A slow spreading plague called chronic wasting disease caused by a protein called prion is killing deer and elk. The disease was first discovered 50 years ago in 1967 when wildlife biologists observed mule develop a strange disease that made the animals lose weight and quickly advance to a zombie-like state before they died. The end-stage symptoms were documented as vacant stares, stumbling gait, drooping heads, ears down, and saliva dripping from the mouth.
In the September issue of Microbiology and Molecular Biology Reviews, Dr. Zabel, and immunologist at Colorado State University, and his former graduate student Aimee Ortega, surveyed what scientists learned about the plague:
- The disease infects herd with a deformed protein called a prion
- Once this disease gets a foothold, it spreads relentlessly. The disease has been documented in as many as 24 states (nearly half the states in the US)
- The disease spreads through direct contact, but through the landscape itself. Sick animals and cadavers spread prions across the land infecting plants and soil for years, perhaps even decades.
Other prion diseases are known to affect livestock or people; not wildlife. One such disease that affects sheep is called “scrapie.” A number of studies show that bone meal contaminated with scrapie prions passed the disease to cows ( aka “mad cow disease”). Scientists have long suspected that deer and related species developed the wasting disease by picking up scrapie from sheep flocks kept at the Colorado State University. The disease later spread to other states and Canada as animals were shipped to private game farms.
Dr. Zabel and his colleagues have found that infected animals can release large numbers of prions. If the deer got sick only by direct contact, the outbreaks would be most severe in the most densely populated areas in the Midwest. But these infections have been the worst in the Rocky Mountains, where there are far fewer animals. Mathematical models suggest that the animals are getting sick from prions in the environment.
It is for this reason, that Dr. Zabel and his colleagues hope to get rid of the prions in the environment through controlled burning of infected habitats. The fires won’t be hot enough to destroy the prions but they may kill enough plants with prions and control the risk to healthy animals. This hypothesis has yet to be tested.
Nikiforuk, Andrew. Andrew Nikiforuk to The Tyee newsgroup, “New Research Sparks Health Canada Warning Deer Plague Might Infect Humans,” June 24, 2017. Accessed July 7, 2017. https://thetyee.ca/News/2017/06/24/Chronic-Wasting-Disease-Research/.
Wehrs, Marc. Marc Wehrs to La Crosse Tribune newsgroup, “Chronic Wasting Disease Spreading among Wisconsin Deer,” April 5, 2016. Accessed July 7, 2017. http://lacrossetribune.com/news/local/chronic-wasting-disease-spreading-among-wisconsin-deer/article_4cb46a33-5df7-5614-a1ee-2f208e1328c8.html.
Zimmer, Carl. “Fire May Be the Only Remedy for a Plague Killing Deer and Elk.” New York Times (New York, NY), June 26, 2017. Accessed July 7, 2017. https://www.nytimes.com/2017/06/26/science/chronic-wasting-disease-deer-elk-prions.html.