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By Kathleen Alexander, DVM PhD
Water is central to all life and a fundamental requirement for human wellbeing and health - from the production of food and drinking water to the provision of adequate sanitation. There is little in life, indeed, that does not require water at some point.
Despite our dependency, surface water resources can, in some instances, have a more insidious influence on our health, creating potential conduits for the movement of waterborne pathogens and antimicrobial resistance, crossing divergent landscapes and human, animal, and wildlife populations.
Botswana provides an important example, a dryland region with only three sources of surface water; water scarcity is an overriding concern across sectors. Competition for scarce surface water resources crosses land type, from urban centers and agriculture productions systems to protected landscapes where water-dependent wildlife species find safe haven.
In a recent paper “The Changing Face of Water: A Dynamic Reflection of Antibiotic Resistance across Landscapes,” published in Frontiers in Microbiology, Claire Sanderson and I report something surprising and significant. In these more pristine landscapes found in Northern Botswana, commercial agriculture and large medical facilities are absent. Even so, we found widespread antimicrobial resistance across surface waters through both urban and protected land areas.
Escherichia coli is a microbe that can be used as an indicator for fecal contamination and antibiotic resistance (AR) dissemination. Using this system, we identified widespread AR in E. coli Isolates obtained from the Chobe River, even within the protected landscapes of the national park up river of the urban center. AR patterns in water were similar to that found in humans and wildlife.
Without commercial agricultural inputs masking other contributors to AR dissemination, results suggest that human inputs alone are sufficient for widespread AR movement in surface water, water that is used by the local population.
What do these findings mean for our understanding of surface water resource management and control of AR? Commercial agriculture, while important in AR dissemination, is likely not the only culprit. Humans, it appears, are capable of directly polluting the environment with AR, independent of agricultural inputs, impacts that can reach beyond urban landscapes. Hence, the singular focus on agriculture as a control point will not likely solve the problem.
How are wildlife and surface waters exposed to human inputs, particularly in protected landscapes? Wildlife, we found, can provide important answers. Each wildlife species is different, not only in how they might look but how they go about the business of living and reproducing. These differences can be leveraged to help us isolate exposure points for AR movement.
Together with Sarah Jobbins (previously of Virginia Tech), we found that resistance was not ubiquitous across wildlife species but rather certain attributes were associated with higher levels of multidrug resistance (MDR, resistance to three or more antibiotics) across wildlife species.
In our paper, “From Whence they Came – Antibiotic-resistant Escherichia Coli in African Wildlife,” we report that MDR was higher in carnivores and urban adapted species (warthogs, baboons). But most interesting was the finding that animals that were associated with the river, such as hippos and waterbuck, had significantly higher levels of MDR than those species that only drank water, such as impala.
These data suggest that the river is an important exposure point even in the national park– but exposure does not arise by simply ingesting water. We still don’t know why this is the case, but we are one step closer to understanding the importance of surface water in AR movement across the human-wildlife-water interface.
This research was funded by the National Science Foundation (NSF) Dynamics of Coupled Natural and Human Systems Awards, CNH #1518486 and CNH #1114953.