Climate change and parasite transmission: how temperature affects parasite infectivity via predation on infective stages

Abstract

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 temperaturedependent, 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.

Latitudinal gradients of parasite richness: a review and new insights from helminths of cricetid rodents

“…Final models were chosen based on lowest AICc scores using model selection functions in R. Significance codes: '*' ≤ 0.05, '**' ≤ 0.01, '***' ≤ 0.001. Disentangling these influences is the topic of previous and ongoing research (Møller et al 2013, Goedknegt et al 2015, Mignatti et al 2016, Gehman et al 2018. λ is an estimate of the phylogenetic signal in the analysis and ranges from 0 (no phylogenetic signal in data) to 1 (Brownian motion).…”

“…when eggs are deposited in the environment for transmission or during free-living larval or adult stages) and can independently affect the host species, which in turn can influence host exposure and susceptibility to infection by helminths. Disentangling these influences is the topic of previous and ongoing research (Møller et al 2013, Goedknegt et al 2015, Mignatti et al 2016, Gehman et al 2018.…”

A niche perspective on the range expansion of symbionts

“…In addition, dispersal of symbionts with free‐living transmission stages can be impeded by off‐host environmental conditions. For instance, ultraviolet radiation and predatory pressure increase mortality in trematode cercariae (Studer & Poulin, ; Goedknegt et al ., ). The enemy release hypothesis provides additional indirect support for the existence of strong filters acting on symbionts during host invasion processes [Keane & Crawley, ; Torchin et al ., ; Prenter et al ., ; Tompkins et al ., ; Roy & Handley, ; Stewart et al ., ; see Colautti et al ., for criticisms].…”

How invasive oysters can affect parasite infection patterns in native mussels on a large spatial scale

“…Due to the crucial role of invasive species in these parasite infection scenarios, the presence and abundance of an invader has the potential to affect local parasite infection levels in native hosts (Kelly et al 2009;Poulin et al 2011;Telfer and Brown 2012). While such effects have been studied experimentally (e.g., Kopp and Jokela 2007;Thieltges et al 2009, Goedknegt et al 2015, surprisingly few studies have attempted to study the effects of invasive species on infection patterns in native hosts in the field (but see Paterson et al 2011Paterson et al , 2013 who used a combined approach). Parasite infection levels in native hosts are not only potentially affected by invasive species but also influenced by many other factors which have been shown to underlie the generally high spatial heterogeneities in infection levels observed in the field (Thieltges and Reise 2007;Byers et al 2008;Wilson et al 2011;Galaktionov et al 2015;Stringer and Linklater 2015).…”