Ecology of Plague

Science Center Objects

In North America, the flea transmitted plague bacterium (Yersinia pestis) has colonized and altered native animal communities and ecosystems for more than a century. Many species have suffered adverse consequences from plague, perhaps none more than the endangered black-footed ferret. Plague has established within the ranges of all North American prairie dog species, which collectively serve as the sole habitat and predominant prey base for the endangered black-footed ferret. This disease causes periodic and sometimes dramatic die-offs of both prairie dogs and ferrets. Plague also threatens the recovery of the threatened Utah prairie dog and declines in other species of conservation concern.

Image: Tagged Prairie Dog

This wild prairie dog has been tagged by scientists in an effort to study the efficacy of a USGS-developed oral sylvatic plague vaccine (SPV) to help immunize prairie dogs against plague. It was released after being tagged and after scientists took hair, whisker, and blood samples.If successful, the SPV could help protect endangered black-footed ferret populations in the western U.S. because the ferrets rely on prairie dogs for food.The SPV project is a collaboration of over 30 organizations and agencies. Public domain.

Because sylvatic plague is a serious threat to prairie dog colonies and the endangered black-footed ferrets (Mustela nigripes) that depend upon them, FORT scientists are investigating the dynamics of plague in the wild. This study is directed toward gaining further understanding of the ecology of plague during periods between epizootic outbreaks of the disease in prairie dogs Cynomys spp.). If enzootic plague is depressing populations of small mammals, an ambitious effort to remove plague could allow increased population densities to develop over a several-year period. Investigators are attempting to reduce the incidence of plague (or eliminate it) from test areas by reducing the population of fleas, which transmit the disease. The initial objectives of this study are to assess efficacy, longevity, and cost of flea control using deltamethrin delivered as dust within burrows and measure population responses of prairie dogs and associated mammals. Research, development, and field trials of vaccines against sylvatic plague in prairie dogs and black-footed ferrets are also underway.

As a key part of this work, FORT hosted the Symposium on the Ecology of Plague and Its Effects on Wildlife in Fort Collins, CO, November 4-6, 2008. This symposium was co-sponsored by the U.S. Geological Survey, the U.S. Fish and Wildlife Service, Colorado State University, and the Centers for Disease Control and Prevention. FORT’s mission in sponsoring this symposium was to increase the ability of scientists and resource managers to understand, evaluate, and mitigate wildlife risks associated with plague. A special issue of Vector Borne and Zoonotic Diseases was published in January 2010 highlighting key presentations and all abstracts from the symposium. The articles and abstracts represent the work of 133 participants from 8 countries and span the range from maintenance dynamics of plague in natural foci; influence of environmental factors and landscape ecology; role of rodents and vector species in transmission; genetics and evolution; management, control, and surveillance; risk factors for humans from plague in wildlife; impacts of plague on wildlife populations; and consequences for conservation of imperiled species.

TSH scientists are conducting research on various aspects of plague ecology and management including: treatment-control studies using vaccines and insecticides to examine effects of enzootic plague on survival rates and other population parameters in various animal communities, field testing the efficacy of a bait-delivered vaccine for prairie dogs, investigating factors involved in plague persistence in the environment, and evaluating potential development of insecticide resistance in fleas. Findings from this research will provide resource managers a better understanding of plague and new tools for managing this disease in wildlife.