Ecology of vector-borne disease in Australia
Date
2025
Authors
Atkinson, Peter Jonathon
Editors
Advisors
Caraguel, Charles
Nielsen, Torben
O'Handley, Ryan
Nielsen, Torben
O'Handley, Ryan
Journal Title
Journal ISSN
Volume Title
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Thesis
Citation
Statement of Responsibility
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Abstract
Canine heartworm, or Dirofilaria immitis, poses a risk to animal welfare due to its ability to cause pathological changes in infected hosts, possibly resulting in heart failure and death. It circulates in both domestic and wild canids, is an accidental infection of felids and is zoonotic in areas with high transmission pressure. Management of heartworm has become a focus of veterinary practice in Australia, Europe and North America, following guidelines for the prevention, diagnosis and treatment of infection produced by numerous industry-funded bodies. Despite these guidelines, many domestic dogs still become infected, reflecting a general unsuitability of the recommendations presented. Critical appraisal of the Australian Heartworm Advisory Panel’s (AHAP) guidelines for prevention and diagnosis of heartworm identified noteworthy omissions of their assessment to risk of disease and interpretation of diagnostic test results. We generated the required evidence for their revision, ultimately aiming to improve the management of heartworm disease in Australia. Notably, since the start of this project, the AHAP guidelines for heartworm prevention are no longer available in the public domain, due to their obsolescence and recognised requirement for review. Initially, we outline key aspects of the biology of D. immitis, including its lifecycle and pathophysiology of disease, as well as details about how infection is diagnosed, prevented and treated in veterinary practice. We then investigate the impact climate has on its transmission across Australia to establish an understanding of infection risk, finding significantly lower prevalence in cooler climates, and identify a possible temperature-dependent threshold for D. immitis hyperendemicity. We then explore how climate change may impact global heartworm epidemiology, highlighting that future changes are likely to be in more densely populated areas and thus be more important than past changes. Next, we assess the accuracy of commonly used diagnostic tests, revealing limitations in both the quantity and quality of current evidence. This prompted us to perform a new diagnostic evaluation study, addressing key gaps and deficiencies previously identified. Recognising the need for accessible tools, we finally present an online dashboard to visualise real-time transmission risk data, enabling veterinarians to assess the local risk of heartworm disease, and therefore target preventative and diagnostic test application. In this thesis, we confirm the risk of heartworm infection, and therefore disease, is variable across Australia. We advocate for a paradigm shift in heartworm management – from a uniform, year-round prevention strategy for all dogs in Australia and vague diagnostic test use, to a targeted approach reflecting how local transmission dynamics impact risk of heartworm disease. Our recommendations suggest tailoring prevention and diagnostic e`orts to individuals at risk of developing heartworm disease, considering the contribution of hyperendemicity, choice of preventative, owner compliance, risk-tolerance and the environment. Overall, they ensure e`orts to prevent and diagnose infections are clinically relevant and resource e`icient. This research provides the foundation for revising Australia’s heartworm management guidelines, whilst also having relevance for heartworm control in other regions with variable transmission risk.
School/Discipline
School of Animal and Veterinary Sciences
Dissertation Note
Thesis (Ph.D.) -- University of Adelaide, School of Animal and Veterinary Sciences, 2025
Provenance
This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legals