What is FIP? 

FIP is associated with a viral infection called feline coronavirus. There are many different strains of feline coronavirus, which differ in their ability to cause disease. Previously, there had been an attempt to classify these strains as either feline infectious peritonitis virus strains (capable of causing the FIP disease) or feline enteric coronavirus strains (essentially harmless strains mainly found in the intestinal tract). It is now recognized that feline enteric coronavirus strains can mutate (change) to the more harmful type of virus and cause FIP. The factors determining why one cat becomes diseased while others remain unaffected are unclear.

Diagnosing FIP is very challenging for many reasons. Unfortunately, there are no laboratory tests available that can distinguish between the enteric coronavirus and the FIP-causing strains. Even when infected with known FIP-causing strains, many cats do not develop FIP disease. The factors determining why one cat becomes diseased while others remain unaffected are unclear.

What are common FIP signs in cats?

• Cats that have been initially exposed to FeCV usually show no obvious symptoms. Some cats may show mild upper respiratory symptoms such as sneezing, watery eyes, and nasal discharge, while others may experience mild gastrointestinal signs such as diarrhea. In most cases, these mild signs are self-limiting. Between 5 and 10% of cats that are exposed to the FeCV develop FIP, and this can occur weeks, months, or even years after initial exposure to FeCV.

• There are two major forms of FIP, an effusive, or “wet” form and a noneffusive, or “dry” form. Regardless of which form they ultimately progress to develop, cats infected with FIPV usually first develop nonspecific signs of disease such as loss of appetite, weight loss, depression, and fever. It is also important to note that cases of the effusive form of FIP can evolve into the non-effusive form and vice-versa.

• Generally speaking, the signs of the noneffusive form, which may include the non-specific signs listed above as well as neurologic signs including seizures and ataxia (abnormal or uncoordinated movements) develop more slowly than those of the effusive form.

• The signs of effusive form of FIP usually develop and progress relatively rapidly and include development of the above-mentioned non-specific signs combined with the accumulation of fluid in body cavities, including the abdomen and the thorax (chest cavity). Affected cats may develop a pot-bellied appearance due to fluid accumulation in the abdomen, and if the fluid accumulation is excessive, it may become difficult for a cat to breathe normally.

How is FIP managed in cats?  

As FIP is an immune-mediated disease, treatment is mainly aimed at controlling the immune response triggered by the infection with the feline coronavirus (FCoV). Immune suppressive drugs such as prednisone or cyclophosphamide may slow disease progression but do not produce a cure.

What is the prognosis in cats?

Once disease develops, without treatment, most individuals deteriorate rapidly, although some cats remain normal for several weeks. 

Management tips for a cat with FIP

• Avoid keeping large groups of cats and having multiple litters of kittens at any one time

• Keep cats in small isolated groups (ideally no more than four cats in each group – this reduces the risk of endemic FCoV infection)

• Have at least one litter box for every two cats, located in easy to clean and disinfect areas

• Keep litterboxes away from food and water bowls, and clean/disinfectant them regularly (at least daily)

• Avoid stress and maintain good hygiene and preventive healthcare for all cats

In a crisis situation:

Contact your veterinarian immediately if your cat suddenly collapses, has uncontrollable seizures, experiences difficulty breathing, behaves aggressively, or vocalizes in pain.