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

Recognizing that there is a need for more scientific studies characterizing the mechanistic pathways linking social stressors (deforestation, habitat fragmentation, climate change), biodiversity, and human disease transmission, EPA developed a Biodiversity and Human Health research initiative to develop and sponsor long-term and pilot research projects.

The Biodiversity and Human Health research projects are the first of their kind at EPA, in subject matter and approach. The approach is interdisciplinary, involving ecologists, public health specialists, social scientists, and earth scientists. One unique part of the studies is that decision-makers are included in the research process, so that new findings of scientific knowledge can quickly be put into practice.

Starting tomorrow, I’ll be making a field site visit to one EPA-sponsored research project.

Rick Ostfeld, of the Cary Institute of Ecosystem Studies is leading a project entitled “Mechanisms Linking Host Biodiversity to Lyme Disease Risk: An Experimental Approach” to investigate how differences in animal community composition affect Lyme disease transmission in Duchess County, NY.

People get Lyme disease by being bitten by a tick infected with the spirochete bacterium, Borrelia burgdorferi. Ticks acquire the Lyme disease bacterium by feeding on small mammals such as white-footed mice (Peromyscus leucopus) and chipmunks that are already infected.

Not all mammals are equally efficient or competent at transmitting the bacteria to ticks when fed upon. In fact, white-footed mice appear to be the most competent animal host reservoir of Lyme disease in the northeastern U.S. So, the more white-footed mice that are in the forest, the greater chance more ticks will be infected, and the greater chance you have of getting bitten by an infected tick.

In a previous blog, I mentioned that 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. Rick and his team will be manipulating the composition of small mammals across a variety of forest plot types to see how high and low levels of mammal diversity may affect Lyme disease infection rates among feeding ticks.

In a seminal paper, Rick and his colleagues proposed the “dilution hypothesis” to help explain how high biodiversity can decrease the risk of Lyme disease transmission. It predicts that infection rates for a specific pathogen (e.g. Lyme disease bacterium) will be lower in highly diverse host communities. Why? The “incompetent” reservoir hosts dilute rates of transmission between vectors (ticks) and competent hosts (white-footed mice). With EPA support, Rick’s team will be collecting and analyzing field data to help characterize the scientific mechanisms that can explain how different levels of biodiversity affect Lyme disease risk.

For more information on EPA’s Biodiversity and Human Health activities, see:
http://www.epa.gov/ncer/biodiversity

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

NOTE: Tweet! Tweet!
Follow the action from our field trip. We’ll posting updates from EPA’s new research Twitter account: @useparesearch.

A medida que las temperaturas a lo largo del continente estadounidense comienzan a calentar, estamos empezando a planificar más actividades al aire libre o a pensar en nuevas maneras para comunicarnos con la naturaleza. Independientemente de si nos interesan actividades como la jardinería, la natación, el escalamiento, la pesca, o visitas a los parques nacionales, muchas podrían producir unos encuentros cercanos indeseados y poco placenteros. No estoy hablando de pumas, osos, lobos o serpientes. Estoy hablando de criaturas mucho más pequeñas como sabandijas molestosas o insectos voladores. Sí, lo sé. No todos los insectos son malos. De hecho, muchos invertebrados desempeñan un papel favorable para el medio ambiente como en el caso de agentes polinizantes como las abejas y las mariposas, o las mariquitas y lombrices (gusanos de tierra). Estas sabandijas que más me preocupan son aquellas plagas como los mosquitos y las garrapatas que pueden transmitir enfermedades. Esas son las que debemos evitar a como dé lugar, si es posible.

Debido a las lluvias copiosas en ciertas áreas de Estados Unidos, podemos anticipar grandes cantidades de mosquitos en áreas urbanas y rurales. El primer consejo para eliminar muchas de estas plagas voladoras con el uso mínimo de sustancias químicas consiste en eliminar su hábitat o sea las áreas donde estos insectos viven y se reproducen alrededor de su hogar. Si usted elimina el agua estancada de los desagües, llantas usadas, juguetes, o cualquier contendor abierto en el cual los mosquitos no pueden reproducirse. Por cierto, los mosquitos no necesitan grandes cantidades de agua para multiplicarse. ¿Sabía usted que sobre 150 mosquitos pueden salir de una cucharada de agua estancada? Si usted tiene baños para aves o pequeñas piscinas para sus hijos, debe cambiar el agua frecuentemente al menos una vez a la semana para evitar que los mosquitos se reproduzcan. Si va a pasar un buen tiempo al aire libre, use repelentes de mosquitos registrados por la Agencia de Protección Ambiental (EPA, por sus siglas en inglés) cuando sea necesario. Sobre todo, lea la etiqueta y siga las instrucciones al pie de la letra. Si hay advertencias de brotes de enfermedades transmitidas por mosquitos en su área, tales como el virus del Nilo Occidental, consulte con su estado o departamento de salud local para más información sobre medidas de control de mosquitos que se hayan implementado en el área donde vive.

Cuando vaya a disfruta de actividades al aire libre, hay otras plagas como las garrapatas que también transmiten enfermedades como la de Lyme, por ejemplo. Si va a ir a un bosque o entrar en áreas de mucho pasto, debe usar ropa adecuada como pantalones y camisas de manga larga. Los repelentes son eficaces también. Por lo tanto, no deje que las plagas arruinen sus vacaciones o sus ratos de ocio al aire libre.

Sobre la autor: Lina M. F. Younes ha trabajado en la EPA desde el 2002 y está a cargo del Grupo de Trabajo sobre Comunicaciones Multilingües. Como periodista, dirigió la oficina en Washington de dos periódicos puertorriqueños y ha laborado en varias agencias gubernamentales.

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.