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Abstract Host competence—the ability to acquire, harbour and transmit infections—drives pathogen spread and persistence in multi‐host communities. Evaluating species‐specific competence is critical for predicting transmission, particularly for generalist fungal pathogens likeBatrachochytrium dendrobatidis(Bd). Despite its central role in disease dynamics, we lack an epidemiologically grounded competence metric that rigorously accounts for how infection intensity affects a host's competence. This knowledge gap limits our ability to compare mechanisms across species and assess their roles in pathogen persistence. To address these challenges, we developed a novel, load‐dependent competence metric using host–pathogen Integral Projection Models (IPMs) that integrates variation in susceptibility, within‐host pathogen growth and pathogen shedding dynamics.We applied this metric to laboratory‐based challenge experiments with three common North American amphibians (Notophthalmus viridescens,Rana clamitansandRana catesbeianus) that persist endemically with Bd. Using dose–response assays and repeated pathogen shedding measurements across species, we asked: (i) is there a consistent, non‐linear relationship between infection intensity and pathogen shedding across species? and (ii) which load‐based traits best predict host competence? We quantified four of five components of host competence—susceptibility, pathogen growth, pathogen survival and load‐dependent shedding—and used these to parameterize species‐specific IPMs, integrating competence into a single relative metric across species.We found that Bd shedding increased non‐linearly with infection intensity, contradicting the standard assumption that Bd shedding is linearly related to infection intensity.Notophthalmus viridescensandR. catesbeianuswere the most competent hosts but through distinct pathways: high susceptibility inN. viridescensand elevated shedding rates inR. catesbeianus. In contrast, density‐dependent reductions in pathogen growth and shedding limitedR. clamitanscompetence. Thus, species‐level competence is not determined by a single trait, but emerges from interactions among multiple load‐based processes.Our results demonstrate that variation in competence emerges from distinct, species‐specific processes across multiple dimensions of competence. By linking individual infection dynamics to population‐level transmission potential, our integrative framework provides a more mechanistic approach to predicting host contributions to community‐level pathogen persistence. Read the freePlain Language Summaryfor this article on the Journal blog.
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This content will become publicly available on August 6, 2027
Spillover dynamics and asynchronous temporal fluctuations in host density and competence drive fungal parasite persistence in multi‐host, seasonal communities
Abstract Parasites routinely persist in seasonal systems while infecting multiple host species. An important question for parasite control is whether parasite persistence is driven by particular host species, specific times of year or their interaction. We have few empirically tractable models to answer this question.We develop a data‐driven model that partitions species‐specific and temporal drivers of parasite persistence from commonly collected surveillance data. Leveraging standard epidemiological theory, our approach demonstrates a novel way to link time‐varying fluctuations in species‐level contributions to parasite persistence directly to time‐integrated parasite persistence in the community as a whole, while using real‐world field data that is tractable to obtain.We applied our approach to 3 years of parasite surveillance data in seasonal amphibian communities persisting with the fungal pathogenBatrachochytrium dendrobatidis(Bd). We asked three questions: (i) Do amphibians trade‐off in their contributions to Bd persistence across the year? (ii) What host characteristics, such as seasonally fluctuating host density or host competence, drive these trade‐offs? and (iii) what are the relative contributions of species compared to periods of high transmission for enzootic Bd persistence?We found that the identity of the amphibian species driving Bd persistence was highly variable through time. Specifically, temporal variability in host density and less so variability in host competence drove the temporal variation in species' contributions to persistence. Moreover, our model identified two distinct mechanisms of Bd persistence: (i) spillover dynamics from a dominant maintenance species and (ii) temporally asynchronous, but equal, contributions of host species to persistence. In both cases, species‐targeted interventions were as effective or more effective than temporal control for reducing the capacity of Bd to persist.Broadly, our results demonstrate that species contributions to parasite persistence can have strong, asynchronous temporal variability, potentially limiting the effectiveness of targeted seasonal parasite control. Our model is designed to link closely with standard parasite surveillance data and is broadly applicable to other host–parasite systems where it can partition who, when and what drive parasite persistence in multi‐host seasonal communities.
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- Award ID(s):
- 2120084
- PAR ID:
- 10709642
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Journal of Animal Ecology
- ISSN:
- 0021-8790
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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