Lyme disease, ecologists, and public health

Last week I wrote about the impacts of swine operations on our water quality. It’s one example of how land use patterns can disrupt the environment and affect public health. That subject came up again this week during a conversation with Dr. Laura Jackson of the Environmental Protection Agency’s National Health and Environmental Effects Research Laboratory (NHEERL), a unit of the EPA’s Office of Research and Development that is housed in Research Triangle Park.

Dr. Laura Jackson of the EPA’s National Health and Environmental Effects Research Laboratory (NHEERL), a unit of the EPA’s Office of Research and Development that is housed in Research Triangle Park.

Dr. Jackson and her colleagues in this RTP lab—more than 100 scientists—conduct research on ecosystem services, those benefits provided by the environment over and above the psychological benefits of being out in nature. These services can have tangible and measurable economic value.

For instance, in a normally functioning ecosystem, vegetation would take up nitrogen and phosphorus from animal waste and keep those nutrients from overburdening groundwater and streams. In last week’s example, when hogs were added to an ecosystem, they knocked it out of balance by depositing more nutrients than the vegetation could handle and by removing plants that could take up the nutrients and provide erosion control. The researchers at the Center for Environmental Farming Systems were developing countermeasures to keep the water clean near hog farming operations and restore ecosystem function.

In addition to cleaning water, vegetation can also scrub pollutants from the air, and the EPA’s Dr. Jackson and her colleagues are looking into the capacity of plantings near roads to filter pollutants from vehicles. Given the connection between tailpipe emissions and respiratory illnesses, this promises to be a fruitful area of research: imagine the cost savings on medication and lost work time if nature can help prevent illness.

Another example of an ecosystem service, Dr. Jackson said, is the ability of urban vegetation to mitigate the “heat-island” effect, reducing the risk of heat stress in vulnerable populations. (Think green roofs.) In this example, nature would not only alleviate illness but eliminate some of the need to burn fossil fuels for air conditioning.

It’s already obvious that ecosystem services can be an important public health tool, and we haven’t even gotten to the topic I called Dr. Jackson to discuss: Lyme disease.

Lyme is of growing concern in the Research Triangle region; more on that in a moment. It is also of particular interest to me, because I am a renegade Durhamite living in New York’s Hudson Valley. My new home is not only the hotbed of Lyme disease but one of the hotbeds of Lyme disease research. It’s almost child’s play to get Lyme disease here, and nearly any symptom that brings you to the doctor will result in blood tests for Lyme and other tick-borne illnesses. They are that common.

At the Cary Institute of Ecosystem Studies, where I am loosely affiliated as a science writer, Dr. Richard S. Ostfeld is leading a team studying the impact of biodiversity on Lyme and other tick-borne illnesses. Long-term research conducted by Ostfeld’s lab reveals that more people get Lyme disease when natural landscapes are fragmented by development and other human activities. Large carnivores who need lots of space are driven away, and white-footed mice, which carry the bacteria that causes Lyme, thrive in the absence of these predators.

Given my newfound geographical interest in Lyme, I was incredibly interested to hear that someone in the Triangle—my beat for this blog—is working on this same topic. Dr. Jackson talked to me about her research findings and about how the EPA is using research like hers to affect decision making.

Dr. Jackson initiated the Lyme research as part of her Ph.D. program in Ecology at UNC-Chapel Hill. Her primary research tool: satellite imagery upon which she plotted records of Lyme disease cases gleaned from existing state health department records. Using an off-the-shelf statistical program, she was able to identify the types of landscapes most associated with high rates of Lyme disease: places where the edges of forests intermixed with herbaceous cover such as lawn or pasture.

And these are the kinds of places where new neighborhoods are being developed, says Jackson. “It’s popular to build out towards ‘green fields’ or undeveloped land,” she says. “People want to be near forests.” On these edges, where deer, ticks, white-footed mice, and people all exist, it’s what she calls “a perfect environment” for the transmission of Lyme disease.

There is no vaccine against Lyme disease in humans; it can be treated with antibiotics, but people can get it many times if infected ticks bite them. Individuals can avoid the disease by dressing appropriately, using bug spray, and checking their skin for ticks. Education in these individual measures is one public health approach to disease prevention.

But to Dr. Jackson, a broader approach to risk is called for. One landowner on a forest edge can clear shrubs to discourage deer, or lay down a strip of wood chips as a buffer between forest and lawn, but unless all of the property owners along an edge do this, she says, the risk factors will remain for the entire nearby population. She believes that whole neighborhoods have to work in concert to reduce risk.

In addition, one goal is to “design out the risk” for Lyme and related diseases by making decisions about land use based on research findings. To that end, she and her EPA colleagues are partnering with Michigan State University’s Digital Watershed to create an online tool that will predict whether developing a particular landscape in a particular way will create a high or low risk for Lyme disease. It will become part of EPA’s online Environmental Decision Toolkit in the future. Using tools like this, it is possible that without spending an extra cent in development costs or public health money, neighborhoods could be designed that work with nature to reduce the risk of Lyme. That is the concept of ecosystem services at work.

Although Dr. Jackson’s original research focused on Maryland, it has implications for the Research Triangle area, where she grew up. “The tick is here,” she says, referring to the black-legged tick that carries the bacterium that causes Lyme. “And the disease is here.” As wildlife habitats are being converted for development, she says, we don’t have the expansive natural habitats that we used to have. Given the style of development happening in the Triangle, she says, “it’s not surprising that Lyme is here.”

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