Feline infectious peritonitis (FIP) is a serious viral infection. The FIP virus can infect any cat but is most common in those younger than 3 years old. It is also more common in multiple cat households. Cats infected with feline infectious peritonitis are are often infected with feline leukemia virus as well.
The FIP virus can cause a wide range of signs, which vary depending on the strength of your cat’s immune system and the body organs most affected. Much of the illness is driven by your cat’s immune response to the FIP virus, rather than by the virus itself.
The most classic form of illness is the “wet” form, in which a thick, yellowish fluid builds up in the chest or abdomen. Cats with the wet form of FIP often have difficulty breathing and a potbellied appearance. In the “dry” form of the disease, specific body organs tend to be affected, such as the liver, kidneys, nervous system, or respiratory system. In both forms of the disease, signs can develop gradually and include weight loss, poor appetite, persistent fever; sluggishness, and dull or rough fur.
Diagnosis is based on signs of illness and various laboratory tests. In the wet form of the disease, your veterinarian may want to take a sample of the fluid in the chest or abdomen. Specific diagnostic blood tests are available, but these are not 100% accurate. X-rays may be needed to evaluate specific organs.
Unfortunately, there is no cure for FIP. Anti-inflammatory medications, and drugs that suppress the immune system can help, but most cats die within months of diagnosis.
Prevention involves isolating affected cats and thoroughly disinfecting all bedding, food and water dishes, etc, before introducing new cats to the household. Early weaning may prevent transmission from mother to kittens. A vaccine against similar viruses is available, but it is not very effective at preventing FIP.