Climate changes are likely to strongly impact disease transmission worldwide, but this may be particularly important in areas that concentrate hosts and their parasites. Watering holes provide an ideal system for investigating the effects of climate changes on disease transmission, as they provide a resource hotspot for a wide range of wildlife and livestock, can have microclimatic effects on parasite survival, and are likely to be strongly affected by climate changes and expanding human development.
In this study, we compare dry and wet season parasite density at permanent and ephemeral watering holes to control sites (> 1km from water) at 17 locations across a steep rainfall gradient in central Kenya. We use dung surveys and helminth egg floatation techniques on environmental matrices (soil, water, and sediment) to test our hypothesis that watering holes have stronger effects in increasing parasite density in drier regions and at permanent water sources. We also test this effect on host density using dung surveys and camera trapping. Finally, we characterize vegetative community and woody cover at all sites to explore potential interactions with parasite survival and host behavior due to predation pressure and food availability.
Results/Conclusions
Preliminary results show that total parasite density and diversity is greater at watering holes relative to controls. Parasite egg density at watering holes is 200% greater than controls as a result of increased host dung density, with this effect being stronger in drier regions. For parasites in soil, density at watering holes is elevated relative to controls, but this effect is an order of magnitude greater for wet soils at the water’s edge. Furthermore, permanent water sources have higher parasite density than seasonally-ephemeral water sources. We also find similar increases in host density at watering holes in drier and warmer regions. However, large-bodied and highly water-dependent species drive this response, while smaller wildlife responses vary over rainfall season. Finally, we found that vegetative structure and plant species composition differs between watering holes and controls, with potential implications that vegetation could also drive differences in host movement and parasite survival in the environment.
Together, these results suggest that both seasonal and long-term climatic factors can substantially influence host and parasite density at water sources. These data also have numerous implications for disease transmission among wild and domestic animals and direct applications for water management and disease monitoring in dryland ecosystems.