Mice, foxes, deer, coyotes, ticks, & Lyme disease

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Coyote, Wind Cave National Park, June 2012; credit: L. Milideo

This is a good tale to follow if you’ve ever wondered why it’s so difficult to know how climate and environmental changes will affect species and ecosystems.  The simple answer: because these systems are very complex,

and the interactions among the various players are multifaceted and often tough to untangle.  Things don’t always go the way we think they will.

What follows is also a great example of the importance of studying, and understanding, the ecosystems around us.

If you live on the East Coast or in the Midwest (USA) and you like to play outside, you’ve probably heard of Lyme disease.  If you’re not familiar with Lyme disease, here’s some information.  In 2012, a team of researchers published a study in the Proceedings of the National Academy of Sciences, looking at the connections among deer, foxes, rodents (and other small mammals), coyotes, and Lyme disease. LiveScience has a really useful story about the research article.

Here are the basics: Lyme disease is spread when animals (or people) are bitten by ticks carrying Lyme disease. Mice and other small mammals are a vector for Lyme disease – a place for the bacteria to maintain a population to spread out from.  Foxes eat small mammals.  Coyote populations are spreading and expanding, and when they do, they drive out foxes.  Fox populations take a dive?  Small mammal populations can expand.  That means a lot more real estate for ticks, and the small mammals spread the disease to the ticks they host.

You might have noticed who’s conspicuously absent from this story: deer.  This is kind of weird considering that the tiny ticks that spread Lyme disease to humans are so strongly associated with deer that they’re often called “deer ticks.”  But the researchers found a connection between Lyme disease and FOX populations, not deer populations.  In other words, not only is the connection not where we thought it was, but the story’s more complicated than we thought it was.  It’s not deer and ticks.  It’s mice and shrews and other small mammals and foxes and coyotes and ticks.

And who knows what other species are involved?  Why are coyotes expanding their territory in the first place, for instance?  That brings in yet another player, since the decline in wolves is probably part of the reason that coyotes have been spreading from their traditional territory in the American plains.  As you can see, asking one question in ecology usually ends up leading to many, many more (as it does in any scientific pursuit).  There’s so much, so much we don’t know.  For this reason and many others, it’s vitally important to continue trying to understand how these ecosystems work.

For example, this whole small-mammal angle could mean finding different ways of approaching Lyme disease prevention.  Now, researchers are looking at ways to fight Lyme disease by starting with the small mammals.  They’re focusing on providing an edible vaccine, to be placed out for small mammals to eat.  Check out this helpful story from NewScientist for all the details.

Who knows where the next unexpected result may lead?

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About laurenwritesscience

I'm bringing scientific news and information to anyone interested, whether you're a scientist, or just love science! My focus is earth science and archaeology but I wander quite a bit.

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