Amphibian pathogen Batrachochytrium dendrobatidis prevalence is correlated with season and not urbanization in central Virginia

Abstract

The global amphibian pathogen Batrachochytrium dendrobatidis (Bd) has been documented among many species throughout the United States, though cases of chytridiomycosis, the resulting disease, have occurred mostly on the west coast. We conducted a 2 yr survey of amphibians along an urban gradient in Virginia, U.S.A., to test whether Bd prevalence among the amphibians sampled varied with urbanization and/or season. A total of 867 adult amphibians from 13 species and 49 tadpoles from 3 species were tested for Bd. The level of urbanization was based on surrounding human population density and anthropogenic disturbance. Bd was detected in 6 species. Bd prevalence was not found to vary with increases in urbanization, but did vary with season. Prevalence peaked in the spring at 45%, when temperatures were between 14 and 25 degrees C, and dropped to below 2% in the autumn. Results from this survey support the hypothesis that Bd is endemic to the studied sites in Virginia. The present study, in concurrence with previous research by other investigators, shows that Bd is affected strongly by weather patterns. Urbanization, defined by human population density, appeared to have minimal impact on the prevalence of Bd. In addition to understanding the geographic distribution of Bd, it is important to understand factors that affect its prevalence if we are to develop approaches to managing this emerging disease.