Feline Infectious Peritonitis (FIP) is caused by a coronavirus. Infections of the intestines with the coronavirus result in a mild gastrointestinal disease -- slight nausea, diarrhea, and vomiting. If the virus manages to get out of the intestines into the body, a much more serious disease develops. This disease affects many different parts of the body with the most commonly affected part being the abdomen where it causes intense inflammation of the peritoneum (the tissue lining of the outside of abdominal organs). Thus, the disease name Feline Infectious Peritonitis.
Infection occurs primarily from inhalation or ingestion of the virus. The virus replicates in the tonsils, the upper airways, and the intestines. If the virus is able to infect a white blood cell during this replication process it gains access to the whole body causing severe systemic disease. If not it stays localized in these tissues causing mild disease. The immune system reacts very strongly to the virus once it becomes systemic resulting in intense inflammation that actually causes the clinical signs associated with FIP.
FIP has two manifestations: effusive and non-effusive. The effusive manifestation is characterized by leakage of protein-rich fluid into the abdomen, chest, sac around the heart, and capsule around the kidneys. Clinical signs include loss of appetite, loss of energy, abdominal distention, difficulty breathing, and jaundice. The non-effusive manifestation is characterized by development of inflammatory nodules in the eyes, brain, kidney, and liver. Clinical signs include jaundice, loss of appetite, loss of energy, inflammation of the eyes, and a variety of neurologic signs such as weakness, incoordination, and seizures.
FIP typically affects young cats (< 5 years) but can affect cats of any age. Cats kept in large groups or that are allowed to roam coming into contact with other cats are at higher risk for developing the disease. Once FIP develops, unfortunately, it is incurable and fatal. Medications that inhibit the immune system may in some cases ameliorate clinical signs and prolong life but even at optimum success they cannot cure the disease. By the time most cats are diagnosed, especially with the effusive manifestation, the disease has progressed to the point that medications offer little or no relief. Within days to months of being diagnosed with FIP, most cats die or are euthanized.
Prevention is the only way currently available to combat this disease. Management factors such as limiting the number of cats housed together and preventing cats from roaming play a key role in reducing likelihood of infection. Intranasal vaccination for FIP is available and has shown to provide protection. Discuss with your veterinarian the risks of FIP exposure for your cat in order to determine the necessity of FIP vaccination.
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