected tissues from the spleen, liver, and kidney are taken for a biopsy [8].
  • IFA, virus neutralization, and ELISA test to check for coronavirus antibodies in body fluids [4, 9, 10]. The term ‘titer’ is used to refer to the number of antibodies detected, with low and high titers indicating the level of antibodies present. However, cats having a high titer count are not necessary at an increased risk of developing FIP, while those with a low number are not necessarily safe [4].
  • PCR (Polymerase chain reaction) test to detect the coronavirus in body tissues and fluid, but it cannot identify the virus strains specific to this condition [4,16].
  • Rivalta test, a simple inexpensive option, done to differentiate between the fluid caused by this disease and other conditions like lymphoma, heart failure, inflammatory liver disease and bacterial peritonitis [5].

Though vets often prescribe the above tests for detecting the condition, the results might not always be accurate. A positive result does, however, indicate the possibility of FIP.

There is hardly any test to differentiate between the avirulent and virulent coronavirus. Fluid analysis can still detect the wet form of the condition, but the diagnosis of the dry form is difficult, with a histopathological test being the only available option [1,21].

A study conducted in 1994, highlighted that cats with possible symptoms along with high levels of coronavirus antibodies and globulins as well as a reduced amount of lymphocytes have about 88.9% possibility of developing FIP [21].

Can feline infectious peritonitis be treated

Though there is no permanent cure, treatment involves managing the symptoms, so the affected cat can live as long and as comfortably as possible.

  • Cytotoxic drugs, antibiotics, and corticosteroids are given for temporary remission [1, 4].
  • Blood transfusions and fluid therapy are undertaken to minimize its breathing difficulties and other discomforts.

Research conducted at the University of Tennessee in 2006, shows that treatment with immunosuppressive drugs, like polyprenyl immunostimulant [1,23], proved successful as one out of the three cats having dry FIP had survived, though this field requires more studies [11,27].

The Kansas State University has mentioned of another new and alternative treatment in their paper which involves antiviral drugs that have said to inhibit the virus from multiplying as well as stopped the condition from spreading further. Cats severely affected with FIP were said to attain normalcy on receiving this treatment [4,26].

When may the cat need euthanization

As survival rate of this disease is nil [3], euthanasia is the best possible option, especially if the cat does not respond to treatment in about three days [1,5,24].

However, before you take the ultimate decision, make sure that your pet is actually affected by the deadly strain, as it is common to euthanize cats after a misdiagnosis.

Is feline infectious peritonitis contagious

Though FIP is not contagious [4], the primary source of transmission of the virus is the feces and saliva of the infected cat [1, 4].

Vets advise owners to keep a month’s gap from the death of the infected cat before introducing a new pet into the house so that the chance of contracting the virus is minimized [1].

In multi-cat households or shelters where chances of infection are as high as 80% to 90% [12], it is recommended to wait for about three months from when a sick cat dies, to check for the condition in the other cats [1]. Even if they are not afflicted, the ones exposed become carriers of FIP, being at risk of infecting any new entrants, particularly if they are below one year of age, due to their undeveloped immune system [1].

However, this disease is not transmitted to humans and dogs [13].

Can you prevent FIP

Vaccines have been developed over the years to reduce chances of the disease, but its success is stull under study due to the unknown nature of mutations leading to the illness [1, 13].  Noted vets like Dr. Addie of the Scotland’s University of Glasgow have mentioned a few safety measures as specified below to lessen instances of the disease [23].

  • Do not keep more than four to five cats in a single shelter, with kittens below four months of age separated from the older ones [14,23].
  • Clean litter boxes using dilute bleach for killing the virus [1].
  • Provide separate litter boxes for each cat as this would reduce the risk of getting exposed to feces of other felines [14].
  • Pregnant and nursing cats should be secluded.
  • Female cats suspected of being carriers of the virus should be separated from their kittens six to eight weeks after their birth as by then the maternal immunity of the latter starts to weaken, increasing their chances of contracting the virus [23].

Prognosis for FIP

FIP has an extremely poor prognosis, with more than 95% of the affected cats having a short life expectancy since detection. In mild cases of the non-effusive form, survival chances can still be a little higher, though those affected with the effusive form die within a month or two after the symptoms are visible [5,12,21].

A study conducted with 43 cats suffering from FIP deduced that they survived for just nine days on an average since detection [5].


    1. Feline Infectious Peritonitis – Vcahospitals.com
    2. Coronavirus in Cats – Petmd.com
    3. FIP – Ncbi.nlm.nih.gov
    4. Cornell Feline Health Center – Vet.cornell.edu
    5. Overview of FIP – Merckvetmanual.com
    6. Feline Infectious Peritonitis Virus – Vetmed.auburn.edu
    7. Feline Infectious Peritonitis (FIP) – Icatcare.org
    8. FIP Diagnosis – Langfordvets.co.uk
    9. FIP – Members.petfinder.com
    10. A New Addition to FIP Diagnostic Tool – Csu-cvmbs.colostate.edu
    11. Research on FIP – Vetmed.Tennessee.edu
    12.  FIP Overview – Healthcommunities.com
    13. FIP: The Silent Killer – Timesofmalta.com
    14. FIP in Cats and Kittens – Peteducation.com
    15. Feline Infectious Peritonitis – Pet360.com
    16. FIP: Rare, Yet Fatal – Vivapets.com
    17. Cholangiohepatitis – Vet.cornell.edu
    18. FIP – Abcdcatsvets.org
    19. Treating FIP – Naturalcathealth.com
    20. FIP – Lbah.com
    21. Cats FIP – Pets.webmd.com
    22. PI to Treat Cats with Non-Effusive FIP – Ncbi.nlm.nih.gov
    23. What is FIP – Stopfip.org
    24. Diagnosis and Clinical Signs of FIP in CNS – Ncbi.nlm.nih.gov
    25. FIP – Brightwoodanimalhospital.com
    26. A Breakthrough in Treating Cats with FIP – Catingtonpost.com
    27. FIP a Dreaded Disease in Cats – Catster.com

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