Does the early frog catch the worm? Disentangling potential drivers of a parasite age-intensity relationship in tadpoles

Thomas R. Raffel, James O. Lloyd-Smith, Stanley K. Sessions, Peter J. Hudson, Jason R. Rohr

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


The manner in which parasite intensity and aggregation varies with host age can provide insights into parasite dynamics and help identify potential means of controlling infections in humans and wildlife. A significant challenge is to distinguish among competing mechanistic hypotheses for the relationship between age and parasite intensity or aggregation. Because different mechanisms can generate similar relationships, testing among competing hypotheses can be difficult, particularly in wildlife hosts, and often requires a combination of experimental and model fitting approaches. We used field data, experiments, and model fitting to distinguish among ten plausible drivers of a curvilinear age-intensity relationship and increasing aggregation with host age for echinostome trematode infections of green frogs. We found little support for most of these proposed drivers but did find that the parsimonious explanation for the observed age-intensity relationship was seasonal exposure to echinostomes. The parsimonious explanation for the aggregated distribution of parasites in this host population was heterogeneity in exposure. A predictive model incorporating seasonal exposure indicated that tadpoles hatching early or late in the breeding season should have lower trematode burdens at metamorphosis, particularly with simulated warmer climates. Application of this multi-pronged approach (field surveys, lab experiments, and modeling) to additional parasite-host systems could lead to discovery of general patterns in the drivers of parasite age-intensity and age-distribution relationships.

Original languageEnglish (US)
Pages (from-to)1031-1042
Number of pages12
Issue number4
StatePublished - Apr 2011

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics


Dive into the research topics of 'Does the early frog catch the worm? Disentangling potential drivers of a parasite age-intensity relationship in tadpoles'. Together they form a unique fingerprint.

Cite this