What Are the Types of Feline Infectious Peritonitis?

There are two main forms of FIP in cats: wet (effusive) and dry (non-effusive). Each type behaves differently, but both are caused by the same mutated virus.

Wet Feline Infectious Peritonitis

Wet FIP is the more recognizable form of the disease. It rapidly progresses, with fluid accumulating in the body cavities. This buildup of fluid will lead to noticeable physical changes, which in turn can affect the heart, lungs, and other organs.

For example, a cat with wet FIP can have a swollen belly, which can mimic other diseases. If this progresses to the chest, it can apply pressure on the lungs and lead to difficulty breathing. 

The common signs of FIP in cats include: 

Abdominal Swelling

The most obvious symptom of wet FIP is fluid buildup in the abdomen, giving the cat a swollen, distended belly. This fluid, known as effusion, can be clear or cloudy with a sticky and viscous consistency. Typically, these fluids contain high amounts of protein.

Many pet owners mistake this swelling for weight gain, but it’s critical to note that cats with wet FIP will often appear thin elsewhere on their bodies, especially around the ribs and spine.

Breathing Difficulties

If the fluid accumulates in the chest cavity rather than the abdomen, it can put pressure on the lungs, making it difficult for the cat to breathe. You’ll notice the signs when your cat starts breathing or panting through its mouth. 

Breathing difficulties are always a concern. If your cat is experiencing problems with breathing, it’s crucial to provide urgent care.

Other Signs

Cats with wet FIP may also display additional symptoms, such as a dull coat, vomiting, increased thirst, and urination.  

Dry Feline Infectious Peritonitis

Dry FIP is more subtle and slower than its wet counterpart. Instead of fluid buildup, it results in the formation of granulomas. Granulomas are masses of inflammatory cells, which can lead to organ damage. 

Cats with dry FIP may exhibit a range of symptoms depending on the organs affected. Neurological and ocular signs are often the most commonly associated symptoms of dry FIP. 

Since the symptoms of dry FIP overlap with other diseases, it’s often harder to diagnose. We may need advanced diagnostic tests to confirm this form of FIP.

Common signs of dry FIP in cats include:

Neurological Symptoms

One of the most concerning manifestations of dry FIP is when it affects the brain or spinal cord. Because of this, neurological symptoms such as tremors and seizures can be possible symptoms. 

Cats can also have difficulty with balance and coordination, which affects their mobility. Some can also experience shifts from their normal behavior. 

Ocular Symptoms

Dry FIP frequently affects the eyes, causing inflammation that can be visibly noticeable. Cats with ocular symptoms may squint, paw at their eyes, or avoid bright lights due to discomfort. Their eyes can also change color and bleed. 

Mixed FIP

In some cases, the symptoms of feline infectious peritonitis might have a combination of both types. While this is less common, it’s also possible to happen. For example, a cat with neurological signs can also exhibit bloating.

What Are the First Signs of FIP in Cats?

Initially, cats with feline infectious peritonitis might not show any loud signs of illness, but subtle changes in their behavior and physical appearance are early clues. While the specific symptoms will depend on the type of FIP, these are signs that generally appear on both forms initially.

• Persistent Fever. One of the earliest signs of feline infectious peritonitis is fever. This type of fever might fluctuate and may not be consistent when observed for long periods.

• Loss of Appetite. Cats with FIP may start eating less or refuse food altogether. This symptom, combined with fatigue, is often mistaken for general stress and other less concerning conditions.

• Weight Loss. Even if your cat appears to eat occasionally, they may begin losing weight. This is another change that will appear subtle at first but will be clearer as the disease progresses. 

• Lethargy and Weakness. A cat that is tired all the time can be a sign of something wrong. You may notice your cat becoming less playful and appearing uninterested in its normal activities. Additionally, they may sleep more than usual. 

How Is FIP in Cats Diagnosed?

Diagnosing feline infectious peritonitis can be challenging, as there’s no definitive way to determine if your cat has the disease. FIP’s symptoms are often similar to those of less concerning diseases, making it impossible to accurately diagnose. 

However, if the symptoms are specific to the types of feline infectious peritonitis, then additional testing could be done to confirm the diagnosis. The presence of fluid buildup, breathing difficulties, and neurological and ocular signs will be the main indicators. 

Diagnostic imaging tools such as X-rays are common tools that can be used to detect the buildup of fluid inside your cat’s body. Additionally, these can check on the condition of your cat’s organs, helping detect any areas of concern.

Currently, the most accurate way to diagnose feline infectious peritonitis is through a biopsy and histological examination. Our vets will usually obtain a sample of the affected tissue and take it to our in-house laboratory for testing. 

How Do You Treat Peritonitis in Cats?

For many years, feline infectious peritonitis was considered untreatable, leaving cats with limited options beyond supportive care. However, with advancements in medication, new FIP treatment options, such as remdesivir and GS-441524, have been effective.

Feline infectious peritonitis was initially considered untreatable, but major breakthroughs and advancements have been effective. This included FIP treatment options such as remdesivir and GS-441524. 

For cats with no access to these antiviral treatments or those in the advanced stages of the disease, supportive care will be the option. These methods aim to improve the cat's life and comfort. 

If your cat’s abdomen has become bloated to the point that certain movements are challenging, we will drain the fluids. Draining reduces the pressure, improving breathing. Additionally, supportive medications can help manage symptoms and alleviate the discomfort. 

Can Cats With FIP survive?

Yes, cats with FIP can survive if treated with modern options such as GS-441524 and remdesivir. If left untreated, FIP is fatal. This means that cats without medical treatment will pass away. 

“A cat’s health is the product of several years of research, cooperation, and love.”

- Dr. Lidija Krvavac

Final Thoughts

While feline infectious peritonitis is still a challenging diagnosis, the veterinary community’s growing understanding of the disease offers hope for improved treatments and outcomes. The continued research for more possible treatments helps give affected cats a chance at a smooth recovery.