Pathogen of the Month
February pathogen of the month:
Chronic Wasting Disease
What is it? Chronic Wasting Disease is a prion disease of cervids (deer, elk, reindeer, moose). Prion diseases are a class of diseases caused by “prions,” which are infectious misfolded proteins that lead to neuro-degenerative changes in the brain. They are usually rapidly progressive and fatal.
CWD was first identified in captive deer in a research facility in the late 1960s in Fort Collins, Colorado and in wild deer in 1981.
By the 1990s, it had been reported in surrounding areas in northern Colorado and southern Wyoming. Once CWD is established in an area, there is a risk that it can remain for a long time in the environment. That means the affected areas are likely to continue to expand over time.
There have been no reports of CWD in humans. Animal studies suggest a potential for risk for non-human primates (such as monkeys); concerns have been raised about the potential for a risk to humans.
Mode of transmission.
Scientists believe CWD proteins (prions) likely spread between animals through body fluids like feces, saliva, blood, or urine, either through direct contact or indirectly through environmental contamination of soil, food or water.
Once introduced into an area or farm, the CWD protein is contagious within deer and elk populations and can spread rather quickly. According to the CDC, CWD prions can remain in the environment for years, so other animals can contract CWD from the environment even after an infected deer or elk has died or moved away.
What is the current status?
The Centers For Disease Control reports that Chronic Wasting Disease has been identified in either farmed or wild cervids in 24 states. That total includes 27 Kansas counties, most of them in the western part of the state but ranging eastward as far as Jewell County in the state’s north-central region. Officials of the Kansas Cervid Breeders Association note, however, that the actual instance of CWD in the state is low, equating to 1 in 200,000 deer.
Its impact in the U.S.
The greatest threat posed by CWD is to the nation’s hunting industry. In a 2006-2007 study, the CDC projected that nearly 20 percent of the U.S. population hunt for deer or elk from time to time, and more than two-thirds said they had eaten venison or other game meat. Since there is no confirmed evidence of the potential for the spread of CWD among humans, this data does not at the moment present a threat beyond that posed to the game industry itself.
The economic threat posed to the $4 billion hunting industry is a separate matter. Experts report that hunters nationwide are purchasing fewer deer licenses, a matter of concern both to states – which derive revenues from the sale of those licenses – and to the domestic cervid farming industry.
Its impact in Kansas
The Kansas Department of Wildlife, Parks and Tourism reports that the first case of CWD in deer was identified in 2001 in Harper County. A 2017 report put the total number of cases statewide at 142
There is no cure for CWD and no method of vaccination or eradication. That means that the focus of health officials is on restraining the disease’s spread. This effort includes restricting the disease’s ability to move from farmed deer/elk populations – breeding farms and ranches – into wild populations and vice versa. This is accomplished by a program of CWD testing conducted at breeding farms. Industry officials are also working to identify genetically resistant animals in the same fashion the sheep industry did for Scrappie. Work also continues on gene editing techniques that might permit development of animals with immunity to CWD.
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Sources: DeerBusters.com, Kansas Department of Wildlife and Parks, CDC; North American Deer Farmers Association; CEEZAD