A description of 'Australian Lyme disease' epidemiology and impact: an analysis of submissions to an Australian senate inquiry

The challenges of living with Debilitating Symptom Complexes Attributed to Ticks (DSCATT) - A qualitative study

OBJECTIVE

We sought to explore the lived experience of people with Debilitating Symptom Complexes Attributed to Ticks (DSCATT) to inform the development of a potential treatment intervention.

METHODS

We conducted one-to-one in-depth, semi-structured interviews with 13 people living in Australia affected by DSCATT. Interviews were transcribed and analysed using thematic analysis.

RESULTS

Although participants attributed the origin of their illness to tick bites, not all were adamant they had Lyme disease. Negative experiences in conventional healthcare were marked and were reported to exacerbate the impact of the illness and affect mental health. Further, these negative experiences propelled participants to seek unapproved treatments (by Australian standards). The desire for the illness to be acknowledged and causative agents identified was pronounced among the participant group.

CONCLUSIONS

Individuals with DSCATT experience significant challenges amid a contentious healthcare landscape surrounding chronic symptoms attributed to ticks in Australia. Our findings suggest the need for empathetic, supportive and patient-centred treatments for this cohort.

IMPLICATIONS FOR PUBLIC HEALTH

DSCATT results in a considerable burden across multiple domains for those affected. Negative experiences with healthcare exacerbate the suffering of people with DSCATT in Australia. New approaches that acknowledge the illness experience of people with DSCATT, alongside evidence-based treatments that encompass biopsychosocial models of care, are needed to tackle this debilitating condition.

Epidemiology of Lyme Disease

Lyme disease is the most common vector-borne illness in North America and Europe. The etiologic agent, Borrelia burgdorferi sensu lato, is transmitted to humans by certain species of Ixodes ticks, which are found widely in temperate regions of the Northern hemisphere. Clinical features are diverse but death is rare. The risk of human infection is determined by the distribution and abundance of vector ticks, ecologic factors influencing tick infection rates, and human behaviors that promote tick bite. Rates of infection are highest among children aged 5 to 15 years and adults aged more than 50 years. In the northeastern United States where disease is most common, exposure occurs primarily in areas immediately around the home. Knowledge of disease epidemiology is important for patient management and proper diagnosis.

Metatranscriptomic profiling reveals diverse tick-borne bacteria, protozoans and viruses in ticks and wildlife from Australia

Tick-borne zoonoses are emerging globally due to changes in climate and land use. While the zoonotic threats associated with ticks are well studied elsewhere, in Australia, the diversity of potentially zoonotic agents carried by ticks and their significance to human and animal health is not sufficiently understood. To this end, we used untargeted metatranscriptomics to audit the prokaryotic, eukaryotic and viral biomes of questing ticks and wildlife blood samples from two urban and rural sites in New South Wales, Australia. Ixodes holocyclus and Haemaphysalis bancrofti were the main tick species collected, and blood samples from Rattus rattus, Rattus fuscipes, Perameles nasuta and Trichosurus vulpecula were also collected and screened for tick-borne microorganisms using metatranscriptomics followed by conventional targeted PCR to identify important microbial taxa to the species level. Our analyses identified 32 unique tick-borne taxa, including 10 novel putative species. Overall, a wide range of tick-borne microorganisms were found in questing ticks including haemoprotozoa such as Babesia, Theileria, Hepatozoon and Trypanosoma spp., bacteria such as Borrelia, Rickettsia, Ehrlichia, Neoehrlichia and Anaplasma spp., and numerous viral taxa including Reoviridiae (including two coltiviruses) and a novel Flaviviridae-like jingmenvirus. Of note, a novel hard tick-borne relapsing fever Borrelia sp. was identified in questing H. bancrofti ticks which is closely related to, but distinct from, cervid-associated Borrelia spp. found throughout Asia. Notably, all tick-borne microorganisms were phylogenetically unique compared to their relatives found outside Australia, and no foreign tick-borne human pathogens such as Borrelia burgdorferi s.l. or Babesia microti were found. This work adds to the growing literature demonstrating that Australian ticks harbour a unique and endemic microbial fauna, including potentially zoonotic agents which should be further studied to determine their relative risk to human and animal health.

Characterising DSCATT: A case series of Australian patients with debilitating symptom complexes attributed to ticks

OBJECTIVES(S)

To characterise the clinical profile, aetiology and treatment responsiveness of 'Australian Lyme', or Debilitating Symptom Complexes Attributed to Ticks.

METHODS

Single-centre retrospective case analysis of patients referred to the Infectious Diseases Unit at Austin Health - a tertiary health service in Heidelberg, Australia - between 2014 and 2020 for investigation and treatment of suspected Debilitating Symptom Complexes Attributed to Ticks. Patients were included if they had debilitating symptoms suggested by either themselves or the referring clinician as being attributed to ticks.

RESULTS

Twenty-nine Debilitating Symptom Complexes Attributed to Ticks cases were included in the analysis. Other than Lyme disease (83%), the most common prior medical diagnoses were Epstein-Barr virus (38%), chronic fatigue syndrome (28%) and fibromyalgia (24%). Prior histories of anxiety (48%) and depression (41%) were common. The most frequently reported symptoms included fatigue (83%), headache (72%) and arthralgia (69%). National Association of Testing Authorities/Royal College of Pathologists of Australasia-accredited serology was not diagnostic of acute infective causes, including Lyme disease, in any patient. Of 25 cases with available data, 23 (92%) had previously been prescribed antimicrobials, with 53% reporting benefit from them. The most common diagnoses made by our hospital were chronic fatigue syndrome (31%), migraines (28%) and fibromyalgia (21%). Only one patient's symptoms were not accounted for by other diagnoses.

CONCLUSION

This is the first case series of patients with Debilitating Symptom Complexes Attributed to Ticks. They had high rates of other medically unexplained syndromes, and no evidence of acute Lyme disease, or any common organic disease process. Debilitating Symptom Complexes Attributed to Ticks remains medically unexplained, and may therefore be due to an as yet unidentified cause, or may be considered a medically unexplained syndrome similar to conditions such as chronic fatigue syndrome.

Illuminating the bacterial microbiome of Australian ticks with 16S and Rickettsia-specific next-generation sequencing

Next-generation sequencing (NGS) studies show that mosquito and tick microbiomes influence the transmission of pathogens, opening new avenues for vector-borne pathogen control. Recent microbiological studies of Australian ticks highlight fundamental knowledge gaps of tick-borne agents. This investigation explored the composition, diversity and prevalence of bacteria in Australian ticks (n = 655) from companion animals (dogs, cats and horses). Bacterial 16S NGS was used to identify most bacterial taxa and a Rickettsia-specific NGS assay was developed to identify Rickettsia species that were indistinguishable at the V1-2 regions of 16S. Sanger sequencing of near full-length 16S was used to confirm whether species detected by 16S NGS were novel. The haemotropic bacterial pathogens Anaplasma platys, Bartonella clarridgeiae, “Candidatus Mycoplasma haematoparvum” and Coxiella burnetii were identified in Rhipicephalus sanguineus (s.l.) from Queensland (QLD), Western Australia, the Northern Territory (NT), and South Australia, Ixodes holocyclus from QLD, Rh. sanguineus (s.l.) from the NT, and I. holocyclus from QLD, respectively. Analysis of the control data showed that cross-talk compromises the detection of rare species as filtering thresholds for less abundant sequences had to be applied to mitigate false positives. A comparison of the taxonomic assignments made with 16S sequence databases revealed inconsistencies. The Rickettsia-specific citrate synthase gene NGS assay enabled the identification of Rickettsia co-infections with potentially novel species and genotypes most similar (97.9–99.1%) to Rickettsia raoultii and Rickettsia gravesii. “Candidatus Rickettsia jingxinensis” was identified for the first time in Australia. Phylogenetic analysis of near full-length 16S sequences confirmed a novel Coxiellaceae genus and species, two novel Francisella species, and two novel Francisella genotypes. Cross-talk raises concerns for the MiSeq platform as a diagnostic tool for clinical samples. This study provides recommendations for adjustments to Illuminaʼs 16S metagenomic sequencing protocol that help track and reduce cross-talk from cross-contamination during library preparation. The inconsistencies in taxonomic assignment emphasise the need for curated and quality-checked sequence databases.

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Bacterial pathogens identified in ticks from companion animals with 16S NGS.

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Sanger sequencing confirmed novel Coxiellaceae gen. sp. and Francisella.

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“Candidatus Rickettsia jingxinensis” was identified with Rickettsia-specific NGS.

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Comparison of taxonomic assignments in 16S sequence databases revealed errors.

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Modifications to the 16S metagenomic library protocol (Illumina) are provided.

Screening for Rickettsia, Coxiella and Borrelia Species in Ticks from Queensland, Australia

Tick bites in Australia are linked to the transmission of a variety of infectious diseases in humans, livestock and wildlife. Despite this recognition, little is currently known about the variety of potential pathogens that are carried and transmitted by Australian ticks. In this study, we attempted to expand knowledge of Australian tick-borne bacterial pathogens by analyzing various tick species from the state of Queensland for potential human pathogens belonging to the Rickettsia, Coxiella and Borrelia genera. A total of 203 ticks, comprising of four genera and nine different tick species, were screened by specific qPCR assays. An overall Rickettsia qPCR positivity of 6.4% (13/203) was detected with rickettsial DNA found in four tick species (Ixodes holocyclus, I. tasmani, Amblyommatriguttatum, and Haemaphysalis longicornis). Amplification and analysis of several rickettsial genes from rickettsial qPCR positive samples identified sequences closely related to but genetically distinct from several previously described cultured and uncultured rickettsial species in the Rickettsia spotted fever subgroup. No ticks were positive for either Coxiella or Borrelia DNA. This work suggests that a further diversity of rickettsiae remain to be described in Australian ticks with the full importance of these bacteria to human and animal health yet to be elucidated.