Posted on January 15th, 2026.

 

Caring for a cat means paying attention to the small changes: how they eat, play, and rest.

 

When serious illnesses like feline infectious peritonitis (FIP) are in the picture, that awareness becomes even more important.

 

The goal is not to worry constantly but to understand what FIP is and what to watch for.

 

FIP can sound intimidating, especially if you have heard it described as rare and serious.

 

However, when you know how it develops, what the symptoms look like, and how vets approach treatment and prevention, you can make calmer, more informed decisions.

 

The aim is simple: catch problems early when possible and give your cat the best quality of life you can.

 

Understanding Feline Infectious Peritonitis

Feline infectious peritonitis (FIP) starts with something surprisingly common: feline coronavirus (FCoV). Many cats, especially those in multi-cat homes, catteries, or shelters, are exposed to FCoV at some point. In most cats, this virus either causes mild digestive upset or no obvious illness at all. The vast majority never develop FIP.

 

In a small number of cats, the virus mutates inside the body and changes how it behaves. This mutation allows the virus to invade immune system cells and spread throughout the body. When this happens, FIP can develop. It is a serious disease, and without treatment it has historically been considered almost always fatal. 

 

FIP appears in different forms that affect the body in distinct ways. The two main forms are effusive (often called “wet” FIP) and non-effusive (“dry” FIP). A third, neurological form can overlap with dry FIP and focuses on the brain and spinal cord. Knowing these categories helps you understand why symptoms can look so varied from one cat to another.

 

Wet FIP is marked by fluid building up in the abdomen or chest. You might see:

• Ascites (abdominal swelling) that makes the belly look rounded or tight
• Fluid in the chest, leading to faster breathing or effort when your cat breathes
• Fever that does not respond to standard medications
• Lethargy and weight loss, even if your cat still seems hungry at first

Dry FIP tends to cause more subtle, localized signs without obvious fluid buildup. In that form, you might notice:

• Steady weight loss and a low-grade fever
• Neurological signs, such as tremors, wobbliness, or seizures
• Eye changes, including cloudiness, redness, or changes in pupil shape or color
• Digestive issues, like vomiting, diarrhea, or reduced appetite

Neurological FIP, which is less common, mainly affects the central nervous system. Cats may develop balance problems, behavior changes, or seizures. Because these signs overlap with other conditions, FIP can be challenging to diagnose. There is no single test that proves FIP, so vets use a combination of history, exam findings, imaging, blood tests, and sometimes tissue samples to reach a likely diagnosis.

 

Recognizing Signs and Symptoms

Recognizing FIP early can be difficult because many signs look like general “not feeling well” symptoms. That is especially true for kittens and young cats, whose immune systems are still developing. Early on, you might just see a cat who seems tired more often, plays less, or is not growing as expected. While these signs are not proof of FIP, they are worth mentioning to your vet, especially in higher-risk settings like multi-cat homes.

 

It helps to think in patterns instead of isolated incidents. A single lazy afternoon is not a red flag. Ongoing lethargy, repeated fevers, or a long-term drop in appetite is different. Keep track of your cat’s weight, food intake, and energy levels. Simple notes on your phone or calendar can make it easier to spot slow, gradual changes that you might otherwise shrug off.

 

Wet FIP often becomes noticeable more quickly because of fluid buildup. A cat’s belly may suddenly look swollen or feel tight, even if they are losing muscle elsewhere. You might also see faster breathing or open-mouth breathing if fluid collects in the chest. These signs are always urgent, whether FIP is the cause or not, and require prompt veterinary care.

 

Dry FIP can move slower and be easier to miss at first. A cat might have:

• On-and-off fevers that do not fully resolve
• Eye changes, like cloudiness, redness, or vision problems
• Neurological symptoms such as stumbling, head tilts, or unusual behaviors
• Gradual, unexplained weight loss despite normal food access

Neurological signs can be particularly upsetting. Affected cats may have seizures, struggle to walk normally, or show sudden behavior shifts. Because many conditions can cause neurological issues, detailed evaluation is important. Your vet may recommend bloodwork, imaging, or referral to a specialist to work out what is going on.

 

Digestive symptoms can appear with either form of FIP. Vomiting, diarrhea, and a drop in appetite might show up alongside other red flags. These issues are common in many feline illnesses, so they do not automatically point to FIP. However, when they appear with persistent fevers, weight loss, or abdominal swelling, they deserve careful investigation.

 

The most important habit is paying attention and acting when something feels “off” for more than a day or two. If your cat is not acting like themself, call your vet and explain what you are seeing. You do not need to decide whether it is FIP before you call; your job is to notice the change and seek help. Together, you and your veterinarian can decide which tests and next steps make sense.

 

Treatment and Prevention Strategies

For many years, FIP was considered untreatable, and care focused only on keeping cats comfortable. That picture is changing. New antiviral medications have given some cats with FIP a chance at meaningful improvement or remission. These treatments are still evolving, regulations vary by region, and they should only be used under veterinary guidance, but they offer more hope than in the past.

 

Today, treatment plans are tailored to the individual cat and the type of FIP. Options your vet may discuss include:

• Antiviral medications designed to target the virus and help control or reverse the disease process
• Supportive care, such as fluids, nutrition support, pain control, and medications to manage inflammation
• Immune-modulating therapies, used in some cases to support the cat’s own immune response
• Treatment of secondary issues, like infections, anemia, or organ strain that can appear alongside FIP

Not every cat will be a candidate for every option, and availability can differ by location. Costs, access, and your cat’s overall health all play a role in what is realistic. If your vet believes FIP is likely, ask them to explain the options clearly and honestly so you can balance quality of life, potential benefits, and practical considerations. Respectable sources and close monitoring are critical; FIP is not a condition to manage alone or with unproven products.

 

Prevention focuses on limiting exposure to feline coronavirus and supporting a strong immune system. While there is no guaranteed way to prevent FIP, smart habits can reduce risk, especially in multi-cat homes or breeding environments. Helpful steps include:

• Good hygiene and litter box care, cleaning boxes daily and avoiding overcrowding
• Thoughtful introductions, quarantining new cats and discussing testing with your vet
• Stress reduction, with enough space, hiding spots, and resources for each cat
• Regular vet visits, so emerging problems are caught before they become severe

Hygiene matters because FCoV is usually spread through feces and shared litter boxes. In homes with several cats, offering multiple boxes and cleaning them often can lower the viral load in the environment. Separating food and litter areas and washing hands between handling different cats are simple habits that help too.

 

Stress management also plays a quiet but important role. Cats under chronic stress may have weaker immune responses, which can make it harder to handle infections of any kind. Providing safe resting spots, vertical space, routine play, and predictable feeding times can all help. High-quality nutrition and preventive care, including vaccines recommended by your vet, support overall resilience.

 

Related: Avoid Holiday Hazards: Foods and Plants Harmful to Cats

 

Keeping Your Cat Safe From FIP

Feline infectious peritonitis is a serious diagnosis, but your awareness and early action can make a meaningful difference. When you understand where FIP comes from, what signs to watch for, and how vets approach treatment, it feels less mysterious and more manageable. You are not expected to have all the answers, only to notice changes and seek help when something does not feel right.

 

At Lil Moon Lions, we care deeply about the long-term health of every Maine Coon we place in a home. We focus on clean, low-stress environments and open communication so new families feel informed and supported.

 

Our Kings and Queens echo the regal lineage of the majestic Maine Coon.

 

We are here, ready to assist you at (804) 802-2098.