Feline Infectious Peritonitis

This blog post comes following some sad news this week. One of our cats that had been adopted a couple of months ago, passed away under general anaesthetic during a routine desexing operation.

We were absolutely devastated to hear this news, and extend our deepest sympathies to her beautiful foster family.

The veterinarians that were performing her procedure suspect she may have been suffering from feline infectious peritonitis (FIP).

Whilst FIP is relatively rare, it is a very serious disease with a 100% mortality rate, no effective treatment or cure, and is extremely difficult to definitively diagnose.

FIP is commonly referred to as the silent killer because cats often don’t show any clinical signs until very late in the course of the disease, as was the case for the beautiful kitten we lost recently.

So what causes FIP?

The virus that causes FIP is actually CORONAVIRUS!

While coronavirus is a ‘new’ virus to many, we have been dealing with it for years and years in the veterinary industry! Please do not get confused though – the coronavirus that causes FIP in cats, is very different to the current pandemic-causing coronavirus (COVID-19).

The thought of people in this world not understanding the extent of how serious the coronavirus pandemic is OR that the pandemic isn’t even real, is very frustrating for me when we see coronavirus infections so often in veterinary medicine, not to mention how scary it can be if these viruses mutate. I’ll explain more about the mutation of the virus below!

It is not uncommon for young kittens to become infected with coronavirus. The coronavirus that infects kittens is called an enteric coronavirus, meaning that the virus focuses on the gastrointestinal tract,and most kittens only experience symptoms such as fever, lethargy and diarrhea. Occasionally they can also experience sneezing, watery eyes, and nasal discharge. It is transmitted by close contact with other infected cats faeces (sharing litter trays, cats housed in groups, etc.)

Once infected, symptoms and shedding of the virus (i.e. when they are contagious to other cats) can last for several weeks! Because this virus loves to circulate between cats living in households together, some cats in households with more than 5 cats may see frequent re-infections.

So why don’t more cats become infected with FIP, if coronavirus is not an uncommon virus in cats?

Many cats infected with coronavirus won’t progress to FIP. In rare cases however (i.e. those that progress to having FIP), the virus will mutate at just the right time. While the immune system is frantically trying to remove coronavirus from the infected individuals gastrointestinal tract via specialized cells called macrophages that eat up all infected material within the body, the virus undergoes a mutation within the cell.

The mutation allows the virus to survive within the macrophage cells, and essentially hijacks these cells. The virus is then able to spread to other areas of the body. As the body tries to kill the infected macrophages, a major immunologic dysfunction occurs, which then leads to organ dysfunction, and in some forms of the disease, fluid build up in the chest or abdomen.

What are the symptoms of FIP?

Following infection with coronavirus, it can take weeks, months or even years for FIP signs to develop.

Initially most cats show non-specific signs such as lethargy, decreased appetite, weight loss and fever. Most of these initial signs are very subtle, and often owners don’t even see these signs, due to cats being very good at disguising signs of illness. They are well known to be the masters of disguise!

In the later stages of the disease, FIP can take on two forms, wet (effusive) and dry (non-effusive).

The wet form often presents in the later stage with fluid accumulation in the abdomen and/or chest.

The dry form tends to progress more slowly, and signs are subtler due to deep inflammation within the nervous system and eyes. The dry form tends to cause more neurological signs in the end stages, such as seizures.

As I mentioned earlier, cats are remarkably good at hiding signs of disease. In my experience, owners sometimes blame themselves for not seeing signs earlier when we find they have a large accumulation of fluid in their chest or abdomen. Or in the case of one of our adopted cats recently, they seem perfectly fine right up until they undergo a stressful event, such as a routine desexing.

I always remind owners that unfortunately cats are masters at hiding signs of illness, and will continue to hide them from their family right up until the end.

Why isn’t there a test available for definitive diagnosis of FIP?

While there is a test for coronavirus, there isn’t a test available to diagnose FIP. This is due to the mutation that occurs to the virus, leading to FIP in some individuals. The mutations are random, and there are too many different mutations that occur to be able to diagnose them all on one test.

If your veterinarian suspects your cat may have FIP, a number of preliminary tests can be performed. These are not definitive tests, however the veterinarian may be able to make assumptions based off a number of findings.

These tests may involve:

  • Blood tests to check protein levels
  • Tests to check if the cat has previously been infected with coronavirus
  • Testing fluid that has been drawn off the chest and/or abdomen if present
  • Surgical biopsy (however most kittens are too unwell for surgery by this stage)

So if there is no treatment, can we do anything for palliation?

Unfortunately there is currently no cure for FIP.

There are palliation drugs available, such as medications that suppress the immune system, however nothing has proven to be very effective so far.

What increases the risk of coronavirus mutation within a cat?

Risk factors that have been associated with increased chances of mutation within a cat infected with coronavirus include:

  • Immune suppression/stress
  • Overcrowding conditions (i.e. more than 5 cats in a household) and in breeding catteries
  • Shared litter trays
  • Genetics
  • Early weaning from the mother cat

Should I be concerned if one of my cats is diagnosed with FIP – will any of my other pets catch the disease?

It is likely that the other cat has been infected with coronavirus, as coronavirus is contagious. The mutated form (FIP) is not contagious. Littermates may have an increased risk of developing FIP due to genetics, however it cannot be passed on to other cats.

It is also species specific, so cannot be passed onto humans, dogs, etc.

RIP Lily

April 2020 – October 2020

Please feel free to leave any questions you may have in the comments.