borrelia hermsii borrelia hermsii borrelia hermsii is a spirochete bacterium that has been implicated as a cause of tick-borne relapsing fever. it is spread by the soft-bodied tick ornithodoros hermsi. borrelia hermsii borrelia hermsii (green) on red blood cells scientific classification domain: bacteria phylum: spirochaetota class: spirochaetia order: spirochaetales family: borreliaceae genus: borrelia species: b. hermsii binomial name borrelia hermsii(davis, 1942) steinhaus, 1946