Cytauxzoon Neitz & Thomas, 1948 and Babesia Starcovici, 1893
(Figures 1-21 through 1-23)
Two genera of the phylum Apicomplexa, Cytauxzoon and Babesia, are included within a group called the piroplasms. These organisms when within the red blood cell appear very similar to malaria parasites. Individual piroplasms possess many of the typical elements of the apical complex that identify the Apicom plexa as such. The piroplasms are similar to the other apicomplexan protozoa in that there is fusion of gametes. The gametes of the piroplasms, however, cannot be morphologically distinguished from each other, i.e., there is no distinguishable macrogamete and microgamete, and thus, they are termed isogamous. For the life cycles that are known, the gametes form within the stomach of the tick vector, and sporozoites that are ultimately produced from the union are found in the salivary glands of the tick. The genus Babesia was originally named for various blood parasites of large animals (Starcovici, 1893), Babesia spp. are also important parasites of dogs (Fig. 1-21 and 1-22). Theileria is a genus of piroplasm parasites that causes disease in African ungulates and other animals (Fig 1-23); in the genus Theileria schizogony also occurs in white blood cells. The genus Cytauxzoon was originally named for similar blood parasites originally found in an African antelope (Neitz and Thomas, 1948). The schizonts of Cytauxzoon spp. occur in macrophages.
Neitz WO, AD Thomas. 1948. Cytauxzoon sylvicaprae gen. nov., spec. nov., a protozoan responsible for a hitherto undescribed disease of the Duiker [sylvicapra grimmia (Linné)]. Onderstep J Vet Sci An Ind 23:63-76.
Starcovici CG. 1893. Bemerkungen über den durch Babes entdecken Blutparasiten und die durch denselben hervorgebrachten Krankheiten, die seuchenhafte Hämoglovinurie des rindes (Babes), das Texasfieber (Th. smith) und der Carceag der Schafe (Babes). Centralblatt Bakteriol14:1-8.
FIGURE 1-21.Babesiacanis trophozoite in a canine red blood cell (Preparation supplied by Dr. P Conrad, College of Veterinary Medicine, University of California-Davis). Giemsa stain.
FIGURE 1-22.Babesiacanis schizont in a canine red blood cell (Preparation supplied by Dr. P Conrad, College of Veterinary Medicine, University of California-Davis). Giemsa stain.
FIGURE 1-23.Theileriaparva in bovine red blood cells. Giemsa stain.