Charlotte Oskam

Advanced sequencing technologies require strict standards for DNA input and integrity. This study addresses the challenge of extracting high-quality, endogenous DNA from smaller arthropods with mixed DNA sources (arthropod, host, and microbiome), using Amblyomma triguttatum as a model organism. We evaluated three tissue types (Whole, Bisected, and Legs), three disruption methods (Undisrupted, Sliced, and liquid nitrogen bead Homogenisation), and two extraction kits (Qiagen DNeasy Blood & Tissue and MagAttract HMW) to optimise DNA yield, quality, and composition. The Qiagen MagAttract High Molecular Weight Kit significantly increased the proportion of large DNA fragments (20-48.5 kbp) by 11-fold compared to the Qiagen DNeasy Blood & Tissue Kit. Aggressive homogenisation methods produced the highest proportion of short fragments (97%, 1-10 kbp). Whole-Homogenised specimens yielded the highest DNA concentration (198 ng µL⁻¹), whereas Bisected-Undisrupted specimens achieved 146 ng µL⁻¹ with a greater proportion of large fragments (3.15%). Bacterial DNA content remained consistent across treatments. Our findings highlight the importance of selecting appropriate extraction methods to ensure optimal DNA quality for advanced sequencing applications. These results provide useful guidelines for optimising DNA extractions from smaller-bodied arthropods (~ 10-20 mg) and establish a framework for future studies to consider DNA quantity, quality, and composition.

Ticks are ectoparasites of major medical, veterinary and ecological importance, transmitting a wide range of pathogens to humans, companion animals and livestock. Understanding the population structure of ticks is essential for uncovering patterns of pathogen transmission, and population genetics provides a powerful method for this purpose. Tick population studies are uniquely challenging as their biology is shaped by complex interactions between hosts, microbiome and environmental factors. The choice of population genetic tools is crucial, as different methods offer varying levels of cost, throughput, resolution and accessibility, which can significantly influence the quality and scope of results. This review traces the evolution of molecular tools in tick population genetics, from early allozyme electrophoresis in the 1970s to advanced whole genome sequencing (WGS) technologies. It critically evaluates key methodologies, including allozyme electrophoresis, random amplified polymorphic DNA (RAPD), microsatellites (STRs), amplified fragment length polymorphisms (AFLP), sequence typing, restriction-site associated DNA sequencing (RADseq) and WGS, highlighting their strengths, limitations and applications. By offering a practical guide to these tools, this review helps researchers select the most appropriate methods for their studies and allows interpretation of results from older tools in the context of modern research. Sequence typing and RADseq currently provide the best balance of cost and practicality, while WGS has great potential once sequencing costs decline. This resource empowers researchers to make informed decisions, maximise the impact of their work and gain deeper insights into disease vector population structure.

Tick bites and tick-related diseases are on the rise. Diagnostic tests that identify well-characterised tick-borne pathogens (TBPs) possess limited capacity to address the causation of symptoms associated with poorly characterised tick-related illnesses, such as debilitating symptom complexes attributed to ticks (DSCATT) in Australia. Identification of local signals in tick-bitten skin that can be detected systemically in blood would have both clinical (diagnostic or prognostic) and research (mechanistic insight) utility, as a blood sample is more readily obtainable than tissue biopsies. We hypothesised that blood samples may reveal signals which reflect relevant local (tissue) events and that the time course of these signals may align with local pathophysiology. As a first step towards testing this hypothesis, we compared molecular signatures in skin biopsies taken from the tick-bite location of human participants, as published in our previous study, together with peripheral blood signatures obtained concurrently. This approach captures differentially expressed molecules across multiple omics datasets derived from peripheral blood (including cellular and cell-free transcriptomics, proteomics, metabolomics, and DNA methylation), and skin biopsies (spatial transcriptomics). Our original data revealed that extracellular matrix organisation and platelet degranulation pathways were upregulated in the skin within 72 h of a tick bite. The same signals appeared in blood, where they then remained elevated for three months, displaying longitudinally consistent alterations of biological functions. Despite the limited sample size, these data represent proof-of-concept that molecular events in the skin following a tick bite can be detectable systemically. This underscores the potential value of blood samples, akin to a liquid biopsy, to capture biomarkers reflecting local tissue processes.

Hybridisation between Australian dingoes and domestic dogs is a controversial area of interest and research. An ongoing canine sterilisation programme in rural and remote Western Australia provided an opportunity to assess the dingo ancestry of camp dogs and opportunities for hybridisation. Blood samples were collected from 345 individual community dogs at 21 locations. Dogs were screened using 23 microsatellite loci and ancestry percentage assigned using an iterative Bayesian assignment algorithm. A single individual was a dingo, 96% were domestic dogs and 3.5% were hybrids. Camp dog and dingo hybridisation in these areas is of little concern in terms of conserving dingo purity.

Tick-associated diseases present challenges due to tridirectional interactions among host-specific responses, tick toxins and salivary proteins as well as microbes. We aimed to uncover molecular mechanisms in tick-bitten skin samples (cases) and contralateral skin samples (controls) collected simultaneously from the same participants, using spatial transcriptomics. Cases and controls analysed using NanoString GeoMx Digital Spatial Profiler identified 274 upregulated and 840 downregulated differentially expressed genes (DEGs), revealing perturbations in keratinization and immune system regulation. Samples of skin biopsies taken within 72 h post tick-bite DEGs had changes in protein metabolism and viral infection pathways as compared to samples taken 3 months post tick-bite, which instead displayed significant perturbations in several epigenetic regulatory pathways, highlighting the temporal nature of the host response following tick bites. Within-individual signatures distinguished tick-bitten samples from controls and identified between-individual signatures, offering promise for future biomarker discovery to guide prognosis and therapy.

In this comprehensive review study, we addressed the challenge posed by ticks and tick-borne diseases (TBDs) with growing incidence affecting human and animal health worldwide. Data and perspectives were collected from different countries and regions worldwide, including America, Europe, Africa, Asia, and Oceania. The results updated the current situation with ticks and TBD and how it is perceived by society with information bias and gaps. The study reinforces the importance of multidisciplinary and international collaborations to advance in the surveillance, communication and proposed future directions to address these challenges.

Bovine anaemia caused by Theileria orientalis group (BATOG) causes significant production and economic losses in Australia's cattle industry. The pathogenic T. orientalis genotypes reported in Australian cattle are type 1 (Chitose) and type 2 (Ikeda). The present study aimed to determine the prevalence and distribution of T. orientalis genotypes in adult lactating cows in Western Australia (WA) dairy herds. A total of 100 whole blood samples from lactating cows from 10 farms were obtained and screened for T. orientalis using polymerase chain reaction (PCR). Sanger sequencing was subsequently used to characterise T. orientalis genotypes isolated from positive samples. A total of thirteen cows (13%; 95% CI: 7.1-21.2%) were positive for T. orientalis, and six out of ten farms (60%; 95% CI: 26.2-87.8%) housed at least one T. orientalis-positive cow. The distribution of T. orientalis was found to be wide and dense in the South west region of WA and the southern coast of WA. The predominant T. orientalis genotype identified was Ikeda (n = 11, 11%; 95% CI: 5.6-18.8%), while the Buffeli genotype was identified in WA for the first time, albeit at a low prevalence (n = 1, 1%; 95% CI: 0.0-5.4%). This study has provided useful epidemiological evidence on the prevalence and distribution of T. orientalis in adult lactating dairy cows in WA dairy farms, and on the importance of conducting widespread surveillance programs for the understanding of BATOG in WA.

Ticks (Acari: Ixodidae) are major disease vectors globally making it increasingly important to understand how altered vertebrate communities in urban areas shape tick population dynamics. In urban landscapes of Australia, little is known about which native and introduced small mammals maintain tick populations preventing host-targeted tick management and leading to human-wildlife conflict. Here, we determined (1) larval, nymphal, and adult tick burdens on host species and potential drivers, (2) the number of ticks supported by the different host populations, and (3) the proportion of medically significant tick species feeding on the different host species in Northern Sydney. We counted 3551 ticks on 241 mammals at 15 sites and found that long-nosed bandicoots (Perameles nasuta) hosted more ticks of all life stages than other small mammals but introduced black rats (Rattus rattus) were more abundant at most sites (33%-100%) and therefore important in supporting larval and nymphal ticks in our study areas. Black rats and bandicoots hosted a greater proportion of medically significant tick species including Ixodes holocyclus than other hosts. Our results show that an introduced human commensal contributes to maintaining urban tick populations and suggests ticks could be managed by controlling rat populations on urban fringes.

Tick-borne diseases (TBDs) are a growing global health concern. Despite extensive studies, ill-defined tick-associated pathologies remain with unknown aetiologies. Human immunological responses after tick bite, and inter-individual variations of immune-response phenotypes, are not well characterised. Current reductive experimental methodologies limit our understanding of more complex tick-associated illness, which results from the interactions between the host, tick, and microbes. An unbiased, systems-level integration of clinical metadata and biological host data - obtained via transcriptomics, proteomics, and metabolomics - offers to drive the data-informed generation of testable hypotheses in TBDs. Advanced computational tools have rendered meaningful analysis of such large data sets feasible. This review highlights the advantages of integrative system biology approaches as essential for understanding the complex pathobiology of TBDs.