What is FIP in cats: Understanding the Deadly Disease

Feline Infectious Peritonitis (FIP) is a devastating illness that affects cats worldwide, causing significant distress for both the pets and their owners. But fear not, as knowledge and support can make a world of difference. In this comprehensive guide, we will delve into the intricacies of FIP, exploring its causes, symptoms, and treatments. We will also shed light on how you can provide the best care possible for your furry companion, offering tips on nutrition, environmental enrichment, and emotional support. Whether you are a cat owner searching for answers or a veterinary professional seeking to expand your knowledge, this article is your go-to resource for all things FIP. So, let’s embark on this journey together and empower ourselves to give our feline friends the love and care they deserve in the face of this deadly disease.


What is FIP (Feline Infectious Peritonitis)?

Feline infectious peritonitis (FIP) is the name given to a common and aberrant immune response to infection with feline coronavirus (FCoV).

FIP is a viral disease that affects cats, causing a range of symptoms and often leading to fatal outcomes. FIP is caused by a mutated form of the feline coronavirus, which is a common virus that infects many cats without causing any serious health issues. However, in some cases, the virus mutates and is then able to cause FIP. This mutation occurs within the cat’s own body, making it difficult to prevent or predict. Once the mutated virus is present, it can lead to a systemic inflammatory response that affects various organs, such as the liver, kidneys, and brain.

The symptoms of FIP can vary depending on the form of the disease, which can be either “wet” or “dry.” In the wet form, fluid accumulates in the cat’s abdomen or chest, leading to distension and difficulty breathing. In the dry form, granulomas, or small inflammatory lesions, form in different organs, causing a range of symptoms, including weight loss, fever, and neurological abnormalities. It’s important to note that FIP can affect cats of all ages, but it is more common in young kittens and cats with weakened immune systems.

microscopic shot of a virus

Causes and Transmission of FIP

The exact causes of FIP are still not fully understood, but it is believed to be a result of a combination of factors, including the cat’s immune response, genetics, and the presence of the feline coronavirus. While the feline coronavirus is highly contagious among cats, not all cats who are exposed to it will develop FIP. The mutation of the virus within the cat’s body plays a crucial role in the development of the disease.

FIP can be transmitted through direct contact with an infected cat’s bodily fluids, such as saliva or nasal discharge. It can also be transmitted through indirect contact, such as sharing litter boxes or food bowls. The virus can survive in the environment for several weeks, making it important to practice good hygiene and sanitation measures, especially in multi-cat households or catteries. It’s worth noting that FIP is not contagious to humans or other species, so there is no need to worry about transmission to yourself or other pets.

Clinical FIP symptom

FIP can manifest in three forms: wet (effusive), dry (non-effusive) and neuro/ocular FIP

  • Wet FIP is characterized by the accumulation of fluid in the abdomen or chest, leading to breathing difficulties and a distended abdomen.
  • Dry FIP involves granulomas—small collections of inflammatory cells—in various organs. These granulomas can interfere with the function of the affected organs, leading to a wide range of symptoms.
  • There’s also a form that affects the brain and nervous system, known as neurological FIP, which can cause neurological symptoms such as seizures and loss of coordination.


Diagnosing effusive FIP

Diagnosis of the effusive form of the disease has become more straightforward in recent years. Detection of viral RNA in a sample of the effusion (liquid drained from body), such as by reverse transcription polymerase chain reaction (RT-PCR) is diagnostic of effusive FIP. However, that does require that a sample be sent to an external veterinary laboratory. Within the veterinary hospital there are a number of tests which can rule out a diagnosis of effusive FIP within minutes:

  1. Measure the total protein in the effusion: if it is less than 35 g/L, FIP is extremely unlikely.
  2. Measure the albumin to globulin ratio in the effusion: if it is over 0.8, FIP is ruled out; if it is less than 0.4, FIP is a possible—but not certain—diagnosis
  3. Examine the cells in the effusion: if they are predominantly lymphocytes (a type of white blood cell), then FIP is excluded as a diagnosis.

Diagnosing non-effusive FIP

Non-effusive FIP is more difficult to diagnose than effusive FIP because the clinical signs tend to be more vague and varied: the list of differential diagnoses is therefore much longer. Non-effusive FIP diagnosis should be considered when the following criteria are met:

  1. History: the cat is young (under 2 years old) and purebred: over 70% of cases of FIP are in pedigree kittens.
  2. History: the cat experienced stress such as recent neutering or vaccination.
  3. History: the cat had an opportunity to become infected with FCoV, such as originating in a breeding or rescue cattery, or the recent introduction of a purebred kitten or cat into the household.
  4. Clinical signs: the cat has become anorexic or is eating less than usual; has lost weight or failed to gain weight; has a fever of unknown origin; intra-ocular signs; jaundice.
  5. Biochemistry: hypergammaglobulinaemia; raised bilirubin without liver enzymes being raised.
  6. Hematology: lymphopenia; non-regenerative—usually mild—anaemia.
  7. Serology: the cat has a high antibody titre to FCoV: this parameter should be used with caution, because of the high prevalence of FCoV in breeding and rescue catteries.
  8. Non-effusive FIP can be ruled out as a diagnosis if the cat is seronegative, provided the antibody test has excellent sensitivity. In a study which compared various commercially available in-house FCoV antibody tests,[19] the FCoV Immunocomb (Biogal) was 100% sensitive; the Speed F-Corona rapid immunochromatographic (RIM) test (Virbac) was 92.4% sensitive and the FASTest feline infectious peritonitis (MegaCor Diagnostik) RIM test was 84.6% sensitive.

Treatment Options for FIP

Traditional Treatment Options

Traditional treatment for FIP is mainly supportive and includes fluid therapy to address dehydration and anti-inflammatory drugs to control inflammation and fever. Fluid therapy can help replace the fluids lost due to vomiting, diarrhea, or lack of appetite, while anti-inflammatory drugs can help reduce the inflammation caused by the disease. However, these treatments do not address the underlying cause of the disease and are mainly aimed at improving the cat’s quality of life.


A 2018 study published by Murphy et al. demonstrated that GS-441524, a less chemically complex parent nucleoside (also patented by Gilead), was highly effective against experimentally induced FIP at a dosage of 4.0 mg/kg subcutaneously every 24 h for 12 weeks (84 days) in 10 laboratory cats. This gives us hope to treat FIP cats.

Experimental Treatments and Clinical Trials

There are ongoing clinical trials exploring new treatments for FIP. Participating in these trials can provide access to cutting-edge treatments and contribute to our understanding of the disease. I’ve had patients who have participated in these trials, and while it’s not a guarantee of a cure, it does offer hope for a potential breakthrough in FIP treatment.

Preventing FIP in Cats

Preventing FIP can be challenging, as the disease is complex and multifactorial. Minimizing stress and maintaining good hygiene are key aspects of prevention. Providing a clean and sanitary environment for your cat, including regular litter box cleaning and disinfection of shared spaces, can help reduce the risk of transmission. If you have multiple cats, consider separating them temporarily if one of them is diagnosed with FIP to prevent further spread of the virus.

Vaccination against feline coronavirus is available, but its effectiveness in preventing FIP is still a topic of debate. Consult with your veterinarian to understand the benefits and limitations of vaccination in your cat’s specific situation. It’s worth noting that vaccination cannot guarantee complete protection against FIP, especially in cats with a higher risk of developing the disease.

Conclusion and Resources for Further Information

FIP is a challenging and devastating disease, but with knowledge, support, and proper care, you can make a significant difference in your feline friend’s life. Understanding the causes, symptoms, and treatment options of FIP is essential for providing the best care possible. Remember to work closely with your veterinarian, who can guide you through the diagnosis and treatment process. Stay informed and seek support from trusted sources, such as reputable veterinary websites, support groups, and scientific publications. Together, we can empower ourselves to give our feline friends the love and care they deserve in the face of this deadly disease.

For further information and resources on FIP, consider visiting the following websites:

[The Winn Feline Foundation]

[Cornell Feline Health Center]

[American Association of Feline Practitioners]

[FIP Doctor saves 10,000+ FIP cats]

Remember, knowledge is power, and by staying informed, you can be a strong advocate for your feline friend and help create a better future for cats affected by FIP.

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