The bacterial biome of ticks and their wildlife hosts at the urban–wildland interface

<jats:p>Advances in sequencing technologies have revealed the complex and diverse microbial communities present in ticks (Ixodida). As obligate blood-feeding arthropods, ticks are responsible for a number of infectious diseases that can affect humans, livestock, domestic animals and wildlife. While cases of human tick-borne diseases continue to increase in the northern hemisphere, there has been relatively little recognition of zoonotic tick-borne pathogens in Australia. Over the past 5 years, studies using high-throughput sequencing technologies have shown that Australian ticks harbour unique and diverse bacterial communities. In the present study, free-ranging wildlife (<jats:italic>n</jats:italic>=203), representing ten mammal species, were sampled from urban and peri-urban areas in New South Wales (NSW), Queensland (QLD) and Western Australia (WA). Bacterial metabarcoding targeting the 16S rRNA locus was used to characterize the microbiomes of three sample types collected from wildlife: blood, ticks and tissue samples. Further sequence information was obtained for selected taxa of interest. Six tick species were identified from wildlife: <jats:italic>Amblyomma triguttatum</jats:italic>, <jats:italic>Ixodes antechini</jats:italic>, <jats:italic>Ixodes australiensis</jats:italic>, <jats:italic>Ixodes holocyclus</jats:italic>, <jats:italic>Ixodes tasmani</jats:italic> and <jats:italic>Ixodes trichosuri</jats:italic>. Bacterial 16S rRNA metabarcoding was performed on 536 samples and 65 controls, generating over 100 million sequences. Alpha diversity was significantly different between the three sample types, with tissue samples displaying the highest alpha diversity (<jats:italic>P</jats:italic><0.001). <jats:italic> <jats:named-content content-type="phylum"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.808" xlink:type="simple">Proteobacteria</jats:ext-link> </jats:named-content> </jats:italic> was the most abundant taxon identified across all sample types (37.3 %). Beta diversity analysis and ordination revealed little overlap between the three sample types (<jats:italic>P</jats:italic><0.001). Taxa of interest included <jats:italic> <jats:named-content content-type="family"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.978" xlink:type="simple">Anaplasmataceae</jats:ext-link> </jats:named-content> </jats:italic>, <jats:italic> <jats:named-content content-type="genus"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.1357" xlink:type="simple">Bartonella</jats:ext-link> </jats:named-content> </jats:italic>, <jats:italic> <jats:named-content content-type="genus"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.7813" xlink:type="simple">Borrelia</jats:ext-link> </jats:named-content> </jats:italic>, <jats:italic> <jats:named-content content-type="family"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.2389" xlink:type="simple">Coxiellaceae</jats:ext-link> </jats:named-content> </jats:italic>, <jats:italic> <jats:named-content content-type="genus"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.2304" xlink:type="simple">Francisella</jats:ext-link> </jats:named-content> </jats:italic>, <jats:italic> <jats:named-content content-type="genus"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.14712" xlink:type="simple">Midichloria</jats:ext-link> </jats:named-content> </jats:italic>, <jats:italic> <jats:named-content content-type="genus"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.4615" xlink:type="simple">Mycoplasma</jats:ext-link> </jats:named-content> </jats:italic> and <jats:italic> <jats:named-content content-type="genus"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.952" xlink:type="simple">Rickettsia</jats:ext-link> </jats:named-content> </jats:italic>. <jats:italic> <jats:named-content content-type="family"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.978" xlink:type="simple">Anaplasmataceae</jats:ext-link> </jats:named-content> </jats:italic> bacteria were detected in 17.7% (95/536) of samples and included <jats:italic> <jats:named-content content-type="genus"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.979" xlink:type="simple">Anaplasma</jats:ext-link> </jats:named-content> </jats:italic>, <jats:italic> <jats:named-content content-type="genus"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.991" xlink:type="simple">Ehrlichia</jats:ext-link> </jats:named-content> </jats:italic> and <jats:italic> <jats:named-content content-type="genus"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.8987" xlink:type="simple">Neoehrlichia</jats:ext-link> </jats:named-content> </jats:italic> species. In samples from NSW, ‘<jats:italic>Ca</jats:italic>. Neoehrlichia australis’, ‘<jats:italic>Ca</jats:italic>. Neoehrlichia arcana’, <jats:italic> <jats:named-content content-type="genus"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.8987" xlink:type="simple">Neoehrlichia</jats:ext-link> </jats:named-content> </jats:italic> sp. and <jats:italic> <jats:named-content content-type="genus"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.991" xlink:type="simple">Ehrlichia</jats:ext-link> </jats:named-content> </jats:italic> sp. were identified. A putative novel <jats:italic> <jats:named-content content-type="genus"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.991" xlink:type="simple">Ehrlichia</jats:ext-link> </jats:named-content> </jats:italic> sp. was identified from WA and <jats:italic> <jats:named-content content-type="species"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.986" xlink:type="simple">Anaplasma platys</jats:ext-link> </jats:named-content> </jats:italic> was identified from QLD. Nine rodent tissue samples were positive for a novel <jats:italic> <jats:named-content content-type="genus"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.7813" xlink:type="simple">Borrelia</jats:ext-link> </jats:named-content> </jats:italic> sp. that formed a phylogenetically distinct clade separate from the Lyme <jats:italic> <jats:named-content content-type="genus"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.7813" xlink:type="simple">Borrelia</jats:ext-link> </jats:named-content> </jats:italic> and relapsing fever groups. This novel clade included recently identified rodent-associated <jats:italic> <jats:named-content content-type="genus"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.7813" xlink:type="simple">Borrelia</jats:ext-link> </jats:named-content> </jats:italic> genotypes, which were described from Spain and North America. <jats:italic> <jats:named-content content-type="genus"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.1357" xlink:type="simple">Bartonella</jats:ext-link> </jats:named-content> </jats:italic> was identified in 12.9% (69/536) of samples. Over half of these positive samples were obtained from black rats (<jats:italic>Rattus rattus</jats:italic>), and the dominant bacterial species identified were <jats:italic> <jats:named-content content-type="species"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.14911" xlink:type="simple">Bartonella coopersplainsensis</jats:ext-link> </jats:named-content> </jats:italic> and <jats:italic> <jats:named-content content-type="species"> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.14910" xlink:type="simple">Bartonella queenslandensis</jats:ext-link> </jats:named-content> </jats:italic>. The results from the present study show the value of using unbiased high-throughput sequencing applied to samples collected from wildlife. In addition to understanding the sylvatic cycle of known vector-associated pathogens, surveillance work is important to ensure preparedness for potential zoonotic spillover events.</jats:p>