Pathogen Interactions, Population Cycles, and Phase Shifts

Abstract

Interspecific pathogen interactions can profoundly affect pathogen population dynamics and the efficacy of control strategies. However, many pathogens exhibit cyclic abundance patterns (e.g. seasonality) and temporal asynchrony between interacting pathogens has the potential to reduce the impact of those interactions. Here we use an extension of our previously published model to investigate the effects of cyclic abundance patterns on pathogen interaction. We demonstrate that for interactions mediated through host immunity, immune memory can maintain the impact of an interaction even when the effector pathogen abundance is low or the pathogen is absent. Paradoxically, immune memory can result in pathogens interacting more strongly when temporally out of phase.We find that interactions between species can not only alter pathogen abundance but can also result in changes to the temporal pattern of the affected species. We further demonstrate that this phenomenon may be observed in a natural host / pathogen data set.Given that there is both a continuing debate as to the relevance of pathogen interactions in natural systems and increasing concern regarding treatment of coinfections of veterinary and medical importance, both the discovery of this measurable shift in cycle in the empirical data and the mechanism by which we identified the shift are important. Finally, as the model structure used here is analogous to simple predator-prey system models we also consider the consequences of these findings in the context of that system.

The helminth community of the Iberian hare, Lepus granatensis (Lagomorpha: Leporidae), in the province of Granada, Spain

“…Interactions between T. retortaeformis and other parasites of lagomorphs may result in changes in the temporal pattern of the affected species. This effect was reported by Lello et al (2008) with respect to Graphidium strigosum. The oxyurid P. ambiguus has been reported to parasitize the large intestine and the caecum of rabbits, cottontails and hares all over the world (Harkness et al, 2010).…”

Parasite–Parasite Interactions in the Wild: How To Detect Them?

“…Cascade effects of parasite-parasite interactions can also translate into modifications of the temporal dynamics of the interacting parasites. Cross-immunity phenomena between two gut helminths of the wild rabbit (Oryctolagus cuniculus) were shown to induce a shift in the seasonal abundance of the two parasites in the rabbit population, forcing them to be out of phase [48].…”

Parasite competition hidden by correlated coinfection: using surveys and experiments to understand parasite interactions

“…But within each of these easily-observed groups exists another community of interacting parasite species. Although most studies focus on single-host-single-pathogen interactions, growing evidence suggests that interactions among co-occurring parasites can influence host pathology, parasite transmission, and the evolution of virulence (Cox 2001, Pedersen and Fenton 2007, Lello et al 2008, Telfer et al 2008, Lively 2009. A promising frontier in understanding parasite interactions within hosts involves applying the principles of community ecology to within-host communities (Pedersen and Fenton 2007, Poulin 2007, Graham 2008.…”