FIP – Feline Infectious Peritonitis

Once in a while, veterinarians disagree. Most of the time it’s because there is more than one way to fix a problem. The scientific world is continuously discovering new tests and solutions, and further questioning the validity of old ones. Unfortunately however, few things are yes or no, black or white. This is why different veterinarians can see the same animal and choose different treatments. It is not necessarily the case that one of the choices is wrong; there are just different roads to reach the same endpoint.

Sometimes it’s good to know why there is debate about a certain method. The FIP vaccination has been controversial since it was introduced. Although the American Association of Feline Practitioners does not recommend this vaccine, some veterinarians still choose to use it. Why? ‘FIP’ stands for feline infectious peritonitis (peritonitis means inflammation of the abdomen). There are two types of FIP: wet and dry. Wet FIP has a distinctive build-up of fluid in the abdomen. The type of FIP (wet or dry) that develops, depends of the type of immune response that the cat’s body creates to fight the virus.

Both wet and dry FIP cause inflammation in the major organs (liver, lungs, kidneys, etc.), damaging these vital structures. By the time FIP is diagnosed, there is a very small chance of survival. Sometimes the disease takes a while to become severe. Once the cat shows severe signs of FIP however, it is untreatable and progresses rapidly. It is actually hard to diagnose FIP in the first place. There is no set test that will give you an exact yes or no. Veterinarians must take into consideration a variety of tests, the cat’s history, and its current problems in order to properly diagnose FIP. FIP is difficult to diagnose because it is not a simple virus. FIP develops from the enteric feline coronavirus (FCoV). FCoV is an extremely common virus that lives in intestinal cells and can cause diarrhea. Many cats have FCoV. It is a fairly harmless virus.

The virus that causes FIP is a mutation of the FCoV. So, in order to develop FIP, the cat must first have FCoV. However, it is estimated that only 1-5% of cats with FCoV develop FIP. It is still not well known why the FIP virus develops in some cats and not in others. There are some factors that can increase a cat’s risk of developing the FIP mutation, such as living in a cattery or suppression of the immune system (e.g. other viruses like Feline Leukemia can destroy immune cells), but the exact cause of the mutation remains unknown.

The difference between FCoV and FIP is great. As mentioned before, FCoV is a common virus (about 30% of house cats have it) that is generally harmless but lives in intestinal cells and may cause some diarrhea (remember, many viruses, bacterias, and parasites can cause diarrhea). FCoV can spread between cats, while FIP cannot spread between cats because it develops from a mutation inside each individual cat. The FIP mutation is uncommon. The virus lives in immune cells, causing lethal inflammation of major organs. We obviously don’t want our cats to get FIP, so researchers set out to make a vaccination.

There is a vaccination available for FIP but there are two issues we need to take into consideration. Is the vaccine effective (does it help prevent disease)? Is the vaccine safe (does it harm any cats)? The FIP vaccine has not consistently been proven to be effective. The vaccine is aimed to prepare the body to fight FCoV, not FIP, since the specific FIP mutation is not well known. This may be a problem. Some cats already have FCoV before they are vaccinated, so the vaccine is useless. Also, the immune response to FCoV (stimulated by the vaccine) may not be sufficient to protect the cat after the virus mutates to FIP. Some studies show a lower FIP mortality rate in vaccinated cats, while others do not. The effectiveness of this vaccine is still in question.

The safety of this vaccine is also in question. It is generally accepted as safe for animals without FIP, but there have been studies linking the FIP vaccination with higher death rates in cats already affected with the beginning stages of FIP. Due to the fact that the clinical signs and organ damage are due to the body’s immune reaction to the virus, it is thought that by using a vaccine to stimulate the body’s immune reaction, we are simply making the disease worse. It’s like stepping on the gas pedal in a runaway car; if the cat already has FIP, the vaccine gives the body more fuel (active immune cells) to speed up the disease process. This is the theory, and there is evidence that supports it. However, some other evidence does not support this theory. So as of now therefore, the safety of the vaccine has not been determined.

FIP is an uncommon, fatal disease that is hard (or impossible) to treat. We would like to have a vaccine to prevent it and even though there is a FIP vaccine available, we must be critical about its efficiency and safety. In medicine there is commonly more than one right answer. Talk to your veterinarian to find out if the FIP vaccination is the right answer for you.

By Ashley O’Driscoll – Pets.ca writer