Feline Infectious Peritonitis (FIP)

 

Cats are prone to catching a number of infections. Of particular interest is the number of slow viral infections that they are susceptible to.

 

FIP is difficult to diagnose and treat.

FIP is a slow viral disease of cats that is characterized by a gradually worsening condition that may not be noticed by an owner until quite late in the disease process, when sudden progression occurs. Weight loss, fever, poor haircoat, a dull attitude, and a bloated abdomen may occur..

This virus is closely related to the feline enteric coronavirus (FECV) and some feel that they overlap in disease production, with FECV tending to be the less harmful version of the coronavirus, causing transient diarrhea in kittens, and the FIP the more pathogenic cousin. According to a number of studies, a conversion from the more benign FECV virus to the pathogenic FIP may occur inside the body of some cats.

Because the disease is more prevalent where there are a number of cats kept together, housing a cat indoors in a solo cat household will prevent exposure to the virus. If you must introduce other cats, introduce only cats that have tested antibody negative (though there are some limitations to this antibody test!).

A vaccine is available which is given in the nostril. Data reports vary on how well the vaccine protects. Your veterinarian can advise you whether this is a suitable protective measure for your cat. Since transmission to kittens occurs while in the late nursing phase, early weaning of the kittens from a queen (at <5 weeks old) and isolation from other cats in a cattery can help to break the transmission cycle.

Testing kittens before sale at 4 months of age will tentatively confirm lack of transmission. Keeping your cat indoors will help prevent contact with infected strays. Cleanliness of the cat’s environment will also help to keep viruses in check. Virus can travel to other cats on dirty food dishes and litter box equipment, or in bowel movements tracked around on shoes.

Depending on how the cat’s immune system responds to the agent, the toxicity of the particular strain of virus, whether the cat has leukemia virus, the breed/family, and the age of the cat, the disorder may take on quite different clinical forms. Kittens and cats less than about three years of age are most susceptible to the virus. Cats that mount a response to the agent experience a spectrum of possible clinical disease.

About 90 of 100 infected cats do not go on to develop clinical disease.

Of the others, the signs expressed depend on which organ the virus causes inflammation in, but the outcome for those cats that develop the disease is not rosy! This is a highly fatal disease (~100%). Once the signs begin, it is a matter of only weeks to a few months until the clinically affected cats die.

The FIP virus enters through the nose and oral cavity, or is derived from FECV in the guts, and sets up in the local lining cells. From here, the virus travels around the body and settles in the cells in and around the blood vessels. It is here that the inflammation reaction begins. Many tissues can be targets including lungs, brain and spinal cord lining, surface of liver, kidney, guts and the omentum, lymph nodes (glands), and the eyes to name a few.

Traditionally, we classify the disease as a dry or wet form. The wet form is most common (~3/4 of cases) and produces excess fluid in the chest and/or abdomen. The dry form refers to the disease when inflammatory lesions occur in the tissues without fluid production. If present, a sample of fluid will be analyzed. X-rays and ultrasound may also show the extent of fluid build up or visualize some of the granuloma lumps, and will help to rule out other causes of fluid buildup such as heart disease in wet FIP cats.

Diagnosis can be a challenge in some cats while alive, especially when the dry form is present, particularly if the lesions are in the central nervous system. Antibody tests (ELISA, IFA) are not always reliable. PCR lab tests identify virus coronavirus coat components, and are still under study but because they have the same problem as antibody tests—they identify generic coronavirus (FECV+ FIP). Research continues in order to discern the two closely related viruses. Biopsy of the inflamed tissues will provide the definite diagnosis of the disease. Not infrequently, a post mortem is used to confirm the diagnosis.

Treatment is of a supportive nature. Fluid may be removed to keep kitty comfortable, appetite stimulants prescribed, and isolation from other cats will be recommended. No drugs will reverse the disease, though some drugs that modulate the immune system may improve quality of life during the terminal illness.