|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. A disintegrating organism was shown within a host cell's phagocytic vacuole.|
In humans, O. tsutsugamushi attacks endothelial cells resulting in vasculitis. The clinical manifestations are characterized by papular rash, headache, fever, chills, and an eschar at the site of the chigger bite, i.e. the mode of human inoculation. The disease can be tested serologically by the detection of significant increases of IFA (indirect fluorescent antibody) in paired serum drawn at the onset of disease, and 2 - 3 weeks later. Traditionally, isolation of the rickettsia from the blood by inoculation intraperitoneally into white mice is the definite confirmatory method.