James Marvel, 2009, Ecology and Evolutionary Biology

Radolfzell am Bodensee, Germany

“The money I received through this grant was used to cover the costs of conducting senior thesis research this past summer in Germany.  I collaborated with Bryson Voirin, a graduate student at the Max Planck Institute for Ornithology who was conducting a pilot project for what is to be his Ph.D.  We shared similar goals in what we wanted to get out of this project, so I had significant liberty in shaping how I wanted the experimental design to look.  We also worked closely with Martin Wikelski, former Princeton professor and current director of the Max Planck Institute for Ornithology, in addition to collaborating with researchers at local universities.”

“The idea behind the project was to use immuno-compromised chickens as sentinel test animals to assess the spatio-temporal abundances of pathogens in a particular environment.  This research was originally going to be conducted in California through UC Davis, but it was moved at the last minute to Germany, where a more accessible facility that would better suit our needs was already in place at the Max Planck Institute.  The first goal then, was to determine which environments we would be investigating, as our original plan to disperse chickens all along the western United States coastline to examine latitudinal and altitudinal gradients.  In the area of Germany where we were working, the landscape was dominated by vast stretches of farmland with isolated patches of forest scattered throughout.  Thus, we decided it would be most interesting and practical to see if we could quantify the degree to which anthropogenic habitat fragmentation affected pathogen dispersal.”

“Once the sites were selected, we began to approach the logistical aspects of both compromising the birds’ immune systems, and ways to keep them alive and fully exposed to the environment for five days.  There are several established methods for immuno-compromising chickens, and after a thorough literature review and discussions with chicken pathologists, we decided the most effective means would be a bursectomy.  This is a procedure in which the bursa of fabricius, an organ responsible for immune responses in birds, is removed from the chickens.  We traveled to a medical school in Hungary to learn this obscure procedure, as the next closest scientist who knew how to perform the operation lived in Japan.  This minimally invasive procedure was performed on day-old chicks, when the tissue was softest, facilitating the organ’s removal.”

“After learning how to bursectomize chickens, we then focused our attention on how to raise them and keep them alive outside when they were in such a fragile state.  At the institute we established a clean room with filtered air and individual cages where we raised the chickens after they had been bursectomized.  We then began to experiment with placing the chickens outside, as no one has ever experimented with taking bursectomized chickens out of a laboratory setting.  We established that they were viable, and proceeded to design cages suitable to keep the chickens alive for the time they spent in the preselected environments.  The greatest obstacle was heating, as chicks need to be kept at 80 – 90˚F during their first weeks.  We collaborated with engineers and local technicians before arriving at the brilliantly simple solution of using a candle.  We tried out dozens of candles before finding graveyard candles that burned for 5-days straight.”

“Once all of this had been set in place, we were ready to put the chickens out in the environment.  We conducted two trials, each involving 81 chickens, divided into 27 cages.  We placed these cages in previously established transects of forest, farmland, and swamp.  After five days in the field, the chickens were collected and blood samples were taken.  I am unfortunately still waiting on the data, but the blood samples just arrived in the United States this week.  They will be sent to a lab in UC Davis where they will be analyzed for pathogen load and acute phase proteins.  This data will hopefully allow us to understand the spatio-temporal distribution of diseases in a patchy environment, in addition to a quantitative assessment of the stress placed upon each chicken’s immune system.  If the data proves informative, a significant aspect of my thesis will be devoted to analyzing how the methodologies we developed may be employed in directing public health policies in different areas.  For example, my collaborator already has plans to employ these methods in the tropics, to assess variability of pathogen virulence.