Relationships between Cytauxzoon felis and African piroplasmids.

A cat which had recovered from Cytauxzoon felis infection following treatment with the anti-theilerial drug, parvaquone, showed an increase in piroplasm parasitemia after splenectomy and its blood was suitable for the preparation of antigen smears for the indirect fluorescent antibody test. High levels of antibodies were found in this cat after recovery, in two other cats sub-lethally infected with piroplasms and in sera of naturally infected bobcats. Cats recovered from piroplasm infection died from cytauxzoonosis when challenged with organ material containing C. felis schizonts. Tests with piroplasm antigens and positive sera of C. felis, South African Babesia felis and African Theileria taurotragi showed no significant serological relationship between C. felis and the African parasites. C. felis was not shown to be infective for splenectomized sheep.