Working with partners from Italy, Kazakhstan, and the US (Louisiana State University), Drs. Jocelyn Mullins and Jason Blackburn developed ecological niche models of Bacillus anthracis, the causative agent of anthrax, to predict the geographic distribution of the disease across the landscape of each country. The work was published in PLOS ONE. Previous studies have built models of the pathogen using outbreak data, which represent multiple genetic lineages of the pathogens. In Dr. Mullins recent work, we showed that within Kazakhstan, the A1.a lineage of B. anthracis had a different ecological envelope than models built using all outbreak data. The A1.a lineage is a broadly geographically distributed lineage with a large number of representative samples in the global pathogen collections that have been used in global phylogenetic analyses. In this study, we focused on building ecological niche models of the pathogen using only occurrence data that had been genotyped using the MLVA-8 genotyping technique to assign each outbreak location to the A1.a lineage. We built models for each country and then tranferred those models onto the other countries. The goal was to determine if we could successfully predict B. anthracis suitable environments across the landscapes using any given country. If the lineage had a single or very broad ecological envelope, then transferred models should predict all three landscapes well. To the contrary, we found that each country was best predicted by the native locations defining pathogen presence. In this way, we were not able to develop a single model that predicted all three landscapes, suggesting that B. anthracis may have adapted to different regional or local ecological conditions on each landscape.
This study presents an exciting direction forward linking ecological niche modeling approaches with phylogenetics to improve our understanding of the geography and ecological conditions associated with pathogen persistence across different landscapes. The results also suggest that these modeling approaches may be best interpreted on native landscapes and future work is needed to identify better approaches for predicting unknown landscapes. Ecological niche models provide researchers and policy makers with tools for estimating the geographic potential for a species on the landscape. From an epidemiological point of view, such models may inform policy by identifying conditions and locations on the landscape where the pathogen may be persisting, providing maps for surveillance planning and educational outreach. This study suggests that such modeling should be coupled with high resolution genetic analyses (improving upon the resolution limits of this current paper) to best predict the geographic potential for the pathogen and anthrax outbreaks. Such modeling remains an important task for anthrax, particularly as we learn more about the persistence of the disease in wildlife populations where vaccination control is untenable. It is also important to understand this disease in agrarian and developing countries where the disease burden in humans is highest.
This work was completed by Dr. Jocelyn Mullins (DVM, PhD) as part of her doctoral dissertation work within the Department of Geography. Dr. Mullins is currently a fellow with the US CDC’s Epidemiological Intelligence Service, stationed in Connecticut’s Department of Health. This work was partially funded by the US Defense Threat Reduction Agency and the the UF Emerging Pathogens Institute.