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FIP in Cats – Understanding Feline Infectious Peritonitis

Image of really sick cat with FIP in cats being carried by a vet assistant.

What is FIP in cats? 

Feline Infectious Peritonitis (FIP) is a viral disease that usually affects younger kittens (under 2 years old) or senior cats. FIP is caused by a mutation of the Feline Coronavirus (FCoV) infection, not to be confused with COVID-19. It is also important to note that studies have shown that FCoV cannot be passed from infected cats to humans.

What are the different forms of FIP?

There are two types of Feline Infectious Peritonitis. The effusive form (wet) happens more commonly and the non-effusive form (dry) is rarer. Both forms of FIP in cats have been associated with abnormalities in the neurological (brain and spine) system, but the non-effusive form appears to involve the nervous system as well. There have been cases of the effusive form of FIP being diagnosed histopathologically in the brains of cats without neurological abnormalities.

What causes Feline Infectious Peritonitis?

Feline Coronavirus (FCoV) is most commonly spread by oral transmission. So places where litter boxes and food bowls are shared, such as catteries or multi-cat households, for example, are at a higher risk of infection. This is mainly due to the fact that infected cats actively shed the virus in feces.

If one or more mutations occur in the FCoV virus, your kitty’s white blood cells may infect other parts of the body with it. When this happens, this virus has mutated into the Feline Infectious Peritonitis Virus (FIPV). The body’s natural inflammatory response is more extreme in areas where infected cells proliferate, often in the abdomen, kidneys, or brain.

Infographic explains how coronavirus in cats (FCoV) gives rise to mutants that lead to the development of feline infectious peritonitis - FIP in cats.


What are the Clinical Signs of wet FIP? 

Some signs and symptoms to look out for when your little one is suffering from the non-effusive (wet) form of FIP in cats include: 

  • loss of appetite
  • weight loss
  • depression
  • fever

Your kitty may also present neurological changes, which may include seizures and ataxia (abnormal or uncoordinated movements). However, these specific symptoms develop more slowly than those of the effusive form of FIP in cats.

What are the Clinical Signs of dry FIP? 

Signs and symptoms of the effusive form of FIP in cats tend to develop and progress fairly quickly and include the symptoms mentioned above combined with the accumulation of fluid in body cavities, including the chest cavity. Affected cats may develop a pot-bellied appearance due to fluid accumulation in their belly, and if the fluid accumulation becomes excessive, it may become difficult for a cat to breathe normally.

Image of really sick cat laying down on the floor to exemplify FIP in cats.


What are the Diagnostic Tests?

In clinical practice, diagnosing feline infectious peritonitis (FIP) in cats remains a challenge. A lot is required in order to properly diagnose this condition, including a complete history, a physical exam, and adequate variety and interpretation of diagnostic tests remain the cornerstone of antemortem diagnosis.

Which are the Treatment Options for FIP? 

Unfortunately, since FIP in cats is a fatal disease, there are no confirmed or approved treatments yet. Despite some studies showing the promising effects of antivirals on Feline infectious peritonitis, these treatments are not yet approved by the Food and Drug Administration (FDA). The good news is that there is one FIP vaccine available. However, the efficacy of the vaccine remains unknown and requires more study. 

How Can I Take Care of a Pet with FIP?

Cats presenting the symptoms listed above often have a very bad prognosis and rapidly get sicker over the days, weeks, and sometimes even months before passing away. So palliative care can offer comfort and support. It is important to keep your kitty as healthy and comfortable as possible, including preventing secondary infections. Good hygiene, a balanced diet, and avoiding overcrowded environments are essential strategies for minimizing the risk of contracting FIP. Litter boxes should be kept clean and away from food and water dishes. Some studies have suggested that cats suspected of having FCov should be kept apart from other cats.