Most infected cats have been healthy before a very sudden onset of severe disease. The course of clinical disease is often swift with clinical signs of lethargy and inappetence within 5 to 20 days after the tick bite. Cats develop a high fever, but the temperature may become low before death. Other clinical findings can be: dehydration, icterus (jaundice), enlarged liver and spleen, lymphadenopathy, pale mucus membranes, respiratory distress, tachycardia or bradycardia, and tick infestation (although ticks are not often found on infected cats since cats typically groom ticks off their fur). Signs of disease seen on blood work include hemolytic anemia, thrombocytopenia, increased or decreased white blood cell numbers, icterus, and elevated liver enzymes. Death usually follows the onset of clinical signs within a few days. However, more recent studies show not all cats develop clinical signs after infection, and some cats survive the infection.

Cytauxzoon felis is a protozoal organism transmitted to domestic cats by tick bites, and whose natural reservoir host is the bobcat. "C. felis" has been found in other wild felid species such as Florida bobcat, eastern bobcat, Texas cougar, and a white tiger in captivity. "C. felis" infection is limited to the family felidae which means that "C. felis" poses no zoonotic (transmission to humans) risk or agricultural (transmission to farm animals) risk. Until recently it was believed that after infection with "C. felis", pet cats almost always died. As awareness of "C. felis" has increased it has been found that treatment is not always futile. More cats have been shown to survive the infection than was previously thought. New treatments offer as much as 60% survival rate.