The Experts below are selected from a list of 1083 Experts worldwide ranked by ideXlab platform

Hume Field - One of the best experts on this subject based on the ideXlab platform.

  • Physiological stress and Hendra Virus in flying-foxes (Pteropus spp.), Australia.
    PLOS ONE, 2017
    Co-Authors: Lee Mcmichael, Craig S Smith, Daniel Edson, Ina Smith, Joanne Meers, David G. Mayer, Steven R. Kopp, Hume Field
    Abstract:

    Pteropid bats (flying-foxes) are the natural reservoir of Hendra Virus, an emergent paramyxoVirus responsible for fatal Infection in horses and humans in Australia. Pteropus alecto (the Black flying-fox) and the paraphyletic P. conspicillatus (the Spectacled flying-fox) appear to be the primary reservoir hosts. Previous studies have suggested that physiological and ecological factors may underpin Infection dynamics in flying-foxes, and subsequent spillover to horses and in turn humans. We sought to examine temporal trends in urinary cortisol concentration in wild Australian flying-fox populations, to elucidate the putative relationship between Hendra Virus Infection and physiological stress. Pooled and individual urine samples were non-invasively collected from under roosting flying-foxes at two latitudinally disparate regions in the eastern Australian state of Queensland. Hendra Virus detection, and (in individual urine samples) sex and species determination were PCR-based. Urinary cortisol measurement used a validated enzyme immunoassay. We found no direct correlation between increased urinary cortisol and Hendra Virus excretion, but our findings do suggest a biologically plausible association between low winter temperatures and elevated cortisol levels in P. alecto in the lower latitude Southeast Queensland roosts. We hypothesize an indirect association between low winter temperatures and increased Hendra Virus Infection and excretion, mediated by the physiological cost of thermoregulation. Our findings and our approach are directly relevant to elaboration of the disease ecology of Nipah Virus and other emerging henipaViruses in bats. More broadly, they inform investigation of emerging disease Infection dynamics across the wildlife/livestock/human interface.

  • PHYSIOLOGIC BIOMARKERS AND Hendra Virus Infection IN AUSTRALIAN BLACK FLYING FOXES (PTEROPUS ALECTO).
    Journal of Wildlife Diseases, 2016
    Co-Authors: Lee Mcmichael, Daniel Edson, Joanne Meers, David G. Mayer, Alice Broos, Steven R. Kopp, Hume Field
    Abstract:

    Abstract Bats of the genus Pteropus (Pteropodidae), colloquially known as flying foxes, are recognized as the natural reservoir of Hendra Virus, a zoonotic paramyxoVirus responsible for mortality in horses and humans. Some previous studies have suggested that physiologic and ecologic factors promote Hendra Virus Infection in flying foxes, and by extension, spillover to horses and humans. However, the impact of Hendra Virus Infection on relevant physiologic biomarkers in flying foxes has not been measured. Over 12 mo in eastern Australia, we captured and sampled 446 individual black flying foxes (Pteropus alecto), a putative primary reservoir host species, and measured a suite of hematologic, plasma biochemistry, and urinary biomarkers. All mean hematologic and biochemical values in both Hendra Virus–positive and Virus–negative cohorts were within the published reference ranges for black flying foxes. We found no association between Hendra Virus Infection (as indicated by PCR detection of Hendra Virus RNA)...

  • RESEARCH ARTICLE Spatiotemporal Aspects of Hendra Virus Infection in Pteropid Bats (Flying-Foxes) in
    2016
    Co-Authors: Hume Field, Daniel Edson, Nina Kung, David Jordan, Stephen Morris, Debra Melville, Peter Kirkl, Craig Smith
    Abstract:

    Hendra Virus (HeV) causes highly lethal disease in horses and humans in the eastern Aus-tralian states of Queensland (QLD) and New South Wales (NSW), with multiple equine cases now reported on an annual basis. Infection and excretion dynamics in pteropid bats (flying-foxes), the recognised natural reservoir, are incompletely understood. We sought to identify key spatial and temporal factors associated with excretion in flying-foxes over a 2300 km latitudinal gradient from northern QLD to southern NSW which encompassed all known equine case locations. The aim was to strengthen knowledge of Hendra Virus ecol-ogy in flying-foxes to improve spillover risk prediction and exposure risk mitigation strate-gies, and thus better protect horses and humans. Monthly pooled urine samples were collected from under roosting flying-foxes over a three-year period and screened for HeV RNA by quantitative RT-PCR. A generalised linear model was employed to investigate spa-tiotemporal associations with HeV detection in 13,968 samples from 27 roosts. There was a non-linear relationship between mean HeV excretion prevalence and five latitudinal regions

  • Flying-Fox Species Density- A Spatial Risk Factor for Hendra Virus Infection in Horses in Eastern Australia
    2016
    Co-Authors: Craig Smith, Nina Kung, Chris Skelly, Billie Roberts, Hume Field
    Abstract:

    Hendra Virus causes sporadic but typically fatal Infection in horses and humans in eastern Australia. Fruit-bats of the genus Pteropus (commonly known as flying-foxes) are the natural host of the Virus, and the putative source of Infection in horses; infected horses are the source of human Infection. Effective treatment is lacking in both horses and humans, and notwithstanding the recent availability of a vaccine for horses, exposure risk mitigation remains an important Infection control strategy. This study sought to inform risk mitigation by identifying spatial and environmental risk factors for equine Infection using multiple analytical approaches to investigate the relationship between plausible variables and reported Hendra Virus Infection in horses. Spatial autocorrelation (Global Moran’s I) showed significant clustering of equine cases at a distance of 40 km, a distance consistent with the foraging ‘footprint ’ of a flying-fox roost, suggesting the latter as a biologically plausible basis for the clustering. Getis-Ord Gi * analysis identified multiple equine Infection hot spots along the eastern Australia coast from far north Queensland to central New South Wales, with the largest extending for nearly 300 km from southern Queensland to northern New South Wales. Geographically weighted regression (GWR) showed the density of P. alecto and P. conspicillatus to have the strongest positive correlation with equine case locations, suggesting these species are more likely a source of Infection of Hendra Virus for horses than P. poliocephalus or P. scapulatus. The density of horses, climate variables and vegetation variables were not found to be a significant risk factors, but the residuals from the GW

  • Temporal Variation in Physiological Biomarkers in Black Flying-Foxes (Pteropus alecto), Australia
    EcoHealth, 2016
    Co-Authors: Lee Mcmichael, Miranda E Vidgen, Joanne Meers, Lauren Goldspink, Amanda Mclaughlin, Steven Kopp, David Mayer, Hume Field
    Abstract:

    Bats of the genus Pteropus (Pteropodidae) are recognised as the natural host of multiple emerging pathogenic Viruses of animal and human health significance, including henipaViruses, lyssaViruses and ebolaViruses. Some studies have suggested that physiological and ecological factors may be associated with Hendra Virus Infection in flying-foxes in Australia; however, it is essential to understand the normal range and seasonal variability of physiological biomarkers before seeking physiological associations with Infection status. We aimed to measure a suite of physiological biomarkers in P. alecto over time to identify any seasonal fluctuations and to examine possible associations with life-cycle and environmental stressors. We sampled 839 adult P. alecto in the Australian state of Queensland over a 12-month period. The adjusted population means of every assessed hematologic and biochemical parameter were within the reported reference range on every sampling occasion. However, within this range, we identified significant temporal variation in these parameters, in urinary parameters and body condition, which primarily reflected the normal annual life cycle. We found no evident effect of remarkable physiological demands or nutritional stress, and no indication of clinical disease driving any parameter values outside the normal species reference range. Our findings identify underlying temporal physiological changes at the population level that inform epidemiological studies and assessment of putative physiological risk factors driving Hendra Virus Infection in P. alecto. More broadly, the findings add to the knowledge of Pteropus populations in terms of their relative resistance and resilience to emerging infectious disease.

Lee Mcmichael - One of the best experts on this subject based on the ideXlab platform.

  • Physiological stress and Hendra Virus in flying-foxes (Pteropus spp.), Australia.
    PLOS ONE, 2017
    Co-Authors: Lee Mcmichael, Craig S Smith, Daniel Edson, Ina Smith, Joanne Meers, David G. Mayer, Steven R. Kopp, Hume Field
    Abstract:

    Pteropid bats (flying-foxes) are the natural reservoir of Hendra Virus, an emergent paramyxoVirus responsible for fatal Infection in horses and humans in Australia. Pteropus alecto (the Black flying-fox) and the paraphyletic P. conspicillatus (the Spectacled flying-fox) appear to be the primary reservoir hosts. Previous studies have suggested that physiological and ecological factors may underpin Infection dynamics in flying-foxes, and subsequent spillover to horses and in turn humans. We sought to examine temporal trends in urinary cortisol concentration in wild Australian flying-fox populations, to elucidate the putative relationship between Hendra Virus Infection and physiological stress. Pooled and individual urine samples were non-invasively collected from under roosting flying-foxes at two latitudinally disparate regions in the eastern Australian state of Queensland. Hendra Virus detection, and (in individual urine samples) sex and species determination were PCR-based. Urinary cortisol measurement used a validated enzyme immunoassay. We found no direct correlation between increased urinary cortisol and Hendra Virus excretion, but our findings do suggest a biologically plausible association between low winter temperatures and elevated cortisol levels in P. alecto in the lower latitude Southeast Queensland roosts. We hypothesize an indirect association between low winter temperatures and increased Hendra Virus Infection and excretion, mediated by the physiological cost of thermoregulation. Our findings and our approach are directly relevant to elaboration of the disease ecology of Nipah Virus and other emerging henipaViruses in bats. More broadly, they inform investigation of emerging disease Infection dynamics across the wildlife/livestock/human interface.

  • physiological biomarkers of Hendra Virus Infection in australian flying foxes pteropus spp
    2017
    Co-Authors: Lee Mcmichael
    Abstract:

    Since 1994 when the disease was first described, there have been over 50 Hendra Virus incidents involving more than 90 confirmed or possible equine cases, and 7 associated human cases, with case fatality rates approaching 90% and 60% respectively. Epidemiological studies suggest that flying-foxes, in particular the Black flying-fox (Pteropus alecto) and the closely related Spectacled flying-fox (P. conspicillatus) are the primary natural reservoir hosts. This research project investigates a hypothesised causal association between ecological and/or physiological stress and Hendra Virus Infection in Pteropus species. During a 12-month study of flying-foxes in Southeast Queensland (SEQ), samples were collected from 446 captured wild P. alecto for analysis of 18 hematologic, 22 biochemical and 8 urinary biomarkers, establishing normal reference ranges and temporal changes for this suite of biomarkers. The population demonstrated statistically significant temporal variation in some biomarkers consistent with life cycle events. In Hendra Virus RNA-positive animals all biomarker mean values were within established normal ranges, but some were significantly different compared to Hendra Virus RNA-negative animals, notably, increased lymphocyte percent, decreased neutrophil percent, decreased plasma triglyceride levels, increased plasma alkaline phosphatase levels and increased urinary protein levels. The study demonstrated that Hendra Virus Infection in P. alecto was sub-clinical, and that there was no apparent relationship with nutritional stress, reproductive stress or extreme metabolic demand, which would have caused substantial changes to biomarker values. The relationship between increased urinary protein levels, decreased triglyceride levels and Hendra Virus Infection is of interest, and may support the premise of urinary tract association and physiological demand with Hendra Virus Infection of P. alecto. In a second study, a method of collection and assay of urinary cortisol to measure physiological stress in roosting flying-foxes was validated. Differences between the four mainland flying-fox species (P. alecto, P. poliocephalus, P. scapulatus, P. conspicillatus) were established through collection of urine samples from a wide geographic range throughout Queensland and New South Wales from single species roosts. Then, over a three-year study, population urinary cortisol and Hendra Virus urinary excretion prevalence was measured from a total of 2208 pooled urine samples from mixed species roosts of flying-foxes from two geographically distinct regions, subtropical SEQ and tropical Far North Queensland (FNQ). An autumn elevation in urinary cortisol in the FNQ population was detected, but no significant seasonal fluctuations in Hendra Virus excretion prevalence were found. Urinary cortisol was significantly elevated in both autumn and winter in the SEQ population, the latter temporally associated with a significant winter elevation in Hendra Virus excretion prevalence. There was also a strong correlation between urinary cortisol concentration and minimum temperature on the day of sampling, with urinary cortisol increasing exponentially as temperature decreased. As mixed species population urinary cortisol measurements have the inherent difficulty of an inability to interpret the effect of species and cohort, a novel urinary collection and molecular analysis method was employed on 464 individual animal urine samples collected from the SEQ roost site over a 12-month study to assess the effects of sex and species on cortisol levels and Hendra Virus excretion status. P. alecto was found to be the only species present at the site excreting Hendra Virus, and there were no significant differences between sex for either Hendra Virus excretion, or urinary cortisol excretion levels. The autumn peak in urinary cortisol is most plausibly primarily driven by the physiological demand of peak mating; the winter peak in urinary cortisol measurements, which is temporally correlated with a pulse in Hendra Virus excretion, is not associated with reproductive stressors and may be driven by the physiological demand of thermoregulation of the historically tropical species P. alecto in a subtropical/temperate niche during winter. The research addresses significant knowledge gaps in relation to baseline physiological biomarkers in flying-foxes, tests hypotheses on risk factors for Hendra Virus Infection in P. alecto, and provides a platform for further investigation of the disease ecology of Hendra Virus in flying-foxes. More broadly, it provides a valuable template for the investigation of the disease ecology of various wildlife-associated emerging zoonoses of public health significance.

  • PHYSIOLOGIC BIOMARKERS AND Hendra Virus Infection IN AUSTRALIAN BLACK FLYING FOXES (PTEROPUS ALECTO).
    Journal of Wildlife Diseases, 2016
    Co-Authors: Lee Mcmichael, Daniel Edson, Joanne Meers, David G. Mayer, Alice Broos, Steven R. Kopp, Hume Field
    Abstract:

    Abstract Bats of the genus Pteropus (Pteropodidae), colloquially known as flying foxes, are recognized as the natural reservoir of Hendra Virus, a zoonotic paramyxoVirus responsible for mortality in horses and humans. Some previous studies have suggested that physiologic and ecologic factors promote Hendra Virus Infection in flying foxes, and by extension, spillover to horses and humans. However, the impact of Hendra Virus Infection on relevant physiologic biomarkers in flying foxes has not been measured. Over 12 mo in eastern Australia, we captured and sampled 446 individual black flying foxes (Pteropus alecto), a putative primary reservoir host species, and measured a suite of hematologic, plasma biochemistry, and urinary biomarkers. All mean hematologic and biochemical values in both Hendra Virus–positive and Virus–negative cohorts were within the published reference ranges for black flying foxes. We found no association between Hendra Virus Infection (as indicated by PCR detection of Hendra Virus RNA)...

  • Temporal Variation in Physiological Biomarkers in Black Flying-Foxes (Pteropus alecto), Australia
    EcoHealth, 2016
    Co-Authors: Lee Mcmichael, Miranda E Vidgen, Joanne Meers, Lauren Goldspink, Amanda Mclaughlin, Steven Kopp, David Mayer, Hume Field
    Abstract:

    Bats of the genus Pteropus (Pteropodidae) are recognised as the natural host of multiple emerging pathogenic Viruses of animal and human health significance, including henipaViruses, lyssaViruses and ebolaViruses. Some studies have suggested that physiological and ecological factors may be associated with Hendra Virus Infection in flying-foxes in Australia; however, it is essential to understand the normal range and seasonal variability of physiological biomarkers before seeking physiological associations with Infection status. We aimed to measure a suite of physiological biomarkers in P. alecto over time to identify any seasonal fluctuations and to examine possible associations with life-cycle and environmental stressors. We sampled 839 adult P. alecto in the Australian state of Queensland over a 12-month period. The adjusted population means of every assessed hematologic and biochemical parameter were within the reported reference range on every sampling occasion. However, within this range, we identified significant temporal variation in these parameters, in urinary parameters and body condition, which primarily reflected the normal annual life cycle. We found no evident effect of remarkable physiological demands or nutritional stress, and no indication of clinical disease driving any parameter values outside the normal species reference range. Our findings identify underlying temporal physiological changes at the population level that inform epidemiological studies and assessment of putative physiological risk factors driving Hendra Virus Infection in P. alecto. More broadly, the findings add to the knowledge of Pteropus populations in terms of their relative resistance and resilience to emerging infectious disease.

  • Spatiotemporal Aspects of Hendra Virus Infection in Pteropid Bats (Flying-Foxes) in Eastern Australia.
    PLOS ONE, 2015
    Co-Authors: Hume Field, Daniel Edson, Lee Mcmichael, Alice Broos, David Jordan, Stephen Morris, Debra Melville, Kerryn Parry-jones, Anja Divljan, Rodney Davis
    Abstract:

    Hendra Virus (HeV) causes highly lethal disease in horses and humans in the eastern Australian states of Queensland (QLD) and New South Wales (NSW), with multiple equine cases now reported on an annual basis. Infection and excretion dynamics in pteropid bats (flying-foxes), the recognised natural reservoir, are incompletely understood. We sought to identify key spatial and temporal factors associated with excretion in flying-foxes over a 2300 km latitudinal gradient from northern QLD to southern NSW which encompassed all known equine case locations. The aim was to strengthen knowledge of Hendra Virus ecology in flying-foxes to improve spillover risk prediction and exposure risk mitigation strategies, and thus better protect horses and humans. Monthly pooled urine samples were collected from under roosting flying-foxes over a three-year period and screened for HeV RNA by quantitative RT-PCR. A generalised linear model was employed to investigate spatiotemporal associations with HeV detection in 13,968 samples from 27 roosts. There was a non-linear relationship between mean HeV excretion prevalence and five latitudinal regions, with excretion moderate in northern and central QLD, highest in southern QLD/northern NSW, moderate in central NSW, and negligible in southern NSW. Highest HeV positivity occurred where black or spectacled flying-foxes were present; nil or very low positivity rates occurred in exclusive grey-headed flying-fox roosts. Similarly, little red flying-foxes are evidently not a significant source of Virus, as their periodic extreme increase in numbers at some roosts was not associated with any concurrent increase in HeV detection. There was a consistent, strong winter seasonality to excretion in the southern QLD/northern NSW and central NSW regions. This new information allows risk management strategies to be refined and targeted, mindful of the potential for spatial risk profiles to shift over time with changes in flying-fox species distribution.

Ina Smith - One of the best experts on this subject based on the ideXlab platform.

  • Physiological stress and Hendra Virus in flying-foxes (Pteropus spp.), Australia.
    PLOS ONE, 2017
    Co-Authors: Lee Mcmichael, Craig S Smith, Daniel Edson, Ina Smith, Joanne Meers, David G. Mayer, Steven R. Kopp, Hume Field
    Abstract:

    Pteropid bats (flying-foxes) are the natural reservoir of Hendra Virus, an emergent paramyxoVirus responsible for fatal Infection in horses and humans in Australia. Pteropus alecto (the Black flying-fox) and the paraphyletic P. conspicillatus (the Spectacled flying-fox) appear to be the primary reservoir hosts. Previous studies have suggested that physiological and ecological factors may underpin Infection dynamics in flying-foxes, and subsequent spillover to horses and in turn humans. We sought to examine temporal trends in urinary cortisol concentration in wild Australian flying-fox populations, to elucidate the putative relationship between Hendra Virus Infection and physiological stress. Pooled and individual urine samples were non-invasively collected from under roosting flying-foxes at two latitudinally disparate regions in the eastern Australian state of Queensland. Hendra Virus detection, and (in individual urine samples) sex and species determination were PCR-based. Urinary cortisol measurement used a validated enzyme immunoassay. We found no direct correlation between increased urinary cortisol and Hendra Virus excretion, but our findings do suggest a biologically plausible association between low winter temperatures and elevated cortisol levels in P. alecto in the lower latitude Southeast Queensland roosts. We hypothesize an indirect association between low winter temperatures and increased Hendra Virus Infection and excretion, mediated by the physiological cost of thermoregulation. Our findings and our approach are directly relevant to elaboration of the disease ecology of Nipah Virus and other emerging henipaViruses in bats. More broadly, they inform investigation of emerging disease Infection dynamics across the wildlife/livestock/human interface.

  • Hendra Virus Infection dynamics in the grey headed flying fox pteropus poliocephalus at the southern most extent of its range further evidence this species does not readily transmit the Virus to horses
    PLOS ONE, 2016
    Co-Authors: Victoria Boyd, K Graham, Shawn Todd, Jeremy J Barr, Ina Smith, Amy L Burroughs, Peter A Durr, J.r. White, G Baverstock
    Abstract:

    Hendra Virus (HeV) is an important emergent Virus in Australia known to infect horses and humans in certain regions of the east coast. Whilst pteropid bats (“flying foxes”) are considered the natural reservoir of HeV, which of the four mainland species is the principal reservoir has been a source of ongoing debate, particularly as shared roosting is common. To help resolve this, we sampled a colony consisting of just one of these species, the grey-headed flying fox, (Pteropus poliocephalus), at the southernmost extent of its range. Using the pooled urine sampling technique at approximately weekly intervals over a two year period, we determined the prevalence of HeV and related paramyxoViruses using a novel multiplex (Luminex) platform. Whilst all the pooled urine samples were negative for HeV nucleic acid, we successfully identified four other paramyxoViruses, including Cedar Virus; a henipaVirus closely related to HeV. Collection of serum from individually caught bats from the colony showed that antibodies to HeV, as estimated by a serological Luminex assay, were present in between 14.6% and 44.5% of animals. The wide range of the estimate reflects uncertainties in interpreting intermediate results. Interpreting the study in the context of HeV studies from states to the north, we add support for an arising consensus that it is the black flying fox and not the grey-headed flying fox that is the principal source of HeV in spillover events to horses.

  • Hendra Virus Infection dynamics in australian fruit bats
    PLOS ONE, 2011
    Co-Authors: Hume Field, Ina Smith, Alice Broos, Carol De Jong, Deb Melville, Craig Smith, Yu Hsin Nina Kung, Amanda Mclaughlin
    Abstract:

    Hendra Virus is a recently emerged zoonotic agent in Australia. Since first described in 1994, the Virus has spilled from its wildlife reservoir (pteropid fruit bats, or ‘flying foxes’) on multiple occasions causing equine and human fatalities. We undertook a three-year longitudinal study to detect Virus in the urine of free-living flying foxes (a putative route of excretion) to investigate Hendra Virus Infection dynamics. Pooled urine samples collected off plastic sheets placed beneath roosting flying foxes were screened for Hendra Virus genome by quantitative RT-PCR, using a set of primers and probe derived from the matrix protein gene. A total of 1672 pooled urine samples from 67 sampling events was collected and tested between 1 July 2008 and 30 June 2011, with 25% of sampling events and 2.5% of urine samples yielding detections. The proportion of positive samples was statistically associated with year and location. The findings indicate that Hendra Virus excretion occurs periodically rather than continuously, and in geographically disparate flying fox populations in the state of Queensland. The lack of any detection in the Northern Territory suggests prevalence may vary across the range of flying foxes in Australia. Finally, our findings suggest that flying foxes can excrete Virus at any time of year, and that the apparent seasonal clustering of Hendra Virus incidents in horses and associated humans (70% have occurred June to October) reflects factors other than the presence of Virus. Identification of these factors will strengthen risk minimization strategies for horses and ultimately humans.

  • Hendra Virus Infection in a veterinarian
    The Medical Journal of Australia, 2006
    Co-Authors: Jeffrey N Hanna, Ina Smith, Carmel T Taylor, J Shield, William J H Mcbride, Dianne L Brookes, Scott B Craig, Greg Smith
    Abstract:

    A veterinarian became infected with Hendra Virus (HeV) after managing a terminally ill horse and performing a limited autopsy with inadequate precautions. Although she was initially only mildly ill, serological tests suggested latent HeV Infection. Nevertheless, she remains well 2 years after her initial illness. Recently emerged zoonotic Viruses, such as HeV, necessitate appropriate working procedures and personal protective equipment in veterinary practice.

Raina K Plowright - One of the best experts on this subject based on the ideXlab platform.

  • spatial dynamics of pathogen transmission in communally roosting species impacts of changing habitats on bat Virus dynamics
    Journal of Animal Ecology, 2021
    Co-Authors: Tamika Lunn, Raina K Plowright, Alison J. Peel, Hamish Mccallum, Peggy Eby, Maureen K Kessler, Olivier Restif
    Abstract:

    The spatial organisation of populations determines their pathogen dynamics. This is particularly important for communally roosting species, whose aggregations are often driven by the spatial structure of their environment. We develop a spatially explicit model for Virus transmission within roosts of Australian tree-dwelling bats (Pteropus spp.), parameterised to reflect Hendra Virus. The spatial structure of roosts mirrors three study sites, and viral transmission between groups of bats in trees was modelled as a function of distance between roost trees. Using three levels of tree density to reflect anthropogenic changes in bats habitats, we investigate the potential effects of recent ecological shifts in Australia on the dynamics of zoonotic Viruses in reservoir hosts. We show that simulated Infection dynamics in spatially structured roosts differ from that of mean-field models for equivalently sized populations, highlighting the importance of spatial structure in disease models of gregarious taxa. Under contrasting scenarios of flying-fox roosting structures, sparse stand structures (with fewer trees but more bats per tree) generate higher probabilities of successful outbreaks, larger and faster epidemics, and shorter Virus extinction times, compared to intermediate and dense stand structures with more trees but fewer bats per tree. These observations are consistent with the greater force of Infection generated by structured populations with less numerous but larger infected groups, and may flag an increased risk of pathogen spillover from these increasingly abundant roost types. Outputs from our models contribute insights into the spread of Viruses in structured animal populations, like communally roosting species, as well as specific insights into Hendra Virus Infection dynamics and spillover risk in a situation of changing host ecology. These insights will be relevant for modelling other zoonotic Viruses in wildlife reservoir hosts in response to habitat modification and changing populations, including coronaViruses like SARS-CoV-2.

  • Relation of seasonal birth pulses and maternal immunity with viral invasion and persistence: A case study of Hendra Virus Infection in a population of black flying foxes (Pteropus alecto)
    2019
    Co-Authors: Jaewoon Jeong, Raina K Plowright, Alison J. Peel, Olivier Restif, Hamish Mccallum
    Abstract:

    Abstract Increasing outbreaks of emerging infectious diseases, originating from wildlife, has intensified interest in understanding the dynamics of these diseases in their wildlife reservoir hosts. Until recently, the effect of seasonal birth pulses and subsequent waning of maternally derived antibodies on epidemics in a wild mammal population has received little attention and has remained obscure. In this study, we explore how population structure, influenced by seasonal breeding and maternally derived immunity, affects viral invasion and persistence, using a hypothetical system loosely based on Hendra Virus Infection in black flying foxes (Pteropus alecto). We used deterministic epidemic models to simulate transient epidemics, following viral introduction into an Infection-free population, with a variety of timings within a year and different levels of pre-existing herd immunity. Moreover, we applied different levels of birth synchrony and different modelling methods of waning maternal immunity to examine the effect of birth pulses and maternally derived immunity, both individually and in combination. The presence of waning maternal immunity dispersed the supply time of susceptible individuals in seasonally breeding populations, hence diminishing the effect of birth pulse. Dampened epidemics, caused by waning maternal immunity, made viral invasion and persistence easier. This study enhanced our understanding of viral invasion, persistence, and timing of epidemics in wildlife populations.

  • Conditions affecting the timing and magnitude of Hendra Virus shedding across pteropodid bat populations in Australia.
    Epidemiology and infection, 2017
    Co-Authors: David J. Páez, Alison J. Peel, Hamish Mccallum, John R Giles, David Jordan, Raina K Plowright
    Abstract:

    Understanding Infection dynamics in animal hosts is fundamental to managing spillover and emergence of zoonotic Infections. Hendra Virus is endemic in Australian pteropodid bat populations and can be lethal to horses and humans. However, we know little about the factors driving Hendra Virus prevalence in resevoir bat populations, making spillover difficult to predict. We use Hendra Virus prevalence data collected from 13 000 pooled bat urine samples across space and time to determine if pulses of prevalence are periodic and synchronized across sites. We also test whether site-specific precipitation and temperature affect the amplitude of the largest annual prevalence pulses. We found little evidence for a periodic signal in Hendra Virus prevalence. Although the largest amplitude pulses tended to occur over winter, pulses could also occur in other seasons. We found that Hendra Virus prevalence was weakly synchronized across sites over short distances, suggesting that prevalence is driven by local-scale effects. Finally, we found that drier conditions in previous seasons and the abundance of Pteropus alecto were positively correlated with the peak annual values of Hendra Virus prevalence. Our results suggest that in addition to seasonal effects, bat density and local climatic conditions interact to drive Hendra Virus Infection dynamics.

  • Reproduction and nutritional stress are risk factors for Hendra Virus Infection in little red flying foxes (Pteropus scapulatus)
    Proceedings of The Royal Society B: Biological Sciences, 2008
    Co-Authors: Raina K Plowright, Craig S Smith, Hume Field, Anja Divljan, Carol Palmer, Gary Tabor, Peter Daszak, Janet E Foley
    Abstract:

    Hendra Virus (HeV) is a lethal paramyxoVirus which emerged in humans in 1994. Poor understanding of HeV dynamics in Pteropus spp. (flying fox or fruit bat) reservoir hosts has limited our ability to determine factors driving its emergence. We initiated a longitudinal field study of HeV in little red flying foxes (LRFF; Pteropus scapulatus) and examined individual and population risk factors for Infection, to determine probable modes of intraspecific transmission. We also investigated whether seasonal changes in host behaviour, physiology and demography affect host–pathogen dynamics. Data showed that pregnant and lactating females had significantly higher risk of Infection, which may explain previously observed temporal associations between HeV outbreaks and flying fox birthing periods. Age-specific seroprevalence curves generated from field data imply that HeV is transmitted horizontally via faeces, urine or saliva. Rapidly declining seroprevalence between two field seasons suggests that immunity wanes faster in LRFF than in other flying fox species, and highlights the potentially critical role of this species in interspecific viral persistence. The highest seroprevalence was observed when animals showed evidence of nutritional stress, suggesting that environmental processes that alter flying fox food sources, such as habitat loss and climate change, may increase HeV Infection and transmission. These insights into the ecology of HeV in flying fox populations suggest causal links between anthropogenic environmental change and HeV emergence.

Daniel Edson - One of the best experts on this subject based on the ideXlab platform.

  • Physiological stress and Hendra Virus in flying-foxes (Pteropus spp.), Australia.
    PLOS ONE, 2017
    Co-Authors: Lee Mcmichael, Craig S Smith, Daniel Edson, Ina Smith, Joanne Meers, David G. Mayer, Steven R. Kopp, Hume Field
    Abstract:

    Pteropid bats (flying-foxes) are the natural reservoir of Hendra Virus, an emergent paramyxoVirus responsible for fatal Infection in horses and humans in Australia. Pteropus alecto (the Black flying-fox) and the paraphyletic P. conspicillatus (the Spectacled flying-fox) appear to be the primary reservoir hosts. Previous studies have suggested that physiological and ecological factors may underpin Infection dynamics in flying-foxes, and subsequent spillover to horses and in turn humans. We sought to examine temporal trends in urinary cortisol concentration in wild Australian flying-fox populations, to elucidate the putative relationship between Hendra Virus Infection and physiological stress. Pooled and individual urine samples were non-invasively collected from under roosting flying-foxes at two latitudinally disparate regions in the eastern Australian state of Queensland. Hendra Virus detection, and (in individual urine samples) sex and species determination were PCR-based. Urinary cortisol measurement used a validated enzyme immunoassay. We found no direct correlation between increased urinary cortisol and Hendra Virus excretion, but our findings do suggest a biologically plausible association between low winter temperatures and elevated cortisol levels in P. alecto in the lower latitude Southeast Queensland roosts. We hypothesize an indirect association between low winter temperatures and increased Hendra Virus Infection and excretion, mediated by the physiological cost of thermoregulation. Our findings and our approach are directly relevant to elaboration of the disease ecology of Nipah Virus and other emerging henipaViruses in bats. More broadly, they inform investigation of emerging disease Infection dynamics across the wildlife/livestock/human interface.

  • PHYSIOLOGIC BIOMARKERS AND Hendra Virus Infection IN AUSTRALIAN BLACK FLYING FOXES (PTEROPUS ALECTO).
    Journal of Wildlife Diseases, 2016
    Co-Authors: Lee Mcmichael, Daniel Edson, Joanne Meers, David G. Mayer, Alice Broos, Steven R. Kopp, Hume Field
    Abstract:

    Abstract Bats of the genus Pteropus (Pteropodidae), colloquially known as flying foxes, are recognized as the natural reservoir of Hendra Virus, a zoonotic paramyxoVirus responsible for mortality in horses and humans. Some previous studies have suggested that physiologic and ecologic factors promote Hendra Virus Infection in flying foxes, and by extension, spillover to horses and humans. However, the impact of Hendra Virus Infection on relevant physiologic biomarkers in flying foxes has not been measured. Over 12 mo in eastern Australia, we captured and sampled 446 individual black flying foxes (Pteropus alecto), a putative primary reservoir host species, and measured a suite of hematologic, plasma biochemistry, and urinary biomarkers. All mean hematologic and biochemical values in both Hendra Virus–positive and Virus–negative cohorts were within the published reference ranges for black flying foxes. We found no association between Hendra Virus Infection (as indicated by PCR detection of Hendra Virus RNA)...

  • RESEARCH ARTICLE Spatiotemporal Aspects of Hendra Virus Infection in Pteropid Bats (Flying-Foxes) in
    2016
    Co-Authors: Hume Field, Daniel Edson, Nina Kung, David Jordan, Stephen Morris, Debra Melville, Peter Kirkl, Craig Smith
    Abstract:

    Hendra Virus (HeV) causes highly lethal disease in horses and humans in the eastern Aus-tralian states of Queensland (QLD) and New South Wales (NSW), with multiple equine cases now reported on an annual basis. Infection and excretion dynamics in pteropid bats (flying-foxes), the recognised natural reservoir, are incompletely understood. We sought to identify key spatial and temporal factors associated with excretion in flying-foxes over a 2300 km latitudinal gradient from northern QLD to southern NSW which encompassed all known equine case locations. The aim was to strengthen knowledge of Hendra Virus ecol-ogy in flying-foxes to improve spillover risk prediction and exposure risk mitigation strate-gies, and thus better protect horses and humans. Monthly pooled urine samples were collected from under roosting flying-foxes over a three-year period and screened for HeV RNA by quantitative RT-PCR. A generalised linear model was employed to investigate spa-tiotemporal associations with HeV detection in 13,968 samples from 27 roosts. There was a non-linear relationship between mean HeV excretion prevalence and five latitudinal regions

  • Spatiotemporal Aspects of Hendra Virus Infection in Pteropid Bats (Flying-Foxes) in Eastern Australia.
    PLOS ONE, 2015
    Co-Authors: Hume Field, Daniel Edson, Lee Mcmichael, Alice Broos, David Jordan, Stephen Morris, Debra Melville, Kerryn Parry-jones, Anja Divljan, Rodney Davis
    Abstract:

    Hendra Virus (HeV) causes highly lethal disease in horses and humans in the eastern Australian states of Queensland (QLD) and New South Wales (NSW), with multiple equine cases now reported on an annual basis. Infection and excretion dynamics in pteropid bats (flying-foxes), the recognised natural reservoir, are incompletely understood. We sought to identify key spatial and temporal factors associated with excretion in flying-foxes over a 2300 km latitudinal gradient from northern QLD to southern NSW which encompassed all known equine case locations. The aim was to strengthen knowledge of Hendra Virus ecology in flying-foxes to improve spillover risk prediction and exposure risk mitigation strategies, and thus better protect horses and humans. Monthly pooled urine samples were collected from under roosting flying-foxes over a three-year period and screened for HeV RNA by quantitative RT-PCR. A generalised linear model was employed to investigate spatiotemporal associations with HeV detection in 13,968 samples from 27 roosts. There was a non-linear relationship between mean HeV excretion prevalence and five latitudinal regions, with excretion moderate in northern and central QLD, highest in southern QLD/northern NSW, moderate in central NSW, and negligible in southern NSW. Highest HeV positivity occurred where black or spectacled flying-foxes were present; nil or very low positivity rates occurred in exclusive grey-headed flying-fox roosts. Similarly, little red flying-foxes are evidently not a significant source of Virus, as their periodic extreme increase in numbers at some roosts was not associated with any concurrent increase in HeV detection. There was a consistent, strong winter seasonality to excretion in the southern QLD/northern NSW and central NSW regions. This new information allows risk management strategies to be refined and targeted, mindful of the potential for spatial risk profiles to shift over time with changes in flying-fox species distribution.

  • Natural Hendra Virus Infection in Flying-Foxes - Tissue Tropism and Risk Factors.
    PLOS ONE, 2015
    Co-Authors: Lauren Goldspink, Miranda E Vidgen, Daniel Edson, Hume Field, John Bingham, Craig S Smith
    Abstract:

    Hendra Virus (HeV) is a lethal zoonotic agent that emerged in 1994 in Australia. Pteropid bats (flying-foxes) are the natural reservoir. To date, HeV has spilled over from flying-foxes to horses on 51 known occasions, and from infected horses to close-contact humans on seven occasions. We undertook screening of archived bat tissues for HeV by reverse transcription quantitative polymerase chain reaction (RT-qPCR). Tissues were tested from 310 bats including 295 Pteropodiformes and 15 Vespertilioniformes. HeV was detected in 20 individual flying-foxes (6.4%) from various tissues including spleen, kidney, liver, lung, placenta and blood components. Detection was significantly higher in Pteropus Alecto and P. conspicillatus, identifying species as a risk factor for Infection. Further, our findings indicate that HeV has a predilection for the spleen, suggesting this organ plays an important role in HeV Infection. The lack of detections in the foetal tissues of HeV-positive females suggests that vertical transmission is not a regular mode of transmission in naturally infected flying-foxes, and that placental and foetal tissues are not a major source of Infection for horses. A better understanding of HeV tissue tropism will strengthen management of the risk of spillover from flying-foxes to horses and ultimately humans.