• Range Writing

Plague in Wyoming Mountain Lions

You may consider plague (aka “The Black Death”) a thing of the past, but it’s not.

Wildlife researchers found that 43 percent of mountain lions in their Teton County, Wyoming study tested positive for plague (Yersinia pestis) in a sampling from 2005 to 2014. Necropsies on 11 mountain lions after their deaths found that four of the animals had died of plague.

The paper noted that a case of human plague was detected in the area during the study (a Boy Scout visiting from another state in 2008). Although the paper mistakenly claims the case was a human fatality, in fact the teenager made a full recovery. Sadly, that was not the case for a Grand Canyon National Park biologist who conducted a necropsy on a dead mountain lion in 2007 without using personal protective equipment, and died six days later after inhaling aerosols from the infected mountain lion. Interestingly, the biologist had concluded the mountain lion died from an attack by another mountain lion, but a later examination by a veterinary pathologist found no wounds consistent with a fatal injury, instead finding a systematic plague infection with isolates indistinguishable from those recovered from the biologist.

A wide variety of wild animals can carry the Y. pestis bacterium without showing any clinical signs. But that isn’t the case for wild cat species. The reintroduction program for Canada lynx in Colorado in the early 2000s provides one such example: 6 lynx tested positive for the bacterium, and five died as the result of plague pneumonia.

Plague is transmitted from flea bites or by animals feeding on rodents and other mammals that are infected with the Y. pestis bacterium. There are about seven human plague cases reported per year in the United States, with most of those cases in the desert southwest. Plaque in humans is a rapidly progressing disease that can lead to death if untreated.

Wild carnivores have been implicated as the source in 12 human plague cases in the United States from 1970 to 2009, including the mountain lion case cited above, 5 cases involving bobcats, three cases involving coyotes, and a gray fox, and a badger. All the cases involved skinning or handling skinned animals, with exposures consistent with transmission through cuts in the hand.

Researchers suggest that those who handle dead animals (hunters, trappers, taxidermists, veterinarians, biologists) should be aware of the potential transmission of plague from wild animals to humans and practice basic safety measures. Anyone who develops symptoms consistent with plague should seek immediate medical attention.

For a detailed synopsis of plague in the United States, read this USGS publication.

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