This 1976 transmission electron microscopic (TEM) image depicted a brain capillary of a mouse that had been experimentally infected with Orientia tsutsugamushi rickettsial micro-organisms. This TEM, revealed that one organism was budding from the luminal surface of a hypertrophic capillary endothelial cell, still covered by a third layer consisting of the host cell's plasma membrane. Others are visible free within the endothelial cell's cytoplasm. Formerly known as Rickettsia tsutsugamushi, O. tsutsugamushi is the pathogen responsible for causing the febrile disease known as scrub typhus. The disease is transmitted to humans through the bite of larval trombiculid mites, i.e., chiggers, that had fed on infected rodents.