Feline infectious peritonitis is caused by the feline coronavirus, which is shed in the saliva and feces. Generally, cats and kittens that become infected by the coronavirus have fairly mild symptoms such as diarrhea and vomiting that resolve without significant medical intervention. However, FIP, a rare form of coronavirus infection, is a deadly disease with no cure. The FIP virus causes multiple changes in the body's immune system, leading to a destruction of the blood vessels that results in an inadequate supply of oxygen to the body's cells. The disease manifests itself in two ways: effusive FIP or non-effusive FIP. The effusive or wet form is characterized by the production of large amounts of fluid throughout the cat's body occurring because the affected cat's immune system releases signals that cause the blood vessels to become more permeable. As a result, fluid and white blood cells leak out of the vessels into the body cavities, causing severe damage throughout the body. When the blood vessels can no longer deliver oxygen-rich blood to the organs, the cells in those organs die, resulting in multi-organ failure and death.
Although there is no fluid production with the dry form of the disease, multi-organ failure can result from this manifestation of the illness as well. In addition, non-effusive FIP can attack the brain, causing neurological disorders such as seizures.
