Cowdry, E.V.Theiler, Arnold, Sir, 1867-1936Union of South Africa. Department of Agriculture2020-12-222020-12-2220201926Cowdry, EV 1926, ‘Cytological studies on Heartwater. I: the observation of Rickettsia ruminantium on the tissues of infected animals’', 11th and 12th Reports of the Director of Veterinary Education and Research Part 1, pp. 161-177.0330-2465http://hdl.handle.net/2263/77455Includes bibliographical referencesThe articles have been scanned in colour with a HP Scanjet 5590; 300dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.A Gram-negative, intracellular, coccus-like micro-organism was found in cases of heartwater in the three species which are susceptible to the disease, namely, goats, sheep, and cattle. The presence of this micro-organism was definitely related to the febrile reaction, and it was absent in controls. It probably occurred throughout the body, but was most easily detected in the renal glomeruli and in the small capillaries of the cerebral cortex. The micro-organism was a typical endothelial parasite, being restricted in distribution to the endothelial cells of the smaller blood-vessels and to portions of them which broke off into the blood stream. It was never observed to cause any injury to the endothelial cells other than mechanical distension through accumulation in large densely packed masses which were characteristically spherical. A typical attribute was the presence of several of these masses with the cytoplasm of a single endothelial cell. In view of the association of this micro-organism with heartwater, which is a disease of ruminants, and thus far the only one in which micro-organisms resembling Rickettsia have been reported, the designation Rickettsia ruminantium is proposed.19 pages : plates, figures, tablesPDFen©1926 Union of South Africa, Dept. of Agriculture (original). © 2020 University of Pretoria. Dept. of Library Services (digital).Veterinary reportsVeterinary medicineHeartwaterRickettsiaRickettsia ruminantiumVeterinary medicine -- South AfricaArticle