High relative humidity and temperature limit disease development and mortality in golden frogs of Panama, Atelopus zeteki, infected with Batrachochytrium dendrobatidis

To combat the loss of species due to emerging infectious diseases,
scientists must incorporate ecological parameters, such as temperature and
humidity, to understand how the environment affects host–pathogen
interactions. The fungal disease chytridiomycosis is a compelling case
study to investigate the role of both temperature and humidity on
infectious disease, as both the fungal pathogen (Batrachochytrium
dendrobatidis, Bd) and the host (amphibians) are heavily influenced by
these abiotic factors. We performed two experiments to investigate the
importance of relative humidity and temperature on frog immunity
(production of antimicrobial skin secretions) and disease development in
captive golden frogs (Atelopus zeteki) of Panama. We found that the
quantity of skin secretions significantly decreased over time in frogs
moved from low to medium and high relative humidity treatments. Following
Bd exposure, frogs in high temperature (26–27 °C) and high relative
humidity (80–90%) had lower pathogen loads and survived significantly
longer than frogs kept in all other treatment conditions, including high
temperature and low relative humidity. These results suggest that high
relative humidity may be an important, although less understood, mediator
of Bd infection and the survival of golden frogs. Because the environment
can drastically alter disease dynamics, understanding how temperature and
humidity influence chytridiomycosis outcomes in golden frogs may be
essential for the success of the reintroduction of captive frogs.