|A fever is an abnormally high body temperature. The normal body temperature for dogs and cats is 100.2 to 102.8°F.
There is a part of the brain responsible for regulating body temperature. It is called the 'thermoregulatory center.' In certain disease processes, chemical compounds called 'pyrogens' are released into the blood, travel to the brain, and basically reset the thermostat to a higher temperature.
There can be multiple causes of a fever. The most common disease process that produces pyrogens, and thus causes fever, is inflammation. Inflammation can be the result of infections, cancer, immune-mediated diseases, some metabolic diseases, and some diseases of internal organs. In some cases, we can not determine what is causing the fever. It is then called a 'fever of undetermined origin' or FUO.