Limits...
Flying-fox species density--a spatial risk factor for Hendra virus infection in horses in eastern Australia.

Smith C, Skelly C, Kung N, Roberts B, Field H - PLoS ONE (2014)

Bottom Line: 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.The density of horses, climate variables and vegetation variables were not found to be a significant risk factors, but the residuals from the GWR suggest that additional unidentified risk factors exist at the property level.Further investigations and comparisons between case and control properties are needed to identify these local risk factors.

View Article: PubMed Central - PubMed

Affiliation: Queensland Centre for Emerging Infectious Diseases, Department of Agriculture, Fisheries and Forestry, Brisbane, Queensland, Australia.

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 GWR suggest that additional unidentified risk factors exist at the property level. Further investigations and comparisons between case and control properties are needed to identify these local risk factors.

Show MeSH

Related in: MedlinePlus

The final GWR model for the spill-over of Hendra virus in eastern Australia, with predicted (A) and residual (B) values.The density of flying-foxes P. alecto and P. conspicillatus had the strongest positive correlation with reported Hendra virus spill-overs (A). An absence of spatial autocorrelation of the residuals suggests additional (as yet unidentified) local risk factors play a role in Hendra virus spill-over from flying-foxes to horses (B).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4061024&req=5

pone-0099965-g003: The final GWR model for the spill-over of Hendra virus in eastern Australia, with predicted (A) and residual (B) values.The density of flying-foxes P. alecto and P. conspicillatus had the strongest positive correlation with reported Hendra virus spill-overs (A). An absence of spatial autocorrelation of the residuals suggests additional (as yet unidentified) local risk factors play a role in Hendra virus spill-over from flying-foxes to horses (B).

Mentions: Of the 15 spatial and environmental variables included in the study (Table 1), six were identified as being statistically significant in the initial and final OLS model (Table 2). Of these six, three had an association in the GWR, with the strength and direction of the correlation varying (Table 2). The density of flying-foxes P. alecto and P. conspicillatus had the strongest positive correlation (>0.5) with reported Hendra virus equine cases. The annual minimum temperature had a weak positive correlation (<0.2) and the density of P. scapulatus had a weak negative correlation (>−0.2). Negligible correlations (−0.1<0.1) were identified for P. poliocephalus, relative humidity (as measured at 0900) and horse population. The predicted (P) and residual (SD) values for a Hendra virus spill-over on horse properties are mapped in Figures 3A and B.


Flying-fox species density--a spatial risk factor for Hendra virus infection in horses in eastern Australia.

Smith C, Skelly C, Kung N, Roberts B, Field H - PLoS ONE (2014)

The final GWR model for the spill-over of Hendra virus in eastern Australia, with predicted (A) and residual (B) values.The density of flying-foxes P. alecto and P. conspicillatus had the strongest positive correlation with reported Hendra virus spill-overs (A). An absence of spatial autocorrelation of the residuals suggests additional (as yet unidentified) local risk factors play a role in Hendra virus spill-over from flying-foxes to horses (B).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4061024&req=5

pone-0099965-g003: The final GWR model for the spill-over of Hendra virus in eastern Australia, with predicted (A) and residual (B) values.The density of flying-foxes P. alecto and P. conspicillatus had the strongest positive correlation with reported Hendra virus spill-overs (A). An absence of spatial autocorrelation of the residuals suggests additional (as yet unidentified) local risk factors play a role in Hendra virus spill-over from flying-foxes to horses (B).
Mentions: Of the 15 spatial and environmental variables included in the study (Table 1), six were identified as being statistically significant in the initial and final OLS model (Table 2). Of these six, three had an association in the GWR, with the strength and direction of the correlation varying (Table 2). The density of flying-foxes P. alecto and P. conspicillatus had the strongest positive correlation (>0.5) with reported Hendra virus equine cases. The annual minimum temperature had a weak positive correlation (<0.2) and the density of P. scapulatus had a weak negative correlation (>−0.2). Negligible correlations (−0.1<0.1) were identified for P. poliocephalus, relative humidity (as measured at 0900) and horse population. The predicted (P) and residual (SD) values for a Hendra virus spill-over on horse properties are mapped in Figures 3A and B.

Bottom Line: 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.The density of horses, climate variables and vegetation variables were not found to be a significant risk factors, but the residuals from the GWR suggest that additional unidentified risk factors exist at the property level.Further investigations and comparisons between case and control properties are needed to identify these local risk factors.

View Article: PubMed Central - PubMed

Affiliation: Queensland Centre for Emerging Infectious Diseases, Department of Agriculture, Fisheries and Forestry, Brisbane, Queensland, Australia.

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 GWR suggest that additional unidentified risk factors exist at the property level. Further investigations and comparisons between case and control properties are needed to identify these local risk factors.

Show MeSH
Related in: MedlinePlus