Microbial agent(s) appearing like small bacteria and multiplying by simple fission, but only within a living host cell.
pl. n. (sing. rickettsia) a group of very small nonmotile spherical or rodlike parasitic bacteria that cannot reproduce outside the bodies of their hosts. Rickettsiae infect arthropods (ticks, mites, etc.), through which they can be transmitted to mammals (including humans), in which they can cause severe illness. The species Rickettsia akari causes *rickettsial pox, R. conorii, R. prowazekii, R. tsutsugamushi, and R. typhi cause different forms of *typhus, R. rickettsii causes *Rocky Mountain spotted fever, and Coxiella burnetii causes *Q fever. —rickettsial adj.... rickettsiae
a disease of mice caused by the bacterium Rickettsia akari and transmitted to humans by mites: it produces chills, fever, muscular pain, and a rash similar to that of *chickenpox. The disease is mild and runs its course in 2–3 weeks. See also typhus.... rickettsial pox