Cytological studies on heartwater I : the observation of Rickettsia ruminantium on the tissues of infected animals

Abstract

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.