Cytauxzoonosis is an emerging, life-threatening infectious disease of domestic cats (Felis catus) caused by the tick-transmitted protozoan parasite Cytauxzoon felis. Cytauxzoon spp. are apicomplexan parasites within the family Theileriidae along with their closest relatives of Theileria spp. C. felis is transmitted to domestic cats by the lone star tick (Amblyomma americanum). The natural host for C. felis is the bobcat (Lynx rufus); reservoir hosts of the parasite include bobcats and domestic cats that survive infection.