Invasion of capillary endothelial cells by Ehrlichia ondiri
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Ultra-thin sections from two infected cattle killed in extremis revealed E. ondiri free in capillary lumens of the heart muscle and in the sinusoidal spaces of the liver and spleen. Similar organisms were seen in the kidney section of one animal and the third eyelid section of the other animal. It was also commonly found in intracytoplasmic vacuoles in the capillary endothelial cells and the von Kupfer cells of the liver. Tangential and transverse capillary sections showed the rickettsial vacuoles protruding into the capillary lumen and causing capillary thrombosis. Adjacent to the alterations on the endothelial wall were extravascular erythrocytes which possibly escaped when the endothelial wall degenerated. The observation of E. ondiri in the capillary endothelial cells may help to explain the pathogenesis of the bovine petechial fever syndrome.