An owner brings a young cat into my clinic. The cat’s been off her food for a few days, has a dull unkempt coat, and is running a fever. Something clicks and the thought “FIP” pops into my head. I take a history, hoping for a simple explanation, such as the cat got into a fight…but, no, she’s strictly indoors and an only pet…and the suspicion of FIP ratchets up a notch.
As a vet, feline infectious peritonitis (FIP) is a condition which leaves me feeling rather helpless because there is no effective treatment (Interferon therapy offers a glimmer of hope, but is not proven.) But before I get carried away, let’s start at the beginning with some facts about FIP.
What is FIP?
FIP does what is says on the label. Decode “FIP” and you understand what it is:
Feline = cat
Infectious = passed between patients
Peritonitis = inflammation of the lining of the abdomen (tummy) and often accompanied by a build-up of fluid
In other words FIP is an infectious condition passed between cats and which causes fluid to build-up in the tummy.
The cause of the infection is a coronavirus…but this is where things stop being simple and quickly get complicated. Remember that name, coronavirus, because we’ll come back to it later.
What are the Symptoms of FIP?
FIP is most common in young cats, under the age of two-years. The virus can be fought off by a strong immune system, but those with a weaker immune system such as the young or elderly (classed as cats over 11-years of age) and somewhat bizarrely, Burmese cats, are most at risk. The Burmese predisposition for FIP isn’t understood, and no-one knows why this should be the case.
FIP takes one of two forms: wet or dry; of which ‘wet’ has more obvious symptoms and kills more quickly, within a matter of weeks. The ‘wet’ form gets its name because fluid builds up in the abdomen, causing a marked potbellied appearance. Whereas the dry form doesn’t produce fluid and the cats survive for a few months.
The symptoms are quite vague and in the early stages can easily be mistaken for the after effects of a cat fight. These include:
- Being off colour
- Decreased appetite
- A dull, starry coat
- Weight loss
- A fever
In the later stages, other signs develop such as:
- Fluid in the chest or belly (with laboured breathing)
- Iritis (inflammation of the iris or coloured part of the eye)
- Deposits in the front chamber of the eye
- Poor co-ordination
How do Cats Catch FIP?
Coronavirus causes FIP, but (and it’s a big ‘but’) not all cats with coronavirus will develop FIP. Time for some statistics:
- Stray cats – 4% have detectable antibodies against coronavirus (in other words they ‘test positive’ for coronavirus)
- Cats in breeding catteries – around 53% test positive
- Show cats – 82% test positive
- Only 10% of these cats go on to become sick with FIP.
The reason for this is that coronavirus has a split personality. There is the first persona, of a common virus which causes harmless, self-limiting diarrhoea; and the second persona is the mutated form of the virus which causes FIP.
To mutate, the coronavirus needs contact with lots of cats, because each time it infects a new cats it mutates a little. Once the virus reaches a critical level of change, it turns into something altogether more sinister and serious.
Those cats most at risk are those who share litter trays in a multi-cat household, hence the high level of coronavirus in breeding establishments (kittens sharing trays with the mother) and amongst households of show cats.
This also has the unfortunate implication that when you buy a purebred kitten from a breeder with several queens, there is a chance the kitten may already have coronavirus and it’s a lottery as to whether they become sick with FIP or not.
How Does the Vet Diagnose FIP?
There’s no denying it, reaching a definitive diagnosis of FIP is a headache. The problem is there is no one, single test that puts a big red ‘Yes’ in the box next to the question: Is this FIP?
Straight away you can see part of the problem; testing positive for coronavirus doesn’t mean the cat has FIP, it just means the cat has been exposed to a bug that causes diarrhoea. (However a negative test does rule out FIP.)
Diagnosing FIP is like having a 1,000 piece jigsaw puzzle with now ideal of what the finished picture looks like. You have to piece together as many pieces as you can, to build the most likely picture.
The tests a vet uses to piece things together are:
- Clinical signs: a belly full of fluid in a young feverish cat is a pretty heavy hint
- Coronavirus titre: A negative result rules out FIP
- Protein levels: FIP changes the balance of proteins in the blood stream, and high globulins with normal albumin levels are a signpost
- Analysis of abdominal fluid: very high protein levels are suspicious
- High AGP levels: Acid glycoprotein (AGP) can help rule out fluid in the belly due to other causes such as cancer or liver disease
- Inflammatory changes such as iritis
- Antigen tests to look for FIP virus: False negatives are common.
Typically, the vet pulls together as much evidence as possible and gives the most appropriate treatment, and hopes against hope the cat gets better. If they don’t, then FIP becomes even more likely.
Treatment for FIP
Sadly, survival rates are low. The patient’s main hope rests on interferon, an antiviral drug which stops the virus reproducing and minimises its effects. It seems to help in some cases and can buy extra time others, but it is not a cure.
If you suspect a cat in your household has FIP, or indeed if they have diarrhoea, then keep them away from your other cats and make sure they use a separate litter tray and feeding bowls. A cat with a healthy immune system that is exposed to a low level of virus may be able to fight off FIP and stay well but with so much at stake it’s not worth taking the risk.
Dr Pippa Elliott BVMS MRCVS is a veterinarian with 27-years’ experience in practice and a special interest in feline medicine and behaviour. Pippa is housekeeping staff to four highly individual cats that conspire to keep her busy opening doors on demand.