FIP (Feline Infectious Peritonitis) is a serious and often fatal viral disease caused by a mutated form of the feline coronavirus (FCoV). While most cats infected with feline coronavirus show no symptoms or mild signs, in certain cases, the virus mutates, leading to a life-threatening condition. FIP primarily affects a cat’s immune system and causes severe inflammation in various organs, making it one of the most challenging diseases in veterinary medicine.

In this article, we'll discuss what FIP is, its causes, symptoms, diagnosis methods, available treatments, and prevention strategies. This comprehensive guide is aimed at helping cat owners understand the disease and how to manage it if their cat is diagnosed.

What is FIP in Cats?

FIP is caused by a mutation of feline coronavirus, which is a common virus found in cats. In most cases, the infection remains mild, confined to the intestines, and often resolves on its own. However, in some cats, the virus mutates and spreads to other organs, leading to FIP. The mutated virus causes inflammation in the blood vessels, leading to damage to organs like the liver, kidneys, brain, and eyes.

Types of FIP

FIP typically manifests in two forms:

1. Effusive (Wet) FIP:
   • Symptoms: The wet form is marked by fluid buildup in the abdominal or chest cavity, which can lead to difficulty breathing, a swollen belly, and lethargy.
   • Common signs include:
     • Abdominal distension (bloating due to fluid buildup)
     • Respiratory distress (difficulty breathing)
     • Fever that doesn't respond to antibiotics
     • Loss of appetite and weight loss
2. Non-effusive (Dry) FIP:
   • The dry form of FIP is characterized by the formation of granulomas (small masses of inflamed tissue) in affected organs, such as the liver, eyes, kidneys, or brain.
   • Symptoms vary depending on the organs affected but may include:
     • Neurological issues (seizures, coordination problems)
     • Eye inflammation, which can lead to vision problems
     • Fever, weight loss, and lethargy

Symptoms of FIP in Cats

FIP presents with a variety of symptoms, depending on whether the cat has the wet or dry form of the disease. Common symptoms include:

• Persistent fever that does not respond to antibiotics
• Loss of appetite and weight loss
• Jaundice (yellowing of the skin and eyes)
• Abdominal or chest fluid accumulation (wet form)
• Neurological signs (in the dry form) such as:
  • Head tilt
  • Tremors
  • Seizures
  • Uncoordinated movement (ataxia)
• Poor coat condition and lethargy

The progression of the disease can be rapid, and without treatment, FIP is typically fatal.

Causes and Risk Factors of FIP

FIP is caused by a mutation of feline coronavirus (FCoV), which is highly contagious among cats, especially in multi-cat households or shelters. Most cats infected with FCoV do not develop FIP; the mutation that leads to FIP occurs in only a small percentage of cases.

Risk factors for FIP include:

• Age: Kittens, particularly those between 6 weeks and 2 years old, are more susceptible to FIP.
• Living conditions: Cats living in multi-cat environments, such as catteries, shelters, or large households, are at greater risk due to the ease of transmission of the virus.
• Immune system: Cats with compromised immune systems, often due to stress or illness, are at increased risk of developing FIP after being infected with feline coronavirus.
• Breed: Certain breeds, such as Persian, Siamese, and Bengal cats, are thought to have a genetic predisposition to developing FIP.

Diagnosis of FIP

Diagnosing FIP is notoriously difficult because its symptoms mimic those of many other diseases. There is no single test that can definitively confirm FIP, but several diagnostic methods are used in combination to support a diagnosis:

• Blood tests: A blood sample may reveal elevated levels of certain proteins, such as total protein and globulin, which can indicate inflammation associated with FIP.
• Fluid analysis: In the wet form of FIP, fluid may accumulate in the abdomen or chest. A sample of this fluid can be taken and analyzed. The fluid is often yellowish and has high protein content.
• PCR test: A Polymerase Chain Reaction (PCR) test can detect the presence of feline coronavirus but cannot confirm FIP. This test only indicates that the cat has been exposed to the virus.
• Imaging: X-rays or ultrasounds can help identify fluid buildup or any abnormalities in organs affected by FIP, such as the liver or kidneys.

Challenges in Diagnosis

FIP shares symptoms with other diseases, such as lymphoma, toxoplasmosis, and leptospirosis, making it difficult to diagnose without a combination of clinical signs, laboratory tests, and imaging.

Treatment for FIP

Historically, FIP was considered incurable and fatal. However, recent advancements in antiviral therapy have provided a glimmer of hope for cats diagnosed with FIP.

1. Antiviral Medications:

• The most effective treatment for FIP is GS-441524, a compound related to remdesivir, the antiviral drug used to treat COVID-19. GS-441524 has shown significant success in treating both the wet and dry forms of FIP.
• Treatment regimen: GS-441524 is administered as a daily injection for several weeks (typically 12 weeks). Many cats treated with GS-441524 show dramatic improvement, and some may even experience a full recovery.
• Success rate: The success rate of GS-441524 has been high, with many cats experiencing significant improvement or even complete resolution of symptoms.

2. Supportive Care:

• While antiviral treatment is essential, supportive care is also necessary. This may include fluid therapy, pain management, and nutritional support to help your cat maintain its strength during treatment.
• If your cat has neurological symptoms, additional medications may be required to manage seizures or inflammation.

3. Corticosteroids:

• In some cases, corticosteroids may be used to reduce inflammation and manage symptoms. However, corticosteroids are not a cure for FIP and are typically used as a temporary measure to alleviate discomfort.

4. Other treatments:

• In some cases, immunosuppressive medications and antibiotics may be prescribed, though these are not considered curative treatments for FIP itself.

5. Prognosis:

• With early treatment and the use of antiviral medications like GS-441524, the prognosis for FIP has improved dramatically. While FIP used to be almost universally fatal, many cats treated early with the right antiviral drugs have shown a good chance of recovery.

Prevention of FIP

Currently, there is no vaccine for FIP that guarantees protection, and the disease remains challenging to prevent. However, you can take steps to reduce the risk of FIP:

• Maintain a low-stress environment: Stress weakens a cat’s immune system and may contribute to the mutation of the feline coronavirus into FIP.
• Clean living spaces: Feline coronavirus spreads through feces, so ensure that your cat’s litter box is cleaned regularly to minimize the risk of exposure.
• Limit exposure to infected cats: In households with multiple cats, try to minimize the risk of cross-contamination by keeping infected cats isolated.
• Support your cat’s immune system: Ensure your cat is well-fed, hydrated, and in good health to help its immune system fight off infections.

Conclusion

FIP is a devastating disease, but recent advancements in antiviral treatment have transformed its prognosis. With early intervention, particularly with antiviral drugs like GS-441524, many cats diagnosed with FIP can experience a full recovery and live healthy, normal lives. If your cat is showing symptoms of FIP, it is crucial to seek veterinary care as soon as possible.

Although the disease remains difficult to prevent, managing stress and maintaining a clean environment can help reduce the risk of infection. If your cat is diagnosed with FIP, consult your veterinarian about the latest treatment options available and discuss the potential for antiviral therapy.