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New effective treatment for Feline Infectious Peritonitis (FIP) | GS-441524 | FIP Cure

Updated: Mar 19

What Causes Feline Infectious Peritonitis?

Feline infectious peritonitis is caused by feline coronavirus. The name coronavirus may cause alarm in people. Don't worry. Unlike the human coronavirus that causes covid 19, feline coronavirus can only be transmitted between cats. In its more benign form the feline coronavirus is called feline enteric virus (FECV). Feline enteric virus infection is very common in cats. It is neither dangerous nor fatal. In most cases the only observable symptom is mild diarrhoea, and is easily treatable by veterinarians.

However, in less than 2% of cases, Feline coronavirus takes on the much more deadly form of feline infectious peritonitis virus (FIPV). Feline infectious peritonitis is nearly always fatal.

Feline infectious peritonitis (FIP) can affect cats of all ages. In the past doctors have prescribed various drugs to treat FIP such as interferon Omega, an immunomodulators, immunosuppressants, steroidal anti-inflammatory drugs, and antibiotic medications. While these veterinary medicines reduce pain and suffering for cats with FIP, they do not treat the root cause of the disease, the FIP virus. Another antiviral drug called GC376 appeared on the scene a few years ago and showed initial promise in a clinical study treating feline infectious peritonitis. However, in subsequent clinical trials GC376 proved ineffective both in a high percentage of FIP cases and in treating subsequent reinfections commonly referred to as relapse cases. An effective treatment for FIP remained elusive to cat owners and veterinarians.

Clinically Effective FIP Treatment | GS441524

A breakthrough in veterinary science occurred when Dr. Niels Pedersen and a team of researchers at the University of California Davis, doing FIP research, decided to use a human antiviral drugs to treat FIPV infection. The idea worked! They treated 31 cats for 12 weeks and demonstrated an efficacy rate of 83%. Desperate cat owners around the world finally had an answer for the FIP virus.

The drug they used is called GS441524. GS441524 antiviral therapy is equally effective treating effusive feline infectious peritonitis (wet FIP) as it is for non-effusive feline infectious peritonitis (dry FIP). This discovery was a giant leap in veterinary medicine. Subsequent clinical trials around the world, conducted on cats with naturally acquired FIP and experimentally infected FIP, reconfirmed UC Davis team's results. A global awareness is now growing amongst cat owners and medical practitioners of nucleoside analog GS441524 and its effectiveness in treating feline infectious peritonitis in cats.

GS441524 is administered through subcutaneous injections. It works by inhibiting FIPV replications. Treated cats show visible signs of recovery within as little as 3-4 days. In addition to eliminating common clinical signs of feline infectious peritonitis symptoms such as fever, lethargy, lack of appetite and abdominal swelling, Gs441524 has proved equally effective in eliminating neurological signs of seizures and physical paralysis. GS441524 can also be used as a diagnostic tool for FIP infection.

While antiviral drug GS 441524 is still waiting for food and drug administration approval in the USA and many other countries, thanks to the internet, it can now be obtained almost anywhere in the world by doctors and cat owners alike through what people often referred to as black market suppliers. Below are some places to look for supply. - Pioneered online ordering of GS 441524. Fast and efficient, with knowledgeable & helpful customer service, established in 2019. - One of the first reputable brands to appear on the market after publication of Dr. Niels Pedersen's clinical study. First company to introduce the oral form of GS 441524.

Facebook Groups - FIP Warriors and FIP Fighters are two of the biggest groups in the USA. FIP Free is the biggest group in Germany.

Today, through Google search, you may quickly find FIP online self-help communities in your area. Feline infectious peritonitis treatment is at the forefront of 21st century veterinary science. However, there are risks associated with this new approach of providing access to desperately needed veterinary medicine. It shifts the responsibility to cat owners. You may encounter multiple people offering GS-441524. Some reliable, others not so savory. So how do you choose the right brand or resellers to purchase from?

BUYING FIP TREATMENT: 3 things you should know!

Choose reputation, not price.

Veterinarians don't buy the cheapest drugs, neither should you. Several months ago news broke in FIP self-help groups across the world that many cats died while undergoing GS-441524 treatment using budget brands of GS-441524 from unknown sellers.

Given the proven effectiveness of GS-441524, this was highly unusual. After investigating and testing, reports surfaced showing that these brands overstated their GS concentration. Their claimed concentration of 15mg/ml was in actuality only between 7-8mg/ml according to some tests.

Furthermore, their formulations were not stable, with observable changes in pH level and viscosity from one production batch to the next. Making quality medicine requires knowledgeable chemists, precise instruments, high quality chemicals, and consistent protocols. None of which can be obtained cheaply. So how can the final product be cheap?

Buy directly from the brand's website or its authorised resellers whenever possible.

Don't know if the person you are buying from is an authorised reseller? Email the brand and verify. If you can't find the brand online, then it is best to avoid it altogether. Because GS is an expensive treatment, there is incentive for a few unscrupulous resellers to dilute with water, or switch from one brand to another during delivery. It doesn't happen often. But it has happened in the past.

Talk to sellers who are knowledgeable about FIP

You are not buying just a veterinary drug, you are buying knowledge. Has the seller demonstrated his/her expertise in the disease and the treatment. Does she answer your questions in a frank and transparent manner? Does she make an effort to understand your cat's situation? Does he/she understand all the potential complications and pitfalls during the treatment? Most importantly, does what he/she say make sense?

FIP can be difficult to diagnose even for experienced veterinarians. Many of FIP symptoms mirror those of other more common illnesses. And because only approximately 1% of cats worldwide contract FIP, when confronted with symptoms that could indicate multiple possible diseases, veterinarians often diagnose and treat for more common diseases. Only when FIP infection has progressed into late stages, and/or when suspicion of more common diseases have been eliminated through testing and treatments, do doctors suspect a FIP infection.

There is currently no definitive test available that can provide a definitive diagnosis of FIP. Veterinarians often have to perform multiple tests, some quick and cheap, others complicated and expensive to arrive at a confident diagnosis. Here is a list of common symptoms:

External symptoms, observable with the naked eyes

  • Lethargy

  • Lack of movement

  • Loss of appetite

  • Persistent fever

  • Yellowing of the gums or eyes, commonly called jaundice

  • Significant swelling in the abdomen

  • Physical paralysis

Internal symptoms, only observable with medical testing

  • low number of red blood cells

  • high number of white blood cells

  • elevated concentrations of protein in the blood

If there is a build-up of fluid in your cat’s abdomen or chest, your veterinarian may collect a sample of the fluid for testing. Fluids with a high protein percentage are an indicator of FIP and will frequently be yellow-tinged. If FIP is suspected, your veterinarian may take an X-ray or ultrasound of your cat.

There are a few other tests that may help support a FIP diagnosis. The immunoperoxidase test can detect white blood cells infected with the virus. Polymerase chain reaction technology can be used to test for the virus in the tissue or body fluid. Sometimes, a biopsy of the infected tissue inside the abdominal cavity may be performed.

Although these tests can help support a veterinarian’s diagnosis, none of them is 100% accurate.

Effusive Feline Infectious Peritonitis a.k.a. Wet FIP

In an affected cat, the virus spreads throughout the body and can cause a wide range of different signs (including peritonitis with the accumulation of fluid in the abdomen, but in other cats, fluid may accumulate in the chest cavity; in others, the virus may cause inflammation affecting the brain, eyes, liver, kidneys or elsewhere).

The effusive form of FIP develops from inflammation of blood vessels (known as ‘vasculitis’). The vasculitis can occur anywhere in the body, affecting any organ or system. Thick, protein-rich fluid oozes from the damaged blood vessels, filling various body cavities.

The most common effusive form of FIP cases that develop fluid accumulation in the abdomen are responsible for the original name of this disease, ‘peritonitis’ referring to the inflammation that occurs in the lining of the abdominal cavity.

Diagnosis of effusive form of FIP is much easier due to obvious visible signs. For example, bloating of the stomach for fluid accumulation in the abdomen and laboured breathing for fluid accumulation in the pleural cavity.

Non Effusive Feline Infectious Peritonitis a.k.a Dry FIP

The Non-effusive form of FIP develops when FIPV virus incites a specific type of inflammatory reaction called granulomatous inflammation. Essentially, a ball of inflammation develops around the virus and damages the surrounding tissue. Any organ or body system can be affected. However, FIPV’s primary targets are the central nervous system and eyes.

Diagnosis of dry form of FIP in the early stages of infection is extremely difficult because symptoms are very similar to other more common feline diseases. The incubation period for dry form of FIPV can often be more than 2 weeks. During the incubation period, cats will look outwardly healthy and normal. However, when symptoms start to appear, it can quickly escalate into late stage infection which is marked by neurological disorders such as physical paralysis and seizures.

Diagnosing FIP in Cats

FIP is difficult to diagnose and may be misdiagnosed as other more common diseases. Clinical signs of FIP in cats: fever, weight loss, diarrhea, lethargy, eyes cloudiness, respiratory distress (coughing up yellowish fluid from throat) and swollen abdomen can be misdiagnosed until the feline infection has advanced to late stages. Diagnosing FIP early is therefore a trial and error process involving multiple tests and experienced veterinary eyes. We have listed some common techniques that your doctor employs to help him or her ascertain that it is a FIP infection.

We have compiled 4 commonly used tests by veterinarians to detect whether your cat has been infected by the feline infectious peritonitis virus (FIPV). There is no single test that can conclusively determine if your cat has contracted Feline Infectious Peritonitis Virus (FIPV). However, these tests do alert medical professionals to potential infections by detecting the antigen inside your cat's body fluid and faecal matters. Experienced veterinarians use these tests, along with experience and trained eyes to determine the likelihood of an FIPV infection.

Titre test for cats
Titre test for cats

1. Titre Test

A titre test measures the level of antibodies circulating in the blood. These antibodies are produced when pathogens such as viruses or bacterias produce a response from the immune system. You can read more about the titre test here.

2. Histopathology

Doctors surgically collect and examine tissue samples. The pieces of tissue are prepared through a process called histology by preserving, thinly slicing or sectioning, and staining the tissue sample with dyes.

Tissue Sample taken from a FIP cat
Tissue Sample taken from a FIP cat

Once prepared, the tissue sections are examined under the microscope by a veterinary pathologist. Histopathology focuses on the architecture of the tissue.

The accuracy of a diagnosis is usually high. However, the downside is that it is slow and expensive. A veterinary pathologist can often offer an opinion on the likely course of the disease, called a prognosis. This information helps your veterinarian to decide the best course of treatment for your pet.

3. Rivalta Test

A simple yet useful test to determine the WET form of FIP. The test is performed by collecting sample fluid from the cat’s abdominal or chest cavity, adding it to a test tube filled with distilled water and one drop of 98% acetic acid. You can see a video of Rivalta Test performed here.

Rivalta test for effusive feline infectious peritonitis
Rivalta test for effusive feline infectious peritonitis

4. Blood Test

A comprehensive blood test is commonly used by veterinarians to determine the likelihood of a FIP viral infection in cats. In the CBC blood test doctors are looking for high white blood cell count and low red blood cell count. The biochemistry profile commonly reveals an increase in total protein and globulins. This increase indicates the inflammatory process as the cat's body responds to the virus. Veterinarians often look at A:G ratios as the first sign of potential FIP infection in cats.

Blood report: signs of FIP infection
Blood report: signs of FIP infection [Credit:]

This sample blood report shows an increase of Total Protein and Globulin (hyperglobulinemia) in a FIP positive cat.

Other tests on the biochemistry profile could, but not necessarily indicate FIP in cats since these problems could also occur with other diseases. For example, if the kidney values are increased in an older cat with suspicion of FIP, some of the possibilities are:

  • Chronic renal failure along with FIP (this cat has 2 different diseases)

  • Chronic renal failure with no FIP

  • FIP causing kidney disease

  • Dehydration due to FIP

  • Dehydration due to disease in some other organ

How to Prevent FIP?

The virus that causes feline infectious peritonitis is not contagious. However, the feline coronavirus FCOV that causes FIP is highly contagious. An infected cats spread FCOV through saliva, urine and other bodily fluids and solids. FIP is more common in multi-litter households. However, solitary cats may contract FIP through contacts with street cats or even at the rescue or breeder's facility. While isolation of a FIP cat is recommended for multi-litter households, the reality is that FCOV may have long been spread to and from other cats.

You may perform a FCOV quick test for your cats. If the result is negative. We recommend completing a FIPV vaccination at your local veterinary clinic. While the effectiveness of the current FIPV vaccine is only ~50%, it does provide a layer of protection and lower the potential risk of contracting a FIP infection.

Keep your cat indoors; if you do let him/her outdoors keep them on a leash so he doesn't come into contact with any saliva droplets or feces and urines left behind by another animal which might carry the virus long after they are gone.


We have written this comprehensive FIP treatment course in the hope that it will lead you to a better understanding of the FIP disease and how to obtain effective FIP treatments. There are still much more information left undiscussed in this article about the feline infectious peritonitis. If you have further questions about the disease or the treatment, contact us at

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