Feline Infectious Peritonitis (FIP) Treatment Guide [2024 Edition]: Latest Information and Treatment Options

Feline Infectious Peritonitis (FIP) is a deadly disease in cats caused by feline coronavirus. Until recently, there was no effective treatment, but the development of new drugs has dramatically changed the prognosis.

This article will provide the latest information on FIP.

What is Feline Infectious Peritonitis (FIP)?

Basic Information and Causes of Feline Infectious Peritonitis (FIP)

FIP is a fatal disease in cats caused by feline coronavirus. Feline coronavirus is attenuated and widely present among cats. The virus is shed in feces and cats become infected orally. FIP virus is a virulent form of feline coronavirus, and it is thought to become an FIP virus through mutation in the body of a cat infected with feline coronavirus. Therefore, cats infected with feline coronavirus have the potential to develop FIP.

However, FIP is complexly related to the immune system of infected cats, so not all cats infected with feline coronavirus will develop FIP.

Although FIP was previously thought not to be contagious, a mass infection occurred in a Taiwanese shelter in 2011, suggesting the possibility of cat-to-cat transmission. In 2023, a mass FIP infection occurred among stray cats on the island of Cyprus, killing many cats. This FIP virus was a recombined virus with canine coronavirus genes, so it is thought to have spread explosively without mutating into FIP virus.

FIP is relatively common in young cats (under 2 years of age) and tends to affect purebred male cats. It is also characterized by its frequent occurrence in multi-cat households.

Types of Feline Infectious Peritonitis (FIP) Symptoms

FIP is broadly divided into two types: effusive (wet type FIP) and non-effusive (dry type FIP). The effusive type is more common, accounting for about 80% of cases.

Common symptoms include lethargy, weight loss, fever, and poor coat condition. In the wet type, ascites and pleural fluid accumulate, leading to difficulty breathing and a distended abdomen.

The dry type is characterized by the formation of granulomas within the body. Symptoms may appear in the eyes, such as cloudy eyes or pupils of different sizes. Lesions may occur in the nervous system, leading to symptoms such as paralysis and seizures.

While these types can occur individually, both symptoms may appear, or the two types of symptoms may appear at different times.

Diagnosis Methods for Feline Infectious Peritonitis (FIP)

The diagnostic guidelines established by the International Society of Feline Medicine and the European Advisory Board on Cat Diseases are currently the latest guidelines.

1. Interview	Gather information suggesting FIP based on breed, age, gender, living environment, and symptoms.
2. Examination	Look for findings suggestive of FIP through physical examination, imaging, and blood tests. If ascites or pleural fluid is present, examine its properties.
3. Special Tests	Detect the virus through histopathological examination, feline coronavirus gene testing, or antigen testing.
4. Diagnosis	Based on the information obtained from 1 to 3, and by comparing it with other diseases, a diagnosis of FIP is made.

The diagnosis of FIP is very complex and progresses rapidly, so even veterinarians often encounter challenging cases.

Current Status and Latest Information on Feline Infectious Peritonitis (FIP) Treatment

Conventional Treatments and Their Limitations

FIP is complexly related to the infected cat's immune system, and various symptoms appear when the immune response goes awry. Therefore, conventional treatments attempted to suppress the runaway immune response. Steroids, immunosuppressants, and interferon therapy were used, but none of them offered significant efficacy.

Introduction to New Treatments (Antiviral Drugs, etc.)

In recent years, the development of treatments for globally prevalent diseases such as COVID-19 and Ebola virus infection has advanced. Treatment methods for FIP using these drugs have been devised, and cases where FIP symptoms disappeared and remission was achieved have been reported.

Currently, treatment methods using antiviral drugs such as Remdesivir and GS-441524 have been announced by the International Society of Feline Medicine. Based on these treatment protocols, numerous FIP cases are being treated. The treatment protocol involves an 84-day administration period.

Antiviral drugs (Remdesivir, GS-441524)	These drugs were developed as treatments for Ebola virus infection, but they have shown high antiviral activity against coronaviruses.
Molnupiravir	This drug was developed as a treatment for COVID-19 and is approved in Japan as a treatment for human COVID-19.

It seems that some new drugs have been available for individual import for several years (e.g., Mutian). However, as these are copies of new drugs, there can be differences in effectiveness, or some may have no medicinal effect at all. The cost is high, and it is risky to import them individually based on self-judgment.

New drugs are not available at all veterinary hospitals. Veterinarians import them from overseas, so you need to find a veterinary hospital that can provide the treatment.

Treatment Success Rates and Side Effects

The response rate for treatment using new drugs is reported to be around 85%. Furthermore, the recurrence rate after remission is considered to be less than 10%.

Common side effects include elevated liver enzymes. It has also been observed that subcutaneous injections of Remdesivir, an injectable drug, can cause pain. With Molnupiravir, a decrease in white blood cells has been noted. Additionally, genotoxicity has been pointed out, and its implications are currently unknown.

Feline Infectious Peritonitis (FIP) Treatment Options and Costs

While the cost of FIP treatment was once said to be 1 million yen for the medication, it has become slightly more affordable now. However, due to the use of imported drugs and the fact that pet insurance does not cover unapproved drugs, the treatment cost remains high.

Since treatment drugs are strictly adjusted based on the cat's condition and weight, regular veterinary visits and examinations are necessary. In most cases, the cat's condition is poor at the start of treatment, requiring hospitalization, so the total treatment cost can be several hundred thousand yen.

Molnupiravir is slightly cheaper than the other two drugs. Therefore, Molnupiravir may sometimes be chosen for economic reasons. However, while there are reports on treatment protocols using Molnupiravir, it is also true that many aspects remain uncertain.

Care During Treatment and Prognostic Management

Supportive Care at Home

During FIP treatment, problems such as loss of appetite can occur. It is necessary to feed them small amounts of wet food. If the cat is in too much discomfort to eat, it is advisable to manage them in a hospital setting. However, if caring for them at home, you can rent an oxygen chamber or administer liquid food through a tube inserted into the nose.

Stress is also considered a factor that can worsen FIP. If you have multiple cats, other cats may also become ill, so isolate them and provide a stress-free environment. Since the coronavirus is excreted in feces, wash your hands thoroughly after cleaning the litter box.

Prognostic Management and Preparing for Relapse Risk

Unfortunately, without new drugs, cats with FIP typically die within a few weeks. Even with new drug treatments, there are cases where the cat does not respond well to the treatment. Since new drug treatments only started in 2021, there is not a lot of data on the prognosis.

It is known that relapses can occur even after treatment. Relapses often happen within a short period after the end of treatment. Even after treatment, it is necessary to continue follow-up visits and examinations as instructed by the veterinarian. If your cat loses its energy or appetite, contact the veterinary hospital immediately.

Prevention and Early Detection of Feline Infectious Peritonitis (FIP)

Infection Prevention Measures and Daily Care

There is no FIP vaccine available in Japan. While one has been developed in the United States, its effectiveness is questionable.

Since vaccination is not possible, if your cat is not currently infected with coronavirus, you need to take measures to prevent infection. Also, even if a cat has feline coronavirus, it does not necessarily develop FIP, so it's important to prevent its onset.

Test for coronavirus infection
Dispose of feces quickly
Avoid multi-cat households
Test for feline AIDS and feline leukemia
Minimize stress

For Early Detection

FIP progresses very rapidly, and it's not uncommon for cats to die while awaiting diagnosis. FIP is common in kittens, so if there is even a slight loss of appetite or energy, seek veterinary attention immediately.

Summary

The advent of new drugs has dramatically changed FIP treatment in recent years. However, the costs are quite high, and the number of hospitals using the drugs outlined in the guidelines is limited.

If FIP is suspected, you should find a hospital yourself or ask your regular veterinarian for a referral. Also, owning only one cat rather than multiple cats helps prevent FIP.