Meeting Abstract
Corticosterone (“CORT”) is the primary vertebrate stress hormone. When secreted at high levels, CORT is generally thought to be immunosuppressive. Despite the known association between stress physiology and disease resistance in domesticated organisms, it is unclear whether these associations are ecologically and evolutionary relevant in wildlife species. We explored these patterns using a 3×3 fully crossed laboratory experiment in which we exposed American toads (Anaxyrus [=Bufo] americanus) to CORT and the pathogenic chytrid fungus Batrachochytrium dendrobatidis (“Bd“). We assessed Bd infection levels and tested how CORT and Bd affected toad resistance, tolerance, and mortality. Exposure to CORT and Bd each increased toad mortality, but these two factors did not interact to affect mortality. Toads that were exposed to high levels of CORT had lower Bd abundance than toads exposed to ethanol controls or low CORT, a pattern opposite that of most studies on domesticated animals. Exposure to high levels of Bd reduced toad tolerance to infection; however, exposure to CORT (and the interaction between CORT dose and Bd dose) was non-significant. We demonstrated that host physiological condition can affect disease outcomes by enhancing toad resistance to infection. However, exposure to CORT also increased mortality and did not affect tolerance to infection. Collectively, these results show that physiological stressors can alter a host’s response to pathogens, but that the outcome might not be straightforward. Future studies that inhibit CORT secretion are needed to better our understanding of the relationship between stress physiology and disease resistance and tolerance in wild vertebrates.
