Cooperative Fish and Wildlife Research Units Program: all
Education, Research and Technical Assistance for Managing Our Natural Resources

Anthrax outbreaks across Africa pose serious threats to people, livestock, and wildlife and can be exacerbated by environmental change. However, little is known about how the quantitative spatial dynamics of host movement and environmental change may affect the spread of Bacillus anthracis – the causative agent of anthrax. Here, we use real-time observation and high-resolution tracking data from a population of common hippopotamus (Hippopotamus amphibius) to explore the relationship between changing river hydrology, H. amphibius movement, and the spatiotemporal dynamics of an active anthrax outbreak. We found that changes in water availability indirectly facilitated the spread of B. anthracis by modulating H. amphibius movements. Our findings reveal that anthrax spread upstream in the Great Ruaha River, which followed the movement patterns of infected H. amphibius, who moved upstream as the river dried in search of remaining aquatic refugia. Moreover, infection by B. anthracis did not appear to influence H. amphibius movement behaviours. Contact rates between H. amphibius and B. anthracis-infected river pools are heterogeneous and the frequency and duration of contacts increase the probability of mortality. While difficult to obtain, the quantitative insights that we gathered during a real-time anthrax outbreak are critical to better understand, predict, and manage future outbreaks.