Borrelia recurrentis causes louse-borne relapsing fever (LBRF) and is transmitted from person to person by the body louse. Spirochetes are introduced not from the bite itself but from rubbing of the insect’s feces into the bite site in response to irritation. Tick-borne relapsing fever (TBRF), a zoonosis usually transmitted via the bite of various Ornithodoros ticks, is caused by multiple Borrelia species. B. miyamotoi can cause relapsing fever but is transmitted to humans from other mammals by hard ticks (e.g., Ixodes scapularis) that also transmit B. burgdorferi and other tick-borne illnesses.