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Ornithodoros species are soft ticks (Family Argasidae). Included in this genus are several vectors of tick-borne relapsing fever (TBRF) in humans, including O. hermsi, which is found in the United States and can transmit the spirochaete bacteria responsible for TBRF.
Ornithodoros hermsi Wheeler (Acari: Argasidae) is the vector of the spirochaete bacterium Borrelia hermsii, the primary cause of TBRF in North America (McCoy et al. 2010). TBRF is endemic to high elevation coniferous forests of the western United States and southern British Columbia, Canada. Patients usually become ill after they have slept in cabins infested with spirochete-infected ticks that feed quickly during the night. The illness has an incubation period ranging from 4 to more than 18 days and is characterized by recurring episodes of fever accompanied by a variety of other manifestations, including headache, myalgia (muscle pain), arthralgia (joint pain), chills, vomiting, and abdominal pain. Relapsing fever is confirmed by the microscopic detection of spirochetes in the patient’s blood. (Dworkin et al. 2002; Schwan et al. 2003 and references therein)
Like other argasids, Ornithodoros ticks have multihost life cycles. Argasid ticks have two or more nymphal stages, each requiring a blood meal from a host. Unlike the ixodid (hard) ticks, which stay attached to their hosts for up to several days while feeding, most argasid ticks are adapted to feeding rapidly (for about an hour), then dropping off the host. (Centers for Disease Control Parasites and Health website)