Carnivorous mice spread deadly plague in prairie dog towns

http://www.eurekalert.org/pub_releases/2010-08/su-cms080310.php

Public release date: 3-Aug-2010
Contact: Mark Shwartz
Stanford University
Carnivorous mice spread deadly plague in prairie dog towns, Stanford study finds

Prairie dogs, once abundant in the Rocky Mountains and Great Plains, have been decimated in recent decades by plague – a virulent bacterial disease spread by fleas.

Plague outbreaks periodically sweep through large prairie dog towns with thousands of inhabitants, killing virtually the entire population within months. Other prairie dogs move in and build a new colony, which eventually is wiped out when the disease returns.

This pattern of re-colonization followed by devastation can occur over many years. The question for scientists is how does plague persist after a colony has been wiped out?

"A fundamental question in disease ecology is what happens to pathogens in between the periods when they cause all of this devastation," said James Holland Jones, an associate professor of anthropology and a center fellow at the Woods Institute for the Environment at Stanford University.

"Previous studies have suggested some sort of magical reservoir for the plague pathogen," Jones said. "Maybe it gets into the soil and infects the re-colonized prairie dog town. Or perhaps it's carried in by some carnivore. Who knows?"

Jones and his colleagues may have finally solved this longstanding mystery. The likely culprit, they say, is the grasshopper mouse, a carnivorous rodent that carries plague-infected fleas across the rigid territorial boundaries separating isolated family groups within the prairie dog colony.

"We found that when grasshopper mouse density gets high enough, you get an epizootic – the animal equivalent of an epidemic – and virtually all of the prairie dogs die," Jones explained.

This finding, published in the July 26 online edition of the Proceedings of the National Academy of Sciences, could have significant implications for understanding how infectious diseases spread in animals and humans.

"Plague, a disease caused by the bacterium Yersinia pestis and the causative agent of Black Death that killed 200 million Europeans in the 14th century, arrived in the United States via San Francisco around 1900 and still infects people worldwide," Jones said.

----- (skipping)

..