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State of Knowledge Regarding Transmission, Spread, and Management of Chronic Wasting Disease in U.S. Captive and Free-Ranging Cervid Populations (2025)

Chapter: Appendix C: Commonly Asked Questions

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Suggested Citation: "Appendix C: Commonly Asked Questions." National Academies of Sciences, Engineering, and Medicine. 2025. State of Knowledge Regarding Transmission, Spread, and Management of Chronic Wasting Disease in U.S. Captive and Free-Ranging Cervid Populations. Washington, DC: The National Academies Press. doi: 10.17226/27449.

Appendix C

Commonly Asked Questions¹

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¹ This appendix does not include references. Citations for the information presented herein are provided in the main body of the report (References).

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What causes CWD?

As with other transmissible spongiform encephalopathies (TSEs), CWD in susceptible cervids results when the normal prion proteins, found in highest concentrations in the central nervous system, encounter misfolded variants of that protein. The misfolded protein causes the normal protein to misfold and become infectious itself. These misfolded prions are relatively resistant to degradation and thus accumulate in the infected animal’s lymphatic and nervous systems, spreading to other tissues and organs via the lymphatic, nervous, and circulatory systems. The spread and accumulation of these misfolded prions damage the infected animal’s brain and other organs, leading to behavioral abnormalities, loss of regular body functions, physical degradation, and ultimately death.

What are the signs that an animal has CWD?

Clinical signs of CWD can differ within and between species, but for most of the long CWD disease course (typically 1.5-2.5 years in white-tailed deer, mule deer, and reindeer; up to 4 years in elk), infected animals appear and behave normally. Infected animals in the later stages of CWD commonly exhibit progressive deterioration of body condition, repetitive movement, periods of somnolence (i.e., drowsiness), fixed stares, altered postures with lowered head and ears, and excess salivation with drooling.

The diagnosis of CWD cannot be made based on these clinical signs because other diseases and conditions exhibit similar signs. Instead, diagnosis relies on detecting evidence of CWD prions—through laboratory testing—in the brain or lymphoid tissues of animals.

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How does CWD spread to new areas?

CWD’s geographical expansion has been promoted by both human-caused and natural factors. Natural cervid movements and migration, social interactions, mating, and many other cervid behaviors (e.g., grooming, maternal interactions, congregation around food and water sources) may have significantly influenced current expansion of the form of CWD found in the United States to new free-ranging cervid populations. Human-facilitated movement of infected animals or carcasses has introduced CWD to new regions and countries. The transportation of CWD-infected cervid parts by hunters, commercial sale of goods containing cervid products contaminated with CWD prions, and the transportation of hay and animal feed contaminated by infectious CWD prions from soil, feces, and cervid parts may contribute to CWD spread and prevalence.

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What is being done to control CWD and who is responsible?

In the United States, the responsibility of managing CWD in free-ranging cervid populations lies primarily with wildlife management agencies. These agencies commit millions of dollars annually to control and manage CWD by employing a host of strategies. To prevent transmission or introduction of CWD, agencies implement regulatory interventions such as live cervid and cervid carcass part movement restrictions, bans on baiting and feeding wild cervids, cervid part disposal restrictions, and mandatory submission of hunter-harvested cervids for CWD surveillance programs. To detect and monitor the prevalence of CWD, agencies often require mandatory submission of hunter-harvested cervids for disease testing and conduct weighted, risk-based surveillance strategies to detect early disease occurrences or outbreaks. If CWD is found in free-ranging cervids, the response actions of wildlife agencies include increased risk-based sampling to delineate disease-affected area; communication and engagement with interested and affected parties; initiation or expansion of CWD-related regulations; and initiation of CWD control measures such as modifications to hunter harvest rates, targeted culling, and mandatory submission of hunter-harvested cervids.

Management of CWD in captive cervid populations primarily falls under the jurisdiction of agricultural agencies that prioritize measures targeting the prevention of disease transmission. These include reliable means of both herd and animal identification, current records of animal inventory and movement, biosecurity protocols, and accurate disease surveillance. If CWD is discovered in a captive herd, management relies on herd-level quarantine, animal movement tracing, and in most cases depopulation with further work done to characterize the extent of the outbreak and minimize its impacts on surrounding wild cervid herds. Indemnity is provided where available to both compensate the herd owner and encourage disease reporting and subsequent control measures.

Why hasn’t CWD been eradicated?

The disease agent of CWD is a misfolded protein: a non-living structure called a prion that is constructed of 256 amino acids. Prions contain no genetic material and cannot be neutralized with conventional pharmaceuticals or sanitizing techniques that are effective against bacterial, viral, fungal, and parasitic diseases. Infectious CWD prions are highly resistant to heat, chemicals, and enzymes, and can persist and remain infectious in the environment for many years. Because CWD prions are non-living proteins, no vaccines or therapeutics have yet been developed that can neutralize them in an infected animal. This, in combination with the disease’s potentially long incubation period, results in an infected animal shedding infectious prions into the environment and directly to other cervids for months—and even years—before the cervid inevitably succumbs to the disease.

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Next Chapter: Appendix D: Published Diagnostic Testing Platforms

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State of Knowledge Regarding Transmission, Spread, and Management of Chronic Wasting Disease in U.S. Captive and Free-Ranging Cervid Populations (2025)

Chapter: Appendix C: Commonly Asked Questions

Appendix C

Commonly Asked Questions¹

Publication information

Suggested citation

My Academies

State of Knowledge Regarding Transmission, Spread, and Management of Chronic Wasting Disease in U.S. Captive and Free-Ranging Cervid Populations (2025)

Chapter: Appendix C: Commonly Asked Questions

Appendix C Commonly Asked Questions1

Appendix C

Commonly Asked Questions¹