FAMILY RICKETTSIACEAE 1083 



ORDER RICKETTSIALES GIESZCZYKIEWICZ. 



(Bull. Intern. Acad. Polon. Sci., Classe Math. Nat., B(l), 1939, 9-30.) 



Small, rod-shaped, coccoid, spherical and irregularly-shaped microorganisms which 

 stain lightly with aniline dyes. Gram-negative. Usually not filterable. Cultivated 

 outside the body, if at all, only in living tissue, embryonated eggs or rarely in media 

 containing body fluids. Parasitic organisms intimately associated with tissue cells 

 and erythrocytes, chiefly in vertebrates and often in arthropods which act as vectors. 

 The intracellular parasites of Protozoa may also belong here. May cause diseases 

 in man or animals, or both. 



Key to the families of order Rickettsiales. 



I. Intracellular parasites, or parasites intimately associated with tissue cells. 

 Do not occur in erythrocytes. Frequently cause diseases of vertebrates trans- 

 mitted by arthropod vectors. 



Family I. Rickettsiaceae, p. 1083. 

 II. Facultative intracellular or extracellular parasites found characteristically in 

 or on the erythrocytes of vertebrates. May be transmitted by arthropod vectors. 



Family II. Bartonellaceae, p. 1100. 

 III. Intracellular parasites found in vertebrate tissues and not transmitted by 

 arthropod vectors. 



Family III. Chlamydozoaceae ,p . llli. 



*PAMILY I. RICKETTSIACEAE PINKERTON. 



(Pinkerton, Parasitology, 28, 1936, 186; Rickettsiales Buchanan and Buchanan, 

 Bacteriology, 4th ed., New York, 1938, 49.) 



Small, often pleomorphic, rod-shaped, ovoid, coccoid and coccus-shaped bacterium- 

 like organisms, intimately associated with arthropod tissues, usually in an intra- 

 cellular position. Stain lightly with aniline dyes. Gram-negative. Have not been 

 cultivated to date in cell-free media. May be parasitic to man and other animals 

 causing diseases (typhus and related ills) that are transmitted by arthropod vectors 

 (lice, fleas, ticks, mites and probably other ectoparasites). 



Key to the genera of family Rickettsiaceae.f 



I. Cells rod-shaped, ellipsoidal and coccoid. 



A. Non-filterable. 



B. Filterable. 



II. Cells spherical, occasionally elongated. 



Genus I. Rickettsia, p. 1084. 

 Genus II. Coxiella, p. 1092. 

 Genus III. Cowdria, p. 1094. 



* Prepared by Dr. Ida A. Bengtson (retired), National Institute of Health, 

 Bethesda, Mar3'land, November, 1946. Through the courtesy of Dr. Edward A. 

 Steinhaus much use was made of material from his book, Insect Microbiology, Ithaca, 

 1946, 763 pp. before it was generally available. 



t Includes only those rickettsiae which have been rather completely studied. 

 For additional rickettsiae, see appendix. 



