Overview

Feline infectious peritonitis (FIP) is a global inflammation caused by a mutated strain of feline enteric coronavirus. The mutation occurs during infection, which allows the coronavirus to bypass the actions of the immune system and infect the white blood cells of the cat. The interaction between the virus and the immune system causes an intensive inflammatory reaction that often affects multiple organs. While the normal coronavirus is contagious, the mutated form is not generally observed in the secretions of a cat affected by FIP; therefore, it is believed that while cats can contract the normal virus, they do not directly contract FIP from one another. The non-mutated coronavirus can cause mild, flu-like symptoms that are readily treatable, while FIP has close to 100% mortality.

Feline coronavirus is transmitted via infected feces, and therefore shared litter box is one of the most frequent ways in which the virus is spread. An active infection lasts weeks to several months, during which the infected cat is contagious. Households with multiple cats are especially at risk. However, the virus is relatively weak in the environment, and can be readily destroyed with household detergents.

The normal feline coronavirus can be found in most multiple-cat households. It is suspected that a cat with compromised immune system may be more susceptible to FIP.

Symptoms and Diagnosis

If a cat contracts the non-mutated form of the feline enteric coronavirus, the cat might develop mild gastrointestinal symptoms such as vomiting and diarrhea, or upper respiratory symptoms such as sneezing and watery eyes. These primary symptoms are usually self-limiting and not lethal.

If the infected cat has immature or compromised immune systems, the lethal form of the disease has more chance to develop. However the onset of FIP may still be vague, and may include general symptoms such as decrease in appetite, depression, weight loss, and fever. In the effusive (wet) form of FIP, the accumulation of immunological tissues will form a yellow, viscous fluid that builds up in the animal’s chest and abdominal cavities. In the non-effusive (dry) form, fluid accumulation is minimal while the animal shows signs of depression, anemia, fever, and weight loss. Other clinical signs include kidney failure, liver failure, pancreatic diseases, neurological impairments, and eye diseases.

Diagnosis is difficult since each cat can display different combinations of above symptoms, and many are similar to other diseases. Antibody tests can detect if the cat has prior exposure to feline coronavirus, but not necessarily the lethal form. A combination of tests, including serum proteins, antibodies, and testing the accumulated fluids can be helpful in diagnosing FIP. An absolute positive diagnosis usually requires a tissue biopsy.

Treatment

To date no effective treatment is available against the lethal form of the infection. Therapy mainly consists of supportive care to mitigate the pain and discomfort caused by the inflammatory response. A vaccine is currently available for FIP, although its efficacy is still debated.