Sunlight-Heated Refugia Protect Frogs from Chytridiomycosis: A Mathematical Modelling Study

The fungal disease chytridiomycosis poses a threat to frog populations worldwide. It has driven over 90 amphibian species to extinction and severely affected hundreds more. Difficulties in disease management have shown a need for novel conservation approaches. We present a novel mathematical model for chytridiomycosis transmission in frogs that includes the natural history of infection, to test the hypothesis that sunlight-heated refugia reduce transmission. This model was fit using approximate Bayesian computation to experimental data where frogs were grouped into sunlight-heated or shaded refugia cohorts. Results show a 40 percent reduction in infection due to sunlight-heating of refugia. Frogs that were infected and recovered had a reduction in susceptibility of approximately 97 percent compared to naive frogs. Our model offers insight into using sunlight-heated refugia to reduce chytridiomycosis prevalence. Importantly, it is the first step in determining the necessary level of refugia in the landscape for frog population recovery and population sustainability.