Grantee Research Project Results

The Effects of Road Salt on Amphibian Disease Dynamics in the Northeastern United States

EPA Grant Number: F13F11099
Title: The Effects of Road Salt on Amphibian Disease Dynamics in the Northeastern United States
Investigators: Hall, Emily Marie
Institution: Washington State University
EPA Project Officer: Packard, Benjamin H
Project Period: August 25, 2014 through August 25, 2016
Project Amount: $84,000
RFA: STAR Graduate Fellowships (2013) RFA Text |  Recipients Lists
Research Category: Fellowship - Zoology , Academic Fellowships

Objective:

This project aims to validate non-invasive techniques to measure hormone levels in the field for different life stages of amphibians and to use these assays to determine whether glucocorticoid levels can be a bioindicator of disease susceptibility. It also seeks to incorporate stress physiology and disease prevalence into a bioclimatic spatial model to map the susceptibility landscape of the wood frog-ranavirus system. It seeks to answer two specific questions: Can osmotic stress of road salt run-off during amphibian development affect immune function and susceptibility to disease? How do environmental variables relate to susceptibility and disease prevalence across the northeastern range of the wood frog?

Approach:

Under a combination of laboratory and field experiments, animals will be reared in experimental road salt mesocosms and enclosures in roadside ponds. Various immunological and physiological assays will examine the hormonal, metabolic and cellular changes between these environmental conditions and maternal origins. Surveying populations using a noninvasive hormone assay and an environmental DNA assay for ranavirus will allow the incorporation of these indicators of disease susceptibility into an ecological niche model of the wood frog to map the “susceptibility landscape” to determine areas at risk for mortality events.

Expected Results:

Roads can affect disease susceptibility of amphibians in two ways, by increasing transmission of diseases and by decreasing host resistance to infection. Roads increase human access to ponds, which could increase local introductions or spread of disease. Slower growth and development of wood frog larvae in roadside ponds indicate an energetic cost that could affect the immune system and ability to resist infection. Thus, populations in areas of high road density or heavy road-salt application will have an increased risk of disease-associated die offs. Results will provide non-invasive assays for monitoring amphibian population health and disease surveillance.

Potential to Further Environmental/Human Health Protection

Populations at high risk for a mortality event and in need of road-salt alternatives or reduction will be pinpointed using the interpolative spatial model. Also, in areas where there is low impact on wetlands, economic assessments can determine salt application levels that balance aquatic ecosystem services with automotive safety. Novel methods developed for environmental assessments of population health and disease risk can be validated for other species. Field survey data of salinity in surface waters can be used to further understand sources of salt in groundwater and drinking water for human health.

Supplemental Keywords:

amphibians, environmental stressors, ranavirus

Progress and Final Reports:

2015

Final