FAMILY I. RICKETTSIACEAE 



945 



Virusov Celovska i Zivotmych, Izd. Akad. 

 Med. Nauk, U.S.S.R., Moskau, 1953, 52 and 

 159.) 



a'ka.ri. Gr. neut.n. akari a mite. 



Minute diplobacilli and bipolarly stained 

 rods. Resemble typical rickettsiae mor- 

 phologicall}^ with an average size, under the 

 electron microscope, of 0.6 by 0.9 to 1.4 mi- 

 crons; very similar to Rickettsia rickettsii 

 from yolk-sac cultures. Occur intracyto- 

 plasmicalh'; have been seen intranuclearly 

 in yolk-sac cells. Non-motile. Stain well by 

 Macchiavello's method, the organisms ap- 

 pearing bright red against a blue back- 

 ground. Stain poorly with methylene blue. 

 Gram-negative. 



Cultivation : Grows in the yolk sac of the 

 chick embryo and in intrarectally injected 

 body lice. No growth on artificial culture 

 media. 



Immunology: Guinea pigs recovered from 

 rickettsialpox of human origin are immune 

 to infection with strains isolated from in- 

 fected mites and from house mice. There is 

 partial to complete experimental cross im- 

 munity with other members of the subgenus 

 Dermacentroxenus . 



Serology: Antigens prepared from in- 

 fected yolk sacs are highly specific except for 

 cross reactions with Rocky Mountain 

 spotted fever group antigens. Sera from 

 convalescent patients fixed complement 

 with the homologous antigen and usually 

 with Rocky Mountain spotted fever anti- 

 gens though at a lower titer. A rising titer 

 against Proteus OX19 has been shown in 

 some convalescent cases. 



Pathogenic for man with initial erythema- 

 tous focal lesion at the site of the mite bite 

 and with adenopathy followed by fever and 



appearance of macular rash. No mortality. 

 Experimental infections have been produced 

 in white mice and guinea pigs by the inocu- 

 lation of infected blood (irregularly), in- 

 fected liver and spleen suspensions, infected 

 brain, infected lymph nodes, tunica wash- 

 ings of infected animals and of infected 

 yolk sacs. Guinea pigs show marked scrotal 

 reactions. It has not been found pathogenic 

 for monkeys, thus distinguishing it from 

 Rickettsia conorii. It is also probably more 

 pathogenic for white mice than isR. conorii. 



Source: Isolated from the blood of a hu- 

 man case of rickettsialpox in New York 

 City. _ 



Habitat: Found in the tissues of human 

 cases and of the mite AUodermanyssns 

 sanguineus Hirst, an ectoparasite of ro- 

 dents. House mice have also been found to 

 be naturally infected. The etiological agent 

 of human rickettsialpox (vesicular rickett- 

 siosis) . Known only in cities on the eastern 

 seaboard of the U. S. A. and in unnamed 

 urban centers of the U.S.S.R. (an original 

 report is by Zhdanov, Korenblit, Lavruskin, 

 Alexandrova and Kiselov, Vrachevnoye 

 Delo (Physician's Work), No. 10, 1950; also 

 see Zhdanov, Communicable Diseases of 

 Humans. Medgiz, Moscow, 1955, 305-366 

 {Gamasoxenus murinus) and Zdrodovskiy 

 and Golinevitch, Treatise on Rickettsia and 

 Rickettsiosis, Medgiz, Moscow, 1956, 276- 

 286 (Dermacentroxenus murinus)). As in the 

 U. S. A., strains of infection were reported 

 from patients, house mice (also gray rats, 

 R. norvegicus) and the same mite vector, A. 

 sanguineus (see Kiselov and Volchanetskaia, 

 in Pavlovsky et al., Nat. Nidi Hum. Dis. 

 and Regional Epidemiol. (Russian), 1955, 

 248-252). 



Subgenus D. Rochalimaea Macchiavello, 1947. 



(Subgenus Rocha-Limae (sic) Macchiavello, Prim. Reunion Interamer. del Tifo, Mexico, 

 1947, 410; Welhynia (sic) Zhdanov and Korenblit, Jour. Microbiol., Epidemiol, 

 and Immimobiol. (Russian), No. 9, 1950, 42; Wolhijnia Zhdanov, Opredelitel 

 Virusov Celovska i Zivotmych, Izd. Akad. Med. Nauk, 

 U.S.S.R., Moskau, 1953, 55 and 164.) 

 The subgeneric name Rochalimaea Macchiavello was validly published and was trans- 

 ferred to the genus Rickettsia (Philip, Canad. Jour. Microbiol., 2, 1956, 265) even though it 

 was originally proposed as a subgenus of Burneiia ( = CoxieUa) and wrongly associated 

 thereby with Coxiella burnetii (Derrick) Philip. 



Ro.cha.li.mae'a. M.L. fem.n. Rochalimaea named for H. da Rocha-Lima, who studied 

 rickettsial agents in human-body lice. 



