Major drivers of biodiversity loss and their impacts on helminth parasite populations and communities

Abstract

The world's biodiversity is in peril. The major threats to biodiversity globally are habitat change, overexploitation, climate change, invasive species and pollution. Not only do these stressors impact free-living organisms, but they affect parasitic ones as well. Herein, this perspective examines the potential consequences of these anthropogenic perturbations on helminth populations and communities, with emphasis on significant developments over the past decade. Furthermore, several case studies are examined in more detail for each of these threats to biodiversity. While effects are widespread and diverse, for the most part all these environmental stressors have negative effects on parasite populations and communities. Those parasites with complex life cycles that are trophically transmitted are often more at risk, although larval parasites with a wide host spectrum, and directly transmitted ectoparasites, appear less threatened and may even benefit. However, differential effects on hosts and parasites, on parasite life cycle stages and on host–parasite interactions made specific predictions difficult and context-dependent. Experimental laboratory and mesocosm studies on specific parasites that test effects on the different life cycle stages, hosts and host–parasite interactions, permitting the determination of net effects of an environmental stressor, yield insightful and sometimes counterintuitive results, although they remain a simplification of real-world complexity. Recent advances in the use of parasites as bioindicators of effects also are discussed.

A biological invasion modifies the dynamics of a host–parasite arms race

“…Our study reinforces the value of biological invasions as model systems in which to explore rapid evolutionary changes not only in invasive species and the native biota affected by them [10], but also in co-adapted interactions among species [48]. Invasive host-parasite systems are ideal in this respect, because the novel evolutionary pressures engendered by range expansion can result in rapid shifts in adaptive optima for both participants in the arms race [11].…”

Helminth-host-environment interactions: Looking down from the tip of the iceberg

“…There is considerable evidence that temperature influences survival and transmission of free-living stages of helminth parasites and indirectly affects parasitic stages within poikilotherm hosts through physiological, behavioural, and immunological mechanisms (Marcogliese 2023). Recognizing that temperature under field conditions is not constant, the impact of a shift in temperature was recently investigated in Dactylogyrus vasator, a monogenean of common carp and goldfish.…”

“…The topic of how climate change is likely to impact helminth infections continues to be an important focus of research, and findings to date have been reviewed extensively (see, for example, Adekiya et al 2019;Rocklöv et al 2021;Marcogliese 2023;Thompson 2023). Over and above the direct impact of shifts in temperature and rainfall on geographical range of hosts and survival of freeliving stages (Marcogliese 2023), a more integrated approach to exploring the impacts of climate change is needed.…”

“…The topic of how climate change is likely to impact helminth infections continues to be an important focus of research, and findings to date have been reviewed extensively (see, for example, Adekiya et al 2019;Rocklöv et al 2021;Marcogliese 2023;Thompson 2023). Over and above the direct impact of shifts in temperature and rainfall on geographical range of hosts and survival of freeliving stages (Marcogliese 2023), a more integrated approach to exploring the impacts of climate change is needed. A systematic review of the anticipated impact of climate change on thermal tolerance for human schistosomiasis revealed that a shift in the geographical distribution of the intermediate hosts to new areas within their thermal tolerance may be expected and that, given the co-evolved relationship of schistosomes and their snail host, the distribution of disease is likely to parallel the new snail distribution (Stensgaard et al 2019).…”

“Till death do us apart”: The common destiny of brown hare and its parasite community

“…Some authors hypothesized that parasite community biodiversity is higher in healthy host populations and ecosystems ( Marcogliese, 2005 ; Hudson et al, 2006 ; Johnson et al, 2013 ). Certainly, environmental pollution can be toxic for free-living parasite stages and anthropization can determine the loss and fragmentation of habitat for both definitive and intermediate hosts ( Lafferty, 2014 ; Marcogliese, 2023 ). In addition, any pressure decreasing host population density is expected to influence the richness of parasite communities negatively ( Morand, 2000 ; Deredec and Courchamp, 2003 ); in the case of European hare living in the study area, the population management could have acted as an additional detrimental factor thanks to the strong exploitation implemented by hunters and to the following capture from protected areas and release in hunting territories usually carried out after the hunting seasons ( Zanin, 2017 , Zanin, 2022 ).…”