Examining the Spatial Relationship between Equine Population and Food Source Vegetation of Flying-Foxes in South East Queensland, Australia Jahnavi Burnham and Albert Chong University of Southern Queensland, Toowoomba, Queensland, Australia jahnavi.pendyala@usq.edu.au, chonga@usq.edu.au Keywords: Hendra virus, flying-foxes, food source vegetation, equine population Hendra virus (HeV) was first identified and described in 1994 following the outbreak of a new disease fatally affecting horses and humans in south-east Queensland. Since the outbreak, there are subsequent incidents reported in eastern Australia mainly in south-east Queensland. Fruits Bats (Pteropus spp.) commonly known as flying-foxes have been identified as the natural host of the virus. This paper examines the spatial relationship(s) between the equine population and food source vegetation of flying-foxes in the study area. A 10 Km range vegetation study on the equine properties in the study area identified the food source vegetation of both black and grey headed flying-foxes. The clustering of the food source vegetation present near the equine properties was studied using Getis-Ord General G Statistic method, which indicated statistically significant high clustering at 3, 5 and 10 Km distance thresholds. Introduction Flying-foxes were consequently identified as the natural reservoirs of Hendra Virus (Halpin et al. 2000). There are strong evidences suggesting the bat to-horse to-human transmission of virus but there are no evidences suggesting the bat-to-human, human-to- human or human-to-horse transmissions (DAF 2015). There were 80 confirmed outbreak events as of December, 2012 (Smith et al. 2014). A vaccine for immunizing the horses was recently released and has been viewed as a single approach to protect horse, human, and environmental health (Middleton et al. 2014). The analysis of the relationship(s) between the Hendra virus outbreaks and the roosting sites in south east Queensland showed a strong relationship (92%) between temporary and seasonal roosting sites rather than the permanent continuous roosting sites and the outbreak locations (Burnham et al. 2015). Spatial autocorrelation revealed significant clustering of black and grey headed flying-fox species in the study area. An investigation of food Sources and roosting sites as potential factors of Hendra virus dispersion identified abundance of food sources for individual species within their minimum foraging range which indicated a strong correlation between their site locations and vegetation present. Equine population density was considered as one of the spatial risk factor for Hendra virus infection in horses in eastern Australia, in a study by Smith et al. (2014) but the result indicated a negligible correlation with the equine outbreak locations and suggested that it was evidently not a significant risk factor. However, the study indicates that there may be additional unidentified ‘local’ risk factors that need to be examined. A cross-

disciplinary study by McFarlane et al. (2011) compared the climatic and vegetation primary productivity variables for the dispersed and heterogenic outbreak sites. This study indicated that the majority of spill overs have occurred within the nightly foraging range of recorded flying fox camps. A three-year longitudinal study to detect virus in the urine of free-living flying-foxes to investigate Hendra Virus infection dynamics by Field et al. (2011) indicated that the virus excretion occurs periodically rather than continuously, and in geographically disparate populations in the state of Queensland. The study suggested that the virus prevalence may vary across the range of flying-foxes in Australia due to the lack of any detection in Northern Territory. The conclusion of the study is that flying-foxes can excrete virus at any time of year, and that the seasonal clustering of Hendra Virus incidents in horses and associated humans reflects factors other than the presence of virus and identifying these factors will strengthen risk minimization strategies. Using a set of spatial analyst tools, this study aims to identify the spatial relationship between the equine population and the food source vegetation of the black and grey headed flying-foxes in the study area. The clustering of the food source vegetation identified near the equine properties was determined using Getis-Ord General G Statistic method. This study serves as a base to establish the initial spatial relationship between the equine population and food source vegetation of flying-foxes that can help to understand the virus dispersion in the study area. Study Area South East Queensland is classified as an interim Australian bioregion, which contains of 11 cities and regional councils (Queensland Government 2009). Figure 1 shows the study area.

Figure 1. Map of south east Queensland.

Data Hendra virus incident data and equine population data was provided by the Queensland Department of Agriculture, Fisheries and Forestry (DAFF) under a data sharing agreement. For this study, a total of 15 equine related incidents that occurred from 1994 to 2011 in the study area are examined. There were a total of 16,986 registered equine properties in the study area. The Queensland vegetation data providing the major vegetation subgroups (MVS) for the study has been collected from the Department of Environment, Australia database. Figure 2 shows the Hendra virus outbreak incidents and registered equine properties in the study area. Further details of the legend of the major vegetation subgroups in the map are presented in Appendix 1. The prevalence of the flying-fox food source vegetation (mainly Eucalyptus varieties) sub groups throughout the study area can be seen in the below figure.

Figure 2. Maps showing the Hendra virus incidents and registered equine properties in the study area.

Methodology Equine Data Sample Selection Using the geo-processing tools in ArcGIS, the properties within 10 km range from the outbreak events were extracted. A random sample of 200 properties from 4,082 properties (5% approximately of the registered equine properties; 1:13 outbreak event & equine property ratio) were selected across the study area for a detailed vegetation study.

Examining the Food Source Vegetation of Flying-foxes close to the Equine Properties Using ‘extract by attribute’ tool, which extracts the cells of a raster dataset based on a logical query, the food source vegetation of the flying-foxes was identified. High/low clustering method was employed to examine the type of food source vegetation of flying-foxes identified close to the equine properties in the study area. This method determine the degree of clustering for either high values or low values using the Getis-Ord General G statistic. Global statistic like Getis-Ord General G assesses the overall pattern and trend of the data. It is an appropriate method if the values are fairly evenly distributed across the study area. Data Analysis and Results Figure 3 shows the random sample of registered equine properties chosen for the vegetation study in the study area.

Figure 3. Sample of registered equine properties.

Figure 4. Food source vegetation within 10 km of the equine population. Figure 4 shows the food source vegetation of the flying-foxes identified within 10 km range of the equine population. The food source vegetation was examined using Getis-Ord General G Statistic method. The clustering of the vegetation was studied at 3, 5 and 10 km from the equine population. The analysis indicated a significant high clustering of the food source vegetation at all distance thresholds. Table 1 shows the high/low clustering report of the food source vegetation at different distance thresholds. Table 1. High/low clustering report of the flying-fox food source vegetation identified near the equine population.

Discussion of the Results This study identified the food source vegetation of black and grey headed flying-foxes present within 10 km of the equine population in the study area (Figure 4). The identification of the food source vegetation in the equine population range indicates a plausible relationship between the type of vegetation present near the equine properties and the Hendra virus incidents. The food source vegetation within 10 km range from individual equine properties was examined using high/low clustering method at three different distance thresholds 3, 5 and 10 km (Table 1). The results indicated statistically

Distance Threshold Getis-Ord General G Statistic Report High/Low Clustering3 Kilometers Observed General G - 0.00005; z-score - 68.14; p-value - 0.00000 High Clusters5 Kilometers Observed General G - 0.00007; z-score - 66.26; p-value - 0.00000 High Clusters10 Kilometers Observed General G - 0.00011; z-score - 57.6; p-value - 0.00000 High Clusters

significant high clustering of the food source vegetation near the equine properties at all three distance thresholds. The food source vegetation study near the outbreak events in the study area was only clustered at 3 km threshold and then started to disperse widely. A further study on the seasonal (flowering & fruiting) food source vegetation of the flying-foxes near the equine population and outbreak events together would be beneficial in understanding the disease outbreaks. Conclusion This study established a primary spatial relationship between food source vegetation of the flying-foxes and the equine population in the study area. A 10 km range vegetation study on the equine properties in the study area identified the food source vegetation of both black and grey headed flying-foxes. The high/low clustering/Getis-Ord General G Statistic method indicated statistically significant high clustering of the food source vegetation identified near the equine population at 3, 5 and 10 km distance thresholds. The presence of significantly clustered food source vegetation of flying-foxes within 10 km range of the equine properties suggests a strong spatial relationship between the two variables. References Burnham J., Chong A., Xiaoye L. and Moore A. (2015). Preliminary spatial analysis of

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