What is feline infectious peritonitis?

Feline infectious peritonitis is a poorly-understood disease that affects cats and is very dangerous. It is caused by a virus called a coronavirus. Most cats that catch a coronavirus do not have any real problems, and it stays benign. It is actually pretty common in cats. However, in some cats, it will remain dormant for some time and then mutate or flare up into peritonitis, a dangerous, active form of the virus.


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The exact mechanism of how this disease works is unknown, and there is a lot of debate about it. What is known is that for some period the cat will have the disease, but it will be dormant. Some vets think it's two weeks, some think it's a year. After that period, something happens that makes it turn dangerous - it could be a mutation, a progression of the disease, but exactly what is not agreed upon.

What are the symptoms?

In its active form, the symptoms are lack of appetite, weight loss, fevers, and lethargy. It can also cause virtually any symptom a cat can get because it often leads to organ failures. There are two basic forms of it. In one, fluid accumulates in the cat's body, which can cause it to look like it has a pot-belly. In the other form, there are no fluids and this does not happen. Sometimes one can turn into the other.

Is there a treatment?

Sadly, no. The prognosis is very bad. Most cats who get this will eventually die, and it is common to euthanize them because the recovery rate is so low. Vets have tried a variety of different treatments, and it is possible to alleviate the symptoms somewhat with drug treatments. Vets have had only sporadic success in treating it, and the treatments that have been tried have not worked consistently.

Can my dog catch it? Can I?

No, dogs cannot catch it, and neither can people. It is safe to have dogs in the house with an infected cat.

Is peritonitis to other cats?

Yes - but the caveat is that if you know that your cat has it, it's probably not contagious anymore. FIP stops being contagious when the symptoms start. It is, however, contagious for several weeks to a month before symptoms start showing. Because the virus can survive outside the cat for at least a few weeks, if your cat has just started showing symptoms it could still be infesting your house. If you've got a friend or neighbor with no cats who can take in the healthy cat for a few weeks, that is a good idea. If they've got cats, do NOT risk infecting their pets.

If you don't have a safe place to keep your healthy cats quarantined, you need to separate the animals in your house if you are keeping your sick cat. Get new food bowls and litter boxes for the healthy cats and confine either them or the sick cat to one room. Before you put them in any room, you need to clean out out - especially for shedded cat fur. A room with hardwood floors is best because you can disinfect it with some bleach mixed in with water. Carpet will be basically impossible to disinfect.

Contact with feces and saliva are the most common infection methods, which is why it is very important to make sure the cats are not using the same bowls or litterboxes.

Some people believe that it is not possible for cats to catch FIP from each other. What they believe happens is that all the cats in the house get a coronavirus from each other, and the virus only becomes dangerous when it mutates inside the individual cat. In most multiple cat households, all the cats will be found to have the coronavirus but only one will actually get the dangerous version of it. My recommendation is to take the precautions anyway. It can't hurt your cats to keep them apart for a few weeks, and if there is a chance it helps them, I would do it. 

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