Cytauxzoonosis is parasite disease caused by parasitic protozoa Cytauxzoon felis and it was first reported in the USA in 1976. This genus was originally described in African grey duiker (Sylvicapra grimmia), but is now known to be common in felids including the domestic cat.
The domestic cat (Felis catus) has been considered an aberrant or dead-end host given the acute and fatal course of disease; however, there are reports of domestic cats surviving natural infection with and without treatment. The bobcat (Lynx rufus) is the natural host, typically experiencing subclinical infection and maintaining chronic parasitemia. Cytauxzoon felis infection has been reported in several other wild felids, such as cougars and panthers, in the absence of overt disease; however, a few lions and tigers have been reported to succumb to illness.
The parasites are transmitted by tick bite. After a cat or other host is bitten by an infected tick the parasites infect mononuclear phagocytes. Within these they undergo asexual reproduction (schizonts). As these leukocytes become engorged with schizonts, they line the lumens of veins and may causing obstruction of blood flow. The schizonts develop into merozoites which eventually cause host cell rupture and enter the blood. These intravascular merozoites infect variable numbers of erythrocytes.