Shifts in landscape heterogeneity and climate can influence animal behavior and movement in ways that profoundly alter disease transmission. Amid accelerating climate and land use changes, it is increasingly important to identify and monitor hotspots of increased animal activity and overlap where disease transmission is likely to occur. Water sources that are foci of animal activity have great potential to promote disease transmission, but there has been very little work to quantify this, nor any comparison across a range of hosts and climatic contexts. In the case of fecal-oral parasites, water resources can aggregate large groups of many different host species in small areas, concentrate infectious material, and function as disease hotspots. This may be exacerbated where water is scarce and for species that require frequent drinking water access.
Working in an East African savanna, we show via experimental and observational methods that water sources increase the density of wild and domestic herbivore feces and thus, the concentration of fecal-oral parasites in the environment, by up to two orders of magnitude. Our results show that this effect is amplified in drier areas and following periods of low rainfall, creating dynamic and heterogeneous disease landscapes across space and time. In addition, we show via camera trapping methods that herbivore grazing behaviors that expose them to fecal-oral parasites are often increased at water sources relative to background sites, thereby creating landscape hotspots of potential disease transmission. Critically, this effect varies markedly by herbivore species, with strongest effects observed for two large, water-dependent animals that are of critical concern for conservation and development: elephants and cattle.
When water availability is reduced – a global pattern that is increasing amid climate changes and growing anthropogenic water use – risk of parasite exposure may increase substantially, posing multiple threats to critical taxa. These findings are important for understanding shifting parasite dynamics for several threatened wildlife species and for pastoral livelihoods in response to changing water supply due to climate changes.