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.
