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The global distribution of Bacillus anthracis and associated anthrax risk to humans, livestock and wildlife

Nature Microbiology volume 4, pages 1337–1343 (2019)Cite this article

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Abstract

Bacillus anthracis is a spore-forming, Gram-positive bacterium responsible for anthrax, an acute infection that most significantly affects grazing livestock and wild ungulates, but also poses a threat to human health. The geographic extent of B. anthracis is poorly understood, despite multi-decade research on anthrax epizootic and epidemic dynamics; many countries have limited or inadequate surveillance systems, even within known endemic regions. Here, we compile a global occurrence dataset of human, livestock and wildlife anthrax outbreaks. With these records, we use boosted regression trees to produce a map of the global distribution of B. anthracis as a proxy for anthrax risk. We estimate that 1.83 billion people (95% credible interval (CI): 0.59–4.16 billion) live within regions of anthrax risk, but most of that population faces little occupational exposure. More informatively, a global total of 63.8 million poor livestock keepers (95% CI: 17.5–168.6 million) and 1.1 billion livestock (95% CI: 0.4–2.3 billion) live within vulnerable regions. Human and livestock vulnerability are both concentrated in rural rainfed systems throughout arid and temperate land across Eurasia, Africa and North America. We conclude by mapping where anthrax risk could disrupt sensitive conservation efforts for wild ungulates that coincide with anthrax-prone landscapes.

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Fig. 1: Global distrubtion of outbreaks by country and geographic locations of anthrax events.
Fig. 2: Global distribution of B. anthracis suitability (probability of occurrence).
Fig. 3: Map of average anthrax vaccination rates per country for all livestock species.

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Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request and approval from appropriate partner country ministries of health or agriculture.

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Acknowledgements

The authors thank D. Pigott for helpful tips on BRT modelling; A. Barner for help obtaining World Animal Health Information System vaccination data; S. J. Ryan for general feedback and technical support; G. Simpson for visualization advice; P. Thornton for access to the global dataset of rural poor livestock keepers; T. A. Joyner for data support; and countless livestock and wildlife managers, clinicians and field technicians for contributing data points. Partial funding for this study was provided by NIH 1R01GM117617-01 to J.K.B. and W.M.G. C.J.C. was supported by the National Socio-Environmental Synthesis Center (SESYNC) under funding received from the National Science Foundation DBI-1639145. K.A. was supported in part under the National Science Foundation (NSF EEID grant 1518663). We also thank the Botswana Government Department of Wildlife and National Parks for their assistance and active collaboration on research directed at understanding Botswana anthrax dynamics.

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Author notes

  1. These authors contributed equally: Colin J. Carlson, Ian T. Kracalik.

Authors and Affiliations

  1. National Socio-Environmental Synthesis Center, University of Maryland, Annapolis, MD, USA

    Colin J. Carlson

  2. Department of Biology, Georgetown University, Washington, Washington DC, USA

    Colin J. Carlson

  3. Spatial Epidemiology & Ecology Research Lab, Department of Geography, University of Florida, Gainesville, FL, USA

    Ian T. Kracalik & Jason K. Blackburn

  4. Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA

    Ian T. Kracalik & Jason K. Blackburn

  5. EcoHealth Alliance, New York, NY, USA

    Noam Ross

  6. Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA, USA

    Kathleen A. Alexander

  7. School of the Coast and Environment, Louisiana State University, Baton Rouge, LA, USA

    Martin E. Hugh-Jones

  8. AgriBio, Centre for Agribiosciences, Biosciences Research, Department of Economic Development, Jobs, Transport and Resources, Bundoora, Victoria, Australia

    Mark Fegan

  9. Department of Environment and Natural Resources, Government of the Northwest Territories, Yellowknife, Northwest Territories, Canada

    Brett T. Elkin

  10. Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada

    Tasha Epp

  11. Parks Canada Agency, Saskatoon, Saskatchewan, Canada

    Todd K. Shury

  12. Center for Disease Surveillance & Research, Institute of Disease Control and Prevention of PLA, Beijing, China

    Wenyi Zhang

  13. Scientific Research Veterinary Institute, Baku, Azerbaijan

    Mehriban Bagirova

  14. Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, CA, USA

    Wayne M. Getz

Authors
  1. Colin J. Carlson
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Contributions

C.J.C., I.T.K. and J.K.B. conceived of the study. J.K.B., M.E.H.-J., I.T.K. and C.J.C. collected and georeferenced data. C.J.C., I.T.K. and J.K.B. designed the models, and C.J.C. ran models and analyses. N.R. contributed R code. All authors contributed to the writing and editing of the draft and approved the study before submission.

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Correspondence to Jason K. Blackburn.

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Supplementary Text and Discussion, Supplementary Figures 1–21, Supplementary Tables 1–33 and Supplementary References.

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Carlson, C.J., Kracalik, I.T., Ross, N. et al. The global distribution of Bacillus anthracis and associated anthrax risk to humans, livestock and wildlife. Nat Microbiol 4, 1337–1343 (2019). https://doi.org/10.1038/s41564-019-0435-4

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