982 



ORDER I. RICKETTSIALES 



Yiengst (Amer. Jour. Vet. Res., 3, 1942, 

 312) state that each organism undergoes 

 growth which is then followed by multiple 

 fission resulting in the formation of eight 

 small spherical bodies. Studies on the life 

 cycle of this organism in arthropods are 

 limited. Regendanz (Zent. f. Bakt., I Abt., 

 Orig., 137, 1933, 214) claims to have demon- 

 strated granules varying from 0.1 to 0.4 

 microns in diameter in the salivary glands 

 of known-infected Dermacentor andersoni 

 and Dermacentor variabilis adult ticks. 



Cultivated on Bass medium. Continued 

 to grow through two generations, but 

 growth could not be detected after the third 

 passage. No growth in a wide variety of 

 bacteriological and tissue-culture media, in 

 chick embryo or in sealed collodion bags 

 containing infective blood which had been 

 placed in the peritoneal cavity of a rabbit. 



Non-filterable with Berkefeld filter (du 

 Toit, Rept. Direct. Vet. Educ. Res., Union 

 So. Africa, Pt. I, 1928, 157). Filterable 

 with a three-pound Mandler filter (Foot, 

 No. Amer. Vet., 35, 1954, 19). 



Immunology: No authentic case of true 

 natural immunity in cattle has been estab- 

 lished. Calves under one year of age show a 

 milder reaction than do older animals. Ac- 

 quired immunity occurs in (1) the latently 

 infected ox, (2) the infected ox after sple- 

 nectomy and recovery from the disease, (3) 

 the non-splenectomized, non-carrier ox fol- 

 lowing infection, and (4) animals other than 

 the ox following infection. Carrier state 

 usually persists for periods longer than 12 

 years. Autosterilization in both non-sple- 

 nectomized and splenectomized cattle is of 

 relatively rare occurrence. A partial cross 

 immunity exists between this organism and 

 A. centrale. 



Serology: Complement fixation has been 

 reported with sera of carrier cattle. About 

 90 per cent of the serum samples drawn from 

 known carriers gave positive results while 

 10 per cent gave discordant reactions. Anti- 

 bodies were detected in the sera of artifi- 

 cially infected animals before the organism 

 was microscopically demonstrable. 



Pathogenicity: Infected blood, washed 

 red blood cells and organ suspensions pro- 

 duce infection by the subcutaneous, intra- 



muscular and intravenous routes. Infectious 

 for cattle, zebu, water buffalo {Babalus bab- 

 alis), bison {Bison bison), African antelopes 

 (white-tailed gnu {Connochaetes gnou), bles- 

 buck (Damaliscus pygargus albifrons) and 

 duiker (Sylvicapra grimmia)) , American deer 

 (southern black-tailed deer and Rocky 

 Mountain mule deer (Odocoileus spp.)), elk 

 and camel (Camehis bactrianus). Sheep and 

 goats develop a submicroscopic infection. 

 The African buffalo {Syncerus caffer) is re- 

 fractory. Rabbits, guinea pigs, white rats, 

 gray rats, white mice, field mice, dogs, cats, 

 ferrets and chickens are all refractory to 

 bovine anaplasmosis. Mortality has been re- 

 corded in cattle, zebu, water buffalo and 

 camel. 



Antibiotic therapy: True sterilization of 

 latent or recognized infection occurs with 

 massive repeated doses of aureomycin and 

 terramycin. 



Source: Observed by Theiler {op. cit., 



1910, 7) in the blood of infected cattle. 

 Habitat: Found in arthropods such as 



Argas persicus, Boophilus annulahis, B. aus- 

 tralis, B. calcaratus, B. decoloratus, B. vii- 

 crophis, Dermacentor albipictus, D. andersoni, 

 D. occidentalus, D. variabilis, Haemaphysalis 

 cinnabarina punctata, Hyalomma excavatum, 

 Ixodes ricinus, I. scapularis, Rhipicephalus 

 bursa, R. sanguineus and R. simus. Also 

 found in the erythrocytes of susceptible 

 animals. World wide distribution. 



2. Anaplasma centrale Theiler, 1911. 

 (1st Rept. Dir. Vet. Res., Union So. Africa, 



1911, 7.) 



cen.tra'le. L. adj. centralis central. 



In blood smears fixed with May-Griinwald 

 and stained with Giemsa, the organisms ap- 

 pear in erythrocytes as irregularly spher- 

 ical, chromatic granules which stain a deep 

 purple color. Vary in diameter from 0.4 to 

 0.95, averaging 0.65, micron. Resembles A. 

 marginale very closely but differs from it bj^ 

 its slightly greater size and by its usually 

 central position in the erythrocyte. Approx- 

 imately 88 per cent of the organisms are 

 situated at or near the center and 12 per 

 cent at or near the margin of the host cell. 

 Usually occurs singly in the red blood cells, 

 but double forms are not uncommon. Rarely 



