Biology subjects

Mahar, J. E.

Publications and source records attributed to Mahar, J. E..

12 recordsLinked to original sources

bioRxiv2026

First detected incursions of avian influenza H5N1 clade 2.3.4.4b into mainland Australia from the Southern Ocean

High pathogenicity avian influenza H5N1 clade 2.3.4.4b has caused a panzootic of devastating impact to poultry and wildlife globally. The Australian continent and broader Oceania until recently remained the last major region without confirmed detections. Here we report the first H5N1 clade 2.3.4.4b detections from two live seabirds - a brown skua and a southern giant petrel - found on the south coast of Western Australia in June 2026. Virus genome sequencing showed that both viruses were most closely related to H5N1 viruses detected recently on sub-Antarctic islands in the Southern Indian Ocean. In time-calibrated phylogeographic analyses, both viruses sampled in Western Australia clustered with viruses from Heard Island, a sub-Antarctic external territory of Australia. Ancestral location reconstruction also identified Heard Island as the most probable source location, although unsampled intermediate locations cannot be excluded. The two Western Australian detections were estimated to be independent incursions from Heard Island, rather than local transmission on mainland Australia. There was no evidence of reassortment with endemic avian influenza viruses in Australia, and both virus sequences retained key avian-like genetic markers and lacked known substitutions for reduced antiviral susceptibility. These detections revealed a Southern Ocean pathway of recurrent H5N1 incursions into Australia, highlighting the risk of potential establishment on the mainland and the need for heightened surveillance and rapid, nationally-coordinated, virus genomic characterisation.

microbiology↗

bioRxiv2024

Genomic and phylogenetic features of the Picobirnaviridae suggest microbial rather than animal hosts

The RNA virus family Picobirnaviridae has traditionally been associated with the gastrointestinal systems of terrestrial mammals and birds, with the majority of viruses detected in animal stool samples. Metatranscriptomic studies of vertebrates, invertebrates, microbial communities, and environmental samples have resulted in an enormous expansion of the genomic and phylogenetic diversity of this family. Yet picobirnaviruses remain poorly classified, with only one genus and three species formally ratified by the International Committee of Virus Taxonomy. Additionally, an inability to culture picobirnaviruses in a laboratory setting or isolate them in animal tissue samples, combined with the presence of bacterial genetic motifs in their genomes, suggests these viruses may represent RNA bacteriophage rather than being associated with animal infection. Utilising a data set of 2,286 picobirnaviruses sourced from mammals, birds, reptiles, fish, invertebrates, microbial communities, and environmental samples, we identified seven consistent phylogenetic clusters likely representing picobirnavirus genera that we tentatively name Alpha-, Beta-, Gamma-, Delta-, Epsilon-, Zeta-, and Etapicobirnavirus. A statistical analysis of topological congruence between virus-host phylogenies revealed more frequent cross-species transmission than any other RNA virus family. In addition, bacterial ribosomal binding site motifs were more enriched in picobirnavirus genomes than in the two groups of established RNA bacteriophage - the Leviviricetes and Cystoviridae. Overall, our findings support the hypothesis that the Picobirnaviridae have bacterial hosts and provide a lower-level taxonomic classification for this highly diverse and ubiquitous family of RNA viruses.

microbiology↗

bioRxiv2024

The diverse viromes of Australian lizards are shaped by host taxonomy and habitat

Lizards inhabit diverse ecologies and evolutionary histories and hence represent a promising group to explore how hosts shape virome structure and virus evolution. Yet little is known about the viromes of these animals. In Australia, squamates (lizards and snakes) comprise the most diverse order of vertebrates, and Australia hosts the highest diversity of lizards globally, with the greatest breadth of habitat use. We used meta-transcriptomic sequencing to determine the virome of nine co-distributed, tropical lizard species from three taxonomic families in Australia and analyzed these data to identify host traits associated with viral abundance and diversity. We show that lizards carry a large diversity of viruses, identifying more than 30 novel, highly divergent vertebrate-associated viruses. These viruses were from nine viral families, including several that contain well known pathogens, such as the Flaviviridae, Picornaviridae, Bornaviridae, Iridoviridae and Rhabdoviridae. Members of the Flaviviridae were particularly abundant across species sampled here, largely belonging to the genus Hepacivirus: 14 novel Hepaciviruses were identified, broadening the known diversity of this group and better defining its evolution by uncovering new reptilian clades. The evolutionary histories of the viruses studied here frequently aligned with the biogeographic and phylogenetic histories of the hosts, indicating that exogenous viruses may help infer host evolutionary history if sampling is strategic and sampling density high enough. Notably, analysis of alpha and beta diversity revealed that virome composition and richness was shaped by host taxonomy, habitat and range size. In sum, we identified a diverse range of reptile viruses that broadly contributes to our understanding of virus-host ecology and evolution.

microbiology↗

bioRxiv2023

Australian terrestrial environments harbour extensive RNA virus diversity

Australia is home to a diverse range of unique native fauna and flora. To address whether Australian ecosystems also harbour unique viruses, we performed meta-transcriptomic sequencing of 16 farmland and sediment samples taken from the east and west coasts of Australia. We identified 2,562 putatively novel viruses across 15 orders, the vast majority of which belonged to the microbe-associated phylum Lenarviricota. In many orders, the novel viruses identified here comprised entirely new clades, such as the Nodamuvirales and Ghabrivirales. Novel viruses also fell between established genera or families, such as in the Cystoviridae and Picornavirales, while highly divergent lineages were identified in the Martellivirales and Ghabrivirales. Viral abundance and alpha diversity were influenced by sampling site, soil type and land use, but not by depth from the surface. In sum, Australian soils and sediments are home to remarkable viral diversity, reflecting the biodiversity of local fauna and flora.

microbiology↗

bioRxiv2023

Divergent hepaciviruses, chuvirus and deltaviruses in Australian marsupial carnivores (Dasyurids) identified through transcriptome mining

Although Australian marsupials are characterised by unique biology and geographic isolation, little is known about the viruses present in these iconic wildlife species. The Dasyuromorphia are an order of marsupial carnivores found only in Australia that include both the extinct Tasmanian tiger (Thylacine) and the highly threatened Tasmanian devil. Several other members of the order are similarly under threat of extinction due to habitat loss, hunting, disease, and competition and predation by introduced species such as feral cats. We utilised publicly available RNA-seq data from the NCBI Sequence Read Archive (SRA) database to document the viral diversity within four Dasyuromorphia species. Accordingly, we identified 15 novel virus species from five DNA virus families (Adenoviridae, Anelloviridae, Herpesviridae, Papillomaviridae and Polyomaviridae) and three RNA virus taxa: the order Jingchuvirales, the genus Hepacivirus, and the delta-like virus group. Of particular note was the identification of a marsupial specific clade of delta-like viruses that may indicate an association of deltaviruses and with marsupial species dating back to their origin some 160 million years ago. In addition, we identified a highly divergent hepacivirus in a numbat liver transcriptome that falls outside of the larger mammalian clade, as well as the first detection of the Jingchuvirales in a mammalian host - a chu-like virus in Tasmanian devils - thereby expanding the host range beyond invertebrates and ectothermic vertebrates. As many of these Dasyuromorphia species are currently being used in translocation efforts to reseed populations across Australia, understanding their virome is of key importance to prevent the spread of viruses to naive populations.

microbiology↗

bioRxiv2022

Gammaretroviruses, novel viruses and pathogenic bacteria in Australian bats with neurological signs, pneumonia and skin lesions

More than 70 bat species are found in mainland Australia, including five species of megabat from a single genus (family Pteropodidae) and more than 65 species representing six families of microbats. The conservation status of these animals varies from least concern to endangered. Research directed at evaluating the impact of microorganisms on bat health has been generally restricted to surveillance for specific pathogens. While most of the current bat virome studies focus on sampling apparently healthy individuals, little is known about the infectome of diseased bats. We performed traditional diagnostic techniques and metatranscriptomic sequencing on tissue samples from 43 individual bats, comprising three flying fox and two microbat species experiencing a range of disease syndromes, including mass mortality, neurological signs, pneumonia and skin lesions. We identified reads from four pathogenic bacteria and two pathogenic fungi, including Pseudomonas aeruginosa in lung samples from flying foxes with peracute pneumonia, and with dermatitis. Of note, we identified the recently discovered Hervey pteropid gammaretrovirus, with evidence of replication consistent with an exogenous virus, in a bat with lymphoid leukemia. In addition, one novel picornavirus, at least three novel astroviruses and bat pegiviruses were identified. We suggest that the most likely cause of peracute lung disease was Pseudomonas aeruginosa, while we suspect Hervey pteropid gammaretrovirus was associated with lymphoid leukemia. It is possible that any of the novel astroviruses could have contributed to the presentation of skin lesions in individual microbats. This study highlights the importance of studying the role of microorganisms in bat health and conservation. IMPORTANCEBats have been implicated as reservoir hosts for zoonotic disease of concern, however, the burden of microorganism including viruses on bat health and disease is understudied. Here we incorporated veterinary diagnostics and RNA sequencing to identify the presence of microbes and viruses with possible pathogenic status in Australian bats with varying disease presentations. These techniques were able to effectively identify and describe several pathogenic species of bacteria and fungi in addition to known and novel viruses. This study emphasises the importance of screening pathogens in cases of bat mortality for the conservation of this diverse order.

microbiology↗

bioRxiv2022

Faecal virome of the Australian grey-headed flying fox from urban/suburban environments contains novel coronaviruses, retroviruses and sapoviruses

Bats are important reservoirs for viruses of public health and veterinary concern. Virus studies in Australian bats usually target the families Paramyxoviridae, Coronaviridae and Rhabdoviridae, with little known about their overall virome composition. We used metatranscriptomic sequencing to characterise the faecal virome of grey-headed flying foxes from three colonies in urban/suburban locations from two Australian states. We identified viruses from three mammalian-infecting (Coronaviridae, Caliciviridae, Retroviridae) and one possible mammalian-infecting (Birnaviridae) family. Of particular interest were a novel bat betacoronavirus (subgenus Nobecovirus) and a novel bat sapovirus (Caliciviridae), the first identified in Australian bats, as well as a potentially exogenous retrovirus. The novel betacoronavirus was detected in two sampling locations 1,375 km apart and falls in a viral lineage likely with a long association with bats. This study highlights the utility of unbiased sequencing of faecal samples for identifying novel viruses and revealing broad-scale patterns of virus ecology and evolution.

microbiology↗

bioRxiv2021

Frequent intergenotypic recombination between the non-structural and structural genes is a major driver of epidemiological fitness in caliciviruses

The diversity of lagoviruses (Caliciviridae) in Australia has increased considerably. By the end of 2017, five variants from three viral genotypes were present in populations of Australian rabbits, while prior to 2014 only two variants were known. To understand the interactions between these lagovirus variants we monitored their geographical distribution and relative incidence over time through a landscape-scale competition study, and from this, revealed potential drivers of epidemiological fitness. Within three years of the arrival of GI.1bP-GI.2 (RHDV2) into Australia, we observed the emergence of two novel recombinant lagovirus variants, GI.4eP-GI.2 (4e-recombinant) in New South Wales and GI.4cP-GI.2 (4c-recombinant) in Victoria. Although both novel recombinants contain the non-structural genes from benign, rabbit-specific, enterotropic viruses, these variants were recovered from the livers of both rabbits and hares that had died acutely. This suggests that determinants of host and tissue tropism for lagoviruses are associated with the structural genes, and that tropism is intricately connected with pathogenicity. Phylogenetic analyses demonstrated that the 4c-recombinant emerged independently on multiple occasions, with five distinct lineages observed. Both new recombinant variants replaced the previous dominant parental RHDV2 in their respective geographical areas, despite sharing an identical or near-identical (i.e., single amino acid change) major capsid protein with the parental virus. This suggests that epidemiological fitness of these recombinants was not driven by antigenic variation in the capsid, implicating the non-structural genes as key drivers of epidemiological fitness. Molecular clock estimates place the GI4.e recombination event in early to mid-2015, while the five GI.4c recombination events occurred from late 2015 through to early 2017. The emergence of at least six viable recombinant variants within a two-year period highlights an unprecedented frequency of these events, detectable only due to intensive surveillance, and demonstrates the importance of recombination in lagovirus evolution.

microbiology↗

bioRxiv2020

Red fox viromes across an urban-rural gradient

The Red fox (Vulpes vulpes) has established large populations in Australias urban and rural areas since its introduction following European settlement. Foxes cryptic and highly adaptable nature allows them to invade cities and live among humans while remaining largely unnoticed. Urban living and access to anthropogenic food resources also influences fox ecology. Urban foxes grow larger, live at higher densities and are more social than their rural counterparts. These ecological changes in urban red foxes are likely to impact the pathogens that they harbour, and foxes could pose a disease risk to humans and other species that share these urban spaces. To assess this possibility, we used a meta-transcriptomic approach to characterise the viromes of urban and rural foxes across the Greater Sydney region in Australia. Urban and rural foxes differed significantly in virome composition, with rural foxes harbouring a greater abundance of viruses compared to their urban counterparts. In contrast, urban fox viromes comprised a greater diversity of viruses compared to rural foxes. We identified nine potentially novel vertebrate-associated viruses in both urban and rural foxes, some of which are related to viruses associated with disease in domestic species and humans. These included members of the Astroviridae, Picobirnaviridae, Hepeviridae and Picornaviridae as well as rabbit haemorrhagic disease virus-2 (RHDV2). This study sheds light on the viruses carried by urban and rural foxes and emphasises the need for greater genomic surveillance of foxes and other invasive species at the human-wildlife interface. ImportanceUrbanisation of wild environments is increasing as human populations continue to expand. Remnant pockets of natural environments and other green spaces in urban landscapes provide invasive wildlife such as red foxes with refuges within urban areas, where they thrive on the food resources provisioned by humans. Close contact between humans, domestic species and foxes likely increases the risk of novel pathogen emergence. Indeed, the vast majority of emerging infectious diseases in humans originate in wild animals. Here, we explored potential differences in viromes between urban fox invaders and their rural counterparts. Viromes of foxes and their ectoparasites comprise a diversity of viruses including those from the Astroviridae, Picobirnaviridae, Hepeviridae, Caliciviridae and Picornaviridae. Microbial surveillance in foxes and other urban wildlife is vital for monitoring viral emergence and for the prevention of infectious diseases.

microbiology↗

bioRxiv2019

Limited overlap in RNA virome composition among rabbits and their ectoparasites reveals barriers to virus transmission

Ectoparasites play an important role in virus transmission among vertebrates. However, little is known about the extent and composition of viruses that pass between invertebrates and vertebrates. In Australia, flies and fleas support the mechanical transmission of viral biological controls against wild rabbits - rabbit haemorrhagic disease virus (RHDV) and myxoma virus. We compared virome structure and composition in rabbits and these associated ectoparasites, sequencing total RNA from multiple tissues and gut contents of wild rabbits, fleas collected from these rabbits, and flies trapped sympatrically. Meta-transcriptomic analyses identified 50 novel viruses from multiple RNA virus families. Rabbits and their ectoparasites were characterised by markedly different viromes: although viral contigs from six virus families/groups were found in both rabbits and ectoparasites, none were vertebrate-associated. A novel calicivirus and picornavirus detected in rabbit caecal content were vertebrate-specific: the newly detected calicivirus was distinct from known rabbit caliciviruses, while the novel picornavirus clustered with the Sapeloviruses. Several Picobirnaviridae were also identified, falling in diverse phylogenetic positions suggestive of an association with co-infecting bacteria. The remaining viruses found in rabbits, and all those from ectoparasites, were likely associated with invertebrates, plants and co-infecting endosymbionts. While no full genomes of vertebrate-associated viruses were detected in ectoparasites, suggestive of major barriers to biological transmission with active replication, small numbers of reads from rabbit astrovirus, RHDV and other lagoviruses were present in flies. This supports the role of flies in the mechanical transmission of RHDV and implies that they may assist the spread of astroviruses.

microbiology↗

bioRxiv2018

The discovery of three new hare lagoviruses reveals unexplored viral diversity in this genus

Our knowledge of mammalian viruses has been strongly skewed toward those that cause disease in humans and animals. However, recent metagenomic studies indicate that most apparently healthy organisms carry viruses, and that these seemingly benign viruses may comprise the bulk of virus diversity. The bias toward studying viruses associated with overt disease is apparent in the lagoviruses (family Caliciviridae) that infect rabbits and hares: although most attention has been directed toward the highly pathogenic members of this genus - the rabbit haemorrhagic disease virus and European brown hare syndrome virus - a number of benign lagoviruses have also been identified. To determine whether wild European brown hares in Australia might also carry undetected benign viruses, we used a meta-transcriptomics approach to explore the gut and liver RNA viromes of these invasive animals. This led to the discovery of three new lagoviruses. While one of the three viruses was only detected in a single hare, the other two viruses were detected in 20% of all hares tested. All three viruses were most closely related to other hare lagoviruses, but were highly distinct from both known viruses and each other. We also found evidence for complex recombination events in these viruses, which, combined with their phylogenetic distribution, suggests that there is likely extensive unsampled diversity in this genus. Additional metagenomic studies of hares and other species are clearly needed to fill gaps in the lagovirus phylogeny and hence better understand the evolutionary history of this important group of mammalian viruses.

microbiology↗

bioRxiv2017

A strain-specific multiplex RT-PCR for Australian rabbit haemorrhagic disease viruses uncovers a new recombinant virus variant in rabbits and hares

Rabbit haemorrhagic disease virus (RHDV, or GI.1), is a calicivirus in the genus Lagovirus that has been widely utilised in Australia as a biological control agent for the management of overabundant wild European rabbit (Oryctolagus cuniculus) populations since 1996. Recently, two exotic incursions of pathogenic lagoviruses have been reported in Australia; GI.1a-Aus, previously called RHDVa-Aus, is a GI.1a virus detected in January 2014, and the novel lagovirus GI.2 (previously known as RHDV2). Furthermore, an additional GI.1a strain, GI.1a-K5 (also known as 08Q712), was released nationwide in March 2017 as a supplementary tool for wild rabbit management. To discriminate between these lagoviruses, a highly sensitive strain-specific multiplex RT-PCR assay was developed, which allows fast, cost-effective, and sensitive detection of the four pathogenic lagoviruses currently known to be circulating in Australia. In addition, we developed a universal qRT-PCR assay to be used in conjunction with the multiplex assay that broadly detects all four viruses and facilitates quantification of viral RNA load in samples. These assays enable rapid detection, identification, and quantification of pathogenic lagoviruses in the Australian context. Using these assays, a novel recombinant lagovirus was detected in rabbit tissues samples, which contained the non-structural genes of GI.1a-Aus and the structural genes of GI.2. This variant was also recovered from the liver of a European brown hare (Lepus europaeus). The impact of this novel recombinant on Australian wild lagomorph populations and its competitiveness in relation to circulating field strains, particularly GI.2, requires further studies.

microbiology↗