Water sources are vital hotspots for wildlife, domestic animals, and humans in arid landscapes, yet they may also facilitate disease transmission among many hosts. Despite this seemingly intuitive observation, there has been relatively little empirical work for multi-pathogen/multi-host systems. This is partially due to two substantial challenges facing disease ecologists: 1) capturing movement and behavior for multiple host species, and 2) identification of pathogens and their relevant hosts. Here, we integrated a range of approaches to overcome these challenges in a study system that is diverse in both hosts and parasites: helminth communities across a broad ungulate assemblage in an East African savanna.
In this study, we investigated how experimental water removal and resupply could change a landscape of parasite transmission risk via shifts in host movement. Using field studies, long-term camera trapping, and citizen scientist contributions, we measured changes in dung density, host aggregation, and species richness following experimental water draining and refilling. To account for parasite transmission among multiple hosts, we conducted metabarcoding on the dung of 13 different ungulate species to reveal likely parasite sharing. Finally, we linked these results to understand how water supply may affect parasite transmission among hosts connected via a network of parasite sharing.
Results/Conclusions
Our results show that daily host species richness at water sources is three times higher than at non-water control sites, and that experimental water removal resulted in a two to ten-fold reduction in aggregation for large bodied animals (elephants and cattle), but with relatively little effect for smaller herbivores. Total dung cover more than doubled at water sources, with largest effects for elephants and cattle. Metabarcoding showed a higher diversity of the parasite community than would be detected using morphological methods, and that more than half of all parasites associated with only one or two host species. However, we also found a small number of generalist parasites that infected several different host species. Of the animals most affected by water removal, elephant parasites were less common in other host species, but cattle shared several parasites with other ungulates. Together these results suggest that cattle have the potential to substantially affect interspecies transmission of these parasites at water sources. These results are likely to be highly relevant given the impact of climate change and human development on water sources in arid lands, in addition to conservation and disease emergence concerns in areas of increasing human-wildlife overlap.