The pathology of experimental cytauxzoonosis

Clinical, gross post mortem, histological and electron-microscopical data were collected from cats serially killed following experimental infection with Cytauxzoon felis. The agent was originally isolated from domestic cats with naturally occurring fatal cytauxzoonosis. Morphologically, the blood phase of feline Cytauxzoon appeared similar or identical to that described for cases of cytauxzoonosis in African ruminants and closely resembled also the blood phases of Theileria spp. and Babesia spp. The tissue phase, which occurred as schizont and merozoite stages within mononuclear phagocytes, was also similar to that seen in African cytauxzoonosis and in theileriosis. The tissue host cells, mononuclear phagocytes, appeared identical in feline and African cases. The Cytauxzoon host cells, however, were distinct from the tissue host cell of Theileria, in which schizogeny takes place within lymphocytes. Another difference was the lack of evidence of Cytauxzoon host-cell division which has been described for Theileria parva.