What is Feline Infectious Peritonitis (FIP)

Feline Infectious Peritonitis (FIP) is a serious and often fatal viral disease in cats. It is caused by a coronavirus, specifically the feline coronavirus (FCoV).


Feline coronavirus is primarily spread in feces and can be transmitted to other cats through the fecal-oral route. This means that a cat can become infected by coming into contact with contaminated litter boxes, bowls, or other surfaces. There are two types of FCoV: feline enteric coronavirus (FECV) and the FIP-producing types. Most cats are infected with FECV, which is relatively harmless and may cause mild diarrhea. However, in some cases, this virus can mutate into a form that can cause FIP.


FIP can present in two forms: effusive (wet) FIP and non-effusive (dry) FIP.

Effusive (wet) FIP: This form is characterized by the accumulation of fluid in the abdomen, chest, or both. Symptoms may include:

Non-effusive (dry) FIP: This form does not have the characteristic fluid accumulation. Instead, it has more varied symptoms which can include:

It's worth noting that FIP can be challenging to diagnose because its symptoms are similar to other diseases.

Treatment options

Historically, FIP was considered fatal with no effective treatment. Supportive care, such as anti-inflammatory drugs, fluid therapy, and nutritional support, was the primary mode of management.

However, in recent years, antiviral drugs have shown promise in treating FIP. GS-441524 and its prodrug, Remdesivir, which was used in the treatment of COVID-19 in humans, has been found effective in treating FIP in some cats. These drugs inhibit the virus's replication. However, they are not approved everywhere for veterinary use yet, and there can be significant costs and other challenges associated with their use.

There are Facebook groups that have certified vets that will prescribe the antiviral drugs. https://www.facebook.com/groups/fipwarriorsoriginal/ & https://www.facebook.com/groups/547566053161468

 Current genetic variants:

All cases of FIP result from a mutation of the less harmful FECV. However, it's the cat's immune response to this mutation, more than the mutation itself, that often determines the development and severity of FIP. While there's ongoing research into the specific genetic variants of the virus, it's equally important to consider the genetic factors of the cat. Some research suggests that certain breeds or genetic lines may be more susceptible to FIP.

It's worth noting that knowledge about FIP is constantly evolving, and new research might provide further insights into the disease's transmission, treatment, and genetic factors. Always consult with a veterinarian for the most up-to-date information and recommendations.

The difference between Feline Infectious Peritonitis (FIP) and Feline Corona Virus (FCOV)

Feline Infectious Peritonitis (FIP) and Feline Coronavirus (FCoV) are related diseases that affect cats, but they have distinct differences in terms of their clinical manifestations, progression, and outcomes.

Feline Coronavirus (FCoV):

Feline Coronavirus is a virus that primarily affects the gastrointestinal tract of cats. Most cats infected with FCoV experience mild or no symptoms at all. FCoV is highly contagious and can spread through direct contact with an infected cat's feces. There are two main forms of FCoV:

Clinical Manifestations:

Feline Coronavirus (FCoV):

- Mild or no symptoms in the majority of cases.

- Mild diarrhea, gastrointestinal upset, and occasionally loss of appetite.

- Generally, cats remain active and show no signs of serious illness.

Feline Infectious Peritonitis (FIP):

- Diverse clinical signs depending on the form of FIP (effusive or non-effusive).

- Effusive (Wet) FIP:

  - Accumulation of fluid in the abdomen (ascites) or chest (pleural effusion).

  - Distended abdomen, labored breathing, lethargy, weight loss.

- Non-Effusive (Dry) FIP:

  - Granulomas in various organs, leading to organ-specific symptoms.

  - Neurological symptoms, ocular issues, organ dysfunction.


Feline Coronavirus (FCoV):

- Most cases resolve on their own with mild or no symptoms.

- Cats may develop immunity to the specific strain of FCoV they were exposed to.

Feline Infectious Peritonitis (FIP):

- Progression varies between effusive and non-effusive forms.

- Effusive FIP progresses rapidly, often leading to death within weeks to months.

- Non-effusive FIP has a slower progression, extending over several months.

- Disease severity can fluctuate, with periods of improvement followed by relapses.


Feline Coronavirus (FCoV):

- Cats infected with FCoV usually recover without any long-term effects.

- In some cases, especially in multi-cat environments, the virus can persist.

Feline Infectious Peritonitis (FIP):

- FIP is a severe and often fatal disease.

- Effusive FIP has a poor prognosis, and affected cats often do not survive beyond a few months.

- Non-effusive FIP also has a poor prognosis, with a more prolonged course but a fatal outcome.

- Despite supportive care, there is no known cure for FIP.

Diagnostic Challenges:

Feline Coronavirus (FCoV):

- Diagnosed through tests detecting the presence of FCoV RNA or antibodies.

- FCoV is common, and exposure does not necessarily lead to FIP.

Feline Infectious Peritonitis (FIP):

- Diagnosing FIP is challenging due to overlapping symptoms with other diseases.

- No definitive diagnostic test exists; diagnosis often requires a combination of clinical signs, laboratory results, and sometimes histopathology.

- A high index of suspicion is needed, especially for distinguishing FIP from other conditions.

While Feline Coronavirus (FCoV) typically causes mild gastrointestinal symptoms and often resolves on its own, Feline Infectious Peritonitis (FIP) is a more serious and complex disease that can lead to severe organ involvement and a poor prognosis. The key distinction lies in the progression and outcome of these conditions, with FIP being a highly challenging disease to diagnose and manage.

Feline Coronavirus (FCoV) is a relatively common virus that usually causes mild gastrointestinal symptoms in cats. Feline Infectious Peritonitis (FIP) is a severe and often fatal disease that results from the mutation of FCoV into its more virulent form, FIPV. The distinction between the two lies in the clinical presentation, severity, and outcome of the infections.