By Dr. Becker
Feline infectious peritonitis, or FIP, is a viral disease caused by certain strains of the feline coronavirus. Most strains, called feline enteric coronavirus, do not cause disease.
How FIP Develops
Most kitties with feline corona infection are asymptomatic during the initial stages. The immune system responds by producing antiviral antibodies to kill off the infection. But in about five to 10 percent of infected cats, it is believed either a mutation of the corona virus or an abnormality in the immune system response allows the infection to progress to FIP.
In FIP, the antibodies that should provide protection actually help infect white blood cells with the virus. These cells, in turn, spread the infection throughout the cat’s body. This results in a very powerful inflammatory response in tissues where the infected cells locate -- frequently in the abdomen, kidneys, or brain.
It’s the interaction of the body’s immune system with the virus that results in disease. It behaves unlike any other viral disease we know of in either animals or people. Sadly, once FIP has involved one or more organs or body systems, the infection is quite progressed and almost always fatal.
Transmission of Feline Infectious Peritonitis
FIP is a disease of both domestic and wild cats. It’s most often seen in young cats living in multi-cat households, shelters, and catteries. Any cat exposed to the feline coronavirus can develop FIP. However, cats with compromised immune systems, those already infected with the feline leukemia virus, geriatric cats, and kittens are most likely to develop the disease. Males are more commonly infected than females, and purebred cats are at an increased risk, especially the Asian breeds.
FIP in symptomatic cats is not highly contagious, because by the time a kitty shows clinical signs of the infection, he is shedding only a small amount of the virus.
Fortunately, FIP is relatively rare in the general cat population. However, feline coronavirus is found in large quantities in the feces and saliva of cats during the acute stage of infection when there are no symptoms. It’s also found to a lesser extent in cats that have recovered, as well as carrier cats.
The coronavirus can be transmitted from one cat to another through physical contact and through exposure to feces. Usually, transmission occurs long before clinical signs are noted. The virus can also live in the environment for several weeks.
The most common route of infection, though, is when an infected mother passes the virus to her kittens. This usually occurs when the litter is between five and eight weeks of age.
The Two Forms of FIP and Their Symptoms
Kitties exposed to the feline coronavirus often have no clear symptoms, although there may be some sneezing, watery eyes, or nasal discharge. Sometimes a cat who has been infected will show mild intestinal signs like diarrhea.
Only a small percentage of cats exposed to the feline coronavirus go on to develop FIP. It can be weeks, months, or even years after exposure before symptoms appear.
Kitties that wind up with FIP often seem to their owners to develop symptoms very suddenly. This is probably due to the ability of cats to mask illness until they’re terribly sick. In addition, initial symptoms are often non-specific. They can include a lack of appetite, weight loss, fever, poor hair coat, and sometimes mild depression.
There are actually two forms of FIP, the effusive or wet form, and the non-effusive or dry form. Cats with the dry form tend to show signs of the illness more slowly. Those signs can include weight loss, depression, anemia, inflammation of the eye, and a stubborn fever that doesn’t respond to antibiotics.
Kitties with the wet form of the disease accumulate fluid in the abdomen and sometimes in the chest. Early on, symptoms may mimic those of the dry form of FIP. But effusive FIP progresses pretty quickly. The cat may suddenly develop a potbelly due to fluid accumulation in the abdomen. In addition, breathing can sometimes be labored due to a buildup of fluid in the chest.
Diagnosing feline infectious peritonitis can be difficult because many of the symptoms are common in many other diseases. In addition, there’s no simple diagnostic test for the condition.
Several tests can detect feline corona antibodies, but they can’t tell what strains are involved. A positive result on an ELISA, IFA, or a virus neutralization test simply means the cat has had exposure to the coronavirus, but not necessarily a strain of the virus that causes FIP.
There is an immunoperoxidase test that can find the presence of viral infected cells in the tissues. But it must be followed by a biopsy to evaluate the affected tissue.
Routine blood tests, including a complete blood count and serum biochemistry profile, can show elevated liver enzymes, anemia, and abnormal blood protein levels, which are typical of kitties with FIP.
Chest and abdominal X-rays may show an abnormal accumulation of fluid.
Blood samples from cats with very high blood protein levels can be submitted for serum protein electrophoresis testing. Cerebral spinal fluid samples can also be analyzed for protein content, which is typically elevated in FIP cats. But the only way to definitively diagnose FIP is by a surgical biopsy of an affected organ (often the intestines) or examination of tissues during an autopsy.
Veterinarians often rely on a presumptive diagnosis, which can be made with a high degree of confidence based on the cat’s history, symptoms, examination of fluids, and a high corona antibody titer.
Unfortunately, there is no cure at the present time for FIP. Once a kitty develops clinical signs of the disease, either the dry or wet form, the prognosis is very poor.
I have had some success in helping several kitties overcome this disease by supportive care and using homeopathic FIP nosodes, cytokine therapy, and IV vitamin C therapy, in addition to immune-modulating nutraceuticals.
I have also attempted to help many kitties that, unfortunately, end up succumbing to the disease. It’s a devastating situation for both the owner and the veterinarian.
The wet form typically progresses very rapidly. Many cats live only a month or two after diagnosis. Cats that have been diagnosed with the dry form may have another year or so with a good quality of life. Unfortunately, the dry form of FIP can progress to the wet form if the cat lives long enough.
Supportive care for FIP patients includes good nutritional and environmental maintenance, alleviating the inflammatory response of the disease, fluid therapy, draining fluid accumulation, and blood transfusions.
Preventing FIP in Your Own Cat
The best way to prevent FIP is to keep your cat’s immune system strong and balanced. This includes feeding a balanced species-appropriate diet; keeping vaccines and other drugs to an absolute minimum; providing a stress-free, enriched environment for your cat; regular wellness checkups with your veterinarian; either keeping your pet indoors at all times or providing a safe outdoor enclosure; and supervising walks with a harness and leash.
Of course, I always advocate rescuing cats rather than buying them, but if you do purchase a purebred cat, only do business with breeders who guarantee their kittens are FIP-free.
In a multi-cat household, it’s important to keep litter boxes clean and located in areas away from food and water bowls. Litter should also be scooped at least once daily, removing all feces, and dumped weekly or every two weeks, at which time the box should be completely and thoroughly disinfected with mild soap and water.
New cats to the household and certainly any cat that might be infected should be kept separate from other cats for a quarantine period.
There is an FIP vaccine available. However, I do not recommend it. It has little to no effectiveness in preventing FIP and is not recommended by the American Association of Feline Practitioners’ Feline Vaccine Advisory Panel. This vaccine causes substantial immune system damage and, in my opinion, should absolutely not be used.