As a new cat owner, protecting your feline’s health is crucial. One of the serious diseases to be aware of is Feline Infectious Peritonitis (FIP). FIP requires early detection and appropriate treatment, but it is a disease that has historically been difficult to diagnose, and until recently, was often fatal due to limited treatment options. Fortunately, as of 2024, significant advances in FIP treatment have improved recovery chances for many cats. In this blog, we’ll explain the basics of FIP, its symptoms, diagnosis, and the latest treatment options.
1. What is Feline Infectious Peritonitis (FIP)?
FIP is a disease caused by a mutation of the feline coronavirus (FCoV). Most cats carry this virus, but it typically causes no harm. However, in some cases, the virus mutates, leading to FIP. This condition predominantly affects young cats and those with weakened immune systems, and once it progresses, it becomes challenging to treat.
FIP is classified into two main forms: wet (effusive) FIP and dry (non-effusive) FIP.
- Wet (effusive) FIP
This form is characterized by fluid accumulation in the abdomen or chest, causing swelling and respiratory distress. It progresses rapidly, and the cat’s health can deteriorate quickly. - Dry (non-effusive) FIP
In this form, solid lesions form on organs or within the brain, and symptoms develop more gradually. Neurological symptoms, eye inflammation, or unsteadiness may be observed.
2. What Are the Symptoms of FIP?
The early symptoms of FIP, such as fever, lethargy, and loss of appetite, are quite general and can be mistaken for other conditions. As the disease progresses, more specific signs may appear, especially depending on whether the cat has the wet or dry form of FIP.
Common symptoms to watch for include:
- Persistent fever (often above 39.5°C)
- Lethargy and lack of movement
- Significant decrease in appetite
- Weight loss
- Swollen abdomen or chest (wet FIP)
- Unsteady walking, vision loss, seizures (dry FIP)
3. How is FIP Diagnosed?
FIP is notoriously difficult to diagnose with certainty. A definitive diagnosis often requires a combination of test results and clinical judgment by your veterinarian.
- Blood Tests
Blood work can reveal signs such as anemia, increased white blood cells, elevated protein levels, and globulins, which can point to FIP. - Imaging
Ultrasounds or X-rays may help identify abnormalities such as fluid accumulation in the abdomen or chest or changes in the organs. - Fluid Analysis
If there is fluid in the abdomen or chest, analyzing its properties—typically a thick, yellowish fluid—can help support a diagnosis of FIP.
4. Latest FIP Treatments: Antiviral Medications
Historically, FIP was considered untreatable, and many cats did not survive the disease. However, since 2021, advances in antiviral treatments have made recovery possible for many cats. The primary drugs now available for FIP treatment include GS-441524, remdesivir, and molnupiravir.
4.1 GS-441524 and Remdesivir
- GS-441524 is the cornerstone of FIP treatment. It is available in an oral form, making it less stressful for cats and easier for owners to administer. It has shown effectiveness in both wet and dry forms of FIP, with a typical treatment duration of 12 weeks (84 days). Dosing is adjusted based on the cat’s weight and condition.
- Remdesivir is another antiviral originally used in humans to treat viral infections, and it has proven effective for FIP. It is administered by injection and is typically used in severe cases or when oral medication is not an option.
4.2 Molnupiravir
A newer treatment option, molnupiravir, was introduced in 2022 in Japan. In one study, 18 cats with FIP were treated with molnupiravir, with a dosage of 10–20 mg/kg given twice daily for 84 days. Fourteen of the treated cats successfully completed the treatment and remained in remission(Molnupiravir treatment of 18 cats with feline infectious peritonitis: A case series).
Molnupiravir is considered a cost-effective treatment with relatively few side effects. While some cats experienced mild liver enzyme elevations, no special interventions were needed, and they recovered. Molnupiravir offers an additional option for FIP treatment, and its use may expand in the coming years.
4.3 Monitoring During Treatment
Most cats show improvement within a few days of starting treatment, particularly with a return of appetite and energy. However, it may take longer for all symptoms to resolve. For example, in wet FIP, fluid in the chest or abdomen may take up to two weeks to dissipate.
Regular weight checks are crucial, as cats often gain weight during treatment, necessitating dosage adjustments. If new neurological or eye symptoms appear, the dose may need to be increased. Careful monitoring during and after treatment is essential to prevent relapse.
5. Follow-Up and Relapse Risk After Treatment
Although the standard treatment duration for FIP is 12 weeks, there is a risk of relapse after treatment ends. The first four weeks after stopping medication are particularly critical, and owners should monitor their cat closely for any signs of recurrence. A relapse may present with different symptoms than those at the initial diagnosis—for example, a cat that had wet FIP may develop dry FIP symptoms upon relapse.
If a relapse is suspected, it is important to consult with your veterinarian immediately for further treatment.
6. Supportive Care for Cats with FIP
In addition to antiviral medication, supportive care plays an important role in the recovery of FIP-infected cats. Cats with decreased appetite may benefit from appetite stimulants or nutritional support. In cases of severe anorexia, a short-term feeding tube may be recommended to ensure adequate nutrition and medication delivery.
For pain management, pain relief medications such as opioids or NSAIDs may be used, particularly in cats with significant fluid accumulation or inflammation. Cats with wet FIP may require regular drainage of chest or abdominal fluid to relieve discomfort and breathing difficulties.
7. Preventing FIP and Managing Your Cat’s Health
While there is no direct way to prevent FIP, reducing exposure to the feline coronavirus (FCoV) that causes the disease is key. In multi-cat households or catteries, maintaining good hygiene and minimizing contact between cats can help reduce the risk of viral transmission. Stress can also trigger the onset of FIP, so creating a calm, low-stress environment for your cat is essential.
Regular veterinary check-ups can help detect early signs of illness, especially in young cats or those with weakened immune systems, who are more susceptible to FIP.
Conclusion
Feline Infectious Peritonitis (FIP) was once a devastating and fatal disease, but recent advances in antiviral treatments have significantly improved outcomes for affected cats. By understanding the differences between the wet and dry forms of FIP and ensuring early diagnosis and treatment, you can help protect your cat’s health.
Monitoring your cat during and after treatment is crucial, and any signs of abnormal behavior should prompt a visit to your veterinarian. We hope this blog helps new cat owners better understand FIP and how to care for their feline companions.
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