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Coyote in Michigan, photo taken by SERS biologist David Marks.

Plague has been identified as a disease of concern to human, wildlife and domestic animal populations within the United States. It is also considered a "Category A" disease by the Department of Homeland Security, meaning it could potentially be used as a bioterrorist agent.


In the US, plague is almost exclusively restricted to the western half of the country (roughly west of the 100th meridian).

Disease Agent

This infectious disease is caused by the bacterium Yersinia pestis and can be primarily vectored by fleas.

Affected Species

Plague mostly affects, and is reservoired 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.

Members of the cat family, Felidae, such as bobcats, mountain lions and domestic cats are particularly susceptible to plague while the Canidae (dog) family, including coyotes, wolves and domestic dogs, tend to be fairly resistant to plague. Because cats are susceptible to plague and can develop the highly-contagious form of the disease (pneumonic plague), they can represent a health threat to people who come in contact with them (ie, sportsmen, wildlife personnel & pet owners). While canids do not tend to develop an active form of plague, they do readily develop antibodies to plague when they come in contact with the disease through scavenging or predation of infected rodents. Testing canid blood for the presence of these antibodies is a convenient and efficient method of monitoring plague exposure in wildlife.

NWDP Activities

NWDP biologists work closely with other WS personnel who conduct wildlife damage management (WDM) activities to protect human health, agriculture and natural resources. For example, collecting samples from coyotes taken during WDM activities to test for the presence of plague antibodies is useful because the coyotes make frequent contact with the infected rodents through predation and scavenging. If contact is made with an infected rodent, the coyote develops a titer (evidence of an immune response), which indicates that plague is likely present in the area.

Plague Surveillance Updates


Thomas Gidlewski , DVM
4101 Laporte Ave
Fort Collins, CO 805021

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