1. Cowdria ruminantium (Cowdry, 1925) Moshkovskiy, (1945) 1947. {Rickettsia ruminantium Cowdry, Jour. Exp. Med., ^2, 1925, 'IZl; Rickettsia (Cowdria) ruminantium Moshkovskiy, Uspekhi Souremennoi Biol. (Russian) (Advances in Modern Biology), 19, 1945, 18; Cowdria ruminantium Moshkov- skiy, Science, 106, 1947, 62; Kurlovia (Cow- dria) ruminantium Zhdanov, Opredelitel Virusov Celovska i Zivotmych, Izd. Akad. Med. Nauk, U.S.S.R., Moskau, 1953, 56 and 166.) ru.mi.nan'ti.um. M.L. neut.gen.pl.n. ru- minantium of Ruminantia, formerly an ordinal name for cud-chewing mammals. Differ morphologically from typical ty- phus-like rickettsiae, showing u.sually spherical and ellipsoidal forms, occasionally bacillary forms. Irregular pleomorphic forms occur. Grow in the cytoplasm but not in the nuclei of cells, sometimes in densely packed masses. Cocci measure 0.2 to 0.5 micron in diameter in the endothelial cells of animals and 0.2 to 0.3 micron in diameter in ticks. In ticks bacillary forms are 0.2 to 0.3 by 0.4 to 0.5 micron and pairs are 0.2 by 0.8 micron. Non-motile. Stain blue with Giemsa's stain; can also be stained by methylene blue and other basic aniline dyes. Gram-negative. Cultivation: Not reported. Immunology: Immunity incomplete after recovery from the infection. The organisms are found in the tissues long after recovery (premunition). There is some evidence of a variety of strains. Pathogenic for goats, sheep and cattle. Transmissible to goats by inoculation of infected blood intrajugularly. The most characteristic lesion is the hj^dropericar- dium of infected animals. The only small animal shown to be susceptible is the ferret. Source: Observed in the endothelial cells of renal glomeruli and in the endothelial cells of the cerebral cortex of animals suffer- ing from heartwater; also observed in the tick Amblyomma hebraeum. Habitat: Found in the bont tick (A. hebraeum) and also in A. variegatum, in which the infection has been shown to be transstadial but not transovarial. The eti- ological agent of heartwater in sheep, goats and cattle in South Africa. Genus V. Neorickettsia Philip et al., 1953. (Philip, Hadlow and Hughes, Riassunti delle Comunicazioni, VI Congresso Internaz. di Microbiol., Roma, 2, 1953, 256; also see Exp. Parasitol., 3, 1954, 336; and Atti del VI Congresso Internaz. di Microbiol., Roma (1953), 4, 1955, 70.) Ne.o.ri.ckett'si.a. Gr. prefix neo- new; M.L. fem.n. Rickettsia type genus of family Rickettsiaceae; M.L. fem.n. Neorickettsia the new Rickettsia. Small, coccoid, sometimes pleomorphic (in the form of short rods, crescents and even rings), intracytoplasmic organisms which occur in the reticulo-endothelial cells of certain mammals and in tissues of at least mature fluke vectors. No intranuclear forms have been observed. Non-filterable. Non-motile. Not cultivable on cell-free media. The etiological agent of a helminth-borne disease of canines. The type species is Neorickettsia helminthoeca Philip et al. 1. Neorickettsia helminthoeca Philip et al., 1953. (Neorickettsia hehnintheca (sic) Philip, Hadlow and Hughes, Riassunti delle Communicazioni, VI Congresso Internaz. di Microbiol., Roma, 2, 1953, 256; also see Exp. Parasitol., 3, 1954, 336; Neorickettsia hehnintheca (sic) Philip, Hadlow and Hughes, Atti del VI Congresso Internaz. di Microbiol., Roma (1953), 4, 1955, 70.) hel.min'thoe.ca. Gr. noun helmins, hel- minthis worm; Gr. noun oicus house; M.L. adj. helminthoecus worm-dwelling. Minute, coccoid and ellipsoidal forms to short rods and clubs, occasionally crescentic and even ring-like. Often form morula-like clusters either singly or in multiple colonies in the cytoplasm of reticuloendothelial cells of infected canines. The most common coc- coid forms range from 0.3 to 0.4 micron in diameter. Non-filterable. Non-motile. In
