ORDER I. RICKETTSIALES BUCHANAN AND BUCHANAN, 1938, emend. GIESZCZKIEWICZ, 1939.
(Buchanan and Buchanan, Bacteriology, 4th ed., New York, 1938, 49; Gieszczykiewicz, Bull. Intern. Acad. Polon. "Sci., Classe Math., B (1), 1939, 9-30.)
Ri.ckett.si.a'Ies. M.L. fern. pi. n. Rickettsiaceae type family of the order; -ales ending to denote an order; M.L. fern. pi. n. Rickeitsiahs the Rickettsiaceae order.
Small, rod-shaped, coccoid and often pleomorphic microorganisms occurring as elementary bodies which are usually intracellular but which may occasionally be facultatively or exclusively extracellular. Ma}' also develop larger "initial bodies" as intracellular, spherical or less regular inclusions. Intracytoplasmic forms may be diffuse, compacted into colonies or morulae and may be located in special situations. Usually non-filterable. Gram-negative. Cultivated outside the host only in living tissues, embryonated chicken eggs or rarely in media containing body fluids. Parasitic organisms almost always intimately associated with not only reticulo-endothelial and vascular endothelial cells or erythrocytes in vertebrates, but also often in invertebrates which may act as vectors. The intracellular parasites of Protozoa and other invertebrates are provisionally assigned here also. May cause diseases in man or other animals or both. Seldom kill the invertebrate hosts.
Key to the families of order Rickettsiales.
I. Parasites, intracellular or intimately associated with tissue cells other than erythrocytes or with certain organs in arthropods; rarely extracellular in arthropods. A. Frequently cause diseases of vertebrates. Transmitted by arthropod vectors. Family I. Rickettsiaceae, p. 934. B. Intracellular parasites found in tissues of vertebrates. Not known to be transmitted by arthropod vectors. Family II. Chlamydiaceae, p. 957. II. Parasites, intracellular or facultatively extracellular; found characteristically in or on the erythrocytes of vertebrates, exceptionally in fixed-tissue cells. A. Small, rod-shaped, bacteria-like cells. At least one species, when cultured, may show a single, polar flagellum. Arthropod transmission established for some members of the family. Family III. Bartonellaceae, p. 968. B. Very small, virus-like particles occurring in the erythrocytes of vertebrates. Transmitted by arthropods. Family IV. Anaplasmataceae , p. 980.
FAMILY I. RICKETTSIACEAE PINKERTON, 1936.<refRevised by Dr. Cornelius B. Philip, Rocky Mountain Laboratory, Hamilton, Montana, January, 1954, from the original by Dr. Ida A. Bengtson, Sixth Edition of the Manual.</ref>
(Parasitology, 28, 1936, 186.)
Ri.ckett.si.a'ee.ae. M.L. fem.n. Rickettsia type genus of the family; -aceae ending to denote a family; M.L. fem.pl .n. Rickettsiaceae the Rickettsia family.
934
