Abstract
Climate change is expected to affect disease risk in many parasite‐host systems, e.g., via an effect of temperature on infectivity (temperature effects). However, recent studies indicate that ambient communities can lower disease risk for hosts, for instance via predation on free‐living stages of parasites (predation effect). Since general physiological theory suggests predation effects to be temperature‐dependent, we hypothesized that increases in temperature may lead to reduced parasite infectivity via elevated consumption rates of free‐living parasite stages (temperature‐predation interaction). We experimentally investigated such interactions in three marine predators of infective parasite stages. Two species (the oyster Crassostrea gigas, and the barnacle Austrominius modestus) significantly reduced cercarial stages of the trematode Renicola roscovita in mussel hosts (Mytilus edulis), while the third (the crab Hemigrapsus takanoi) did not show a reduction of infective stages at all. In barnacles, cercarial consumption significantly interacted with temperature, with lowest infectivity at highest temperatures. Since these patterns reflected the known thermal responses of the three cercarial predators' feeding rates, parasite consumption rates may be predictable from temperature dependent feeding rates. Our results suggest that integrating temperature‐predation interactions into studies on parasite transmission and on climate change effects is essential and that predators of free‐living stages of parasites may play an important role in indirectly mediating disease risk under climate change.
Highlights
Various studies have suggested that climate change may lead to elevated disease risk in wildlife and humans with wide-ranging ecological and economic effects (Harvell et al 2002, Patz et al 2005)
Since cercarial transmission is a crucial step in the trematode life cycle, it has been proposed that global warming might dramatically increase future infection levels in hosts (Marcogliese 2001, Poulin 2006, Poulin and Mouritsen 2006)
The three cercarial predators showed different responses resulting in different cercarial infectivity with increasing temperature (Fig. 1)
Summary
Various studies have suggested that climate change may lead to elevated disease risk in wildlife and humans with wide-ranging ecological and economic effects (Harvell et al 2002, Patz et al 2005). A clear and strong effect of temperature on disease dynamics is known from trematodes (flukes) in which it directly affects crucial steps in their transmission between life cycle stages. The production and emergence of their free-living infective stages (cercariae) in the first intermediate hosts (mollusks) is strongly positively correlated with temperature (see review by Poulin 2006). Species) is positively correlated with temperature (e.g., Evans 1985, Thieltges and Rick 2006, Studer et al 2010). Since cercarial transmission is a crucial step in the trematode life cycle, it has been proposed that global warming might dramatically increase future infection levels in hosts (Marcogliese 2001, Poulin 2006, Poulin and Mouritsen 2006)
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