Plague Surveillance - 1999-2005

The word "plague" may conjure up images of the Black Death, the epidemic that scourged Europe in the Middle Ages. While plague in the United States has rarely reached such epidemic proportions, it has maintained a constant and continued presence since its introduction in the 1920's through California ports. Since then clusters of human cases numbering about a dozen usually occur every year primarily in the Southwest.

Identifying high rates of plague in wild animal populations can be a risk factor for predicting disease in humans and domestic animals such as cats. Plague is also a potential agent of bioterrorism; therefore it is important to know background levels of plague in wild animals to assist in determining whether an outbreak is a possible bioterrorism event.

The Vector-Borne Disease Prevention Program (VBDPP) in cooperation with United States Department of Agriculture (USDA)-Wildlife Services conducts annual surveillance of plague activity statewide. This effort utilizes blood samples from coyotes and other carnivores as indicators for plague.

Coyotes (Canis latrans) and many other carnivores routinely consume rodents as a part of their diet. In nature the bacteria that cause plague, Yersinia pestis, cycles between several rodent species and their fleas. When coyotes capture and eat these rodents they can become infected with plague. While the coyote will not develop a serious disease, an antibody response is triggered that is detectable through blood tests. By sampling coyote blood, one can obtain data that provides a picture of plague activity in a given area. This method is a particularly effective tool because each coyote has "sampled" hundreds of rodent prey and their fleas.

Wildlife Services staff collects specimens during the course of their regular duties. The Plague Branch of the Centers for Disease Control and Prevention in Ft. Collins, Colorado, performs laboratory testing on the specimens. The VBDPP staff use the information gathered for focused control efforts (flea control) and timely public health alerts to health care providers and local residents to prevent human cases of plague.

As illustrated in the accompanying map, there were significant pockets of plague activity in 2005 scattered throughout the State primarily in Washoe, Lincoln, and White Pine Counties. The table below lists those counties with positive results by year from 1999 through 2005:

Counties with positive plague results from 1999 through 2005
Year County Species Number Positive Number Tested Percent Positive
1999 Alpine, CA Coyote 2 4 50.0
Douglas Coyote 13 42 31.0
Elko Domestic Dog 1 4 25.0
Lander Coyote 15 37 40.5
Lyon Coyote 1 4 25.0
Nye Coyote 6 11 54.6
Storey Coyote 1 3 33.3
Washoe Coyote 10 64 15.6
2000 Douglas Coyote 2 27 7.4
Elko Domestic Dog 2 23 8.7
Coyote 6 19 31.6
Eureka Coyote 1 3 33.3
Humboldt Coyote 5 64 7.8
Lander Coyote 2 14 14.3
Lincoln Coyote 1 10 10.0
Lyon Domestic Dog 1 5 20.0
Coyote 3 12 25.0
Nye Domestic Dog 1 11 9.1
Washoe Coyote 2 16 12.5
White Pine Coyote 12 26 46.2
2001 Churchill Coyote 1 40 2.5
Douglas Coyote 10 59 17.0
Elko Domestic Dog 1 1 100
Coyote 14 36 38.8
Esmeralda Coyote 1 2 50.0
Eureka Coyote 4 14 28.6
Humboldt Coyote 8 103 7.8
Lincoln Coyote 6 35 17.1
Lyon Coyote 3 29 10.3
Nye Coyote 5 26 19.2
Pershing Coyote 11 67 16.4
Kit Fox 1 2 50.0
Washoe Coyote 10 85 11.8
White Pine Coyote 6 55 10.9
Mountain Lion 1 4 25.0
2002 Douglas Coyote 2 23 8.7
Elko Coyote 3 25 12.0
Red Fox 1 2 50.0
Humboldt Coyote 3 90 3.3
Lincoln Badger 2 2 100
Nye Coyote 1 9 11.1
Washoe Coyote 5 128 3.9
White Pine Coyote 3 59 5.1
2003 Douglas Coyote 4 21 19.0
Black Bear * 8 14 57.1
Elko Coyote 3 27 11.1
Humboldt Coyote 2 127 1.6
Lander Coyote 1 11 9.1
Lincoln Coyote 4 62 6.5
Lyon Coyote 2 81 2.5
Pershing Coyote 1 30 3.3
Washoe Coyote 3 106 2.8
Mountain Lion 1 1 100
Black Bear 1 8 12.5
White Pine Coyote 4 129 3.1
2004 Elko Coyote 5 90 5.6
Eureka Coyote 1 18 5.6
Humboldt Coyote 4 109 3.7
Lander Coyote 3 30 10.0
Lincoln Coyote 34 171 19.9
Lyon Coyote 5 54 9.3
Nye Coyote 2 16 12.5
Washoe Coyote 14 81 17.3
Mountain lion 1 4 25.0
Yellow-bellied marmot 3 151 2.0
California ground squirrel 1 124 0.8
White Pine Coyote 39 184 21.2
Mountain lion 2 5 40.0
Badger 1 2 50.0
2005 Douglas Mountain lion 1 1 100.0
Elko Coyote 9 105 8.6
Humboldt Coyote 4 92 4.4
Lincoln Coyote 14 149 9.4
Lyon Mountain lion 1 1 100.0
Pershing Coyote 1 53 1.9
Washoe Coyote 15 113 13.3
White Pine Coyote 18 193 9.3
Badger 2 4 50.0

* The Nevada Department of Wildlife (NDOW) staff submitted the black bear samples.

Last modified on 09/03/2015