Genus I. Anaplasma Theiler, 1910* (Rept. Govt. Vet. Bact. for 1908-09, Dept.Agr., Transvaal, 1910, 7-64; alsoseeTrans- vaal Med. Jour., 5, (January) 1910, 110; Bull. Soc. path, exot., S, (March9) 1910, 135; and Trans. Roy. Soc. So. Africa, 2, (October 27) 1910, 69.) A.na.plas'ma. Gr. prefix an- without; Gr. noun plasma anything formed or molded M.L. neut.n. Anaplasma a thing without form. Description same as for the family. The type species is Anaplasma marginale Theiler. Key to the species of genus Anaplasma. I. Cause infections in cattle. A. The etiological agent of malignant anaplasmosis of cattle. 1. Anaplasma marginale. B. The etiological agent of benign anaplasmosis of cattle. 2. Anaplasma centrale. II. Causes anaplasmosis of sheep and goats. 3. Anaplasma ovis. 1. Anaplasma marginale Theiler, 1910. (Theiler, Rept. Govt. Vet. Bact. for 1908-09, Dept. Agr., Transvaal, 1910, 7; Anaplasma theileri Cardamatis, 1911; Anaplasma argen- linum Lignieres, Cent. f. Bakt., I Abt., Orig., 7^, 1914, 133; also see 10« Congres in- tern, de M^d. Vet., Londres, 1914; Ana- plasma rossicum Yakimov and Beliawine, Cent. f. Bakt., I Abt., Orig., 103, 1927, 419.) mar.gi.na'le. L. noun margo, marginis edge, margin; M.L. adj. marginalis mar- ginal. In blood smears fixed with May-Griin- wald and stained with Giemsa's stain, this organism appears in the erythrocytes as one or more chromatic granules which stain a deep purple color. Varies in size from 0.3 to 0.8 micron, averaging about 0.5 to 0.6 mi- cron. Usually round or elliptical in shape, although irregular forms are not uncommon. About 90 per cent of the bodies are situated at or near the margin of the erythrocytes, while 10 per cent are situated at or near the centers of the host cells. DeRobertis and Epstein (Proc. Soc. Exp. Biol, and Med., 77 , 1951, 254) have studied the structure of this organism with the electron microscope: the typical organism occurring at the mar- gin of the erythrocyte appears to be con- stituted of a central, undivided mass and of peripheral elementary bodies, 170 to 220 millimicrons in diameter, of high electron density; in some cases the whole mass of the organism is divided into submicroscopic bodies. Usually occurs singly in the red blood cells, but double forms are not un- common. Rarely three, four, five and even six organisms may be seen in one red blood cell. A halo may sometimes be seen sur- rounding the organism. During the height of the reaction, as many as 50 per cent or more of the erythrocytes may be parasit- ized. Responsible for a variable degree of anemia and icterus. When anemic changes progress, the number of infected erythro- cytes decreases to a point where they can- not be demonstrated microscopically. This phenomenon should be remembered by workers engaged in chemotherapeutic stud- ies, and the disappearance of organisms following the administration of drugs should not, without due consideration, be attrib- uted to the action of the drug. Recovery is usually followed by the asymptomatic re- appearance of the organisms in relatively small numbers for a period varying from 10 to 60 days, sometimes even longer. It is gen- erally assumed that in the mammalian host multiplication of these organisms takes place by simple binary fission. Lotze and
- Prepared by Dr. W. O. Neitz, Department of Agriculture, Division of Veterinary Ser-
vices, Onderstepoort, Union of South Africa, December, 1954.
