Journal Article

Testing the Population‐Level Effects of Stress‐Induced Susceptibility in the Ranavirus–Wood Frog System

Rittenhouse, Tracy A. G., Crespi, Erica J., Brunner, Jesse L., Dahrouge, Nicole C.

2025

Overview

Chronic exposure to physical, chemical, and biotic stressors can make animals more susceptible to infections. Such stress‐induced susceptibility is widely expected to make disease—and epidemics—more likely and more severe. However, whether the impacts of stressors on individuals scale up to population‐level outcomes is uncertain, both theoretically and empirically. We initiated ranavirus epidemics in replicate mesocosm populations of larval wood frogs (Lithobates sylvaticus) exposed to conditions known to impact their individual susceptibility to ranavirus infections: low and high salinity crossed factorially with ambient or elevated temperatures. Contrary to expectations, epidemics were no more likely or more severe in stressful conditions, although increased temperatures did speed their progression. We discuss several potential reasons why the effects of stressors did not scale up to epidemics, but our results suggest caution in assuming the individual‐level effects of even well‐studied stressors necessarily scale simply to population‐level outcomes. Experimental ranavirus epidemics in populations of wood frog tadpoles were used to the hypothesis that individual‐level effects of stress and temperature predict population‐level outcomes. In contrast to conventional wisdom, environmental stressors did not appreciably change the outcome or severity of 96 replicate experimental epidemics in mesocosms.

• Publisher: John Wiley & Sons, Inc,John Wiley and Sons Inc,Wiley
• Subject: amphibian disease / Amphibians / Chronic exposure / Climate change / Cyanobacteria / Disease Ecology / epidemic / Epidemics / Frogs / High temperature / Hypotheses / Infections / Influence / mesocosms / Microbiota / Mortality / Parasites / Salinity / scaling / Scaling up / stress‐induced susceptibility / Water temperature