Preparing for invasion: Assessing risk of infection by chytrid fungi in southeastern plethodontid salamanders
Brenna Friday1,2, Chace Holzheuser1,3, Karen R Lips1
1Department of Biology, University of Maryland, College Park, Maryland, USA.
Abstract:
Understanding the responses of naïve communities to the invasion of multihost pathogens requires accurate estimates of susceptibility across taxa. In the Americas, the likely emergence of a second amphibian pathogenic fungus (Batrachochytrium salamandrivorans, Bsal) calls for new ways of prioritizing disease mitigation among species due to the high diversity of naïve hosts with prior B. dendrobatidis (Bd) infections. Here, we applied the concept of pathogenic potential to quantify the virulence of chytrid fungi on naïve amphibians and evaluate species for conservation efforts in the event of an outbreak. The benefit of this measure is that it combines and summarizes the variation in disease effects into a single numerical index, allowing for comparisons across species, populations or groups of individuals that may inherently exhibit differences in susceptibility. As a proof of concept, we obtained standardized responses of disease severity by performing experimental infections with Bsal on five plethodontid salamanders from southeastern United States. Four out of five species carried natural infections of Bd at the start of the experiments. We showed that Bsal exhibited its highest value of pathogenic potential in a species that is already declining (Desmognathus auriculatus). We find that this index provides additional information beyond the standard measures of disease prevalence, intensity, and mortality, because it leveraged these disease parameters within each categorical group. Scientists and practitioners could use this measure to justify research, funding, trade, or conservation measures.
Insights
New research introduces pathogenic potential to assess amphibian susceptibility to the chytrid fungus Batrachochytrium salamandrivorans (Bsal). This method prioritizes conservation for vulnerable species facing fungal disease outbreaks.
Area of Science:
- Ecology
- Pathogen Dynamics
- Conservation Biology
Background:
- Amphibian populations face threats from multihost pathogens like chytrid fungi.
- The emergence of Batrachochytrium salamandrivorans (Bsal) in the Americas necessitates prioritizing disease mitigation strategies.
- Existing methods for assessing disease impact lack a unified approach across diverse amphibian taxa.
Purpose of the Study:
- To introduce and validate the concept of "pathogenic potential" as a metric for quantifying chytrid fungal virulence in naïve amphibians.
- To evaluate the conservation priorities of plethodontid salamander species in response to Bsal infection.
- To provide a standardized index for comparing disease effects across different amphibian species and populations.
Main Methods:
- Experimental infections were conducted using Bsal on five species of plethodontid salamanders from the southeastern United States.
- Standardized disease severity responses were measured to calculate pathogenic potential.
- The presence of prior B. dendrobatidis (Bd) infections was noted in four of the five tested species.
Main Results:
- Pathogenic potential was highest in Desmognathus auriculatus, a species already experiencing population decline.
- The study demonstrated the utility of pathogenic potential in integrating disease prevalence, intensity, and mortality.
- Varied susceptibility to Bsal was observed among the tested salamander species.
Conclusions:
- Pathogenic potential offers a comprehensive index for assessing amphibian disease risk and prioritizing conservation efforts.
- This metric can guide research, funding allocation, trade regulations, and conservation actions for amphibian populations.
- Understanding species-specific susceptibility is crucial for managing emerging infectious diseases in amphibians.
