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 p..., , We obtained Panamanian golden frogs (Atelopus varius) from the Maryland zoo as part of the captive breeding program 'Project Golden Frog'. For each frog, we measured mass to the nearest 0.01 g, and snout-vent length (SVL) to the nearest 0.1 mm using calipers and scales. For experiment one, we placed frogs in either high RH (relative humidity), medium RH, or low RH conditions. We collected skin swab samples to test for Bd presence and infection intensity using standardized swabbing techniques. To collect frog skin secretions, we induced half of the frogs from each treatment group to secrete their store of secretions from cutaneous granular glands by administering a stimulatory injection of 40 nmol/gram of norepinephrine (NE) below the skin surface (Rollins-Smith et al. 2005, Woodhams et al. 2006). The remaining frogs from each RH group were given shots of sterile saline as a control. Following a month at each humidity treatment, we injected frogs once again with either norepinephrine or ...,