National Wildlife Disease Program (NWDP)

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.

Location
In the US, plague is almost exclusively restricted to the western half of the country (west of the 102nd meridian).

Disease Agent
This infectious disease is caused by the bacterium Yersinia pestis and is 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 tend to 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 the canid’s blood for the presence of these antibodies is a convenient and efficient method of monitoring the area’s rodent population for plague activity.

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. 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.

When the presence of plague is detected through lab diagnostic testing, this evidence is shared with local health officials, both human and veterinarian. Once alerted to the presence of the disease in their area, health personnel can be on the look-out for patients exhibiting plague's flu-like symptoms (fever, chills, swollen lymph nodes, etc.). Plague symptoms so closely resemble other common diseases that physicians and verterinarians who have not been alerted that plague is active in their area may fail to consider plague in their diagnostic testing. Because plague is generally not a commonly-encountered disease, health providers who are unaware of its presence are likely to only test for the more commonly-encountered illnesses, thus delaying the true diagnosis. When detected early, plague infections can be readily treated with antibiotic drugs with excellent results. A delay in the diagnosis, even for a short period, can make treatment much more difficult and could lead to fatal illness.


Plague Surveillance Updates
Plague Surveillance Update Volume 1, Issue 1, October 2010
NWDP Sylvatic Plague Surveillance Update May 2011

More information on plague:
Center for Disease Control- Plague
TOPOFF 3 Background, Biological Agents (Homeland Security Factsheet)

Contact:
Thomas Gidlewski, DVM
Thomas.Gidlewski@aphis.usda.gov
(970)266-6350
USDA/APHIS/WS
4101 Laporte Ave
Fort Collins, CO 805021