Towards an eco-epidemiological framework for managing freshwater crayfish communities confronted with crayfish plague
Creators: name: Bozzuto, Claudio
name: Schmidt-Posthaus, Heike
name: Adrian-Kalchhauser, Irene
name: Pisano, Simone Roberto Rolando
Publisher: name: Taylor & Francis
Year: 2024
Subjects: subject: Ecology
subject: FOS: Biological sciences
subject: Biological Sciences not elsewhere classified
subject: Computational Biology

description: Wildlife diseases figure prominently among the main causes of biodiversity loss worldwide. Especially fungal and fungus-like pathogens are on the rise, wreaking havoc across the tree of life by threatening species persistence and destabilizing ecosystems. A worrisome example are freshwater crayfish species in Eurasia and Oceania, facing the dual challenge of introduced competitive crayfish species and an introduced water mold (<i>Aphanomyces astaci</i>) causing crayfish plague<i>. A. astaci</i> locally extinguishes susceptible native crayfish populations, while non-native individuals (mostly from North America) remain largely unaffected. Despite its significant impact and its ∼150 years of presence in Europe, studies and disease management recommendations for crayfish plague that are firmly rooted in epidemiological theory are scarce. Here, we present a practical eco-epidemiological framework to understand how multi-species crayfish communities react to crayfish plague introductions. The framework is based on the observation that the dynamics of crayfish communities are mainly determined by life-history characteristics, within- and among-species competition, effects of generalist predators (including fishing), and host-pathogen interactions. From this ecological and epidemiological context, we derive fundamental epidemiological metrics, single-host species and community-level basic reproduction numbers (<i>R</i><sub>0</sub>). We investigate how host species densities affect the likelihood of a disease outbreak in a crayfish community, and we demonstrate that a community’s <i>R</i><sub>0</sub> value is simply the sum of the community’s single-host species <i>R</i><sub>0</sub> values, adjusted for competition and predation. We further demonstrate how <i>R</i><sub>0</sub> can be used to guide preventative and mitigation actions for crayfish communities. For example, we show how <i>R</i><sub>0</sub> expressions – even without a detailed parametrization – can be used to construct regional risk rankings for different crayfish communities, for an effective allocation of resources to local conservation plans. Our eco-epidemiological framework will also be of interest to the management of other aquatic host-pathogen systems with water-borne pathogen transmission as the main route of pathogen spread. Fungal and fungus-like pathogens are on the rise globally and are taking a heavy toll on biodiversity, including crayfish species in many parts of the world. To aid management of native crayfish species confronted with highly competitive introduced crayfish and crayfish plague, we present and discuss a flexible eco-epidemiological framework. The framework – and derived simple results from it – offers a sound and holistic basis for the planning and implementation of mitigation actions, for crayfish communities and other freshwater species affected by fungal pathogens with a mainly water-borne transmission.