Rickettsia can be diagnosed by

Rickettsia can be diagnosed by Giemsa stain.
The rickettsiae are a diverse collection of obligately intracellular Gram-negative bacteria found in ticks, lice, fleas, mites, chiggers, and mammals. They include the genera Rickettsiae, Ehrlichia, Orientia and Coxiella.
Giemsa stain named after German chemist and bacteriologist Gustav Giemsa is a nucleic acid stain used in cytogenetics and for the histopathological diagnosis of malaria and other parasites.
Giemsa stain is used in Giemsa banding, commonly called G-banding, to stain chromosomes and is often used to create a karyogram (chromosome map). It can identify chromosomal aberrations such as translocations and rearrangements.