Updated February 2024

FELINE INFECTIOUS PERITONITIS (FIP)
INFORMATION FOR CAT OWNERS
By Dr. Stephanie Sorrell, Prof. Séverine Tasker, Dr. Sam Taylor,
Dr. Emi Barker, and Prof.Danielle Gunn-Moore
Over the last few years great progress has been made in the treatmentof feline infectious peritonitis (FIP). This previously deadly disease can
now be successfully managed. However, it remains a serious condition
and this document is written to help owners understand the available
medications and how they are used to treat cats with FIP.

Email help service for your vet:
fipadvice@gmail.com

This booklet has been designed by
Bova groupwww.bova.vet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 andonly infects cats. Feline coronavirus is commonly found in the faeces of cats andresearch has shown that infection is very common among cats. Thankfully, in
most, it causes mild diarrhoea or no signs at all. However, in a small number ofcats, 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 thedifference between a coronavirus causing FIP, and one causing no signs ofillness. 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 isdiagnosed more often in young cats under 2 years of age, pedigree cats andcats 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 yrs usuallydeveloping the disease
between 3-16 months

Pedigree catsMulticat households

Male cats are at slightly
increased risk

What signs do cats with FIP show?
Cats with FIP can 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
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Additionally, the disease can cause fluid
to accumulate in the abdomen/belly,
chest and occasionally around the heart

Different types of FIP"Wet FIP"
in which fluid(so called ‘wet’ FIP) so owners may

develops in a body

notice a swollen, rounded belly or the cat

cavity – especially

may have difficulty breathing. The non-the abdomen

effusive (‘dry’) form can affect any organ

and/or chest

including the intestines, lymph nodes,
brain, kidneys and eyes. Many cats have

"Dry FIP"

a combination of ‘wet’ and ‘dry’ forms ofwhen no fluid

FIP and some cats have pale, slightly

forms

yellow gums.
If the brain or spinal cord is affected catswill show signs such as fits, an abnormal
way of walking (wobbly gait), changes in"Neurological FIP"
Brain and/or
spinal cord

behaviour or trembling for example.
If the eyes are affected they may lookcloudy, bloody or with different pupil"Ocular FIP"

sizes, and the cat may show signs ofaffecting thepain such as holding the eye or eyeseyes

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 thediagnosis and the veterinarian will look at the available information, and try torule out other conditions that can look like FIP (some infections, liver diseases
and types of cancer) before considering a treatment trial for FIP.
Email help service for your vet: fipadvice@gmail.com

Cats with FIP tend to have some typical abnormalities:
Blood tests: often show high protein levels, low red blood cells (anaemia) andelevated markers of inflammation;
Fluid samples: typically yellow in colour, high in protein and containinflammatory cells; the fluid can also be sent to the laboratory to look forcoronavirus;
Ultrasound scans: can identify fluid and abnormalities in organs such as thekidneys, liver, intestines and lymph nodes and can be used to guide obtaining
needle samples for testing;
Advanced imaging: for cats with neurological signs MRI or CT scanning may
be required along with sampling fluid from around the brain/spinal cord. thistype of imaging often requires referral.
Some laboratory tests are less helpful for making a diagnosis of FIP
including:Feline coronavirus antibody tests (serology): this test shows a cat has metcoronavirus but as the virus is so common, many cats will test positive that do
not have FIP. Some cats with FIP who are severely unwell can test negative
as their antibodies are used up in trying to fight the disease.
Faecal (poo) testing for coronavirus: as many cats are coronavirus infectedand therefore can pass coronavirus in their poo, ‘faecal shedding’ is commonand does not mean the cat has FIP, or will develop FIP.

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, although
they can be expensive.

Email help service for your vet: fipadvice@gmail.com

Available drugs include:
Remdesivir: an injectable medication given under the cat’s skin or into a veinand reserved for very sick cats unable to take oral medication(tablets/suspensions);
GS-441524: tablets or a suspension (liquid) that can be used from day 1 oftreatment and is usually the preferred treatment;
EIDD-1931: tablets used in cases not responding to adequate dosages of GS441524 or relapsing (becoming unwell again with FIP after initially improving).
Current recommendations are to treat for 12 weeks to allow full clearance of thedisease. This can seem a long time but gives cats the best chance of recovery. It
may be that shorter courses can be recommended in the future but for now 12weeks of treatment is required. Different types of FIP require different amounts(dosages) of antiviral medication, FIP cats showing neurological and/or ocular signs
being treated with higher dosages. However, there is variation in how cats
respond, and adjustments may be needed during the treatment period. If a cat is
not responding as expected, the amount of antiviral medication may need to beincreased.
How to give tablets or suspensions (liquids)
Oral medications (tablets or suspensions) can begiven in a treat (liquid paste or putty-type treats canwork well) after a short period without food (at leastan hour). The treatment will be given for 12 weeks. Itis important that medicating is not a negative
experience for the cat. Tips include:
Removing food overnight can ensure the cat ishungry in the morning and keener to accept
treats, and the same in the evening;
Avoid putting medications in/on a main meal as it can deter the cat fromeating and be hard to decide if all of the medication has been taken;
Try to associate giving medication with positive experiences such asgrooming, stroking or playing (if enjoyed by the cat);
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Try different treat textures and types, plus small amounts of strong flavoured
foods such as tuna or chicken in which to hide medications
For cats that will not take medication in food, giving tablets or liquids directly
into the mouth may be needed and your vet practice can demonstratetechniques and be contacted if owners are finding it difficult. See
https://icatcare.org/advice/how-to-give-your-cat-a-tablet/ for more
information.
Side effects of treatment
Antiviral medications are generally well tolerated but any changes in a cat’s healthor behaviour should be discussed with the veterinarian. Remdesivir injections canbe painful and painkillers/medications to reduce anxiety may be needed. Otherside effects may include changes in blood test results (mild elevations in liver
enzymes and changes in white blood cells) that generally have no effect on a cat’shealth. Side effects should be discussed with the veterinarian supervising the FIPtreatment.
Other supportive treatments
Various other treatments may help cats with FIP during their antiviral treatment.
Very unwell cats may need to be hospitalised for management of dehydration andlack of nutrition and to start their antiviral treatment.
Many cats with FIP will benefit frompainkillers and anti-nausea drugs at
diagnosis and cats with changes intheir brain or eyes may need additional
medications. It is very important catswith FIP eat well during treatment asoften they have lost weight, sooccasionally feeding tubes andappetite stimulants are required.

How are cats monitored during and after treatment?
Cats with FIP treated with antiviral medications should improve rapidly. Appetite anddemeanour/mood and high temperature should improve in just a few days andfurther monitoring may include:
Examinations: veterinarians can assess cats for normalisation of theirtemperature, resolution of changes in the eyes and brain and changes in theorgans;
Blood tests: proteins may take several weeks to become normal, initiallypossibly increasing if fluid in wet FIP cases is reabsorbed;
Body weight: it is very important to accurately and regularly weigh cats with FIP
as they may need increases in medication as they grow and gain weight, andfailure to gain weight could indicate adjustments in treatment are needed;
Fluid assessment: collections of fluid should reduce over 2-3 weeks and can bemonitored by the veterinarian measuring the cat’s belly diameter with a tapemeasure is a cost effective but less accurate alternative;
Importantly, owners should monitor their cats at home for appetite, and energy
levels and weighing cats with scales for babies weekly can provide very usefulinformation.

Information for your vet
Bova Group provides resources andadditional reading for your vet,available here:
https://bit.ly/FIP_resources

Email help service for your vet: fipadvice@gmail.com

How successful is the treatment of FIP?
Research has shown that about 85% of cats will respond to treatment. Thesecats appear to be cured and long-term follow-up over 2-3 years has shown theyremain healthy in most cases. It is early days in the experience of treating FIP.
Further research will help improve understanding, but it is hoped that treated catswill be cured. Some cats may ‘relapse’ and become unwell with FIP again during
or after treatment so all treated cats should see their veterinarian if they show
signs of illness again. A small number of cats do not respond to treatment, often if
they are very unwell when they are diagnosed, and other cats can respond for ashort time and then become unwell again (relapse). Adjustments in treatment canhelp in some cases and should be discussed with the veterinarian supervising
their care.
What to do if you need more advice on treatment of FIPYour veterinarian will be best placed to help and treatment of FIP is a teamapproach between you and your veterinary clinic doing the best for your cat. As
we are still learning about the treatment of FIP with antivirals, a team of feline
experts have set up an email help service for vets at fipadvice@gmail.com andhave answered 2000 emails from around the world about FIP. Please ask yourveterinarian to email for help if they need to discuss the diagnosis or treatment ofa suspected case of FIP.

The feline expert team cannot provide advice directly to owners for patients who
are not under their care, so please make sure it is your veterinarian who emails andthat they send the medical details for each case. Further information for veterinary
teams is available at: https://bit.ly/FIP_resources
More detail on FIP can be found on the International Cat Care website:
https://icatcare.org/advice/feline-infectious-peritonitis-fip

Updated February 2024

Email help service for your vet: fipadvice@gmail.com