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A number of genera and species of ticks in the families Argasidae (soft ticks) are of public health importance. Included in this group are ticks in the genus Carios that are vectors of the spirochete bacteria causing tick-borne relapsing fever in Central and South America. (Centers for Disease Control Parasites and Health website) Recent investigations have suggested that Carios kelleyi, which is normally a parasite of bats, may sometimes bite humans and transmit Borrelia spirochaetes that could cause TBRF. Carios kelleyi is widely distributed in the United States and Canada and has also been reported from Costa Rica. Unlike many species of argasid ticks that have fast-feeding larvae, C. kelleyi larvae are slow feeders, apparently requiring one to several weeks to engorge. (Schwan et al. 2009 and references therein)
Members of the family Argasidae 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.