LYME-Chain Reaction

Every few years there’s an increase in the number of acorns produced by oak trees. Scientists don’t know why this happens, but they have noticed a surprising correlation between this abundance of acorns and Lyme disease– an illness which is spread by ticks to thousands of people every year. I’m Jim Metzner, and this is the Pulse of the Planet, presented by the American Museum of Natural History.

Richard Ostfeld is with the Institute of Ecosystem Studies.

“What we’ve been finding out is that acorn production by the oak trees sets off what we consider an ecological chain reaction that influences Lyme disease risk. And the way that works is that acorns are an extremely desirable food resource for a number of animal species. The two that are critical to Lyme disease are the white tailed deer and the white footed mouse.

So what happens in the fall of a good acorn year, when tremendous quantities of acorns are produced, those acorns draw white tailed deer into oak dominated forests in the fall. The fall is the time when these white tailed deer are infested by the adult stage of the tick. So wherever the deer are in the fall, that’s the site where larval ticks hatch out of eggs the following summer.”

But white footed mice also thrive on acorns, and just as the ticks are hatching, a new generation of mice is born in the oak forests.

“So the mice reach a peak in the same place, and the same time, as these hordes of larval ticks. And it turns out that the mice are the place where the larval ticks can pick up the Lyme disease agent, this bacterium, and then become dangerous to us later on.”

Here’s a question to think about. Years ago, passenger pigeons thrived on acorns in northeastern forests, until the pigeons were rendered extinct by human beings. If the passenger pigeon had survived to help keep the acorn supply in check, would we still have had a Lyme disease epidemic?

Pulse of the Planet is presented by the American Museum of Natural History. Additional funding for this series has been provided by the National Science Foundation. I’m Jim Metzner.

LYME-Chain Reaction

Certain natural cycles may start a chain reaction resulting in a periodic outbreak of Lyme disease.
Air Date:07/31/1998
Scientist:
Transcript:

Every few years there's an increase in the number of acorns produced by oak trees. Scientists don't know why this happens, but they have noticed a surprising correlation between this abundance of acorns and Lyme disease-- an illness which is spread by ticks to thousands of people every year. I'm Jim Metzner, and this is the Pulse of the Planet, presented by the American Museum of Natural History.

Richard Ostfeld is with the Institute of Ecosystem Studies.

"What we've been finding out is that acorn production by the oak trees sets off what we consider an ecological chain reaction that influences Lyme disease risk. And the way that works is that acorns are an extremely desirable food resource for a number of animal species. The two that are critical to Lyme disease are the white tailed deer and the white footed mouse.

So what happens in the fall of a good acorn year, when tremendous quantities of acorns are produced, those acorns draw white tailed deer into oak dominated forests in the fall. The fall is the time when these white tailed deer are infested by the adult stage of the tick. So wherever the deer are in the fall, that's the site where larval ticks hatch out of eggs the following summer."

But white footed mice also thrive on acorns, and just as the ticks are hatching, a new generation of mice is born in the oak forests.

"So the mice reach a peak in the same place, and the same time, as these hordes of larval ticks. And it turns out that the mice are the place where the larval ticks can pick up the Lyme disease agent, this bacterium, and then become dangerous to us later on."

Here's a question to think about. Years ago, passenger pigeons thrived on acorns in northeastern forests, until the pigeons were rendered extinct by human beings. If the passenger pigeon had survived to help keep the acorn supply in check, would we still have had a Lyme disease epidemic?

Pulse of the Planet is presented by the American Museum of Natural History. Additional funding for this series has been provided by the National Science Foundation. I'm Jim Metzner.