FIP: What You Need to Know

This deadly viral disease is rare and hard to diagnosis. Its important to learn how to protect your cat.

Among the various illnesses that can bring an end to your cats life, none is more lethal than feline infectious peritonitis (FIP), which primarily affects young cats (less than two years of age) and cats that are 10 years of age and older. While the name of the


disease suggests an inflammation solely involving the peritoneum – the membrane that lines the feline abdominal cavity and covers the organs that lie within it – the condition can ravage an affected animals entire system.

FIP is a relatively rare viral disease, affecting less than one percent of all cats presented to veterinarians for treatment. But it is incurable and almost always fatal. Although the disease is most prevalent by far in multi-cat households, animal shelters and overcrowded breeding catteries, every cat owner should be aware of its viral origins, its clinical signs and the ways in which the risk of its occurrence can be minimized.

Environmental Presence. The origin of the microrganism that causes FIP – feline infectious peritonitis virus (FIPV) – can be traced to feline coronavirus (FCoV), a virus with a structure resembling the corona of the sun. It is found in members of the cat family – cougars, lions, jaguars and leopards, as well as domestic cats.

“There are perhaps thousands of feline coronaviruses that vary slightly in their genetic structures,” says Richard Goldstein, DVM, associate professor of clinical sciences. “They are all different to one extent or another, and the vast majority of them are harmless. But they mutate like crazy, and we believe that its a mutated form of a relatively harmless coronavirus that is responsible for FIP. Many cats are infected with feline coronavirus, but only a few get sick with FIP.”

Feline coronaviruses are shed in an infected animals saliva and feces, explains Dr. Goldstein, and an uninfected cat most often picks up the virus either by ingesting or inhaling it. It can also be picked up through contact with virus-contaminated objects or surfaces in a cats environment, primarily in poorly maintained litter boxes.

The intensity with which the virus replicates within the new hosts body – especially in certain white blood cells – depends to a great extent on the reaction to the invading microorganism that is mounted by the animals immune system. If the cats immune response is strong and the viral invasion is weak, exposure to FCoV will rarely result in obvious clinical disease, although some cats may experience mild upper respiratory problems (sneezing, watery eyes and nasal discharge) and others may experience gastrointestinal illness and fleeting bouts of diarrhea. These animals will soon recover. However, if an infected cats immune response is weak or the viral infection is powerful, full-blown FIP – with lethal and widespread systemic involvement – is apt to develop.

Signs of Infection. The onset of FIP may be sudden, especially in kittens. Or the signs may increase gradually in severity over a period of weeks or months. In many cases, the initial signs include a subtle decline in appetite, weight loss and fever. Eventually, the disease will almost always manifest itself in either of two forms – “wet” or “dry” – which are distinguished primarily by the extent to which fluid accumulates in one or more of a cats body cavities. However, this distinction is not absolute; the forms can actually transform into each other, and the amount of fluid present in an affected cat can change over the course of time.

The most common clinical sign of “wet” FIP is a progressive accumulation of fluid within the chest cavity, the abdominal cavity or both. Respiratory distress may develop when the buildup of abdominal fluid becomes excessive or, more likely, when the fluid accumulation in the chest becomes oppressive and puts pressure on the affected animals lungs. Other salient clinical signs may include increasingly diminished appetite and weight loss, high fever, anemia and the yellowing of the animals mucous membranes and skin (jaundice).

In “dry” or noneffusive FIP, little fluid accumulation is present, but the affected animal will also show signs of declining appetite, fever, weight loss and jaundice. In addition, cats with this form of the disease may have clinical signs that are typically associated with impairment of a wide variety of its internal organs and systems. It may, for example, show signs of kidney and liver failure, pancreatic disease, neurologic dysfunction and ocular disease.

“Wet” FIP is marked by a more rapid onset and swifter progression than “dry” FIP. Affected kittens with effusive FIP will typically survive for only a few days to a few weeks, while adult cats may linger for several months. Cats with noneffusive FIP may survive for longer periods of time, but virtually all infected cats will eventually die from it.

Elusive Diagnosis. A definitive diagnosis of FIP is hard to come by. A test for antibodies in an ailing cats blood can show only that the animal has been exposed at some point to a coronavirus, but it cannot prove beyond a doubt that the animal has FIP. “Many cats – the majority in some multiple-cat environments – will test positive for coronavirus antibodies,” Dr. Goldstein points out, “but chances are theyll all remain perfectly healthy. The only way you can achieve a definitive diagnosis is to find evidence of the virus in tissue that is exhibiting characteristics of FIP – tissue taken from a swollen mass in the abdomen, for example, or from a lumpy kidney. If you can biopsy the tissue before an animal dies, that can give you a diagnosis, but, sad to say, this kind of tissue biopsy is usually done post-mortem.”

Diagnosis of FIP is most often based on tests that exclude all other conditions that might cause the clinical signs. “You collect pieces of the puzzle,” says Dr. Goldstein, “and eventually you start to conclude that FIP is quite possibly the cause of the animals illness.”

No cure for FIP yet exists. Treatment for a cat diagnosed with the disease consists only of supportive care and, perhaps, efforts to alleviate an afflicted animals self-destructive inflammatory response to the viral infection. A vaccine developed for FIP prevention has existed since 1991. Owners should discuss with their veterinarians the ongoing controversy surrounding the FIP vaccine and its value.

Lower the Risk. The majority of affected animals are kittens or very young cats, especially those living in multi-cat environments, and that feline coronavirus is most commonly transmitted by an uninfected cats exposure to the feces of an infected cat. The risk goes up in an environment that becomes overcrowded, especially if young cats are present or are being born into it. The worst-case scenario happens when good litter-box hygiene is not being practiced in such an environment.