FIP in cats

What is FIP?

FIP, or feline infectious peritonitis, is not caused by a dangerous external virus, but by a mutation of a normally harmless feline coronavirus that is a natural part of the intestinal flora of the majority of cats and usually causes only mild diarrhea. In a few cases, however, this otherwise harmless virus mutates so significantly in the cat's body that it becomes a virus that triggers FIP. Why this mutation occurs in some cats and not in others depends primarily on the individual's immune system and stress level. Young cats under two years of age, animals from multi-cat households or breeding facilities, and male animals are particularly at risk, as they are more likely to be under stress or have a high viral load.
The "normal" feline coronavirus (FECV) is detectable in 54–97% of all multi-cat households and is usually completely harmless. It is only the mutation in the body that enables the virus to infect certain immune cells – known as macrophages – and spread throughout the entire organism.

Is FIP contagious? No, because the mutated coronavirus is not directly transmissible, as the mutation takes place inside the cat's body.

Risk factors for the development of FIP

FIP is particularly common in young cats: more than half of all affected animals are younger than two years old. Gender also plays a role, as male cats are statistically more likely to contract the disease than females. Another major influencing factor is the cat's environment. In multi-cat households, breeding facilities, or animal shelters, the viral load is naturally higher, and stress—such as from moving, socialization, neutering, or other illnesses—facilitates the mutation of the harmless coronavirus into the FIP-causing variant. Purebred cats are slightly overrepresented in the statistics, but this is not due to a genetic predisposition, but rather because they are more often kept in groups and are therefore exposed to the same stress and infection factors as other cats in larger populations.

Recognize signs

The symptoms of FIP can vary greatly and often begin with rather unspecific changes that can also occur in many other diseases. Many affected cats initially appear unusually calm or lethargic. They sleep more than usual, lose interest in their surroundings, and appear less active overall.

Other signs include:

• Loss of appetite, weight loss
• fever
• Ascites (approx. 39% of cases)
• Neurological symptoms (approx. 20% of cases)
• Jaundice (approx. 19% of cases)
• Eye changes

FIP forms

FIP is not a uniform disease, but can manifest itself in very different ways. Depending on how the cat's immune system reacts and which organs are affected, different forms of the disease can occur. The most well-known are the wet and dry forms, but eye and neurological manifestations also occur. Occasionally, the forms of the disease even occur in combination. This mixed form combines characteristics of different forms of the disease. Each of these forms has typical symptoms and varies in severity, which sometimes makes diagnosis more difficult.

• Effusive FIP: Fluid accumulation in the abdomen or chest. The abdomen becomes distended, and breathing difficulties may occur. This is the most common form (approx. 64% of cases).
• Dry (non-effusive) FIP: nodules/granulomas in organs, weight loss, fever, organ symptoms (approx. 23% of cases)
• Ocular FIP: uveitis, reddened eyes, vision loss (approx. 6% of cases)
• Neurological FIP: ataxia, seizures, paralysis

Are you unsure whether your cat is showing signs of FIP and needs to be examined by a veterinarian?
Calingo customers can request a veterinary consultation free of charge, 24/7, from the comfort of their own home—simply click on the telemedicine button at the bottom right.

diagnosis

Since there is no single reliable test for FIP, the diagnosis is made step by step—this is referred to as the "building block principle." Veterinarians jointly evaluate the medical history, clinical examination, blood values, ultrasound findings, and, if necessary, special laboratory tests such as PCR from fluids or tissue samples.

The most important building blocks:

• Medical history and clinical examination
• blood test
• ultrasound
• Pathogen detection (not from feces! PCR is performed on effusions and cerebrospinal fluid obtained by lumbar puncture)

Depending on the individual case, additional tests may be necessary, such as a urine test, additional laboratory tests, or further imaging procedures such as X-rays or a CT scan, in order to confirm the diagnosis of FIP or to rule out other diseases with certainty.

therapy

An antiviral therapy (GS-441524) has been legally available in Switzerland since September 2025. The therapy involves administering the medication orally, once a day, for approximately 6 weeks (please note: the exact treatment protocols may vary depending on the regimen and individual situation).
Accompanying therapy, such as fluid therapy, painkillers, anti-inflammatory drugs, appetite stimulants, or treatment of secondary bacterial infections, is indicated depending on the severity of the disease.
The survival rate is approximately 80-92%, and relapses are rare. Early initiation of therapy greatly increases the chances of survival.

Although a diagnosis of FIP may initially sound frightening to many cat owners, the situation has changed fundamentally in recent years. Thanks to today's safe and effective treatment options, the vast majority of affected cats have a good chance of making a full recovery. Early diagnosis, close veterinary supervision, and consistent treatment are crucial.

With the legal availability of the drug, cat owners now have options that were not possible in the past. FIP is no longer a hopeless diagnosis—on the contrary, with the right support, your cat can lead a healthy and happy life again.

Does Calingo pay the costs associated with FIP?

Yes. Since the drug for treating FIP can now be administered officially and legally, Calingo covers the costs incurred within the scope of the applicable insurance conditions (in accordance with the General Terms and Conditions of Insurance). This means that both the diagnosis and the treatment—including the antiviral drug and any necessary follow-up examinations—are covered by the insurance, provided that the cat is insured accordingly.

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