Monday, November 26, 2012

Are Predators our Friends?

A recent publication in the journal Proceedings of the National Academy of Sciences (PNAS) suggests that they are. This study conducted by Levi and colleagues finds that, contrary to popular belief, large and expanding deer populations may not be solely to blame for the initial emergence of Lyme disease in the US northeast or its continued expansion.

Image obtained from wikimedia commons
Instead, the authors contend that loss of small mammal predators like foxes and their replacement by less efficient predators like coyotes, could be to blame. Over the time period in which Lyme disease emerged and human cases increased, there was an ongoing decline in red fox populations and coincident expanding coyote populations. In fact, the researchers found that "changes in predator abundance are more closely linked with increases in Lyme disease than are changes in deer abundance." Red foxes are very efficient small mammal predators, often killing far more than they can eat, caching their kills for later consumption, in times of high small mammal abundance. Thus, red foxes may have kept populations of small mammals (e.g. mice or chipmunks) that are integral hosts for both the ticks and Lyme bacteria in check.

This study is important in drawing attention to predators as important drivers of disease emergence, like Lyme disease. This research further underscores the importance of ecology to the understanding of Lyme disease and provides new direction for field studies of Lyme disease ecology.

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