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Viral ecology of Western Australian microbat communities

Prada, Diana (2020) Viral ecology of Western Australian microbat communities. PhD thesis, Murdoch University.

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Anthropogenic influences on the resilience of ecosystems, the species they support, and the interactions they govern, has resulted in an escalation of impacts across human health, their economies, and the persistence of native flora and fauna globally [1–3]. Emerging infectious diseases (EIDs) of animal origin (zoonoses) are a notable sequelae to globalisation, urban expansion, and habitat modification, which collectively bring together species and their attendant pathogens with alarming and increasing frequency. Examples include Nipah virus, which led to the culling of thousands of pigs in Malaysia in 1998 [4]; the emergence of highly pathogenic avian influenza, with continuous outbreaks causing important losses to local economies [5]; and infectious respiratory coronaviruses, which initially affected Asia in 2003 [6], the Middle East in 2012 [7], and finally the emerging global socioeconomic crisis from pandemic SARS-CoV-2 in 2019-2020 [8]. Equally, there are many examples of novel pathogens or shifting pathogen dynamics resulting in wildlife species facing extinction risks, including the impacts of chytrid fungus (Bactrachochytrium dendrobatidis) in frog populations worldwide [9], the astonishing mortality events associated with White-nose syndrome (WNS) in North American bats caused by the introduction of Pseudogymnoascus destructans to the continent [10], as well as the recent mortality events involving the Bellinger River snapping turtle (Myuchelys georgesi) in Australia due to an emerging nidovirus [11].

Pathogen transmission from wildlife into human systems (spillover) is not novel. However, the incidence of these events appears to be increasing [12,13] and propelled by human-mediated impacts on climate, degradation and loss of natural habitat, rapid global transportation, and the increased interactions between humans, livestock and wildlife at the ever-expanding urban and agricultural frontiers [14–16]. Combined, these processes create opportunities for un-natural contact between species that had been previously separated, thereby altering host-microbe dynamics that induce pathogenicity and facilitate spillover events, a key step in the emergence of disease agents [17].

The connection between wildlife, inherent microbial diversity, and the anthropogenic actions impacting this relationship, calls for multidisciplinary approaches that integrate host ecology, disease agent biology, and environmental factors to better understand transmission, persistence and distribution of pathogens in the landscape, as well as the fine scale processes that lead to disease emergence [18–20]. Examples of such effective multidisciplinary approaches applied to the management of wildlife disease agents include predictions of White-nose syndrome infection fronts inferred from bat movements [21,22], evaluation of rabies vaccination zones based on dispersal dynamics of raccoons in the USA [23], transmission dynamics and mechanisms of persistence of henipaviruses in Africa [24], and rabies outbreak predictions based on the dispersal patterns of its bat host in Perú [25].

Integrative approaches have widely been advocated for the study of bats and their role as reservoirs of viral agents of zoonotic potential, as an avenue to inform mitigation actions for EIDs [18–20]. Their wide distribution, ability to exploit human associated environments, ability to sustain a high viral diversity, and their involvement in recent EIDs such as Ebola virus, Nipah virus and infections respiratory coronaviruses [6–8,26,27], make this group of particular interest for such disease ecology research. Identifying the environmental, ecological and host processes that alter viral-bat relationships and may cascade into pathogen emergence has important applications for EID risk management, providing an evidence-base for EID prevention and preparedness activities. However these research frameworks generally require datasets across substantial spatiotemporal scales to draw meaningful conclusions, and as such have primarily focused on agents that emerged historically such as Nipah virus, Hendra virus, Marburg virus, paramyxoviruses of unknown zoonotic potential, and lyssaviruses [24,28–31].

In Australia, studies of bat viral disease dynamics have largely focused on the association of pteropid bats to Hendra virus and to a lesser extent Australian bat lyssavirus (ABLV) [32–35]. Such research is largely driven by public health concerns related to the high case fatality rate of Hendra virus outbreaks. Fundamental baseline data on the viral composition, dynamics and host associations of insectivorous bats in the country is limited to only a small number of studies [36,37], resulting in substantial knowledge gaps to inform public health policy or conservation management objectives.

In light of this lack of baseline data, this project aimed to address the knowledge gap around the viral and host dynamics of Australian insectivorous bats using a multidisciplinary approach. It integrates virology, molecular ecology, community ecology and epidemiology to describe the viral diversity and associations in microbats, small (< 20gr ) echolocating bats with an insectivorous diet, of the southwest of Western Australia.

The project is not motivated by any evidence suggestive of zoonotic threats to local human populations, although it does take an initial focus on viral families of zoonotic potential. It describes the viral characteristics of presumed healthy bat communities and discusses the results from an ecological perspective. In doing so, it aims to provide an overview of the natural viral associations within wild bat communities. The results will improve hypothesis generation for these poorly studied species and the viral agents they host, providing insights into species-viral interactions and therefore viral dynamics in the region, which may feed into policy from a public health as well as conservation perspective.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): College of Science, Health, Engineering and Education
Supervisor(s): O'Dea, Mark, Jackson, Bethany and Spencer, Peter
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