Fig 6. Anti-Rickettsia immunohistochemistry demonstrating numerous organisms in the skin of animals inoculated with R. parkeri at 4 dpi as opposed to rare Rickettsia in the tick-only animal.

Photomicrographs of skin sections stained with a polyclonal anti-Rickettsia antibody at 4 dpi. (A) Rare cells contain positive, brown-staining, rickettsial organisms in the tick-only animal. (B) Abundant positive, brown-staining, organisms in a section from an animal in the R. parkeri-only group. (C) Similarly, many organisms are noted in an animal from the tick + R. parkeri group. The red-framed images at the bottom are higher magnification views of the red-boxed areas in the top images. Black-framed insets are higher magnification images of the black-boxed areas and highlight the coccobacilli morphology of the positively stained rickettsial organisms.