Metagenomic resolution of spotted-fever group Rickettsia tasmanensis and novel DNA viruses in Australian wildlife ticks, with spatial modelling of Rickettsia exposure zones.

Abstract

Australia's spotted fever group (SFG) rickettsiae cause significant illness, yet microbial diversity in wildlife ticks remains incompletely understood. Metagenomic sequencing of nine tick pools representing three Ixodidae species, Ixodes tasmani, I. holocyclus, and Haemaphysalis bancrofti, from Australian wildlife revealed a genome of a novel SFG Rickettsia species from I. tasmani ticks collected from koalas in New South Wales. Phylogenomic analysis confirmed this as a distinct species closely related to Rickettsia tasmaniensis fragments previously reported from Tasmanian devils. Additionally, we discovered four novel DNA Anellovirus species forming a new genus 'Sintorquevirus' and one Circovirus from likely vertebrate blood meals, revealing wildlife viral diversity. Species distribution modelling of I. tasmani for assessing Rickettsia risk revealed suitable habitat along Australia's eastern coastlines, with overlap between vector distribution, marsupial hosts, and population centres. This identified potential Candidatus R. tasmanensis exposure zones in coastal regions where positive samples originated, highlighting areas for surveillance.