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 Ornithodoros and Carios that are vectors of tick-borne relapsing fever.
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.