From: Andy Soos, ENN
Published March 1, 2010 04:02 PM

Plague in the Wild

When one thinks of plague one thinks of the Black Plague in Europe in the Dark Ages that was spread by rodents. However, plague also affects wildlife where a reservoir of the disease is maintained. Plague, a flea borne bacterial disease introduced to North America in the late 1800s, spreads rapidly across a landscape, causing devastating effects to wildlife and posing risks to people. Conservation and recovery efforts for imperiled species such as the black footed ferret and Utah prairie dog are greatly hampered by the effects of plague. Eruptions of the fatal disease have wiped out prairie dog colonies, as well as dependent ferret populations, in many locations over the years.

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Plague has been identified as a disease of concern to human, wildlife and domestic animal populations within the United States. This infectious disease is caused by the bacterium Yersinia pestis and is primarily vectored by fleas. This same bacteria caused three human epidemics in recorded history; today, wildlife act as reservoirs for the bacteria throughout the world in arid areas.

Plague mostly affects, and is found within, rodent populations such as chipmunks, ground squirrels and prairie dogs, but can also affect other mammals, such as carnivores and scavengers that feed on rodents. Plague represents a health and safety threat to humans, especially in places where humans and rodents interface. There are currently about a dozen human plague cases reported each year.

In new research (special issue of Vector-Borne and Zoonotic Diseases), it is demonstrated that plague continues to affect the black footed ferret, one of the most critically endangered mammals in North America, as well as several species of prairie dogs, including the federally threatened Utah prairie dog even when the disease does not erupt into epidemic form.

“The impacts of plague on mammal populations remain unknown for all but a few species, but the impact on those species we have studied raises alarms as well as important questions about how plague might be affecting conservation efforts in general,” said Dean Biggins, a wildlife biologist with the U.S. Geological Survey and co-author of two papers in the special issue.

Biggins’ and his colleague’s research indicates that plague may be maintained in the wild within colonies of prairie dogs, the primary food of black footed ferrets, without causing the large scale, rapid die off of prairie dogs that is commonly observed. The mechanisms of the bacterium’s low level presence and survival, as well as the absence of a large scale die off of prairie dogs, remain under investigation.

“The overall difficulty of detecting plague in the absence of a large scale die off serves as a warning for those dedicated to wildlife conservation and human health,” Biggins said. “Hazards from plague may exist even where there have never been epidemics that caused widespread and readily detectable levels of mortality among local rodents such as prairie dogs.”

Two years ago, for example, a National Park Service employee in Arizona died of plague contracted from an infected cougar that he had found dead, even though a plague epidemic had not been observed in resident prairie dog populations.

For further information: http://www.usgs.gov/newsroom/article.asp?ID=2405&from=rss&utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+UsgsNewsroom+%28USGS+Newsroom%29&utm_content=Google+Reader

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