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Foxes, Land Conservation, and Lyme Disease

How does land conservation reduce the transmission of Lyme disease? Dr. Tim Hofmeester’s research suggests that predators, like foxes, reduce the number of ticks that become infected with the bacteria that causes Lyme disease by controlling the tick’s preferred host species, the white-footed mouse. It’s a fascinating area of research that reminds us there is still much to learn about the complex interactions between species in a healthy ecosystem. Paul Elconin, Weantinoge’s Director of Land Conservation, was quoted in this News Times article about the work Weantinoge is doing to protect large areas of high-quality forest so predators have the space to thrive.

Lyme disease is caused by a bacteria, Borrerlia burgdorferi, and transmitted to humans through the bite of an infected tick, most commonly the deer tick (Ixodes scapularis). Ticks become infected only if they feed on an animal that carries B. burgdorferi. In the eastern United States, upwards of 90% of white-footed mice carry the bacteria and this mouse is one of the most common host species for the deer tick.

Over two years, Dr. Tim Hofmeester compared the number of ticks on mice from areas with healthy predator populations to the number of ticks on mice caught in low predator areas. Mice caught in the areas with healthy predator populations had only 10 to 20 percent as many ticks as those from the low predator area. Fewer newly hatched ticks feeding on white-footed mice means that fewer adult ticks will carry the B. Burgdoferi bacteria, “The predators appear to break the cycle of infection,” said Dr. Hofmeester.

Lyme disease is more complicated than a single tick bite. Habitat fragmentation, hunting, and the removal of larger predators like cougars may all figure into the dwindling of small mammal predators like foxes, weasels, bobcats, and fishers. Land conservation can play a role by protecting large tracts of land that small mammal predators require. As research continues, will public health officials consider land conservation to protect small predator species as one way to slow the spread of Lyme disease? The New York Times notes, “Nothing else — like culling deer or spraying lawns with tick-killing pesticide — has worked so far to stem the incidence of tick-borne disease, which is spreading in the Midwestern United States, in parts of Canada and at higher altitudes across Europe.”