Ornithodoros tick. Coloured scanning electron micrograph (SEM) of an ornithodoros tic. Ornithodoros species are vectors for various human and animal diseases. Borrelia bacteria that cause Tick-borne relapsing fever (TBRF) are transmitted to humans through the bite of infected Ornithodoros. African swine fever virus (ASFV) is a large, double-stranded DNA virus. It is the causative agent of African swine fever (ASF). The virus causes a hemorrhagic fever with high mortality rates in domestic pigs. It persistently infects its natural hosts, warthogs, bushpigs, and Ornithodoros, which likely act as a vector, with no disease signs. It does not cause disease in humans. Magnification: x15 when printed at 10cm wide.