Greenversations

Each week we write about the science behind environmental protection. Previous Science Wednesdays.

About the author: Montira Pongsiri, PhD, MPH, is an Environmental Health Scientist in EPA’s Office of the Science Advisor.

I was first associated with EPA as a STAR Fellow studying the risks and tradeoffs of using pesticides to control infectious diseases. Today, I’m an EPA scientist focusing on infectious diseases in the wider framework of ecosystem services, the direct and indirect benefits people derive from ecosystems.

The primary questions I am helping EPA explore are: What is the underlying mechanism of disease emergence, and do changes in biodiversity play a role?

Our research projects are unique in their interdisciplinary approach, involving ecologists, public health specialists, social scientists, and earth scientists, and also by including decision-makers early in the process to help ensure that new findings can be used to make better decisions.

At one field site in northwest Connecticut, an opossum is checked for ticks, which are removed and collected to test for the presence of the Lyme disease bacterium, Borrelia burgdorferi.

One area we’re studying is Lyme disease risk (chronicled previously by Melissa Anley-Mills and Aaron Ferster). Research partner Richard Ostfeld of the Cary Institute of Ecosystem Studies hypothesizes that a greater diversity of native mammal hosts could help decrease the risk of people getting Lyme disease. How? People get Lyme disease through tick bites, and ticks acquire the Lyme disease agent by feeding on mammals such as mice and squirrels. Not all mammals are equally efficient, or “competent,” in transmitting the disease agent to the ticks. So perhaps having a greater diversity of mammalian species, with their varying capabilities of transmitting the pathogen, could “dilute” the rates by which ticks get infected. Lower rates of tick infection equal lower risk of human infection.

There is also a connection between animal diversity and landscape condition. Forest destruction and fragmentation in the U.S. have been shown to reduce mammalian species diversity and to increase populations of the white-footed mouse—the most competent host of Lyme disease.

With the support of a new STAR grant, Ostfeld and his colleagues are testing this hypothesis by manipulating mammalian host communities in forest fragments and studying the effects on pathogen transmission rates.

When we better understand the mechanisms linking biodiversity and human disease through this and other research studies, we may be able to develop environmentally-based and behavioral approaches to both promote conservation as well as to reduce the risk of human disease – a win-win for environment and public health.

In addition to the Cary Institute of Ecosystem Studies, other EPA research partners include the CDC, Yale, NASA Ames, UCLA, the Institute for Bird Populations, Rutgers, and the NJ Department of Environmental Protection.

Each week we write about the science behind environmental protection. Previous Science Wednesdays.

About the author: Aaron Ferster, a science writer in EPA’s Office of Research and Development, is a regular contributor to Science Wednesday.

Last Spring, a pair of barred owls took up residence in the upper reaches of a tree just past the edge of our yard. They announced their presence during dinner one warm evening, a series of deep hoots in a pattern birders describe as “who-cooks-for-you.”

We caught a brief glimpse of one as it leaned off its perch and in a long, silent swoop faded into the shadows of the woods behind our house, disappearing like a ghost.

The owls didn’t disappear for long. The girls soon discovered a trove of owl pellets beneath the roost. By picking the pellets apart we learned what the owls were eating. Sometimes there were crayfish claws or fish scales, but the owl’s main course must have always included small mammals. Every pellet contained the tiny white vertebra and jaw bones of mice.

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	Curtis Tackett adds a handful of sunflower seeds to one of the small, humane traps the survey team sets to survey mammal diversity. After examining the small animals, the team sets them free. (Click image to enlarge.)

Could owls and other wild neighbors be good for health by reducing the relative abundance of tick-infected mice? Last week I got to tag along with a team of Yale researchers surveying mammal diversity in the forests of Connecticut, part of an EPA-funded effort to explore just such questions.

Naturally, the team is taking a much more scientific approach than sifting through a handful of owl pellets. Instead, they set out small aluminum traps to humanely capture a representative sample of the local small mammal population.

Every critter caught was identified, ear-tagged (if not previously captured, a regular occurrence), and weighed. Before they were set free, each animal was thoroughly inspected and any black-legged ticks found were collected for further analysis. After the first day, we joined forces with another team conducting a similar survey of birds, part of an ongoing population study now sharing their efforts with the Yale team.

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	Field coordinator Kim Tsao carefully examines each a white-footed mouse, counting and removing black-legged ticks for further analysis for the bacterium that causes Lyme disease. (Click image to enlarge.)

The few days I spent with the survey team is a small part of a larger, two-year study to better understand of the links between biological diversity, land use, and Lyme disease. I was happy to have the chance to escape the office for a few days in favor of the forest. It reminded me once again how fun it is to explore the woods and to learn more about our wild neighbors, some of which might prove to be important for our health.