Brunner Lab: Current Research

Research in the Brunner Lab:

We are interested in the evolutionary ecology of zoonotic and wildlife disease--very broadly, how parasites get around, stick around, and kill. We focus on questions with a theoretical basis and an applied focus. We try to integrate experiments, surveys, and a variety of quantitative tools to look at a problem from multiple angles. In general, we focus on amphibian disease ecology, but we also have several projects involving tick-borne disease.

Amphibian disease ecology:

Amphibian disease ecology: ranavirus and chytridiomycosis. Ranaviruses and the fungal pathogen, Batrachochytrium dendrobatidis (Bd), are two emerging pathogens in amphibians. Bd has been associated with amphibian declines and extinctions the world. Ranavirus epidemics decimate amphibians in natural populations and aquaculture. Little known, however, about these important pathogens in amphibian communities in the Northeast. We are beginning to get the sense that these pathogens are common, but there are many unanswered questions. Which host species are most susceptible? Are some reservoirs for the others? Is there one wide-spread or or many local types of ranavirus? We are using active sampling (e.g., pond visits, roadkill surveys) and passive surveillance (i.e., submitted samples) to establish where, when, and in which species these diseases occur. We are also conducting a series of experiments in the laboratory and mesocosm to answer basic epidiomiological and pathological questions.

Development of Batrachochytrium dendrobatidis zoospores.
Top: Ambystoma larvae showing signs of ranavirus infection. Bottom: Pilot study of disease transmission. (Yes, that is a kiddie pool.)

Host behavior and disease transmission. Detailed knowledge of how infectious agents are transmitted is key to predicting whether an infectious disease will invade, persist, and spread, and to designing control strategies. Yet we know very little about how transmission works in real world systems. Much of our present understanding stems from models that assume hosts contact each other randomly, like molecules colliding in a chemical reaction. Animals, however, are not molecules; they mate, forage, fight, and flock, and these behaviors can drive the spread of disease.
We are beginning a series of mesocosm experiments with the ranavirus-amphibian model system to study how common host behaviors, such as foraging for food and avoiding predators, shape transmission dynamics. Essentially, we will initiate mini-epidemics in mesocosm with various treatments (e.g., presence of predator cues) and then fit various models of transmission to the data on the number of larvae that get infected. We are also developing some techniques to more directly measure contact rates between animals in mesocosms. This should be interesting!

Tick-borne disease ecology:

Climate change and range expansion of blacklegged ticks (Ixodes scapularis). Black-legged ticks vector Lyme disease and several other emerging infectious diseases in North America. As recently as the 1960's blacklegged ticks were (apparently) restricted to island refuges off the New England coast, but they are now ubiquitous throughout much of the Northeast. How did these ticks move so far so quickly? What stops their continued expansion? How will they respond to a changing climate?
We are beginning a series of manipulative experiments at ESF and the Cary Institute to help determine how (or whether) winter temperatures limit ticks, which will help us answer that last question about climate change. We are also exploring alternative sources of data we can use to test different models of range expansion so that we can better predict (and prepare for) the future spread of these and other vectors of zoonotic disease.
Buck and Shannon removing mice from a site in Dutchess County, NY.

Experimental tests of the "dilution effect." The dilution effect hypothesis posits that biodiversity can reduce disease transmisison. While there has been a great deal of support for this hypothesis, especially in the Lyme disease system, there are few experimental tests, especially at an ecologically relevant scale. We are currently conducting a large-scale, manipulative experiment in which we are altering small mammal communities in forest fragments in Dutchess County, New York to see how these changes in the host community influence the risk of tick-borne disease in these fragments. We are removing mice from some fragments and add them to others (and the same with squirrels) and will see whether we can then predict the prevalence of the agents of Lyme disease, babesiosis, and human granolocytic anaplasmosis in the tick populations. These projects are headed by Dr. Richard S. Ostfeld and Felicia Keesing and involve a number of collaborators.