The cells parasitized in host by Rickettsia are

The cells parasitized in host by Rickettsia are vascular endothelial cells.
Rickettsia is a genus of nonmotile, gram-negative, nonspore-forming, highly pleomorphic bacteria.
These are obligate intracellular parasites that invade vascular endothelial cells in target organs, damaging them and producing increased vascular permeability with consequent oedema, hypotension and hypoalbuminaemia.