940 



ORDER I. RICKETTSIALES 



636; Rickettsia {Rickettsia) orientalis Philip, 

 Amer. Jour. Hyg., 37, 1943, 305; Dermacen- 

 troxenus orientalis Moshkovskiy, Uspekhi 

 Souremennoi Biologii (Advances in Modern 

 Biology), 19, 1945, 13; Rickettsia orientalis 

 var. tropica Hayakawa and Hokari, A com- 

 parative study of Japanese and tropical 

 (scrub typhus) tsutsugamushi diseases (R. 

 orientalis var. tropica), Tokyo, 1947, 35; 

 Zinsser a orientalis Macchiavello, Prim. 

 Reunion Interamer. del Tifo, Mexico, 1947, 

 416; Rickettsia {Zinsser a) tsutsugamushi 

 Philip, Ann. N. Y. Acad. Sci., 56, 1953, 487; 

 Tromhidoxenus orientalis Zhdanov and 

 Korenblit, Jour. Microbiol., Epidemiol, and 

 Immunobiol. (Russian), No. 9., 1950, 42; 

 also see Zhdanov, Opredelitel Virusov 

 Celovska i Zivotmych, Izd. Akad. Med. 

 Nauk, U. S. S. R., Moskau, 1953, 54 and 160.) 



tsu.tsu.ga.mu'shi. From two Japanese 

 ideographs transliterated tsutsuga some- 

 thing small and dangerous, and mushi a 

 creature now known to be a mite. 



Small, pleomorphic bacterium-like micro- 

 organisms, usually wider and less sharply 

 defined than the cells of Rickettsia prowa- 

 zekii, R. typhi, R. rickettsii and Coxiella 

 burnetii. Ellipsoidal or rod-shaped, often 

 appearing as a diplococcus or as a short 

 bacillus with bipolar staining resembling 

 that of the plague bacillus. Diffuselj^ dis- 

 tributed in the cytoplasm of the cell. 0.3 to 

 0.5 by 0.8 to 2.0 microns. Non-motile. 

 Colored purplish with Giemsa's stain and 

 red against a blue background with Mac- 

 chiavello's stain. Stains well with azur III 

 and methylene blue. Gram-negative. 



Cultivation: Grows in plasma tissue cul- 

 ture of mammalian cells, on the chorio- 

 allantoic membrane and in the yolk sac of 

 the chick embryo and in rabbit testes and in 

 the endothelial cells overlying Descemet's 

 membrane of the rabbit eye. The only 

 species of Rickettsia known to separate in 

 the interface during ether treatment after 

 harvest of yolk sacs. Wej^er (Acta Tropica, 

 11, 1954, 194) has reported the unusual dif- 

 ficulty of growth in inoculated arthropods. 



Resistance to chemical and physical 

 agents: Readily inactivated by heat and 

 chemical agents. Destroyed by 0.1 per cent 

 formalin and 0.5 per cent phenol. Killed in 

 10 minutes at 50° C. 



Immunology: Immunity conferred by 

 infection, which is probably influenced by 

 strain differences, appears less complete 

 than that found in typhus and Rocky 

 Mountain spotted fever. Strains from 

 several different areas have been found to 

 cross immunize in guinea pigs, but the true 

 relationship of the disease occurring in dif- 

 ferent localities remains to be determined. 

 Reciprocal cross immunity between mite 

 strains and human strains has been demon- 

 strated in rabbits, hamsters and mice. 



Serology: Antigens from different strains 

 vary in sensitivity when tested by comple- 

 ment fixation with immune sera. There are 

 probably a number of different types on the 

 basis of complement fixation with immune 

 sera. Possesses a common antigenic factor 

 with Proteus OXK. 



Pathogenic for man, monkeys, gibbons, 

 guinea pigs, hamsters, rats, voles, mice, 

 gerbilles, rabbits (by intraocular injection) 

 and chick embryo. There is a wide variation 

 in the virulence of different strains for lab- 

 oratory animals: infection with a few is 

 established with difficulty while other 

 strains may cause a high mortality. The 

 white mouse is the laboratory animal of 

 choice. Infection may persist in the brains 

 of white rats for at least 98 days. A febrile 

 reaction may occur in guinea pigs. Passage 

 in guinea pigs and mice is accomplished by 

 inoculation of peritoneal washings, spleen 

 or blood from an infected animal, passage 

 in rabbits by intraocular or intratesticular 

 inoculation of blood, lymph node or organ 

 emulsions of infected native animals. As- 

 cites and enlarged spleen, often with a 

 fibrinous deposit, are characteristic. A 

 specific toxin, lethal for white mice, has been 

 reported in the Gilliam strain. In man an 

 eschar often develops at the site of the mite 

 bite with accompanying adenopathy. A 

 febrile reaction with exanthema occurs, and 

 mortality is variable in different localities 

 but remains about the same in a given focus. 

 In rabbits, infection of Descemet's mem- 

 brane follows intraocular injection of in- 

 fected material. 



Source: Observed by Hayashi in smears 

 and sections of the lesion (eschar) at the 

 site of the mite bite and in smears and sec- 



