Feline infectious peritonitis (FIP) is a complicated disease that is still not completely understood. The disease is most often seen in kittens and young cats. FIP is not treatable and is almost invariably fatal when a kitten or cat becomes symptomatic.
Feline Infectious Peritonitis and the Feline Coronavirus
Feline infectious peritonitis (FIP) is caused by infection with a virus known as the feline coronavirus. However, infection with the feline coronavirus is a commonplace event and most cats that become infected either experience no symptoms of disease at all or experience minor gastrointestinal symptoms that resolve relatively quickly. Large numbers of healthy cats test positive for the feline coronavirus itself. Fortunately, only a small number of these cats actually develop the disease known as feline infectious peritonitis.
Cats that succumb to feline infectious peritonitis mount an abnormal immune response to infection with the feline coronavirus infection. It is the combination of the abnormal immune response together with the coronavirus infection that causes the symptoms of the disease known as FIP. However, why some cats develop an abnormal immune response is not completely understood.
Some cats that have proven to be susceptible to developing feline infectious peritonitis have had a familial relationship and, as a result, a genetic component to susceptibility to FIP has been suggested. However, many unanswered questions remain regarding the pathophysiology of feline infectious peritonitis and the exact relationship between FIP and the feline coronavirus.
Symptoms of FIP in Cats
There are two forms of feline infectious peritonitis seen in infected cats: the dry form and the wet form.
- The effusive or wet form of FIP causes damage to the serosa, leading to ascites (accumulation of fluid within the abdominal cavity) or pleural effusion (accumulation of fluid within the chest cavity). Fluid may accumulate in both cavities simultaneously. The course of the wet form of the disease is generally fairly rapid.
- The dry form of FIP causes pyogranulamatous changes in the tissues and organs of the body and the symptoms of the disease will vary depending on which tissues and organs are affected. Frequently, changes are seen in the eyes, the kidneys, the liver, the intestinal tract, the lungs or the nervous system. The dry form of the disease tends to progress more slowly than the wet form, but both forms are usually fatal.
Often, the early symptoms of feline infectious peritonitis, particularly with the dry form, are subtle and insidious, consisting of weight loss, lethargy and a decreased appetite.
Diagnosis of Feline Infectious Peritonitis
Unfortunately, diagnosis of feline infectious peritonitis is difficult. Though testing for the feline coronavirus is fairly simple, many healthy cats test positive for the virus and there are currently no tests that can detect whether a cat is likely to mount the abnormal immune response that combines with the coronavirus to cause the symptoms of feline infectious peritonitis. Therefore, there is no accurate laboratory test to distinguish between the feline coronavirus infection and the more dangerous feline infectious peritonitis.
Most often when FIP is suspected, a combination of clinical findings and symptoms consistent with feline infectious peritonitis together with positive antibody titers to the feline coronavirus and other abnormal laboratory values such as a lymphopenia (abnormally low lymphocyte count in the blood) and a hyperglobulinemia (elevated globulin levels in the blood) are used to confirm the diagnosis. When exudates are present in the abdominal or chest cavities, a gamma globulin level greater than 32% in the fluid may be an additional diagnostic clue to the presence of FIP.
Treatment of FIP in Infected Cats
The prognosis for cats and kittens that are symptomatic for FIP is poor at best. However, in some cases, particularly in the dry form of the disease, supportive treatment may prove beneficial, at least for a time. Treatments with prednisolone, chlorambucil, cyclophosphamide and melphalan have all been attempted.
Feline infectious peritonitis (FIP) is a complex and potentially devastating disease of cats. Most often affecting kittens and young cats, the disease is difficult to diagnose and treat and is frequently fatal for affected cats.
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