Combining genetic diversity and spatio-temporal data to characterize the spatial ecology of anthrax across multiple scales

This dissertation explores the relationships between genetic diversity and ecology for Bacillus anthracis, the causative agent of anthrax. The work addresses two major questions about these relationships, namely, the possibility of ecological differences between genetic lineages and the use of genetic information to understand outbreak dynamics. First, ecological niche modeling using the Genetic Algorithm for Rule-Set Production (GARP) was used to compare the ecological niche of a single genetic sub-lineage of the pathogen to that of a broader collection. Sub-lineage specific niche models were then tested for transferability to novel landscapes on which the same genetic grouping was found. Second, high resolution genetic analyses were used in conjunction with spatial analyses to explore potential transmission pathways within a single, large, anthrax outbreak. High resolution genotyping was then applied to a larger collection of anthrax isolates from multiple outbreaks. These outbreaks involved diverse host groups, from single host species to combinations of wildlife and livestock, and three major genetic lineages. Results of the ecological niche modeling support ecological differences between sub-lineages of B. anthracis and suggest that predictive models of anthrax persistence can be refined by characterizing the local population's genetic structure and using the dominant genotype for niche modeling. Transferred models appear to be negatively affected by either genetic-ecological differentiation at a different level of genetic analysis then employed in this study, or by methodological restraints on transferability. The results of the spatial analyses suggest that anthrax transmission events occur within a limited spatial area, and, with high resolution genetic analysis, that areas of high transmission correspond to higher genetic diversity during an outbreak. In addition, there is evidence that wildlife and domesticated animals share either a common source of B. anthracis infection or are in close contact to facilitate transmission during an outbreak, emphasizing the importance of anthrax surveillance in wildlife in areas where livestock is also managed. This work includes the first genetically informed ecological niche models for B. anthracis and the first effort to combine multiple levels of genetic analysis with spatial analyses to understand anthrax outbreak dynamics. The results should guide approaches to future additional investigations of anthrax ecology.