78 | How to REALLY understand, recognise and successfully care for patients with FIP

PodcastFeline MedicineInfectious disease
Written By Laura Jones

In episode 78, we’re chatting about a topic that has changed dramatically in the last few years - feline infectious peritonitis, or FIP.

 

When I started nursing, FIP was my LEAST favourite disease. I hated it - seeing so many young, gorgeous cats suffering so much with nothing we could do about it. I remember being told in practice that every FIP cat needed euthanising, because there was no point trying to do anything else. However, now that treatment options exist, we’re seeing many more cases, and with that, we’re using a lot more of our nursing skills when caring for them.

To nurse these patients confidently (and well!), we need to understand what FIP is, how it impacts our patients, how we recognise and diagnose it, and how we can make a difference to these patients as nurses and technicians.

So, whether you’re heading into a shift, listening in wards whilst preparing your patient’s treatments, relaxing with a cuppa or walking the dog, let’s spend the next half an hour breaking down FIP together.

Let’s start with what FIP really is.

Feline infectious peritonitis, or FIP, is caused by a mutation of feline coronavirus (aka FCoV).

Now, thanks to 2020-2021, the word ‘coronavirus’ has been heavily stigmatised, and this actually resulted in many people giving up their cats, believing that they had (or could spread) COVID-19.

Feline enteric coronavirus is NOT the same as COVID-19. It’s a common pathogen that typically causes a mild infection, with most cats showing no or mild clinical signs. 

The virus spreads via the faecal-oral route, either after inhalation or ingestion of contaminated faecal material, or via contact with fomites or an infected cat.

Once ingested, the virus replicates and spreads to the GI tract, where it causes transient self-limiting diarrhoea and sometimes vomiting. Rarely, respiratory signs may also be observed, although many patients remain asymptomatic.

Just how common is FCoV?

Most cats will have been exposed to FCoV at some point in their life.

The virus spreads via direct contact (eg, through mutual grooming) or indirect contact across contaminated bedding, litter trays, bowls and other surfaces. 

Infected queens can also transmit the virus to kittens, and the risk of infection increases where multiple cats are in close contact. For this reason, FCoV is particularly prevalent in younger cats, in rescue centres, breeding colonies, and multi-cat households. Kittens can start shedding the virus from around 9 to 10 weeks old, although shedding in kittens as young as 4 weeks has been reported in the literature.

But what does that have to do with FIP?!

FCoV is usually harmless after initial signs subside. However, in a small percentage of cats (typically younger cats, although the disease can also occur in older patients), the virus mutates.

The mutated form enters and replicates inside white blood cells, specifically monocytes and macrophages, causing FIP.

What happens when a patient develops FIP?

When the virus mutates and infects macrophages, it rapidly spreads throughout the body. The infected white blood cells become activated, causing inflammatory proteins (called cytokines) to be released, and triggering an inflammatory and immune system response. This leads to vasculitis, inflammatory lesions and effusions, depending on the type of FIP the patient has.

And speaking of those FIP types…

We describe our patients as having ‘wet’ (aka effusive) and ‘dry’ (aka non-effusive) FIP. 

Patients with effusive FIP are easier to spot - these guys have the classic straw-coloured, protein-rich, thick fluid within their pleural and/or abdominal cavities that we think of when we hear the word ‘FIP’.

And the non-effusive form? Well, it isn’t as easy to identify. Dry FIP causes granulomatous (inflammatory) lesions to develop in the patient’s organs. This form of the disease presents with vague clinical signs, such as fever and lethargy, alongside other changes depending on the organs affected.

In many patients, a mixed form of FIP is seen, combining both body cavity effusions and granulomatous lesions. 

So, that’s what FIP is - but which cats get it?

There are several established risk factors for FIP, including:

  • Age (cats <2 years old and >13 years old are commonly affected; the incidence of disease reduces in middle-aged cats)

  • Group housing

  • Sex and neutering status (some studies document a predisposition for FIP in male cats, with entire males particularly at risk)

  • Breed (purebred cats are at increased risk of developing FIP, with increased susceptibility reported)

  • Stress (some studies suggest stress increases the risk of FIP, with nearly 57% of FIP cats having a previous stressful event noted in one study)

  • Retroviral infection (as discussed in episode 77, FeLV and FIV cause immunosuppression and can be a risk factor for FIP). 

What clinical signs do FIP cats present with?

Clinical signs will depend to some extent on the type of FIP our patient has. Most signs are non-specific and include:

  • Lethargy

  • Anorexia or inappetence

  • Waxing and waning pyrexia

  • Enlarged lymph nodes

  • Weight loss

  • Failure to grow/gain weight in kittens

  • Jaundice

Aside from this, patients with effusive or wet FIP commonly present with:

  • Ascites

  • Abdominal distension

  • Pleural effusion

  • Respiratory signs associated with pleural space disease (eg. tachypnoea, dyspnoea, mouth-breathing, restricted breathing pattern)

Patients with dry or non-effusive FIP may also present with neurological or ocular signs such as ataxia, seizures, head tilt, behavioural changes, or evidence of uveitis and retinopathies on fundic examination.

As FIP is a multi-systemic disease with a very varied clinical presentation, we’ll see significant differences in how these patients present - they don’t fit neatly into a ‘dry’ or ‘wet’ tickbox, and varied (and sometimes subtle) signs are present.

Ok, we think our patient might have FIP. What next?

The bad news is that diagnosing FIP is often really challenging. There’s no one single definitive test for FIP (aside from post-mortem), so, instead, we base our diagnosis on a combination of:

  • The patient’s history, signalment and physical examination findings

  • Biochemistry and haematology

  • Coronavirus antibodies (in some cases)

  • Coronavirus PCR testing

  • Cytology from effusions or FNAs of granulomatous lesions (if possible)

  • Diagnostic imaging (eg abdominal ultrasound)

Common findings in FIP-positive cats include:

  • Hyperglobulinaemia with low albumin:globulin ratio 

  • Elevated alpha-1 acid glycoprotein (A1-AGP) levels

  • Lymphopenia

  • Non-regenerative anaemia

  • Elevated liver enzymes

  • Hyperbilirubinaemia

  • Straw-coloured, thick, protein-rich effusion

  • Pyogranulomatous inflammation on FNAs

Before we move on to treatment, it wouldn’t be right of me not to mention FCoV testing.

Coronavirus testing isn’t easy, and the results need careful interpretation.

Testing FCoV antibody levels only tells us whether a cat has previously been exposed to coronavirus, NOT FIP specifically. Since we know FCoV infection is common (with approx 60+% of cats affected), a positive antibody test isn’t particularly useful, especially in the absence of relevant clinical signs or other supportive test results.

It also takes time for these patients to make those antibodies. By this time, they’ve finished shedding the virus, so there’s no need to panic about isolating a patient based on a positive antibody test - there’s a good chance they’re not actively shedding FCoV.

Unlike antibody testing, PCR tests for coronavirus look for viral DNA within the sample. However, since these cannot distinguish between ‘normal’ FCoV and FIP, they are of limited use. In addition, most FIP cats have a very low viral load, meaning there’s less virus to detect.

The preferred test is immunocytochemistry (ICC). This is usually performed on centrifuged effusion samples. If the test is positive and the patient’s examination findings and other tests support the diagnosis, FIP is very likely. However, false positive results may be observed in FIP-negative cats.

The takeaway?

No test is perfect; instead, our job as nurses and technicians is to know the limitations of each method and recognise that the tests are just one piece of the puzzle.

Let’s take a look at treatment, because we finally CAN.

Until recently, FIP was pretty much always fatal. But in 2021, all of that changed when antiviral medications finally became legally available in the UK. There are now many legal preparations in other countries as well, although not everywhere, so please check your local legislation if you’re tuning in from abroad. 

Those antiviral medications include remdesivir and GS-441524 (which I’ll call GS for simplicity across the rest of the episode).

These drugs inhibit viral replication, with success rates exceeding 84% in studies. Various treatment protocols exist, including:

  • Injectable remdesivir only

  • Oral GS only

  • Combination treatment: injectable remdesivir initially, then transitioned to oral GS for the remainder of the course.

Patients receive daily treatment for 12 weeks, with higher doses administered to those with ocular signs.

A quick note from me on remdesivir: it stings, especially when administered subcutaneously. We tend to give it slowly via IV (diluted) to prevent that in the hospital.

Ok, that’s antivirals - what else?

Aside from remdesivir or GS, it’s all about good quality supportive care. This means:

  • Providing nutritional support to maintain body condition and ensure the patient meets their calorie needs

  • Administering analgesia where needed

  • Managing effusions via thoracocentesis or abdominocentesis if needed (eg, if the pleural effusion is interfering with ventilation and causing respiratory compromise)

  • Administering antiemetics, appetite stimulants, and IV fluids where needed, depending on the individual patient.

And what about nursing these patients?

As nurses and technicians, our role is vast and includes careful monitoring (particularly neurological and respiratory monitoring) alongside supporting hydration, nutrition, eliminations, and general nursing care. In severe cases, patients may be recumbent and need intensive management.

We also need to consider infection control, and, like FeLV and FIV, there are some misconceptions surrounding FIP as well. FIP itself isn’t contagious - the underlying coronavirus is, but most cats aren’t actively shedding this when they come in with FIP. So isolation and strict barrier nursing aren’t always needed. These cats can be barrier nursed in the normal ward, following good hygiene protocols.

Lastly, there’s client support. FIP is a challenging disease that requires a long and expensive treatment course, and educating and supporting clients is essential for successful completion.

Discuss with them how to administer medications, when to return for follow-up appointments, what to look out for at home, and how to maintain a stress-free environment. 

FIP treatment has made significant progress in the last four years.

With newer antiviral treatments, the prognosis has changed from almost certain death to potentially complete remission. Neurological FIP is still more difficult to treat and carries a poorer prognosis than other forms; however, many cats do respond well when treatment is initiated early, accompanied by intensive nursing care and monitoring. 


So there you have it - a whistle-stop tour of FIP and FCoV, how they differ, the problems they cause, and how we manage them. Let’s take a second to recap what we’ve discussed this episode:

  • FIP is caused by a mutation of feline coronavirus and can present as effusive, non-effusive, or mixed forms.

  • It mostly affects young cats in multi-cat environments, although a biphasic presentation is also observed, with the disease being more common in older cats (>13 years).

  • Clinical signs vary and include pyrexia, effusions, neurological or ocular changes, and weight loss.

  • Diagnosis is based on a combination of history, clinical signs, blood results, and supportive tests, rather than relying solely on coronavirus testing.

  • Antivirals have revolutionised treatment, alongside supportive treatment and nursing care.

Did you enjoy this episode? If so, I’d love to hear what you think. Take a screenshot and tag me on Instagram (@vetinternalmedicinenursing) so I can give you a shout-out and share it with a colleague who’d find it helpful!

Thanks for learning with me this week, and I’ll see you next time!


References and Further Reading

Laura Jones
Next

77 | How FeLV and FIV actually affect your patient - and the exact care they need