Snail species diversity impacts the infection patterns of Echinostoma spp.: Examples from field collected data

Abstract

Rapid losses of biodiversity due to the changing landscape have spurred increased interest in the role of species diversity and disease risk. A leading hypothesis for the importance of biodiversity in disease reduction is the dilution effect, which suggests that increasing species diversity within a system decreases the risk of disease among the organisms inhabiting it. The role of species diversity in trematode infection was investigated using field studies from sites across the U.S. to examine the impact of snail diversity in the infection dynamics of both first and second intermediate larval stages of Echinostoma spp. parasites. The prevalence of Echinostoma spp. sporocysts/rediae infection was not affected by increases in snail diversity, but significant negative correlations in metacercariae prevalence and intensity with snail diversity were observed. Additionally, varying effectiveness of the diluting hosts was found, i.e., snail species that were incompatible first intermediate hosts for Echinostoma spp. were more successful at diluting the echinostome parasites in the focal species, while H. trivolvis, a snail species that can harbor the first intermediate larval stages, amplified infection. These findings have important implications not only on the role of species diversity in reducing disease risk, but the success of the parasites in completing their life cycles and maintaining their abundance within an aquatic system.

Community disassembly and disease: realistic—but not randomized—biodiversity losses enhance parasite transmission

“…Similar 'identity effects' for particular species in diluting infection among focal hosts has also been demonstrated for other disease systems (e.g. [49]). Debate surrounding the dilution effect hypothesis has often centred around whether observed changes in infection levels stem from shifts in host diversity or in host species composition.…”

Interactions between two functionally distinct aquatic invertebrate herbivores complicate ecosystem- and population-level resilience

“…Both species of herbivore represented in our experiment are known to to be important in nitrogen cycling and likely both raise nitrogen concentrations (e.g., Paterson et al, 2002 ; Mulholland et al, 1991 ; Griffiths & Hill, 2014 ). Although the experimental snail populations may appear small, 1–3 snail per 1L of water represents a high density ( Zimmermann, Luth & Esch, 2017 ). Thus, the effect of snails on nutrients may be consistent with expectations based on natural systems ( Hall Jr, Tank & Dybdahl, 2003 ).…”

Exploring how ecological and epidemiological processes shape multi-host disease dynamics using global sensitivity analysis

“…Many studies have argued that the relationships species richness (i.e., the number of host species) and disease levels in a focal host are likely to be context dependent (LoGiudice et al, 2008; Randolph and Dobson, 2012; Rohr et al, 2020; Halliday et al, 2020). Previous empirical studies (Telfer et al, 2005; Dizney and Ruedas, 2009; Searle et al, 2016; Levine et al, 2017; Hydeman et al, 2017; Zimmermann et al, 2017; Luis et al, 2018) and theoretical studies (Dobson, 2004; Rudolf and Antonovics, 2005; Joseph et al, 2013; Mihaljevic et al, 2014; O’Regan et al, 2015; Searle et al, 2016; Faust et al, 2017; Roberts and Heesterbeek, 2018; Cortez and Duffy, 2021; Cortez, 2021) have shown that whether the addition of a host species leads to increased or decreased disease in a focal host depends on the specific characteristics (e.g., competitive ability or disease competence) of the host species that are present in the community and added to the community. The time varying signs and magnitudes of the global sensitivities in this study suggest that the context dependent relationships may also depend on the time scale of interest.…”

“…Many empirical studies have shown that the absence or presence of a second host species can increase or decrease levels of disease in a focal host species (Telfer et al, 2005; Dizney and Ruedas, 2009; Searle et al, 2016; Levine et al, 2017; Hydeman et al, 2017; Zimmermann et al, 2017; Luis et al, 2018). This empirical work is complemented by modeling studies exploring how specific processes shape disease dynamics in two-host communities (Rudolf and Antonovics, 2005; O’Regan et al, 2015; Searle et al, 2016; Roberts and Heesterbeek, 2018; Cortez and Duffy, 2021).…”