|Description:||This 1976 transmission electron microscopic (TEM) image depicted a hypertrophic peritoneal mesothelial cell of mouse that had been experimentally infected intraperitoneally with Orientia tsutsugamushi rickettsial micro-organisms. In this TEM, several organisms were visible, free within the host cell's cytoplasm. One O. tsutsugamushi appeared within a phagocytic vacuole, still bearing a third outer membrane layer of probable host cell origin.|
Scrub typhus is an acute febrile disease caused by Orientia tsutsugamushi. The disease occurs mainly in the large triangular region extending from Japan in the north, to Australia in the southwest, and the South Pacific Islands in the southeast. Humans are infected by the bite of the larva of the trombiculid mite harboring O. tsutsugamushi. This pathogen attacks endothelial cells resulting in vasculitis. The clinical manifestations are characterized by a papular rash, headache, fever, chills, and an eschar at the site of the chigger bite.