Feline Infectious
Peritonitis (FIP)
What is feline infectious peritonitis?
FIP is a severe disease in cats caused by feline coronavirus. COVID-19 is also caused by a coronavirus but the coronavirus causing FIP is not the same and only infects cats. Feline coronavirus is commonly found in the feces of cats and research has shown that infection is very common among cats.
Thankfully, in most, it causes mild diarrhea or no signs at all. However, in a small number of cats, the virus changes (mutates) inside the cat, and interacts with the cat's immune system in a certain way, resulting in FIP. Finding coronavirus in a cat doesn't mean they have FIP, and it is not possible to consistently tell the difference between a coronavirus causing FIP, and one causing no signs of illness. Further tests must be performed by a veterinarian to diagnose FIP.
Which cats develop FIP?
We do not know why certain cats develop FIP and others do not, but it is diagnosed more often in young cats under 2 years of age, pedigree cats and cats in multicat homes (eg homes with several cats, breeding environments, shelters). The disease is however also diagnosed in older cats and cats in single cat environments.
Less than 2 years usually developing the disease between 3-16 months
Pedigree cats
Multicat households
Male cats are at slightly increased risk
What signs do cats with FIP show?
Cats with FIP show a variety of signs as the disease can affect any organ in the body. The most common signs are:
Lethargy/tiredness
Eating less and losing weight
A high temperature
Additionally, the disease can cause fluid to accumulate in the abdomen/belly, chest and occasionally around the heart (so called ‘wet’ FIP) so owners may notice a swollen, rounded belly or the cat may have difficulty breathing. The non-effusive (‘dry’) form can affect any organ including the intestines, lymph nodes, brain, kidneys and eyes. Many cats have a combination of ‘wet’ and ‘dry’ forms of FIP and some cats have pale, slightly yellow gums.
If the brain or spinal cord is affected cats will show signs such as fits, an abnormal way of walking (wobbly gait), changes in behaviour or trembling for example. If the eyes are affected they may look cloudy, bloody or with different pupil sizes, and the cat may show signs of pain such as holding the eye or eyes closed.
How is FIP diagnosed?
FIP can be difficult to diagnose and require several tests including blood tests and scans to investigate. In some cases, it is not possible to confirm the diagnosis and the veterinarian will look at the available information, and try to rule out other conditions that can look like FIP (some infections, liver diseases and types of cancer) before considering a treatment trial for FIP.
Cats with FIP tend to have some typical abnormalities:
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Blood tests: often show high protein levels, low red blood cells (anemia) and elevated markers of inflammation;
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Fluid samples: typically yellow in colour, high in protein and contain inflammatory cells; the fluid can also be sent to the laboratory to look for coronavirus;
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Ultrasound scans: can identify fluid and abnormalities in organs such as the kidneys' liver, intestines and lymph nodes and can be used to guide obtaining needle samples for testing;
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Advanced imaging: for cats with neurological signs MRI or CT scanning may required along with sampling fluid from around the brain/spinal cord. This type of imaging often requires referral.
How is FIP treated?
In the past, there was no effective treatment for FIP but thankfully times have changed and there are several antiviral medications available with good results in treating FIP. These drugs are legally available in many countries and have been shown to be safe and effective.
