|Description:||This 1978 transmission electron microscopic (TEM) image depicted a brain capillary of mouse that had been experimentally infected intravenously with Orientia tsutsugamushi rickettsial micro-organisms. In this micrographic view revealed pericapillary edema, the capillary lumen was partially occluded by a thrombus, and flanking the thrombus, a hypertrophic endothelial cell containing a visible organism free within its cytoplasm.|
Formerly known as Rickettsia tsutsugamushi, Orientia tsutsugamushi is the pathogen responsible for causing the febrile disease known as "scrub" typhus, which is also known as "river", or "flood" typhus. The disease is transmitted to humans through the bite of larval trombiculid mites, i.e., chiggers that had fed on infected rodents. The disease is characterized by the formation of a cutaneous ulcerative lesion at the site of the mite bite, which evolves into a blackened eschar known as "tache noire". The initial ulcer is followed by localized lymphadenopathy, fever, and a generalized maculopapular rash.