Detection of tick-borne bacterial DNA (Rickettsia sp.) in reptile ticks Amblyomma moreliae from New South Wales, Australia

Ticks are major arthropod vectors of disease, transmitting tick-borne pathogens during blood meal episodes. Rickettsia spp. and Borrelia spp. are two tick-borne pathogens of zoonotic concern previously identified in DNA isolates from the tick genera Amblyomma and Bothriocroton associated with reptilian hosts in Australia. Some reports suggest that these reptile ticks bite and attach to humans via accidental parasitism and transmit disease, with the tick Bothriocroton hydrosauri known to transmit Rickettsia honei or Flinders Island Spotted Fever Rickettsia to humans. This descriptive study aims to identify the ticks collected from wild reptiles submitted to veterinary clinics and captured by snake rescuers from New South Wales (NSW), Australia, and detect the presence of tick-borne bacterial DNA using quantitative polymerase chain reaction (qPCR) to detect Rickettsia spp. and Bartonella spp. and conventional nested-PCR to detect Borrelia spp. Morphological identification revealed ticks removed from one eastern blue-tongued lizard (Tiliqua scincoides scincoides) from North-Eastern NSW (Lismore), one eastern blue-tongued lizard from the Greater Sydney area (Canley Heights), one diamond python (Morelia spilota spilota) from the Greater Sydney area (Woronora Heights) and one red-bellied black snake (Pseudechis porphyriacus) from the Greater Sydney Area (Cronulla) in New South Wales were Amblyomma moreliae. No ticks were positive for Bartonella spp. and Borrelia spp. DNA using real-time PCR targeting ssrA gene and nested PCR targeting Borrelia-specific 16S rRNA gene, respectively. Real-time PCR targeting gltA, ompA, ompB and 17kDa gene of Rickettsia spp. revealed 14 out of 16 ticks were positive. The undescribed Rickettsia sp. DNA was identical to that previously recovered from reptile ticks in Australia and closely related to Rickettsia tamurae and Rickettsia monacensis, both of which are aetiologic pathogens of the Spotted Fever Group Rickettsiosis (SFGR). These results accentuate the ongoing need for increased study efforts to understand zoonotic potential of bacteria from reptile ticks and the tick-reptile-human relationship.