Environmental determinants influencing anthrax distribution in Queen Elizabeth Protected Area, Western Uganda

Margaret Driciru, Innocent B. Rwego, Sood A. Ndimuligo, Dominic A. Travis, Elibariki R. Mwakapeje, Meggan Craft, Benon Asiimwe, Julio Alvarez, Samuel Ayebare, Katharine Pelican

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Bacillus anthracis, the bacteria that causes anthrax, a disease that primarily affects herbivorous animals, is a soil borne endospore-forming microbe. Environmental distribution of viable spores determines risky landscapes for herbivore exposure and subsequent anthrax outbreaks. Spore survival and longevity depends on suitable conditions in its environment. Anthrax is endemic in Queen Elizabeth Protected Area in western Uganda. Periodic historical outbreaks with significant wildlife losses date to 1950s, but B. anthracis ecological niche in the ecosystem is poorly understood. This study used the Maximum Entropy modeling algorithm method to predict suitable niche and environmental conditions that may support anthrax distribution and spore survival. Model inputs comprised 471 presence-only anthrax occurrence data from park management records of 1956–2010, and 11 predictor variables derived from the World Climatic and Africa Soil Grids online resources, selected considering the ecology of anthrax. The findings revealed predicted suitable niche favoring survival and distribution of anthrax spores as a narrow-restricted corridor within the study area, defined by hot-dry climatic conditions with alkaline soils rich in potassium and calcium. A mean test AUC of 0.94 and predicted probability of 0.93 for anthrax presence were registered. The five most important predictor variables that accounted for 93.8% of model variability were annual precipitation (70.1%), exchangeable potassium (12.6%), annual mean temperature (4.3%), soil pH (3.7%) and calcium (3.1%). The predicted suitable soil properties likely originate from existing sedimentary calcareous gypsum rocks. This has implications for long-term presence of B. anthracis spores and might explain the long history of anthrax experienced in the area. However, occurrence of suitable niche as a restricted hot zone offers opportunities for targeted anthrax surveillance, response and establishment of monitoring strategies in QEPA.

Original languageEnglish (US)
Article numbere0237223
JournalPloS one
Issue number8
StatePublished - Aug 2020

Bibliographical note

Publisher Copyright:
This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.


  • Animals
  • Anthrax/epidemiology
  • Bacillus anthracis/physiology
  • Climate
  • Conservation of Natural Resources
  • Disease Outbreaks
  • Ecosystem
  • Environment
  • Humans
  • Microbial Viability
  • Models, Biological
  • Risk Factors
  • Soil/chemistry
  • Soil Microbiology
  • Spores, Bacterial/physiology
  • Uganda

PubMed: MeSH publication types

  • Research Support, Non-U.S. Gov't
  • Journal Article


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