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Science Wednesday: Biodiversity and Lyme disease – In the Field

2009 July 22

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.

image of authorFor 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.

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

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.

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7 Responses leave one →
  1. Steve Irving permalink
    July 22, 2009

    While biodiversity at the mammal level is certainly important, what about the effects on biodiversity of microbes resulting from personal care products like antibiotics and antibacterial soap? It would seem that breeding bugs that defeat the man made defenses which have made modern civilization possible has a lot of immediate potential for adverse human health consequences. Shouldn’t this be part of the biodiversity and human health initiative?

  2. Michael E. Bailey permalink
    July 22, 2009

    The issue of biodiversity and its impact on lyme illness is of great importance to all persons who enjoy camping or going to open space and wilderness areas. From this and earlier research, it sounds like its time to reintroduce more native species back into the wild to help be a break on the illness spread as well help create a more natural ecosystem. I also think that we should have a program that looks at superbugs and their resistance to traditional bacteria controls like soap and antibiotics. Michael E. Bailey.

  3. July 23, 2009

    Since the injection of the lyme vaccine can confer the pathology of lyme disease upon those receiving the vaccines…..it is immune complex disease, I am very sure that what needs to be addressed in the contamination to those of the New England areas with vaccines they are administered for whatever reason. I believe they are having the lyme disease injected into them via vaccinations. Since no safety studies are done on the vaccines, there would be no finding what you do not bother to look for. If you understand the high level of vaccine contamination and lack of safety, you can see this is the largest liklihood for transmission of lymes to all the New England areas sporting epidemic levels of lyme. CHECK THE VACCINES, EVEN FLU.

  4. Socrates permalink
    July 26, 2009

    Rick Ostfeld has an agenda, to focus attention on the white-footed mouse and other small mammals, and keep the focus off of the white-tailed deer.

    While it’s true that the small mammals are the hosts for the disease, it is our overabundance of deer that allows the overabundance of the deer tick (black-legged tick, ixodes scapularis).

    The mice help the ticks in the first year of their two-year life cycle, but the deer give the transportation and last blood meal for the adult tick. Studies have shown that if you reduce the deer density to about 10 per square mile, you dramatically reduce the tick abundance, and Lyme disease is dramatically reduced also. But certain “scientists” do not want to address the deer issue head-on.

    Ostfeld’s latest “study” is to try to connect the acorn crop with the white-footed mouse and then connect all that to incidence of Lyme disease. True, the mice love acorns, but to isolate that connection would be to ignore the fact that deer love acorns, too. It would take hundreds of mice to equal one deer’s appetite for acorns.

    It looks like a new leap of ignoring the problem–instead of “blame it on the mice,” we’re going to have “blame it on the acorns.”

    Also, beware of any “scientist” who is going to make a statement about biodiversity without qualifying what the term means. You don’t assess biodiversity by looking at one or a dozen species. If you really want to tell us about the biodiversity of the Northeast, there are hundreds of species of flora and fauna to answer for.

  5. Barb H. permalink
    July 27, 2009

    I think we are beyond the point of figuring out the “why’s”–it is pretty obvious that human encroachment is responsible for many problems affecting wildlife and the health (biodiversity) of the environment, which in turn affects human health. Lyme Disease is such a serious problem here and in Europe, that research related to finding a cure will be far more beneficial. Let’s face it: there is no way we can reverse the trend—the same issues apply as with agricultural pests. You attempt to fix the problem by increasing natural predators, but only create more (sometimes worse) problems because there is no way to go back down the line and fix it all–it remains out of balance. It would be far better to make people well so they can take care of their families, be well enough to work and pay taxes, while others have the luxury of time to research other aspects of the problem. If I am dying of cancer, I really don’t care why I might have gotten it. By the time, if ever, anyone figures that out, the disease will have killed me. Encroachment will continue–let’s deal with the reality of that.

  6. Gen N. permalink
    August 7, 2009

    Growing up in a large city of over two million people, my experience with urban folks is that biodiversity means more animals and weeds, which leads to more pests and disease. It’s interesting to know that lyme disease is transported via deers and white-footed mice, but how do you translate this information to people who would rather have the status quo of energy- and water intensive landscaping versus an energy- and water efficient natural landscaping that would increase biodiversity?

  7. Dave permalink
    March 29, 2011

    I have had lyme disease since 1993. Thank you all the intersting information

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