Jul 17, 2017

Why this adorable mouse is to blame for the spread of Lyme disease

Virginia
USA
by
Lindsey Bever
,
Washington Post
The white-footed mouse. Photo: Cary Institute of Ecosystem Studies
The white-footed mouse. Photo: Cary Institute of Ecosystem Studies

The critters run through forest floors throughout the eastern United States, snatching up acorns and other tree seeds, berries and bugs.

White-footed mice — known for their wide eyes and ears, long tails and snow-white bellies and the feet from which they get their name — are often overlooked by humans, hiding out by the billions in U.S. forests, shrubby thickets and even wooded wetlands. But there's one creature that knows them well: the tick.

Scientists say white-footed mice, which are primary carriers of the Lyme bacterium Borrelia burgdorferi, are a highly popular host of black-legged ticks — which consequently makes them a key culprit in the spread of Lyme disease.

For Lyme disease transmission, “essentially, the only way people can get infected is through a tick bite,” said Richard Ostfeld, senior scientist at Cary Institute of Ecosystem Studies.

Scientists say that white-footed mice are posing a particularly high risk to humans this year. A bountiful acorn harvest a couple of years ago gave them the sustenance needed to reproduce in greater numbers and climate change may be pushing them to expand their range toward the north.

“That's something of a worry because where the mice go, so too go the infected ticks,” said Ostfeld, who is co-heading the Cary Institute's Tick Project, along with his wife, Felicia Keesing, a biology professor at Bard College in New York.

Ostfeld said there are areas in the United States where Lyme disease is rare and, in those places, few or none of the white-footed mice are infected. But in an endemic area such as one that extends from Virginia to Maine, at least half and sometimes up to 90 percent of the mice are infected with Lyme bacteria.