Host-parasite interactions are an integral part of ecosystems that influence both ecological and evolutionary processes. Humans are currently altering environments the world over, often with drastic consequences for host-parasite interactions and the prevalence of parasites. The mechanisms behind the changes are, however, poorly known. Here, we explain how host-parasite interactions depend on two crucial steps--encounter rate and host-parasite compatibility--and how human activities are altering them and thereby host-parasite interactions. By drawing on examples from the literature, we show that changes in the two steps depend on the influence of human activities on a range of factors, such as the density and diversity of hosts and parasites, the search strategy of the parasite, and the avoidance strategy of the host. Thus, to unravel the mechanisms behind human-induced changes in host-parasite interactions, we have to consider the characteristics of all three parts of the interaction: the host, the parasite and the environment. More attention should now be directed to unfold these mechanisms, focusing on effects of environmental change on the factors that determine encounter rate and compatibility. We end with identifying several areas in urgent need of more investigations.
Humans are currently altering aquatic ecosystems through overfishing and nutrient loading. This is altering ecosystems through top-down and bottom-up processes. In the Baltic Sea, the removal of top predators has increased the density of mesopredators, while eutrophication has boosted primary production. Using a mesocosm experiment, we show that a high density of a mesopredator-the threespine stickleback Gasterosteus aculeatus-increases the biomass of primary production not transferred to higher trophic levels under simplified ecosystem conditions. However, no effect of stickleback density on algae biomass is detected in the field, although stickleback gut inspection reveals that stickleback are feeding on amphipods, and stickleback density tends to correlate negatively with amphipod density in the field. This suggests that trophic cascades induced by the mesopredator release are attenuated in the field and do not reach primary producers. This is probably caused by the complexity of the ecosystem where many processes regulate the food web, such as bottom-up effects, the presence of alternative prey and density-dependent predation and distribution. However, the degree to which the ecosystem will be able to buffer further changes, if human disturbances continue, is unknown. Trophic cascades that reach primary producers could have drastic consequences for the ecosystem by promoting the accumulation of drifting algal mats that alter the benthic habitat.
Summary1. Recent research in biomedicine and in ecology has linked disease emergence and resurgence with human-induced environmental change. Water bodies, in particular, have dramatically changed during the past century due to artificial enrichment of nutrients from diverse sources (e.g. agriculture, forestry, waste discharges). A growing number of studies, reviewed in this synthesis, highlights how these alterations are tightly linked to changes in host-parasite interactions and impact wildlife health. 2. Direct responses of aquatic ecosystems to the disturbance include changes in the community of primary producers and cause indirect responses such as turbidity, oxygen depletion and foodweb alteration; a phenomenon known as anthropogenic eutrophication. Ultimately, eutrophication causes a wide range of effects on host-parasite interactions which should all be considered to predict infection probability and outcome in disturbed areas. 3. Future research should encompass a more fundamental and holistic view of eutrophication, considering altogether the multitude of environmental changes encountered in eutrophied sites. Stronger collaborations among disease biologists and aquatic ecologists are necessary to better understand and manage wildlife health at impacted water bodies.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.