Amphibian populations are declining globally and one cause is emerging infectious diseases. Ranaviruses are responsible for the majority of amphibian mass mortality events in North America, yet research into factors that govern host susceptibility is limited. Ecological stressors may be important components contributing to the emergence of infectious diseases, and two known stressors are predation and development. In response to predators, prey may adaptively alter their behavior, morphology, and life history traits. Although enhancing survival, stress responses may also negatively impact immune functions if they persist in an organism. Thus, a constant threat of predators could increase the susceptibility of an organism to pathogen infection and contribute to the emergence of infectious diseases. Evidence also exists that there are varying degrees of immune system development across different amphibian life stages and that susceptibility to ranaviruses may differ across these life stages. Unfortunately, studies comparing the susceptibility of amphibians to pathogens at different developmental stages are rare. My research focuses on determining the impacts of natural stressors on ranavirus emergence.
The objectives of my study are:
1) Quantify the effects of amphibian development on ranavirus pathogenicity, and
2) Quantify the effects of predators on ranavirus pathogenicity.
I am also performing surveillance for ranavirus outbreaks in larval amphibian populations among 40 wetlands over two years in the Cumberland Plateau and the Tennessee River Ridge and Valley physiographic regions. Lastly, I am working in collaboration with Dr. Jason Hoverman. He is comparing the relative susceptibility of amphibian species across multiple families to novel verses endemic ranavirus strains.
Through experimental challenges at the JARTU facility, we have documented numerous physiological changes that are associated with ranavirus infection and morbidity. Gross signs included edema (swelling, Fig. 1), erythema (reddening, Fig. 1, 2), loss of pigmentation, and hemorrhages. Behavioral signs include problems with buoyancy, lethargy, inappetence, and erratic swimming. Internal gross signs included swollen organs, hemorrhaging of organs and fat bodies (Fig. 3), congested blood vessels, and paleness of the organs (Fig. 3). Most internal signs were associated with the kidney and liver, which is not surprising considering these organs are known targets of ranaviral infection.
Figure 1: Edema and erythema of Hyla chrysoscelis.
Figure 2: Erythema of Rana clamitans.
Figure 3: Hemorrhaging of fatbodies and paleness of liver.
I grew up in a small town in middle Tennessee approximately 60 miles south of Nashville. I graduated with honors from the University of Tennessee with a B.S. in Wildlife and Fisheries Science, and was recruited into the UT Center for Wildlife Health to conduct Ranavirus research. While I was an undergraduate, I conducted two independent studies on grassland snake populations, was an intern with the Tennessee Wildlife Resources Agency, assisted with grassland songbird research in middle Tennessee, and worked for a year with Dr. Gordon Burghardt with multiple species of snakes and monitor lizards (above photo). I also was very active in the UT student chapter of The Wildlife Society, and volunteered on various projects. My passion is herpetology and wildlife photography. I am also an avid birder, hunter, and fisherman.
(Larval Ambystomatid necropsy for Ranavirus testing)