Emydomyces testavorans Infection and Shell Disease Prevalence in Threatened Northwestern Pond Turtle Populations of the San Francisco Bay Area, USA
Surveys of Northwestern Pond Turtles in California’s Bay Area revealed low but widespread occurrence of Emydomyces testavorans, with pathogen loads far lower than those in Washington populations. Despite this low prevalence, turtles showed high rates of shell disease, underscoring the need to investigate other ecological or genetic factors driving disease in the region.
Subject Tags
- Coastal
- Ecosystem management
Abstract
In Northwestern Pond Turtles (Actinemys marmorata), the fungus Emydomyces testavorans (Emte) is of special interest due to its potential to have negative health impacts on both captive and wild turtle populations. The full effects of this fungus on Northwestern PondTurtle fitness are not yet understood, and up to a few years ago, Emte was originally thought to be restricted to the northern range of the host in Washington State. In 2020, however, Red-eared Sliders (Trachemys scripta) living with Northwestern Pond Turtles in California were found infected with Emte, raising the need to expand pathogen monitoring in this region. We captured and tested Northwestern Pond Turtles for Emte across five populations in the San Francisco Bay Area of California, USA, between 2021 and 2023. We found a low prevalence of Emte positive qPCR samples across the Californian populations, and the pathogen loads of positive individuals were low compared to reference samples from Washington state. These observations suggest that Emte is broadly distributed in the San Francisco Bay Area, but concentrations of the fungus were low. Despite the low prevalence of Emte in California, we observed a high frequency of turtle shell disease, raising the need to further explore the etiology of shell disease in this area and a need to further nvestigate the genetic or ecological mechanisms behind these observations.
Citation
White, A., Lim, T., Culver, E., Timmer, M., Bushell, J., Muttlow, A., ... & Hernández-Gómez, O. (2025). Emydomyces testavorans Infection and Shell Disease Prevalence in Threatened Northwestern Pond Turtle Populations of the San Francisco Bay Area, USA. Herpetological Conservation and Biology, 20(3), 457-465.
TNC Authors
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Max R. Lambert
Director of Science. Washington
The Nature Conservancy
Email: max.lambert@tnc.org