Feline infectious peritonitis, commonly known as FIP, is a serious disease in cats associated with feline coronavirus. Many cats may be exposed to feline coronavirus during their lifetime, but only a small percentage develop FIP. When FIP occurs, it can affect different parts of the body and may appear in several clinical forms, including wet, dry, ocular, and neurological patterns. Common signs may include persistent fever, low appetite, weight loss, abdominal fluid, breathing difficulty, eye changes, or neurological abnormalities. Because these signs can overlap with many other diseases, any cat suspected of having FIP should be evaluated by a licensed veterinarian. 

This article explains what FIP is, how it may appear, what signs cat owners should watch for, and why product verification, reliable information, and veterinary guidance are important when learning about FIP-related care.

What Is FIP in Cats?

FIP stands for feline infectious peritonitis. It is a severe disease associated with feline coronavirus, often shortened as FCoV. In many cats, feline coronavirus may cause no obvious signs or only mild gastrointestinal or respiratory signs. However, in a small percentage of infected cats, the virus and the cat’s immune response may contribute to the development of FIP. Cornell Feline Health Center notes that most cats exposed to feline enteric coronavirus do not develop FIP, while a smaller percentage may develop the disease weeks, months, or even years after exposure. 

FIP is considered complex because it does not always look the same from one cat to another. Some cats develop fluid accumulation in the abdomen or chest. Others may show inflammation in organs, the eyes, or the nervous system without obvious fluid buildup. Because of this variation, FIP can be difficult to recognize early.

For cat owners, the most important point is this: FIP should not be judged by one sign alone. A swollen belly, fever, low appetite, weight loss, eye change, or neurological sign may raise concern, but none of these signs alone can confirm FIP.

Why FIP Can Be Difficult to Recognize

FIP often begins with vague signs. A cat may seem tired, eat less, lose weight, or have a fever that does not respond as expected. These signs may also occur with many other conditions, including liver disease, kidney disease, heart disease, cancer, immune-mediated disease, bacterial infection, or other viral disease.

Merck Veterinary Manual describes the onset of FIP as often gradual, with severity increasing over time. Signs may include persistent fever, appetite loss, weight loss, depression, fluid buildup, breathing difficulty, organ involvement, eye signs, or central nervous system signs. 

This is why veterinary evaluation is essential. A veterinarian may need to review the cat’s history, physical examination findings, imaging, bloodwork, fluid analysis, and other test results before deciding whether FIP is likely.

Common Symptoms of FIP in Cats

FIP signs can vary depending on the form and severity of disease. Some cats show only mild changes at first, while others become very ill quickly.

Common signs may include:

Persistent fever
A fever that lasts for days or weeks and does not respond as expected may raise concern. However, fever can also occur with many other infections or inflammatory diseases.

Low appetite
Cats with FIP may eat less, refuse food, or show reduced interest in meals.

Weight loss or poor growth
Weight loss, muscle loss, or failure to gain weight may occur, especially in younger cats.

Lethargy or weakness
Affected cats may sleep more, hide, play less, or appear generally unwell.

Abdominal fluid
Some cats develop a swollen or rounded abdomen due to fluid accumulation.

Breathing difficulty
If fluid builds up in the chest, breathing may become labored or faster than normal.

Eye changes
Some cats may show cloudiness, inflammation, color changes, or vision-related concerns.

Neurological signs
Balance problems, tremors, seizures, abnormal walking, head tilt, or weakness may occur when the nervous system is involved.

Because these signs are not specific to FIP, they should be treated as warning signs rather than a final diagnosis.

Wet FIP

Wet FIP is also called effusive FIP. This form is commonly associated with fluid accumulation in the abdomen, chest, or both.

Cats with wet FIP may show:

A swollen belly
Fluid in the abdomen may cause visible abdominal enlargement.

Breathing difficulty
Fluid in the chest may make breathing difficult or rapid.

Low appetite and weight loss
Even when the belly looks larger, the cat may be losing muscle and body condition.

Lethargy and fever
General illness signs are common.

Wet FIP can sometimes look more obvious than dry FIP because fluid buildup may be visible. However, abdominal fluid can also occur with other diseases, so fluid alone does not prove FIP. Imaging and fluid analysis may be recommended by a veterinarian.

Dry FIP

Dry FIP is also called non-effusive FIP. This form may not produce obvious fluid buildup. Instead, it may involve inflammatory lesions in organs such as the kidneys, liver, lymph nodes, intestines, brain, or eyes.

Cats with dry FIP may show:

Long-term fever
A persistent fever may be one of the earlier concerns.

Weight loss
Gradual weight loss or failure to gain weight may occur.

Poor appetite
Reduced appetite is common but not specific.

Organ-related signs
Depending on the organs involved, cats may show jaundice, digestive problems, enlarged lymph nodes, kidney-related changes, or other abnormalities.

Dry FIP can be harder to identify because its signs are often vague. Many owners may only notice that their cat is “not acting right” or is slowly losing weight.

Ocular FIP

Ocular FIP refers to FIP with eye involvement. It may appear alone or along with other signs.

Possible signs include:

Cloudy eyes
The eye may look hazy or cloudy.

Eye inflammation
Redness, discomfort, or squinting may occur.

Color changes
The iris may appear different in color.

Vision-related concerns
The cat may bump into objects, hesitate to jump, or seem less visually aware.

Eye signs should always be checked by a veterinarian. Eye inflammation may be caused by FIP, but it can also occur with trauma, other infections, immune disease, glaucoma, or other conditions.

Neurological FIP

Neurological FIP involves the brain, spinal cord, or nervous system. It can be one of the most concerning forms because signs may affect movement, balance, behavior, or coordination.

Possible signs include:

Wobbly walking
The cat may appear uncoordinated or unstable.

Head tilt
A tilted head may suggest neurological or vestibular involvement.

Tremors
Shaking or tremor-like movements may occur.

Seizures
Some cats may have seizure episodes.

Weakness or difficulty jumping
The cat may struggle to climb, jump, or walk normally.

Neurological signs require prompt veterinary attention. They can occur with FIP, but also with toxoplasmosis, inner ear disease, trauma, tumors, inflammatory disease, or other infections.

How Veterinarians Approach FIP Diagnosis

FIP can be difficult to diagnose because there is no simple single screening test that confirms every case. VCA Hospitals notes that a working diagnosis is typically based on clinical history and supportive laboratory data, and that routine bloodwork may show changes such as high protein levels or organ involvement; however, no blood test alone confirms FIP. 

A veterinarian may consider:

Physical examination
Checking fever, hydration, body condition, breathing, abdominal distension, eye changes, and neurological signs.

Bloodwork
Looking at white blood cells, anemia, globulin, albumin, bilirubin, liver values, kidney values, and the albumin/globulin ratio.

Imaging
Ultrasound or X-rays may help detect abdominal or chest fluid and organ changes.

Fluid analysis
If fluid is present, a veterinarian may examine its color, protein content, cell count, and other characteristics.

FCoV-related testing
Coronavirus antibody or PCR testing may provide context, but results must be interpreted carefully.

Biopsy or tissue testing
In difficult cases, tissue examination may be needed to help distinguish FIP from other diseases.

Because FIP can resemble many other conditions, diagnosis should be based on the full clinical picture, not one test result.

When Cat Owners Should Contact a Veterinarian

Cat owners should contact a veterinarian promptly if a cat shows signs such as:

Persistent fever
Especially if it does not respond as expected.

Loss of appetite
Particularly if the cat is eating little or nothing.

Rapid weight loss
Especially in kittens or young cats.

Swollen abdomen
A rounded belly may indicate fluid or another serious issue.

Breathing difficulty
This should be treated as urgent.

Eye inflammation or cloudiness
Eye changes may worsen quickly and need examination.

Neurological signs
Wobbliness, tremors, seizures, or abnormal walking require prompt evaluation.

Early veterinary evaluation can help identify whether the issue is FIP or another condition that requires attention.

Product Information, Verification, and Batch Traceability

When cat owners are learning about FIP-related product options, reliable product information matters. A product should have clear details such as ingredient information, strength, form, pack size, registration information, verification support, batch traceability, and customer assistance.

For example, cat owners reviewing a GS-441524-related product may want to check:

Active ingredient information
The product should clearly identify the ingredient.

Strength and form
The amount per tablet or unit should be clearly stated.

Registration-related information
Official registration or regulatory classification, if available, should be easy to review.

Batch traceability
Batch-related information can help users confirm product details.

Verification support
A verification page or support process can help reduce uncertainty.

Customer support
Support should be available for product questions, order-related questions, and verification assistance.

Cat owners can review NeoFipronis® Product Information, Registration Information, and About NeoFipronis® resources on the official website for product-related details.

Key Facts About FIP

FIP is associated with feline coronavirus
Many cats may be exposed to feline coronavirus, but only some develop FIP.

FIP can appear in multiple forms
Wet, dry, ocular, and neurological patterns may occur.

Symptoms can be vague
Fever, low appetite, weight loss, and lethargy may be early signs.

Fluid buildup is not always present
Dry FIP may occur without obvious abdominal or chest fluid.

Diagnosis can be complex
Veterinary evaluation and supportive testing are important.

FIP signs overlap with other diseases
Never assume FIP based on one sign alone.

Frequently Asked Questions

What does FIP stand for?

FIP stands for feline infectious peritonitis, a serious disease in cats associated with feline coronavirus.

Is FIP the same as feline coronavirus?

No. Feline coronavirus exposure is common in cats, but most exposed cats do not develop FIP. FIP occurs in a smaller percentage of cats and involves a more serious disease process. Cornell Feline Health Center notes that many cats exposed to feline enteric coronavirus show no obvious signs or only mild signs, while a smaller percentage develop FIP. 

What are the most common signs of FIP?

Common signs may include persistent fever, low appetite, weight loss, lethargy, abdominal fluid, breathing difficulty, eye changes, or neurological signs.

What is wet FIP?

Wet FIP, or effusive FIP, is commonly associated with fluid accumulation in the abdomen or chest.

What is dry FIP?

Dry FIP, or non-effusive FIP, may involve inflammatory changes in organs without obvious fluid accumulation.

Can eye problems be related to FIP?

Yes, eye involvement can occur in some cats with FIP, but eye problems may also have many other causes. A veterinarian should examine any cat with eye changes.

Can neurological signs occur with FIP?

Yes. Neurological signs such as wobbliness, tremors, seizures, head tilt, or abnormal movement may occur in some cases, but these signs also have other possible causes.

Can a blood test confirm FIP?

A blood test alone usually cannot confirm FIP. VCA Hospitals explains that a working diagnosis is typically based on clinical history and supportive laboratory data, but no blood test by itself confirms FIP. 

Should I consult a veterinarian if I suspect FIP?

Yes. FIP is serious and can resemble many other diseases. A licensed veterinarian should evaluate your cat and guide health-related decisions.

Conclusion

FIP is a serious and complex disease associated with feline coronavirus. It may appear as wet, dry, ocular, or neurological disease, and its signs can overlap with many other conditions. Cat owners should watch for warning signs such as persistent fever, low appetite, weight loss, abdominal fluid, breathing difficulty, eye changes, or neurological abnormalities. However, only a veterinarian can evaluate the full clinical picture and determine the most appropriate next steps.

When reviewing FIP-related product information, cat owners should look for clear ingredient details, product verification, batch traceability, registration information, and customer support. Reliable information can help reduce uncertainty and support better decision-making.

Disclaimer: This article is for educational purposes only and does not replace veterinary diagnosis, treatment decisions, or medical advice. Please consult a licensed veterinarian for health-related decisions.