Which of the following is a symptom of Feline Infectious Peritonitis?

Fluid accumulation in the abdomen, known as ascites, is a hallmark symptom of Feline Infectious Peritonitis (FIP). This occurs due to inflammation of the blood vessels, leading to increased permeability and resulting in fluid leaking into the abdominal cavity. The accumulation of this fluid can lead to significant respiratory distress and pain in affected cats, making it one of the most notable clinical signs.

FIP is caused by a mutation of the feline coronavirus and typically presents in two forms: the wet (effusive) form, which is characterized by the fluid accumulation, and the dry (non-effusive) form, which may involve granulomas in various organs. However, it is the wet form, associated with fluid buildup in the abdomen, that prominently displays this symptom.

Other options like chronic cough and severe vomiting could occur in various other conditions affecting cats but are not specific indicators of FIP. Hyperthermia, or elevated body temperature, can occur due to many infectious and inflammatory diseases, but alone does not indicate FIP and is not a primary symptom associated specifically with this disease.