Invited Speaker Australian Society for Microbiology Annual Scientific Meeting 2021

Shotgun metagenomic sequencing of Australian Ixodes spp reveals novel vertebrate viruses and formalises the potential human pathogen Rickettsia tasmanensis as present in New South Wales Koala populations. (#81)

Rhys Parry 1
  1. University of Queensland, Fairfield, QLD, Australia

In Australia, ticks are hematophagous vectors of the bacteria Coxiella burnetii, the causative agent of Q fever, and several Rickettsia spp infections associated with Scrub typhus and spotted fever group (SFG) disease. Up to 12 species of hard ticks (Ixodidae) take blood meals from humans in addition to a wide range of mammalian hosts, including marsupial and monotreme species. To explore the incidence of bacterial, viral, and protozoan parasites from a range of common hard ticks, we subjected pools of Ixodes tasmani, Ixodes holocyclus and Haemaphysalis bancrofti to high-throughput metagenomic gDNA sequencing. These ticks were sampled from animals presented to veterinarian hospitals in South-East Queensland (QLD) and Central New South Wales (NSW). Results indicated that hard ticks harbour a range of novel DNA viruses from the Anelloviridae (n=8) and Circoviridae (n=1) families. In addition to novel viruses, a draft Rickettsia genome (1,202,398bp total size, 42 contigs, N50:46,675) was assembled from two pools of I. tasmani ticks isolated from Koalas (Phascolarctos cinereus). Based on species demarcation criteria and OrthoANI scores (<99.19%), this Rickettsia assembly is not any SFG species identified in Australia and likely represents a new Rickettsia species most closely related to Rickettsia slovaca with 97.4% similarity. Further analysis of published fragments of rickettsial bacteria identified from I. tasmani ticks from NSW and Tasmania suggests the identity of this bacteria is likely Rickettsia tasmaniensis identified from Tasmanian devils. This study provides evidence of an additional Rickettsia species present in mainland Australia with the potential to cause human rickettsial disease.