Pet Illnesses

Feline Infectious Peritonitis (FIP/Coronavirus)

Feline Infectious Peritonitis (FIP) is an important disease that all cat owners should be aware of. In simplest terms, it can be described as a progressive and fatal immune-mediated, systemic disease of domestic and wild cats. The infectious agents responsible for this unforgiving disease are certain strains of Feline Infectious Peritonitis Viruses (FIPV).

FIPVs are interesting in that they are formed when another type of virus, known as Feline Enteric Coronavirus (FeCV) mutates. FeCVs are very contagious between cats and many are commonly infected, especially in catteries.

In fact, studies have demonstrated that 20-30% of the general cat population have been exposed to these viruses, whilst up to 85% of cats are exposed to FeCV in catteries. Fortunately, infection with FeCV produces inapparent or only mild gastrointestinal signs. At worst, cats will have a fever, vomiting and diarrhoea lasting only a few days.

Importantly though, in small percentage of these cases (approximately 5%) the FeCV will mutate into a FIPV.

Once this occurs, the virus gains the ability to cause a systemic infection. The exact reasons why these mutations occur are unknown. In addition, the nature of these mutations varies, leading to variation in the ability of the virus to cause disease. For instance, a young healthy cat may resist a less capable FIPV, whereas an old, immuno-suppressed cat (due to stress or concurrent disease) will not stand a chance.

Furthermore, individual virus variation not only influences its ability to cause disease, but also affects the specific organs damaged by the virus. This is very important from a diagnostic perspective as it masks our ability to clearly identify the disease without invasive testing.


FIP cases can present with either a dry or wet form of the disease.

In the dry form, there is no fluid buildup in the abdomen and/or chest. These cases often have inflammation of the lining of the abdominal contents (e.g. white nodular lesions covering the intestines, liver, spleen)

In the wet form, there is a thick viscous yellowish fluid in the abdomen and/or chest cavity.

Depending on the virulence and form of the infectious agent, symptoms vary from case to case but can include:


This is where it gets difficult:

a) In the wet form of FIP, a vet can easily collect fluid from the chest or abdomen without the need for surgery,

b) In the dry form of FIP, this may mean an anaesthetic and exploratory surgery of the abdomen to collect affected tissue. This can be risky an already very ill cat.


Unfortunately, there is no specific treatment available at this stage for FIP.

It is a case of treating the symptoms and trying to correct dehydration, maintain organ function and prevent secondary bacterial infections complicating the picture by giving anti-biotics.

Euthanasia is eventually the best option.

See also...
Feline Infectious Peritonitis case