Research

There are currently three broad research areas being pursued in my laboratory. 

(1) Disease dynamics in freshwater trematode systems.

Digenetic trematodes are a diverse group of parasitic flatworms (Phylum Platyhelminthes; Class Trematoda; Subclass Digenea).  They can infect all vertebrate classes, and are common parasites in freshwater systems containing aquatic snails, which serve as obligate first intermediate hosts. Most digenetic trematodes infect three successive host species, although there is considerable variation in the life cycle.  In an ecological sense, trematodes can be viewed as representative of a group of wildlife parasites and pathogens that have complex life-cycles involving multiple host or vector species that operate at very different spatial scales.  Research in the Belden lab is focused both on understanding the factors that influence trematode dynamics in free-living wildlife populations, and also on using trematode systems as experimental models for elucidating some of the general underlying ecological mechanisms that operate in host-parasite systems. 

Collaborators: Jeremy Wojdak (Radford), Bernie Fried (Lafayette College), Korine Kolivras (VT Geography), Anne Zajac (VT VetMed), Fred Benfield (VT Biological Sciences)

(2) The role of beneficial skin bacteria in preventing amphibian infection. 

Infectious disease is devastating many amphibian populations.  While much of my previous work has focused on identifying the causes of amphibian declines, one problem I have grappled with is what to do once we know the cause.  How can we actually save amphibians?  We’re hoping this project, addressing the role of beneficial bacteria in preventing infection, has the potential to save a few species.  Beneficial bacteria (probiotics) are used in humans, livestock and for aquaculture.  If we can learn enough about the bacterial microbiota that lives on amphibian skin, we may actually be able to use some of them for the treatment and prevention of disease in natural populations. 

Collaborators: Reid Harris (JMU)

(3) Amphibian responses to environmental stressors.

As a postdoctoral research associate, I initiated a project examining whether environmental stressors, acting via the neuroendocrine “stress axis” could impact susceptibility of larval amphibians to disease.  Corticosterone, the main glucocorticoid stress hormone in amphibians, has been implicated for its immunosuppressive role.  In early experiments, we verified that treatment with exogenous corticosterone could result in altered immunity and increased trematode infection rates.  However, attempts to maintain elevated (=immunosuppressive) levels of corticosterone in response to natural manipulations of density, which will elevate corticosterone levels in the laboratory, were unsuccessful.  A key remaining question is whether corticosterone levels are ever maintained at elevated, chronic levels in wild populations, or whether this link between glucocorticoids and immunosuppression mainly occurs in humans and other social species, where chronic stress can be survived.  We are currently pursuing these ideas, and beginning to explore the meaning of variation in baseline corticosterone levels for free-living amphibians.