“Do mice get Lyme Disease?”

Well over a year ago (yes, it takes me a really long time to get to some of these questions), Daddyo came home from work primed with a fascinating story about how a bad acorn harvest in the fall of 2011 would mean The Five-Year-Old would to endure more bug spray than usual in the summer of 2012.

How can the acorn crop predict The Five-Year-Old’s exposure to bug spray?

White footed mouse (Photo: US Fish & Wildlife Service)
The white footed mouse, the type implicated in the spread of Lyme Disease. (Photo: US Fish & Wildlife Service)

By now, most of my readers in the Northeast will probably know the story, but I’ll sum up anyway. 2010 was a great year for acorns, leading to a bumper crop of field mice, chipmunks, and other wee beasties that use acorns as their primary food source. That in turn led to a massive increase in ticks, which use the field mice, chipmunks, and other wee beasties as their primary food source.

But in 2011, the acorn harvest was lean. Experts predicted the failed acorn crop would devastate the field mice populations, forcing a legion of ticks to forage elsewhere for their supper. All those hungry ticks were expected to converge on larger prey, like deer and humans instead–a menu switch that could lead to a bumper crop for Lyme disease in the Northeast. Hence the uptick in bug spray usage in The Five-Year-Old’s future.

Do mice get Lyme Disease?

One of the side effects of having a parent who works in the medical profession is The Five-Year-Old knows an awful lot about disease relative to other five-year-olds (or really, even her Mommyo). On hearing that the same ticks that give us Lyme Disease also feast on mice, she naturally wanted to know “Do the mice get Lyme Disease too?”

Turns out, no. Although mice are carriers for the bacteria that causes Lyme Disease, they don’t appear to be susceptible to it. As this Medscape article puts it, mice “are infested, not infected.”

That makes mice an important reservoir for Lyme disease in the United States, although not the only one. Chipmunks and shrews can also carry the Lyme Disease bacteria.

A 2007 study led by a University of Pennsylvania biologist shows that cute little guys like this one harbor up to 13% of infected ticks. (Image: John Witherspoon)
A 2007 study led by a University of Pennsylvania biologist shows that these cute little guys harbor up to 13% of infected ticks. (Image: John Witherspoon)

Although deer are often blamed for the spread of Lyme disease, the same study suggests that their role is more nuanced. Having a lot of deer around means there will be plenty of food to support a dense tick population, but the deer only rarely transmit the bacteria that causes Lyme Disease to those ticks.

How Lyme Disease is Transmitted

Not all ticks are infected with the bacteria causing Lyme Disease. Instead, they pick it up after feeding on mice and other animals infected with it. The ticks then pass that infection along to their next host. Fortunately for us, that process is a relatively slow one. It can take 24 to 36 hours for a tick to transmit the infection to a human host.

And that mean that taking just a few common sense precautions when you and your five-year-0ld explore the great outdoors can reduce your risk of getting Lyme Disease.

Preventing Lyme Disease

  • Wear light colored clothes
  • Check clothes and exposed skin for ticks
  • Use insect repellant containing DEET
  • Avoid sitting on rock walls
  • Keep long hair back
  • At the end of the day, do a full body check of yourself, your children, and your pets

If you find a tick, remove it and keep an eye on the bite. The first symptoms of Lyme Disease can take anywhere from 3 to 30 days to appear. If you develop a rash, fever or joint pain, call your doctor immediately. Early detection can make a world of difference when it comes to treating Lyme Disease.

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