Diagnosis: FIP

Among the dreadful illnesses that can bring an end to your cats life, none is more lethal than a viral disease called 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 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 multicat households, animal shelters and overcrowded breeding catteries, every cat owner should be aware of its viral origins, the clinical signs that suggest its presence and the ways in which the risk of its occurrence can be minimized.

Environmental Presence

A virus is a microorganism that, while comparatively simple in composition, has a relentless drive to replicate within a hosts system. In the process of reproduction, the viruss genetic makeup may change, resulting in the creation of a mutated virus, sometimes with its own peculiar characteristics. 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 on its outer surface. It is found in members of the cat family – cougars, lions, jaguars and leopards as well as domestic cats.

“There are clouds, swarms, perhaps thousands of feline coronaviruses that vary slightly in their genetic structures,” says James Richards, DVM, director of Cornell Universitys Feline Health Center and the editor-in-chief of CatWatch. “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.”

Intense Replication

Feline coronaviruses are shed in an infected animals saliva and feces, explains Dr. Richards, 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.

u 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).

u In “dry” or noneffusive FIP, little fluid accumulation is present, but the afffected 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 cats afflicted with this infectious viral disease will eventually die from it.

Elusive Diagnosis

A definitive diagnosis of FIP, says Dr. Richards, is “hard to come by.” A test for antibodies in an ailing cats blood, he notes, 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,” he 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.”

Consequently, he explains, 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. Richards, “and you put those pieces together, 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. It is licensed for the vaccination of cats at or over 16 weeks of age, with booster vaccinations given three to four weeks later and annually thereafter. Although the vaccine appears to be safe, various studies have yielded mixed results concerning its efficacy. Owners are advised to discuss with their veterinarians the ongoing controversy surrounding the FIP vaccine and its value.

Lowering the Risk

Most owners have little to worry about regarding FIP, Dr. Richards says. But they should keep in mind that the vast majority of affected animals are kittens or very young cats, especially those living in multicat environments, and that feline coronavirus is most commonly transmitted by an uninfected cats exposure to the feces of an infected cat. Says Dr. Richards: “The risk of FIP in, say, a single-cat household is virtually nil, but the risk goes up in an environment that becomes more 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. If you have several cats, you should always have as many litter boxes as there are cats, plus one extra litter box. And you should scoop the litter boxes at least once a day. This will go a long way toward reducing the chances that one of your cats will come in contact with another cats feces.” v