Mechanisms by which predators mediate host–parasite interactions in aquatic systems

• Published in: Trends in parasitology 2021-10, Vol.37 (10), p.890-906
• Main Authors: Lopez, Laura K., Duffy, Meghan A.
• Format: Article
• Language: English
• Subjects: disease; healthy herds; infection; parasite; predation; prey
• ISSN: 1471-4922; 1471-5007
• DOI: 10.1016/j.pt.2021.06.006

It is often assumed that predators reduce disease prevalence and transmission by lowering prey population density and/or by selectively feeding on infected individuals. However, recent studies, many of which come from aquatic systems, suggest numerous alternative mechanisms by which predators can influence disease dynamics in their prey. Here, we review the mechanisms by which predators can mediate host–parasite interactions in aquatic prey. We highlight how life histories of aquatic hosts and parasites influence transmission pathways and describe how such pathways intersect with predation to shape disease dynamics. We also provide recommendations for future studies; experiments that account for multiple effects of predators on host–parasite interactions, and that examine how predator–host–parasite interactions shift under changing environmental conditions, are particularly needed. Predators mediate host–parasite interactions in their prey by lowering prey population density, selectively consuming infected individuals, feeding on free-living parasites, spreading disease propagules, inflicting injury on prey, and trait-mediated indirect effects.Whether predation increases or decreases parasite prevalence and transmission in prey depends on various factors, including habitat features, predator foraging behavior, parasite transmission mode, and prey life history.Understanding how predator foraging behavior affects parasite mortality and transmission could help to predict how predation influences parasite populations in prey.More research is needed to understand how mechanisms that can occur simultaneously, such as trait-mediated indirect effects and density-mediated indirect effects, interact, and how global change will alter predator–host–parasite interactions.